SEC Filing | Summit Midstream Corporation

View:

Download DOC

Download PDF

Download XLS

Use these links to rapidly review the document
Table of Contents Prospectus Supplement
TABLE OF CONTENTS

Table of Contents

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-191493

PROSPECTUS SUPPLEMENT
(To Prospectus dated November 8, 2013)

Summit Midstream Partners, LP
6,500,000 Common Units
Representing Limited Partner Interests

We are offering 6,500,000 common units representing limited partner interests in Summit Midstream Partners, LP.

Our common units trade on the New York Stock Exchange under the symbol "SMLP." On May 7, 2015, the last reported trading price of our common units was $30.75.

Investing in our common units involves risks. See "Risk Factors" beginning on page S-17 of this prospectus supplement and page 2 of the accompanying base prospectus and the other risk factors incorporated by reference into this prospectus supplement and the accompanying base prospectus.

	Per Common Unit		Total

Price to the public	$	30.75	$	199,875,000
Underwriting discounts and commissions⁽¹⁾	$	1.00	$	6,500,000
Proceeds to Summit Midstream Partners, LP (before expenses)	$	29.75	$	193,375,000

⁽¹⁾: Please read "Underwriting" for a description of all underwriting compensation payable in connection with this offering.

We have granted the underwriters the option to purchase 975,000 additional common units from us on the same terms as set forth above within 30 days from the date of this prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities described herein or passed on the adequacy or accuracy of this prospectus supplement. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the common units on or about May 13, 2015, through the book-entry facilities of The Depository Trust Company.


Joint Book-Running Managers
Barclays	BofA Merrill Lynch	Goldman, Sachs & Co.
Morgan Stanley	Wells Fargo Securities	Baird
Citigroup	Deutsche Bank Securities	RBC Capital Markets
Co-Managers
BB&T Capital Markets		U.S. Capital Advisors

Prospectus Supplement dated May 7, 2015.

Table of Contents

You should rely only on the information contained or incorporated by reference in this prospectus supplement, the accompanying base prospectus and any free writing prospectus that we may provide to you. Neither we nor the underwriters have authorized anyone to provide you with additional or different information. If anyone provides you with additional, different or inconsistent information, you should not rely on it. You should not assume that the information contained in this prospectus supplement or the accompanying base prospectus is accurate as of any date other than the date on the front of this prospectus supplement or the accompanying base prospectus. You should not assume that the information contained in the documents incorporated by reference in this prospectus supplement or the accompanying base prospectus is accurate as of any date other than the respective dates of those documents. Our business, financial condition, results of operations and prospects may have changed since those dates. We are not, and the underwriters are not, making an offer to sell the securities described herein in any jurisdiction where the offer or sale is not permitted.

Table of Contents

Prospectus Supplement

		Page

ABOUT THIS PROSPECTUS SUPPLEMENT			S-ii
SUMMARY			S-1
RISK FACTORS			S-17
USE OF PROCEEDS			S-18
CAPITALIZATION			S-19
PRICE RANGE OF COMMON UNITS AND DISTRIBUTIONS			S-20
MATERIAL TAX CONSIDERATIONS			S-21
UNDERWRITING			S-23
VALIDITY OF THE COMMON UNITS			S-28
EXPERTS			S-28
WHERE YOU CAN FIND MORE INFORMATION			S-28
INCORPORATION BY REFERENCE			S-28
FORWARD-LOOKING STATEMENTS			S-29

Base Prospectus


About this Prospectus			ii
Where You Can Find More Information			ii
Forward-Looking Statements			iv
Who We Are			1
Risk Factors			2
Use of Proceeds			3
Ratio of Earnings to Fixed Charges			4
Description of Our Common Units			5
Description of Debt Securities and Guarantees			7
Provisions of Our Partnership Agreement Relating to Cash Distributions			15
The Partnership Agreement			29
Material U.S. Federal Income Tax Consequences			43
Tax Consequences of Ownership of Debt Securities			60
Selling Unitholder			61
Investment in Summit Midstream Partners, LP by Employee Benefit Plans			63
Plan of Distribution			65
Validity of the Securities			67
Experts			67

S-i

Table of Contents

ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes the terms of this offering of common units. The second part is the accompanying base prospectus, which provides more general information about the securities we may offer from time to time, some of which may not apply to this offering of common units. Generally, when we use the term "prospectus," we are referring to both parts combined. If the information varies between this prospectus supplement and the accompanying base prospectus, you should rely on the information in this prospectus supplement.

In making an investment decision, prospective investors must rely on their own examination of us and the terms of the offering, including the merits and risks involved. None of Summit Midstream Partners, LP, the underwriters or any of their respective representatives is making any representation to you regarding the legality of an investment in our common units by you under applicable laws. You should consult with your own advisors as to legal, tax, business, financial and related aspects of an investment in our common units.

Any statement made in this prospectus or in a document incorporated or deemed to be incorporated by reference into this prospectus will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or in any other subsequently filed document that is also incorporated by reference into this prospectus modifies or supersedes that statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus. Please read "Where You Can Find More Information" in this prospectus supplement.

The information in this prospectus supplement is not complete. You should review carefully all of the detailed information appearing in this prospectus supplement, the accompanying base prospectus and the documents we have incorporated by reference before making any investment decision.

S-ii

Table of Contents

SUMMARY

This summary highlights information included or incorporated by reference in this prospectus. This summary does not contain all of the information that you should consider before investing in our common units. For a more complete understanding of this offering and our common units, you should read the entire prospectus supplement, the accompanying base prospectus and the documents incorporated by reference, including our historical financial statements and the notes to those financial statements, which are incorporated herein by reference from our annual report on Form 10-K for the year ended December 31, 2014 and our quarterly report on Form 10-Q for the quarter ended March 31, 2015. Please read "Where You Can Find More Information" on page S-28 of this prospectus supplement. Please read "Risk Factors" beginning on page S-17 of this prospectus supplement and the other documents incorporated by reference in that section for more information about important risks that you should consider carefully before investing in our common units.

Unless the context otherwise requires, references in this prospectus to the "Partnership," "we," "our," "us" or like terms, refer to Summit Midstream Partners, LP and its subsidiaries. Unless the context otherwise requires, references in this prospectus to "Summit Investments" refer to Summit Midstream Partners, LLC, a Delaware limited liability company, the ultimate owner of our general partner and our predecessor for accounting purposes (the "Predecessor"), and its subsidiaries. "SMP Holdings" refers to Summit Midstream Partners Holdings, LLC, a Delaware limited liability company and wholly owned subsidiary of Summit Investments. Our "general partner" refers to Summit Midstream GP, LLC, a Delaware limited liability company and wholly owned subsidiary of SMP Holdings. References in this prospectus to "Energy Capital Partners" or our "Sponsor" refer collectively to Energy Capital Partners II, LLC and its parallel and co-investment funds.

Summit Midstream Partners, LP

We are a growth-oriented limited partnership focused on developing, owning and operating midstream energy infrastructure assets that are strategically located in the core producing areas of unconventional resource basins, primarily shale formations, in North America. We provide natural gas gathering, treating and processing services pursuant to primarily long-term and fee-based natural gas gathering and processing agreements with our customers and counterparties. We currently operate in four unconventional resource basins: (i) the Appalachian Basin, which includes the Marcellus Shale formation in northern West Virginia; (ii) the Williston Basin, which includes the Bakken and Three Forks shale formations in northwestern North Dakota; (iii) the Fort Worth Basin, which includes the Barnett Shale formation in north-central Texas; and (iv) the Piceance Basin, which includes the Mesaverde formation and the Mancos and Niobrara shale formations in western Colorado and eastern Utah. Our results are driven primarily by the volumes of natural gas that we gather, treat and process across our systems. As of March 31, 2015, our gathering systems had more than 2,300 miles of pipeline and over 250,000 horsepower of compression. During the three months ended March 31, 2015, we gathered an average of 1,583 MMcf/d of natural gas.

We have a diverse group of customers and counterparties comprising affiliates and/or subsidiaries of some of the largest crude oil and natural gas producers in North America. A significant percentage of our revenue is attributable to our anchor customers. Our anchor customers and the systems that serve them are as follows:

•: Antero Resources Corp. ("Antero"), which is the anchor for the Mountaineer Midstream system;
•: EOG Resources, Inc. ("EOG") and Oasis Petroleum, Inc., which are the anchors for the Bison Midstream system;
•: Chesapeake Energy Corporation, which is the anchor for the DFW Midstream system; and

S-1

Table of Contents

•: Encana Corporation ("Encana") and WPX Energy, Inc. ("WPX"), which are the anchors for the Grand River Gathering system.

We generate a substantial majority of our revenue under long-term, primarily fee-based natural gas gathering and processing agreements. We believe the fee-based nature of these agreements enhances the stability of our cash flows by limiting our direct commodity price exposure. During the three months ended March 31, 2015, we generated approximately 97% of our revenue, net of pass-through items, from fee-based gathering and processing services. In addition, substantially all of our gas gathering and processing agreements include areas of mutual interest, or AMIs. Our AMIs cover more than 1.4 million acres in the aggregate and provide that any natural gas produced from wells drilled by our customers within the AMI will be shipped on or processed by our gathering systems. Certain of our gas gathering and processing agreements include minimum volume commitments or minimum revenue commitments, or collectively MVCs. To the extent a customer does not meet its MVC, it must make payments to cover the shortfall of natural gas not shipped or processed, either on a monthly, quarterly or annual basis. We have designed our MVC provisions to ensure that we will generate a certain amount of revenue from certain customers over the life of the respective gas gathering or processing agreement, whether by collecting gathering or processing fees on actual throughput or from cash payments to cover any MVC shortfall. As of March 31, 2015, we had remaining MVCs totaling 3.7 Tcf. These MVCs had a weighted-average remaining life of 9.2 years (assuming minimum throughput volumes for the remainder of the term) and average approximately 1,212 MMcf/d through 2019.

We believe that we are positioned for growth through the increased utilization and further development of our existing midstream assets. In addition, we intend to grow our business through the execution of new, and the expansion of existing, strategic partnerships with large producers to provide midstream services for their upstream exploration and production projects. We also intend to continue expanding our operations and diversifying our geographic footprint through asset acquisitions from Summit Investments and third parties, although Summit Investments has no obligation to offer any assets to us and we have no obligation to acquire the assets that they offer to us, if any.

Our Midstream Assets

Mountaineer Midstream system. The Mountaineer Midstream system is located in the Appalachian Basin and currently serves Antero under a long-term, fee-based contract to gather natural gas. The Mountaineer Midstream system targets liquids-rich natural gas production from the Marcellus Shale formation in Doddridge and Harrison counties in West Virginia. This natural gas gathering and compression system serves as a critical inlet to MarkWest Energy Partners, L.P.'s Sherwood Processing Complex, a primary destination for liquids-rich natural gas in northern West Virginia. During the third quarter of 2014, throughput capacity on the Mountaineer Midstream system was increased to 1,050 MMcf/d to support Antero's current and future anticipated drilling activities. We expect volumes to continue to grow on this system during 2015 as new Antero wells are connected by other third parties upstream of our system. With this expansion, we believe the Mountaineer Midstream system will enhance its strategic position as a primary source of natural gas deliveries to the Sherwood Processing Complex.

Bison Midstream system. The Bison Midstream system is located in the Williston Basin in Mountrail and Burke counties in North Dakota and gathers, compresses and treats associated natural gas that exists in the crude oil stream produced from the Bakken and Three Forks shale formations. These formations are primarily targeted for crude oil production and producer drilling decisions and activity are based largely on the prevailing price of crude oil. As such, natural gas volume throughput on the Bison Midstream system is also impacted by the prevailing price of crude oil. Our gathering agreements for the Bison Midstream system are long-term, primarily fee-based, and provide diversity of commodity price exposure for us relative to our other natural gas midstream operations. Natural gas gathered on the Bison Midstream system is delivered to Aux Sable Midstream LLC's Palermo

S-2

Table of Contents

Conditioning Plant in Palermo, North Dakota and then delivered to its 2.1 Bcf/d natural gas processing plant in Channahon, Illinois. We continue to develop the Bison Midstream system to extend our gathering reach, increase capacity, increase our receipt points and maximize throughput. Since its acquisition in 2013, we have increased capacity and improved system reliability by adding pipeline, continuing to connect additional pad sites located within our AMIs and installing additional compression.

DFW Midstream system. The DFW Midstream system is located in the Fort Worth Basin, primarily in southeastern Tarrant County, the largest natural gas producing county in Texas. We consider this area to be the core of the core of the Barnett Shale because of the quality of the geology and the high production profile of the wells drilled to date. We designed the DFW Midstream system to benefit from incremental volumes arising from high-density, infill drilling on existing pad sites that are already connected to the gathering system and, as such, would not require significant additional capital expenditures. Development of the DFW Midstream system has enabled our customers to efficiently produce natural gas by utilizing horizontal drilling techniques from pad sites within our AMIs that are already connected to the gathering system. Given the urban nature of southeastern Tarrant County, we expect that the majority of future natural gas drilling in this area will occur from existing pad sites. We believe that the AMIs underpinning our system are substantially undeveloped compared with other areas in the Barnett Shale due to the historical lack of gathering infrastructure. Furthermore, we believe the production profile of wells drilled within our AMIs and flowing on the DFW Midstream system will continue to attract drilling activity over the long term as producers become more selective in their drilling locations and focus on the core areas of certain basins to maximize their returns.

Grand River Gathering system. The Grand River Gathering system is located in the Piceance Basin in western Colorado and eastern Utah and gathers and processes natural gas from the Mesaverde formation and the Mancos and Niobrara shale formations. In addition to agreements with Encana, WPX and Black Hills Exploration and Production, Inc., Grand River Gathering is underpinned by other long-term, fee-based gathering and processing agreements. The Grand River Gathering system compresses, dehydrates, processes and/or discharges natural gas to downstream pipelines serving (i) Enterprise Product Partners L.P.'s ("Enterprise") Meeker Natural Gas Processing Plant, a 1.8 Bcf/d processing facility located in Meeker, Colorado, (ii) Williams Partners L.P.'s Northwest Pipeline system and (iii) Kinder Morgan, Inc.'s TransColorado Pipeline system. Processed natural gas liquids ("NGLs") from Grand River Gathering are injected into Enterprise's Mid-America Pipeline system.

The Grand River Gathering system is primarily a low-pressure gathering system that was originally designed to gather natural gas produced from directional wells targeting the liquids-rich Mesaverde formation. The Mesaverde is a shallow, tight sands geologic formation that producers have targeted with directional drilling for several decades. We also gather natural gas from our customers' wells targeting the emerging Mancos and Niobrara shale formations, which underlie the Mesaverde formation, via a new medium-pressure gathering system. Based on our customers' current drilling activities, we anticipate that the majority of our near-term throughput on this system will continue to originate from the Mesaverde formation. We expect to continue to pursue additional volumes on the low pressure system to more fully utilize the existing throughput capacity. In addition, we believe that the Grand River Gathering system is optimally located for expansion to gather production from the emerging Mancos and Niobrara shale formations.

S-3

Table of Contents

The following table provides information regarding our gathering systems as of, or for the three months ended, March 31 for the periods indicated:

	Mountaineer Midstream				Bison Midstream				DFW Midstream				Grand River⁽¹⁾

	2015		2014		2015		2014		2015		2014		2015		2014
Miles of pipeline (as of March 31)		49		40		392		352		128		122		1,778		1,780
Aggregate average throughput (for the three months ended March 31) (MMcf/d)		547		286		18		12		403		348		615		665

⁽¹⁾: Includes contribution from Red Rock Gathering Company, LLC during the period from January 1, 2014 to March 18, 2014 due to the common control aspect of our March 18, 2014 acquisition of all of the membership interests in Red Rock Gathering Company, LLC from a subsidiary of Summit Investments.

Recent Developments

Acquisition of the Polar and Divide System. On May 6, 2015, SMP Holdings, Polar Midstream, LLC, a Delaware limited liability company and indirect wholly owned subsidiary of SMP Holdings ("Polar"), and Epping Transmission Company, LLC, a Delaware limited liability company and indirect wholly owned subsidiary of SMP Holdings ("Epping"), entered into a contribution agreement with us pursuant to which SMP Holdings agreed to contribute to us, via a wholly owned subsidiary of SMP Holdings, all of the issued and outstanding membership interests of Polar and Epping for a total purchase price of $255.0 million, subject to customary purchase price adjustments (the "Acquisition"). The assets to be acquired as a result of the Acquisition include certain crude oil and produced water gathering systems and transmission pipelines serving producers operating in the Williston Basin (the "Polar and Divide System"). The Acquisition is expected to close before May 31, 2015, subject to customary closing conditions, and will be funded with (i) the net proceeds from the sale of common units by us in this offering, (ii) borrowings under our amended and restated senior secured revolving credit facility (the "revolving credit facility") and (iii) a capital contribution from our general partner to maintain its 2.0% general partner interest. The terms of the Acquisition were approved by the conflicts committee of the board of directors of our general partner, which committee consists entirely of independent directors, and by the entire board of directors of our general partner. This offering is not contingent upon the closing of the Acquisition.

The Polar and Divide System consists of more than 295 miles of crude oil and produced water pipelines, spanning throughout the central and western parts of Williams and Divide counties in North Dakota, from the Missouri River to the Canadian border. These assets are underpinned by long-term, fee-based gathering agreements with multiple producers, including anchor customers Whiting Petroleum Corp. and SM Energy Company. Several of these gathering agreements include rate redetermination mechanisms which effectively serve to protect the Polar and Divide System's cash flows by resetting the gathering rate upward in the future in the event that the customer does not attain certain minimum production thresholds.

The Polar and Divide System began operating in May 2013 and currently has a maximum aggregate throughput capacity of 80,000 barrels per day, or bbls/d, of crude oil and produced water. In the first quarter of 2015, the Polar and Divide System gathered over 48,000 bbls/d of crude oil and produced water from pad sites, central receipt points and truck unloading stations, an increase from approximately 33,500 bbls/d for the year ended December 31, 2014. For the year ended December 31, 2014, 100% of the revenue on the Polar and Divide System was generated from fee-based services. Crude oil is currently delivered to the COLT Hub in Epping, North Dakota and produced water is delivered to producer-owned and third-party injection wells located throughout the Williston Basin. There are two development projects currently underway to provide customers of the Polar and Divide

S-4

Table of Contents

System with additional delivery points for crude oil, including (i) an interconnect with Enbridge's North Dakota Pipeline System that is being developed by Epping and (ii) the Stampede Lateral, which is being developed by a subsidiary of Summit Investments to interconnect with Global Partners LP's ("Global") Basin Columbus rail hub near Columbus, North Dakota.

In connection with the Acquisition, SMP Holdings granted us an exclusive six-month option to purchase the Stampede Lateral, a 46-mile, 10-inch diameter crude oil transmission pipeline project with throughput capacity of 50,000 bbls/d that runs from the Polar and Divide System to Global's Basin Columbus rail hub for delivery to East Coast markets. If the conflicts committee of the board of directors of our general partner elects to exercise this option, we will pay SMP Holdings $35.0 million for the Stampede Lateral. This option may not be exercised until certain project milestones are met.

First Quarter 2015 Distribution. The board of directors of our general partner declared a cash distribution to our unitholders of $0.565 per unit on all outstanding common and subordinated units for the quarter ended March 31, 2015. The cash distribution is payable on May 15, 2015 to unitholders of record at the close of business on May 8, 2015. This distribution represents an increase of $0.005 per unit, or 0.9%, over the distribution paid in respect of the fourth quarter of 2014. Since our initial public offering in October 2012, we have increased our quarterly distribution level to our unitholders by 41% over our minimum quarterly distribution. Purchasers of common units in this offering will not be entitled to receive the first quarter cash distribution.

Our Business Strategies

Our principal business strategy is to increase the amount of cash distributions we make to our unitholders over time. Our plan for continuing to execute this strategy includes the following key components:

•: Pursuing accretive acquisition opportunities from Summit Investments. We intend to pursue opportunities to expand our asset base by acquiring midstream assets and joint venture interests that are owned and operated by and under development at Summit Investments. In addition to its significant ownership interest in us, Summit Investments owns and operates, and seeks to acquire and develop, crude oil, natural gas and water-related midstream assets in service and under construction in geographic areas in which we currently operate as well as in geographic areas outside of our current areas of operations. For example, in December 2014, Summit Investments announced an agreement to develop and operate a new 500 MMcf/d natural gas gathering system in the Utica Shale ("Summit Utica"). Summit Utica will gather, compress and deliver natural gas produced by XTO Energy Inc. into Energy Transfer Partners L.P.'s 2.1 Bcf/d high-pressure Utica Ohio River Trunkline Project, which is currently under construction, and other downstream delivery points. While Summit Investments has indicated that it intends to offer us the opportunity to acquire its interests in its various midstream assets, it is not under any contractual obligation to do so and we are unable to predict whether or when such opportunities may arise. In its role as a midstream development vehicle for our Sponsor, we believe that Summit Investments' development efforts mitigate potential development and cash flow timing risks associated with large-scale greenfield development projects that would otherwise be borne by us.
•: Maintaining our focus on fee-based revenue with minimal direct commodity price exposure. As we expand our business, we intend to maintain our focus on providing midstream energy services under fee-based arrangements. Our midstream services are provided under primarily long-term and fee-based contracts with original terms up to 25 years. Currently, all of the contracts associated with assets owned and being developed by Summit Investments are fee-based. We believe that our focus on fee-based revenues with minimal direct commodity price exposure is essential to maintaining stable cash flows.

S-5

Table of Contents

•: Capitalizing on organic growth opportunities to maximize throughput on our existing systems. We intend to continue to leverage our management team's expertise in constructing, developing and optimizing our midstream assets to grow our business through organic development projects. We believe that our broad and geographically diverse operating footprint provides us with a competitive advantage to pursue organic development projects that are designed to extend our geographic reach, diversify our customer base, expand our midstream service offerings, increase the number of our hydrocarbon receipt points and maximize volume throughput.
•: Diversifying our asset base by expanding our midstream service offerings and exploring acquisition and development opportunities in various geographic areas. Our natural gas gathering operations in the Marcellus, Bakken, Three Forks and Barnett shale plays and the Piceance Basin currently represent our core business. However, we intend to diversify our service offerings. For example, following the completion of the Acquisition, we will provide crude oil and produced water gathering services to producers in the Williston Basin. We also intend to diversify our operations into other geographic regions, through both greenfield development projects and acquisitions from affiliated and non-affiliated parties.
•: Partnering with producers to provide midstream services for their development projects in high-growth, unconventional resource plays. We seek to promote commercial relationships with established and well-capitalized producers who are willing to serve as anchor customers and commit to long-term MVCs and AMIs. We will continue to pursue partnership opportunities with established producers to develop new infrastructure in unconventional resource basins that we believe will complement our existing midstream assets and enhance our overall business by facilitating our entry into new basins. These opportunities generally consist of a strategic acreage position in an unconventional resource play that is well-positioned for accelerated production but has limited existing midstream energy infrastructure to support such growth.

Our Competitive Strengths

We believe that we will be able to continue to execute the components of our principal business strategy successfully because of the following competitive strengths:

•: Strategically located assets in core areas of prolific unconventional basins supported by partnerships with large producers. We believe our assets are strategically positioned within the core areas of four established unconventional resource basins. The geologic formations in the basins served by our assets have either relatively low drilling and completion costs, highly economic production profiles, or a combination of both, which we believe incentivizes producers to develop more actively than in more marginal areas.
•: Fee-based revenues underpinned by long-term contracts with AMIs and MVCs. A substantial majority of our revenue for the year ended December 31, 2014 and the three months ended March 31, 2015 was generated under long-term and fee-based gathering and processing agreements. We believe that long-term, fee-based gathering and processing agreements enhance the stability of our cash flows by limiting our direct commodity price exposure.
•: Capital structure and financial flexibility. At March 31, 2015, we had $796.0 million of total indebtedness and the unused portion of our $700.0 million revolving credit facility totaled $504.0 million. Under the terms of our revolving credit facility, our total leverage ratio (total net indebtedness to consolidated trailing 12-month EBITDA, as defined in the credit agreement) was approximately 3.9 to 1.0 at March 31, 2015, which compares with a total leverage ratio upper limit of not more than 5.0 to 1.0, or not more than 5.5 to 1.0 for up to 270 days following certain acquisitions (as defined in the credit agreement).

S-6

Table of Contents

•: Experienced management team with proven record of asset acquisition, construction, development, operation and integration expertise. Our senior leadership team has an average of over 20 years of energy experience and a proven track record of identifying, consummating and integrating significant acquisitions in addition to partnering with major producers to construct and develop midstream energy infrastructure.
•: Relationships with large and committed financial sponsor. Our Sponsor, Energy Capital Partners, is an experienced energy investor with a proven track record of making substantial, long-term investments in high-quality energy assets. We believe the relationship with our Sponsor is a competitive advantage, as it brings not only significant financial and management experience, but also numerous relationships throughout the energy industry that we believe will continue to benefit us as we seek to grow our business.

Our Sponsor

Energy Capital Partners, together with its affiliated funds, is a private equity firm with over $13.0 billion in capital commitments that is focused on investing in North America's energy infrastructure. Energy Capital Partners has significant energy and financial expertise to complement its investment in us, including investments in the power generation, midstream oil and gas, electric transmission, energy equipment and services, environmental infrastructure and other energy-related sectors.

Principal Executive Offices and Internet Address

Our principal executive offices are located at 1790 Hughes Landing Blvd, Suite 500, The Woodlands, Texas 77380, and our telephone number is (832) 413-4770. Our website is located at www.summitmidstream.com. We make available our periodic reports and other information filed with or furnished to the Securities and Exchange Commission, or SEC, free of charge through our website, as soon as reasonably practicable after those reports and other information are electronically filed with or furnished to the SEC. Information on our website or any other website is not incorporated by reference herein and does not constitute a part of this prospectus.

S-7

Table of Contents

Partnership Structure

The table and diagram below illustrate our organization and ownership after giving effect to this offering, assuming that the underwriters do not exercise their option to purchase additional common units:


Public Common Units	53.5	%
SMP Holdings Units:
Common Units	7.9	%
Subordinated Units	36.6	%
General Partner Interest	2.0	%

Total	100.0	%

⁽¹⁾: Energy Capital Partners, through its ownership of Class A Interests, controls Summit Midstream Partners, LLC and, therefore, Summit Midstream GP, LLC.

S-8

Table of Contents

The Offering


Common units offered by us		6,500,000 common units; 7,475,000 common units if the underwriters exercise in full their option to purchase additional common units.
Units outstanding before this offering		34,495,468 common units and 24,409,850 subordinated units.
Units outstanding after the offering		40,995,468 common units, or 41,970,468 common units if the underwriters exercise in full their option to purchase an additional 975,000 common units from us, and 24,409,850 subordinated units.
Use of proceeds		We expect to receive net proceeds of approximately $197.3 million, including our general partner's proportionate capital contribution of approximately $4.1 million to maintain its 2% general partner interest in us, or approximately $226.9 million if the underwriters exercise their option to purchase additional units in full, in each case after deducting underwriting discounts and commissions and estimated offering expenses, from the sale of 6,500,000 common units offered by this prospectus. We intend to use the net proceeds from this offering to fund a portion of the purchase price of the Acquisition. This offering is not contingent upon the closing of the Acquisition. If the Acquisition does not close, we will use the net proceeds received by us in this offering and the related capital contribution to us by our general partner for general partnership purposes.
		Please read "Use of Proceeds."
Cash distributions		Our partnership agreement requires us to distribute all of our cash on hand at the end of each quarter, less reserves established by our general partner and payment of fees and expenses. We refer to this cash as "available cash," and it is defined in our partnership agreement. Please read "Provisions of our Partnership Agreement Relating to Cash Distributions" in the accompanying base prospectus.
Issuance of additional units		We can issue an unlimited number of units without the consent of our unitholders. Please read "The Partnership Agreement—Issuance of Additional Partnership Interests" in the accompanying base prospectus.

S-9

Table of Contents


Limited voting rights		Our general partner manages and operates us. Common unitholders have only limited voting rights on matters affecting our business. Common unitholders have no right to elect our general partner or its directors on an annual or continuing basis. Our general partner may not be removed except by a vote of the holders of at least 66²/3% of the outstanding units voting together as a single class, including any units owned by our general partner and its affiliates, including SMP Holdings. After giving effect to this offering and assuming that the underwriters exercise their option to purchase additional common units in full, SMP Holdings will own an aggregate of 44.7% of our common and subordinated units, which gives SMP Holdings the ability to prevent the removal of our general partner.
		Please read "The Partnership Agreement—Voting Rights" in the accompanying base prospectus.
Estimated ratio of taxable income to distributions		We estimate that if you own the common units you purchase in this offering through the record date for distributions for the period ending December 31, 2017, you will be allocated, on a cumulative basis, an amount of federal taxable income for that period that will be 20% or less of the cash distributed to you with respect to that period. Please read "Material Tax Considerations" in this prospectus supplement.
Material tax consequences		For a discussion of other material federal income tax consequences that may be relevant to prospective unitholders who are individual citizens or residents of the United States, please read "Material Tax Considerations" in this prospectus supplement and "Material U.S. Federal Income Tax Consequences" in the accompanying base prospectus.
Exchange listing		Our common units trade on the NYSE under the symbol "SMLP."
Risk factors		You should carefully read and consider the information beginning on page S-17 of this prospectus supplement set forth under the heading "Risk Factors" and all other information set forth in this prospectus, including the information incorporated herein by reference, before deciding to invest in our common units.

S-10

Table of Contents

Summary Historical Financial and Operating Data

The following table presents, as of the dates and for the periods indicated, the summary historical consolidated financial and operating data for us and our Predecessor. The following table should be read in conjunction with "Selected Financial Data," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the financial statements and related notes appearing in our Annual Report on Form 10-K for the year ended December 31, 2014 and in our Quarterly Report on Form 10-Q for the quarter ended March 31, 2015, which are incorporated by reference into this prospectus supplement. For the purposes of the financial data presented below, our results of operations for the period from January 1, 2012 through October 3, 2012, the closing date of our initial public offering, include the results of operations of our Predecessor. Please read "Management's Discussion and Analysis of Financial Condition and Results of Operations—Results of Operations—Items Affecting the Comparability of Our Financial Results" in our Annual Report on Form 10-K for the year ended December 31, 2014 and in our Quarterly Report on Form 10-Q for the quarter ended March 31, 2015. Moreover, our historical results are not necessarily indicative of results that may be expected for any future period.

The summary historical consolidated financial data presented as of December 31, 2014 and 2013 and for the years ended December 31, 2014, 2013 and 2012 have been derived from the audited consolidated financial statements of the Partnership and our Predecessor, which are incorporated by reference in this prospectus supplement. The summary historical consolidated financial data presented as of March 31, 2015 and for the three months ended March 31, 2015 and 2014 have been derived from our unaudited condensed consolidated financial statements, which are incorporated by reference in this prospectus supplement.

The following table includes our and our Predecessor's historical EBITDA, adjusted EBITDA and distributable cash flow, which have not been prepared in accordance with accounting principles generally accepted in the United States, or GAAP. EBITDA, adjusted EBITDA and distributable cash flow are presented because we believe they are helpful to management, industry analysts, investors, lenders and rating agencies and may be used to assess the financial performance and operating results of our fundamental business activities. For the definitions of EBITDA, adjusted EBITDA and distributable cash flow and reconciliations thereof to their most directly comparable financial measures calculated in accordance with GAAP, please see "—Non-GAAP Financial Measures" below.

S-11

Table of Contents

	Summit Midstream Partners, LP

	Three months ended March 31,						Year ended December 31,
	2015			2014			2014			2013			2012
	(Dollars in thousands)
Statement of Operations Data:
Revenues:
Gathering services and other fees	$	56,054		$	50,072		$	235,033		$	205,346		$	154,139
Natural gas, NGLs and condensate sales and other		12,776			26,356			96,597			88,606			20,476
Amortization of favorable and unfavorable contracts⁽¹⁾		(251	)		(226	)		(944	)		(1,032	)		(192	)

Total revenues		68,579			76,202			330,686			292,920			174,423
Costs and expenses:
Cost of natural gas and NGLs		6,695			15,281			58,094			44,233			3,224
Operation and maintenance		17,429			19,181			76,272			72,465			53,882
General and administrative		8,351			7,886			34,017			30,105			22,182
Transaction costs		—			537			730			2,841			2,025
Depreciation and amortization		22,143			19,642			82,990			69,962			36,674
Loss on asset sales, net		—			—			442			113			—
Goodwill impairment		—			—			54,199			—			—
Long-lived asset impairment		—			—			5,505			—			—

Total costs and expenses		54,618			62,527			312,249			219,719			117,987

Other income		1			1			1,189			5			9
Interest expense		(12,118	)		(7,144	)		(40,159	)		(19,173	)		(7,340	)
Affiliated interest expense		—			—			—			—			(5,426	)

Income (loss) before income taxes		1,844			6,532			(20,533	)		54,033			43,679
Income tax expense		(177	)		(159	)		(631	)		(729	)		(682	)

Net income (loss)	$	1,667		$	6,373		$	(21,164	)	$	53,304		$	42,997



Statement of Cash Flows Data:
Net cash provided by (used in):
Operating activities	$	49,541		$	48,509		$	147,935		$	140,689		$	89,392
Investing activities		(14,855	)		(345,100	)		(443,872	)		(518,791	)		(77,296	)
Financing activities		(48,018	)		286,638			302,008			387,125			(16,224	)
Balance Sheet Data (at period end):
Cash and cash equivalents	$	13,096					$	26,428		$	20,357
Accounts receivable		44,069						83,612			67,877
Property, plant, and equipment, net		1,234,229						1,235,652			1,158,081
Total assets		1,828,988						1,894,874			1,883,739
Total debt		796,000						808,000			586,000
Other Financial Data:
EBITDA⁽²⁾	$	36,355		$	33,543		$	103,556		$	144,195		$	93,302
Adjusted EBITDA⁽²⁾		50,007			46,619			193,778			164,839			105,946
Capital expenditures⁽³⁾		11,914			40,100			128,325			109,376			77,296
Acquisition of gathering systems⁽⁴⁾		2,941			305,000			315,872			458,914			—
Distributable cash flow⁽²⁾⁽³⁾		35,902			33,733			139,611			128,141			90,947
Operating data:
Miles of pipeline (end of period)		2,347			2,294			2,348			2,283			1,874
Aggregate average throughput (MMcf/d)		1,583			1,311			1,418			1,138			952

⁽¹⁾: The amortization of favorable and unfavorable contracts relates to gas gathering agreements that were deemed to be above or below market at the acquisition of the DFW Midstream system. We amortize these contracts on a units of production basis over the life of the applicable contract.
⁽²⁾: See "—Non-GAAP Financial Measures" below for additional information on EBITDA, adjusted EBITDA and distributable cash flow as well as their reconciliations to the most directly comparable GAAP financial measure. EBITDA and adjusted EBITDA include transaction costs. These unusual expenses are settled in cash.
⁽³⁾: See "Liquidity and Capital Resources" in our Annual Report on Form 10-K for the year ended December 31, 2014 and the quarterly report on Form 10-Q for the quarter ended March 31, 2015 for more information on

S-12

Table of Contents

capital expenditures. In the fourth quarter of 2012, we began tracking maintenance capital expenditures for the purposes of calculating distributable cash flow. Prior to the fourth quarter of 2012, we did not distinguish between maintenance and expansion capital expenditures. For the year ended December 31, 2012, distributable cash flow includes an estimate for the portion of total capital expenditures that were maintenance capital expenditures for the nine months ended September 30, 2012.

⁽⁴⁾: Reflects cash paid (including working capital adjustments) and value of units issued, if any, to fund acquisitions and/or drop downs.

Non-GAAP Financial Measures

We define EBITDA as net income or loss, plus interest expense, income tax expense, and depreciation and amortization, less interest income and income tax benefit. We define adjusted EBITDA as EBITDA plus adjustments related to MVC shortfall payments, impairments and other noncash expenses or losses, less other noncash income or gains. We define distributable cash flow as adjusted EBITDA plus cash interest received, less cash interest paid, senior notes interest, cash taxes paid and maintenance capital expenditures.

EBITDA, adjusted EBITDA and distributable cash flow are used as supplemental financial measures by our management and by external users of our financial statements such as investors, commercial banks, research analysts and others.

EBITDA and adjusted EBITDA are used to assess:

•: the financial performance of our assets without regard to financing methods, capital structure or historical cost basis;
•: the ability of our assets to generate cash sufficient to support our indebtedness and make cash distributions to our unitholders and general partner;
•: our operating performance and return on capital as compared to those of other companies in the midstream energy sector, without regard to financing or capital structure; and
•: the attractiveness of capital projects and acquisitions and the overall rates of return on alternative investment opportunities.

In addition, adjusted EBITDA is used to assess:

•: the financial performance of our assets without regard to the impact of the timing of minimum volume commitments shortfall payments under our gas gathering agreements or the timing of impairments of other noncash income or expense items.

Distributable cash flow is used to assess:

•: the ability of our assets to generate cash sufficient to support our indebtedness and make future cash distributions to our unitholders; and
•: the attractiveness of capital projects and acquisitions and the overall rates of return on alternative investment opportunities.

EBITDA, adjusted EBITDA and distributable cash flow are not financial measures presented in accordance with GAAP. We believe that the presentation of these non-GAAP financial measures provides useful information to investors in assessing our financial condition and results of operations.

Net income or loss and net cash provided by operating activities are the GAAP financial measures most directly comparable to EBITDA, adjusted EBITDA and distributable cash flow. Our non-GAAP financial measures should not be considered as alternatives to the most directly comparable GAAP financial measure. Furthermore, each of these non-GAAP financial measures has limitations as an analytical tool because it excludes some but not all items that affect the most directly comparable GAAP financial measure.

S-13

Table of Contents

We compensate for the limitations of EBITDA, adjusted EBITDA and distributable cash flows as analytical tools by reviewing the comparable GAAP financial measures, understanding the differences between the financial measures and incorporating these data points into our decision-making process.

EBITDA, adjusted EBITDA or distributable cash flow should not be considered in isolation or as a substitute for analysis of our results as reported under GAAP. Because EBITDA, adjusted EBITDA and distributable cash flow may be defined differently by other companies in our industry, our definitions of these non-GAAP financial measures may not be comparable to similarly titled measures of other companies, thereby diminishing their utility.

Non-GAAP Reconciliations Items to Note

The following items should be noted when reviewing our non-GAAP reconciliations:

•: EBITDA, adjusted EBITDA, distributable cash flow and net cash provided by operating activities include transaction costs. These unusual expenses are settled in cash.
•: Adjustments related to MVC shortfall payments account for (i) the net increases or decreases in deferred revenue for MVC shortfall payments and (ii) our inclusion of expected annual MVC shortfall payments. We include a proportional amount of these historical or expected minimum volume commitment shortfall payments in each quarter prior to the quarter in which we actually receive the shortfall payment.
•: The goodwill impairment recognized in the year ended December 31, 2014 relates to the Bison Midstream system of our Williston Basin segment.
•: The long-lived asset impairment recognized in the year ended December 31, 2014 relates to the DFW Midstream system of our Barnett Shale segment.
•: The impact of purchase price adjustments reflects certain balances previously recognized in connection with the Predecessor's purchase accounting for the Legacy Grand River system that we wrote off during the fourth quarter of 2014. This write off was recognized in other income.
•: Senior notes interest represents the net of interest expense accrued and paid during the period.
•: Maintenance capital expenditures are cash expenditures (including expenditures for the addition or improvement to, or the replacement of, our capital assets or for the acquisition of existing, or the construction or development of new, capital assets) made to maintain our long-term operating income or operating capacity. In the fourth quarter of 2012, we began tracking maintenance capital expenditures for the purposes of calculating distributable cash flow. Prior to the fourth quarter of 2012, we did not distinguish between maintenance and expansion capital expenditures. For the year ended December 31, 2012 the calculation of distributable cash flow includes an estimate for the portion of total capital expenditures that were maintenance capital expenditures.
•: Interest expense presented in the net income-basis non-GAAP reconciliation includes amortization of deferred loan costs while interest expense presented in the cash flow-basis non-GAAP reconciliation is adjusted to exclude amortization of deferred loan costs.

S-14

Table of Contents

Net Income-Basis Non-GAAP Reconciliation

The following table presents a reconciliation of our net income to EBITDA, adjusted EBITDA and distributable cash flow for the periods indicated.

	Summit Midstream Partners, LP

	Three months ended March 31,						Year ended December 31,
	2015			2014			2014			2013		2012
	(Dollars in thousands)
Reconciliation of Net Income to EBITDA, Adjusted EBITDA and Distributable Cash Flow
Net income (loss)	$	1,667		$	6,373		$	(21,164	)	$	53,304	$	42,997
Add:
Interest expense		12,118			7,144			40,159			19,173		12,766
Income tax expense		177			159			631			729		682
Depreciation and amortization		22,143			19,642			82,990			69,962		36,674
Amortization of favorable and unfavorable contracts		251			226			944			1,032		192
Less:
Interest income		1			1			4			5		9

EBITDA	$	36,355		$	33,543		$	103,556		$	144,195	$	93,302



Add:
Adjustments related to MVC shortfall payments		12,340			12,013			26,565			17,025		10,768
Unit-based compensation		1,312			1,063			4,696			3,506		1,876
Loss on asset sales, net		—			—			442			113		—
Goodwill impairment		—			—			54,199			—		—
Long-lived asset impairment		—			—			5,505			—		—
Less:
Impact of purchase price adjustment		—			—			1,185			—		—

Adjusted EBITDA	$	50,007		$	46,619		$	193,778		$	164,839	$	105,946



Add:
Cash interest received		1			1			4			5		9
Less:
Cash interest paid		22,812			14,308			31,524			9,016		8,283
Senior notes interest		(11,171	)		(6,500	)		6,733			12,125		—
Cash taxes paid		—			—			—			660		650
Maintenance capital expenditures		2,465			5,079			15,914			14,902		6,075

Distributable cash flow	$	35,902		$	33,733		$	139,611		$	128,141	$	90,947

S-15

Table of Contents

Cash Flow-Basis Non-GAAP Reconciliation

The following table presents a reconciliation of our net cash provided by operating activities to EBITDA, adjusted EBITDA and distributable cash flow for the periods indicated.

	Summit Midstream Partners, LP

	Three months ended March 31,						Year ended December 31,
	2015			2014			2014			2013			2012
	(Dollars in thousands)
Reconciliation of Net Cash Provided by Operating Activities to EBITDA, Adjusted EBITDA and Distributable Cash Flow:
Net cash provided by operating activities	$	49,541		$	48,509		$	147,935		$	140,689		$	89,392
Add:
Interest expense		11,327			6,540			37,389			16,927			5,882
Income tax expense		177			159			631			729			682
Impact of purchase price adjustment		—			—			1,185			—			—
Changes in operating assets and liabilities		(23,377	)		(20,601	)		(18,738	)		(10,526	)		(769	)
Less:
Unit-based compensation		1,312			1,063			4,696			3,506			1,876
Interest income		1			1			4			5			9
Loss on asset sales, net		—			—			442			113			—
Goodwill impairment		—			—			54,199			—			—
Long lived asset impairment		—			—			5,505			—			—

EBITDA	$	36,355		$	33,543		$	103,556		$	144,195		$	93,302



Add:
Adjustments related to MVC shortfall payments		12,340			12,013			26,565			17,025			10,768
Unit-based compensation		1,312			1,063			4,696			3,506			1,876
Loss on asset sales, net		—			—			442			113			—
Goodwill impairment		—			—			54,199			—			—
Long lived asset impairment		—			—			5,505			—			—
Less:
Impact of purchase price adjustments		—			—			1,185			—			—

Adjusted EBITDA	$	50,007		$	46,619		$	193,778		$	164,839		$	105,946



Add:
Cash interest received		1			1			4			5			9
Less:
Cash interest paid		22,812			14,308			31,524			9,016			8,283
Senior notes interest		(11,171	)		(6,500	)		6,733			12,125			—
Cash taxes paid		—			—			—			660			650
Maintenance capital expenditures		2,465			5,079			15,914			14,902			6,075

Distributable cash flow	$	35,902		$	33,733		$	139,611		$	128,141		$	90,947

S-16

Table of Contents

RISK FACTORS

An investment in our common units involves risk. You should carefully read the risk factor set forth below as well as the risk factors included under the caption "Risk Factors" beginning on page 2 of the accompanying base prospectus, as well as the risk factors included in Item 1A. "Risk Factors" in our Annual Report on Form 10-K for the year ended December 31, 2014, as updated by our subsequent Current Reports on Form 8-K and Quarterly Reports on Form 10-Q, together with all of the other information included or incorporated by reference in this prospectus supplement. If any of these risks were to occur, our business, financial condition, results of operations or prospects could be materially adversely affected. In such case, the trading price of our common units could decline, and you could lose all or part of your investment.

The Acquisition may not be completed as anticipated, or if completed, may not be beneficial to us.

The Acquisition is expected to close before May 31, 2015 and is subject to satisfaction of customary closing conditions, including the completion of this offering. If these conditions are not satisfied or waived, the Acquisition will not be consummated. There is no assurance that the Acquisition will close on or before that time, or at all. Accordingly, if you decide to purchase our common units, you should be willing to do so whether or not we complete the Acquisition.

If we consummate the Acquisition, we will be subject to additional risks, in particular the risk that we fail to realize the expected profitability, growth or accretion from the acquisition. The consummation of the Acquisition involves additional potential risks, including:

•: environmental or regulatory compliance matters or liabilities;
•: title issues or environmental or regulatory compliance matters or liabilities or accidents;
•: construction cost overruns and delays resulting from numerous factors, many of which may be out of our control;
•: the temporary diversion of management's attention from our existing businesses;
•: the incurrence of significant charges, such as asset devaluation or restructuring charges; and
•: the incurrence of unanticipated liabilities and costs for which indemnification is unavailable or inadequate.

If we consummate the Acquisition and if these risks or other unanticipated liabilities were to materialize, any desired benefits of the acquisition may not be fully realized, if at all, and our future financial performance and results of operations could be negatively impacted.

S-17

Table of Contents

USE OF PROCEEDS

We expect to receive net proceeds of approximately $197.3 million, including our general partner's proportionate capital contribution of approximately $4.1 million to maintain its 2.0% general partner interest in us, or approximately $226.9 million if the underwriters exercise their option to purchase additional units in full, in each case after deducting underwriting discounts and commissions and estimated offering expenses, from the sale of 6,500,000 common units offered by us pursuant to this prospectus supplement. We intend to use the net proceeds from this offering to fund a portion of the purchase price of the Acquisition. If the underwriters exercise their option to purchase additional common units after we have closed the Acquisition, we intend to use the net proceeds from the sale of such additional common units (i) to partially fund the acquisition of the Stampede Lateral, if we exercise our option, or (ii) for general partnership purposes, including the repayment of debt. This offering is not contingent upon the closing of the Acquisition. If the Acquisition does not close, we will use the net proceeds received from this offering and the related capital contribution to us by our general partner for general partnership purposes.

S-18

Table of Contents

CAPITALIZATION

The following table sets forth our cash and cash equivalents and capitalization as of March 31, 2015, on an actual basis and as adjusted to reflect this offering of common units and the application of the net proceeds as described under "Use of Proceeds."

	As of March 31, 2015

	Actual		As adjusted
	(In thousands)
Cash and cash equivalents	$	13,096	$	13,096



Debt:
Revolving credit facility⁽¹⁾	$	196,000	$	253,750	⁽²⁾
7.50% Senior notes due 2021		300,000		300,000
5.50% Senior notes due 2022		300,000		300,000

Total long-term debt		796,000		853,750

Partners' Capital:
Common limited partner capital		630,241		823,332
Subordinated limited partner capital		279,524		279,524
General partner interest		24,100		28,225

Total partners' capital	$	933,865	$	1,131,081

Total capitalization	$	1,742,961	$	1,984,831

⁽¹⁾: Reflects balance under our revolving credit facility at March 31, 2015. As of April 30, 2015 we had $196.0 million of borrowings outstanding under our revolving credit facility.
⁽²⁾: Includes $57.8 million borrowed under our revolving credit facility to fund a portion of the purchase price for the Acquisition.

You should read our financial statements and notes thereto that are incorporated by reference into this prospectus supplement and the accompanying base prospectus for additional information about our capital structure. The table above does not reflect any common units that may be sold to the underwriters upon exercise of their option to purchase additional common units.

S-19

Table of Contents

PRICE RANGE OF COMMON UNITS AND DISTRIBUTIONS

Our common units trade on the NYSE under the symbol "SMLP." On May 7, 2015, the last reported trading price of our common units was $30.75. As of April 30, 2015, there were approximately 63 holders of record of our common units. The following table sets forth the high and low sales prices of our common units as well as the amount of cash distributions declared and paid during each quarter for the periods indicated.

	Common Unit Price

	Common Unit Price				Distributions per Common Unit
Quarter Ended	High		Low		Distributions per Common Unit			Record Date	Payment Date
June 30, 2015 (through May 7, 2015)	$	36.82	$	30.70			⁽¹⁾	⁽¹⁾	⁽¹⁾
March 31, 2015	$	41.17	$	30.31	$	0.5650		May 8, 2015	May 15, 2015
December 31, 2014	$	51.44	$	32.30	$	0.5600		February 6, 2015	February 13, 2015
September 30, 2014	$	56.49	$	46.50	$	0.5400		November 7, 2014	November 14, 2014
June 30, 2014	$	51.25	$	40.53	$	0.5200		August 7, 2014	August 14, 2014
March 31, 2014	$	43.98	$	34.72	$	0.5000		May 8, 2014	May 15, 2014
December 31, 2013	$	38.20	$	30.66	$	0.4800		February 7, 2014	February 14, 2014
September 30, 2013	$	35.40	$	31.62	$	0.4600		November 7, 2013	November 14, 2013
June 30, 2013	$	35.40	$	26.04	$	0.4350		August 7, 2013	August 14, 2013
March 31, 2013	$	28.50	$	18.67	$	0.4200		May 8, 2013	May 15, 2013

⁽¹⁾: The distributions attributable to the quarter ending June 30, 2015 have not yet been declared or paid. We are required to declare and pay quarterly cash distributions within 45 days following the end of the quarter.

S-20

Table of Contents

MATERIAL TAX CONSIDERATIONS

The tax consequences to you of an investment in our common units will depend in part on your own tax circumstances. Although this section updates and adds information related to certain tax considerations, it should be read in conjunction with the risk factors included under the caption "Tax Risks" in our Annual Report on Form 10-K for the year ended December 31, 2014, and with "Material U.S. Federal Income Tax Consequences" in the accompanying base prospectus, which provides a discussion of the principal federal income tax considerations associated with our operations and the purchase, ownership and disposition of our common units. The following discussion is limited as described under the caption "Material U.S. Federal Income Tax Consequences" in the accompanying base prospectus. You are urged to consult with your own tax advisor about the federal, state, local and foreign tax consequences particular to your circumstances.

Ratio of Taxable Income to Distributions

We estimate that a purchaser of common units in this offering who owns those common units from the date of closing of this offering through the record date for distributions for the period ending December 31, 2017, will be allocated, on a cumulative basis, an amount of federal taxable income for that period that will be 20% or less of the cash distributed with respect to that period. Thereafter, we anticipate that the ratio of allocable taxable income to cash distributions to the unitholders will increase. Our estimate is based upon many assumptions regarding our business operations, including assumptions as to our revenues, capital expenditures, cash flow, net working capital and anticipated cash distributions. These estimates and assumptions are subject to, among other things, numerous business, economic, regulatory, legislative, competitive and political uncertainties beyond our control. Further, the estimates are based on current tax law and tax reporting positions that we will adopt and with which the IRS could disagree. Accordingly, we cannot assure you that these estimates will prove to be correct.

The actual ratio of allocable taxable income to cash distributions could be higher or lower than expected, and any differences could be material and could materially affect the value of the common units. For example, the ratio of allocable taxable income to cash distributions to a purchaser of common units in this offering will be higher, and perhaps substantially higher, than our estimate with respect to the period described above if:

•: gross income from operations exceeds the amount required to make minimum quarterly distributions on all units, yet we only distribute the minimum quarterly distributions on all units; or
•: we make a future offering of common units and use the proceeds of the offering in a manner that does not produce substantial additional deductions during the period described above, such as to repay indebtedness outstanding at the time of this offering or to acquire property that is not eligible for depreciation or amortization for federal income tax purposes or that is depreciable or amortizable at a rate significantly slower than the rate applicable to our assets at the time of this offering.

Alternative Minimum Tax

Each unitholder will be required to take into account his distributive share of any items of our income, gain, loss or deduction for purposes of the alternative minimum tax. The current minimum tax rate for noncorporate taxpayers is 26% on the first $185,400 of alternative minimum taxable income in excess of the exemption amount and 28% on any additional alternative minimum taxable income. Prospective unitholders are urged to consult with their tax advisors as to the impact of an investment in units on their liability for the alternative minimum tax.

S-21

Table of Contents

Tax Exempt Organizations and Other Investors

Ownership of common units by tax-exempt entities, including employee benefit plans and IRAs, and foreign investors raises issues unique to such persons. The relevant rules are complex, and the discussions herein and in the accompanying base prospectus do not address tax considerations applicable to tax-exempt entities and foreign investors, except as specifically set forth in the accompanying base prospectus. Please read "Material U.S. Federal Income Tax Consequences—Tax-Exempt Organizations and Other Investors" in the accompanying base prospectus.

Administrative Matters

Additional Withholding Requirements. Withholding taxes may apply to certain types of payments made to "foreign financial institutions" (as specially defined in the Internal Revenue Code) and certain other non-U.S. entities. Specifically, a 30% withholding tax may be imposed on interest, dividends and other fixed or determinable annual or periodical gains, profits and income from sources within the United States ("FDAP Income"), or gross proceeds from the sale or other disposition of any property of a type which can produce interest or dividends from sources within the United States ("Gross Proceeds") paid to a foreign financial institution or to a "non-financial foreign entity" (as specially defined in the Internal Revenue Code), unless (i) the foreign financial institution undertakes certain diligence and reporting, (ii) the non-financial foreign entity either certifies it does not have any substantial U.S. owners or furnishes identifying information regarding each substantial U.S. owner or (iii) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules. If the payee is a foreign financial institution and is subject to the diligence and reporting requirements in clause (i) above, it must enter into an agreement with the U.S. Treasury requiring, among other things, that it undertake to identify accounts held by certain U.S. persons or U.S.-owned foreign entities, annually report certain information about such accounts, and withhold 30% on payments to noncompliant foreign financial institutions and certain other account holders. Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States governing these requirements may be subject to different rules.

These rules generally will apply to payments of FDAP Income and will apply to payments of relevant Gross Proceeds made on or after January 1, 2017. Thus, to the extent we have FDAP Income or have Gross Proceeds after the specified date that is not treated as effectively connected with a U.S. trade or business (please read "Material U.S. Federal Income Tax Consequences—Tax-Exempt Organizations and Other Investors" in the accompanying base prospectus), unitholders who are foreign financial institutions or certain other non-U.S. entities may be subject to withholding on distributions they receive from us, or their distributive share of our income, pursuant to the rules described above.

Prospective investors should consult their own tax advisors regarding the potential application of these withholding provisions to their investment in our common units.

Legislative Developments

The present federal income tax treatment of publicly traded partnerships, including us, or an investment in our common units may be modified by administrative, legislative or judicial interpretation at any time. For example, from time to time, members of Congress and the President propose and consider substantive changes to the existing federal income tax laws that affect publicly traded partnerships, including the elimination of partnership tax treatment for publicly traded partnerships. Any modification to the federal income tax laws and interpretations thereof may or may not be retroactively applied and could make it more difficult or impossible to meet the exception for us to be treated as a partnership for federal income tax purposes. Please read "Material U.S. Federal Income Tax Consequences—Partnership Status" in the accompanying base prospectus. We are unable to predict whether any such changes will ultimately be enacted. However, it is possible that a change in law could affect us, and any such changes could negatively impact the value of an investment in our common units.

S-22

Table of Contents

UNDERWRITING

Barclays Capital Inc., Merrill Lynch, Pierce, Fenner & Smith Incorporated, Goldman, Sachs & Co., Morgan Stanley & Co. LLC, Wells Fargo Securities, LLC, Robert W. Baird & Co. Incorporated, Citigroup Global Markets Inc., Deutsche Bank Securities Inc. and RBC Capital Markets, LLC are acting as the joint book-running managers of this offering, and Barclays Capital Inc. is acting as the representative of the underwriters named below. Under the terms of an underwriting agreement, which we will file as an exhibit to our current report on Form 8-K and incorporate by reference in this prospectus supplement and the accompanying base prospectus, each of the underwriters named below has severally agreed to purchase from us the respective number of common units shown opposite its name below.

Underwriters		Number of Common Units

Barclays Capital Inc.			1,170,000
Merrill Lynch, Pierce, Fenner & Smith Incorporated			780,000
Goldman, Sachs & Co.			780,000
Morgan Stanley & Co. LLC			780,000
Wells Fargo Securities, LLC			780,000
Robert W. Baird & Co. Incorporated			455,000
Citigroup Global Markets Inc.			455,000
Deutsche Bank Securities Inc.			455,000
RBC Capital Markets, LLC			455,000
BB&T Capital Markets, a division of BB&T Securities, LLC			195,000
USCA Securities LLC			195,000

Total			6,500,000

The underwriting agreement provides that the underwriters' obligation to purchase the common units depends on the satisfaction of the conditions contained in the underwriting agreement including:

•: the obligation to purchase all of the common units offered hereby (other than those common units covered by their option to purchase additional common units as described below), if any of the common units are purchased;
•: the representations and warranties made by us to the underwriters are true;
•: there is no material change in our business or the financial markets; and
•: we deliver customary closing documents to the underwriters.

Commissions and Expenses

The following table summarizes the underwriting discounts and commission we will pay to the underwriters. These amounts are shown assuming both no exercise and full exercise of the underwriters' option to purchase additional common units. The underwriting fee is the difference

S-23

Table of Contents

between the initial price to the public and the amount the underwriters will pay to us for the common units.

			Total

	Per Common Unit		No Exercise		Full Exercise
Public offering price	$	30.75	$	199,875,000	$	229,856,250
Underwriting discounts	$	1.00	$	6,500,000	$	7,475,000
Proceeds to Summit Midstream Partners, LP (before expenses)	$	29.75	$	193,375,000	$	222,381,250

The representative of the underwriters has advised us that the underwriters propose to offer the common units directly to the public at the public offering price on the cover of this prospectus supplement and to selected dealers, which may include the underwriters, at such offering price less a selling concession not in excess of $0.60 per common unit. After the offering, the representative may change the offering price and other selling terms. Sales of common units made outside of the United States may be made by affiliates of the underwriters. The offering of the common units by the underwriters is subject to receipt and acceptance and subject to the underwriters' right to reject any order in whole or in part.

The expenses of this offering that are payable by us are estimated to be $250,000 (excluding underwriting discounts and commissions). We have also agreed to reimburse the underwriters for certain of their expenses as set forth in the underwriting agreement, which are not expected to exceed $20,000.

Option to Purchase Additional Common Units

We have granted the underwriters an option, exercisable for 30 days after the date of the underwriting agreement, to purchase, from time to time, in whole or in part, up to an aggregate of 975,000 common units at the public offering price less underwriting discounts and commissions. To the extent that this option is exercised, each underwriter will be obligated, subject to certain conditions, to purchase its pro rata portion of these additional common units from us based on the underwriter's percentage underwriting commitment in the offering as indicated in the table at the beginning of this Underwriting section.

Lock-Up Agreements

We, our general partner and certain of its affiliates, the directors and executive officers of our general partner and SMP Holdings have agreed that, without the prior written consent of Barclays Capital Inc., we and they will not directly or indirectly (1) offer for sale, sell, pledge, or otherwise dispose of (or enter into any transaction or device that is designed to, or could be expected to, result in the disposition by any person at any time in the future of) any of our common units (including, without limitation, common units that may be deemed to be beneficially owned by us or them in accordance with the rules and regulations of the SEC and common units that may be issued upon exercise of any options or warrants) or securities convertible into or exercisable or exchangeable for common units (other than, among other things, (i) the common units being sold in this offering, (ii) common units issued pursuant to employee benefit plans, qualified option plans or other employee compensation plans existing on the date hereof; provided, that any recipient of such common units must agree in writing to be bound by these provisions for the remaining term of the lock-up period, (iii) common units or any securities convertible or exchangeable into common units as payment of any part of the purchase price for any businesses that we acquire; provided, that any recipient of such common units must agree in writing to be bound by these provisions for the remainder of the lock-up period or (iv) common units or any securities that are convertible or exchangeable into common units pursuant to

S-24

Table of Contents

an effective registration statement that is filed pursuant to clause (3) below or (v) common units disposed of by certain executive officers or directors of our general partner to satisfy tax withholding obligations in connection with the vesting of equity awards), (2) enter into any swap or other derivatives transaction that transfers to another, in whole or in part, any of the economic consequences of ownership of the common units, (3) make any demand for or exercise any right or file or cause to be filed a registration statement, including any amendments thereto, with respect to the registration of any common units or securities convertible, exercisable or exchangeable into common units or any of our other securities (other than (i) any registration statement on Form S-8 or (ii) a registration statement solely relating to the entrance by us into a definitive agreement related to an acquisition; provided, that notwithstanding anything to the contrary, the prior approval of Barclays Capital Inc. shall be required in the event we file, or participate in the filing of, a registration statement during the lock-up period prior to the entrance by us into a definitive agreement related to an acquisition) or (4) publicly disclose the intention to do any of the foregoing, in each case for a period of 45 days after the date of this prospectus supplement.

Barclays Capital Inc., in its sole discretion, may release the common units and other securities subject to the lock-up agreements described above in whole or in part at any time with or without notice. When determining whether or not to release common units and other securities from lock-up agreements, Barclays Capital Inc. will consider, among other factors, the holder's reasons for requesting the release, the number of common units and other securities for which the release is being requested and market conditions at the time.

Indemnification

We, and certain of our affiliates have agreed to indemnify the several underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended, and to contribute to payments that the underwriters may be required to make for these liabilities.

Stabilization, Short Positions and Penalty Bids

The representative may engage in stabilizing transactions, short sales and purchases to cover positions created by short sales, and penalty bids or purchases for the purpose of pegging, fixing or maintaining the price of the common units, in accordance with Regulation M under the Securities Exchange Act of 1934:

•: Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum.
•: A short position involves a sale by the underwriters of common units in excess of the number of common units the underwriters are obligated to purchase in the offering, which creates the syndicate short position. This short position may be either a covered short position or a naked short position. In a covered short position, the number of common units involved in the sales made by the underwriters in excess of the number of common units they are obligated to purchase is not greater than the number of common units that they may purchase by exercising their option to purchase additional common units. In a naked short position, the number of common units involved is greater than the number of common units in their option to purchase additional common units. The underwriters may close out any short position by either exercising their option to purchase additional common units and/or purchasing common units in the open market. In determining the source of common units to close out the short position, the underwriters will consider, among other things, the price of common units available for purchase in the open market as compared to the price at which they may purchase common units through their option to purchase additional common units. A naked short position is more likely to be created if the underwriters are concerned that there could be downward pressure on the price of

S-25

Table of Contents

the common units in the open market after pricing that could adversely affect investors who purchase in the offering.

•: Syndicate covering transactions involve purchases of the common units in the open market after the distribution has been completed in order to cover syndicate short positions.
•: Penalty bids permit the representative to reclaim a selling concession from a syndicate member when the common units originally sold by the syndicate member are purchased in a stabilizing or syndicate covering transaction to cover syndicate short positions.

These stabilizing transactions, syndicate covering transactions and penalty bids may have the effect of raising or maintaining the market price of our common units or preventing or retarding a decline in the market price of the common units. As a result, the price of the common units may be higher than the price that might otherwise exist in the open market. These transactions may be effected on the NYSE or otherwise and, if commenced, may be discontinued at any time. Specifically, prior to purchasing the common units being offered pursuant to the preliminary prospectus supplement, on May 7, 2015, Barclays Capital Inc. purchased, on behalf of the syndicate, 613,788 common units at an average price of $30.94196 per unit in stabilizing transactions.

Neither we nor any of the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of the common units. In addition, neither we nor any of the underwriters make any representation that the representative will engage in these stabilizing transactions or that any transaction, once commenced, will not be discontinued without notice.

Electronic Distribution

A prospectus supplement and the accompanying base prospectus in electronic format may be made available on the Internet sites or through other online services maintained by one or more of the underwriters and/or selling group members participating in this offering, or by their affiliates. In those cases, prospective investors may view offering terms online and, depending upon the particular underwriter or selling group member, prospective investors may be allowed to place orders online. The underwriters may agree with us to allocate a specific number of common units for sale to online brokerage account holders. Any such allocation for online distributions will be made by the representative on the same basis as other allocations.

Other than the prospectus supplement and the accompanying base prospectus in electronic format, the information on any underwriter's or selling group member's web site and any information contained in any other web site maintained by an underwriter or selling group member is not part of the prospectus supplement and the accompanying base prospectus or the registration statement of which this prospectus supplement and the accompanying base prospectus form a part, has not been approved and/or endorsed by us or any underwriter or selling group member in its capacity as underwriter or selling group member and should not be relied upon by investors.

Stamp Taxes

If you purchase common units offered by this prospectus supplement and the accompanying base prospectus, you may be required to pay stamp taxes and other charges under the laws and practices of the country of purchase, in addition to the offering price listed on the cover page of this prospectus supplement and the accompanying base prospectus.

Relationships

The underwriters and certain of their affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial

S-26

Table of Contents

advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. The underwriters and certain of their affiliates have, from time to time, performed, and may in the future perform, various commercial and investment banking and financial advisory services for the issuer and its affiliates, including Summit Investments and SMP Holdings, for which they received or may in the future receive customary fees and expenses.

In the ordinary course of their various business activities, the underwriters and certain of their affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers, and such investment and securities activities may involve securities and/or instruments of the issuer or its affiliates. If the underwriters or their affiliates have a lending relationship with us, certain of those underwriters or their affiliates routinely hedge, and certain other of those underwriters or their affiliates may hedge, their credit exposure to us consistent with their customary risk management policies. Typically, the underwriters and their affiliates would hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities or the securities of our affiliates, including potentially the shares of common stock offered hereby. Any such credit default swaps or short positions could adversely affect future trading prices of the shares of common stock offered hereby. The underwriters and certain of their affiliates may also communicate independent investment recommendations, market color or trading ideas and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

FINRA

Because the Financial Industry Regulatory Authority, Inc., or FINRA, views the common units offered hereby as interests in a direct participation program, the offering is being made in compliance with Rule 2310 of the FINRA Rules. Investor suitability with respect to the common units will be judged similarly to the suitability with respect to other securities that are listed for trading on a national securities exchange.

Selling Restrictions

Notice to Prospective Investors in Hong Kong

The common units have not been offered or sold and will not be offered or sold in Hong Kong, by means of any document, other than (a) to "professional investors" as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance; or (b) in other circumstances which do not result in the document being a "prospectus" as defined in the Companies Ordinance (Cap. 32) of Hong Kong or which do not constitute an offer to the public within the meaning of that Ordinance. No advertisement, invitation or document relating to the common units has been or may be issued or has been or may be in the possession of any person for the purposes of issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to common units which are or are intended to be disposed of only to persons outside Hong Kong or only to "professional investors" as defined in the Securities and Futures Ordinance and any rules made under that Ordinance.

S-27

Table of Contents

VALIDITY OF THE COMMON UNITS

The validity of the common units will be passed upon for us by Latham & Watkins LLP, Houston, Texas. Certain legal matters in connection with the common units offered hereby will be passed upon for the underwriters by Baker Botts L.L.P., Houston, Texas.

EXPERTS

The consolidated financial statements of Summit Midstream Partners, LP incorporated in this prospectus by reference from the Partnership's Annual Report on Form 10-K for the year ended December 31, 2014, and the effectiveness of Summit Midstream Partners, LP's internal control over financial reporting have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their reports, which are incorporated herein by reference. Such consolidated financial statements have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We have filed a registration statement with the SEC under the Securities Act of 1933, as amended, that registers the offer and sale from time to time of our common units and debt securities, including the common units covered by this prospectus supplement. The registration statement, including the attached exhibits, contains additional relevant information about us and our securities. In addition, we file annual, quarterly and current reports with the SEC. Our SEC filings are available over the internet at the SEC's website at www.sec.gov. You also can read and copy any document we file at the SEC's public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for more information on the public reference room and its copy charges. You also can obtain information about us at the offices of the New York Stock Exchange, 20 Broad Street, New York, New York 10005.

We also make available free of charge on our internet website at www.summitmidstream.com our annual reports on Form 10-K, our quarterly reports on Form 10-Q, our current reports on Form 8-K and any amendments to those reports, as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. Information contained on our website is not incorporated by reference into this prospectus supplement or the accompanying base prospectus and you should not consider information contained on our website as part of this prospectus supplement or the accompanying base prospectus.

INCORPORATION BY REFERENCE

The SEC allows us to "incorporate by reference" the information we have filed with the SEC. This means that we can disclose important information to you without actually including the specific information in this prospectus supplement or the accompanying base prospectus by referring you to other documents filed separately with the SEC. The information incorporated by reference in this prospectus supplement and the accompanying base prospectus is an important part hereof and thereof. Information that we later provide to the SEC, and that is deemed to be "filed" with the SEC, will automatically update information previously filed with the SEC and may replace information in this prospectus supplement and the accompanying base prospectus and information previously filed with the SEC.

We incorporate by reference in this prospectus supplement the documents listed below and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities

S-28

Table of Contents

Exchange Act of 1934, as amended (excluding information deemed to be furnished and not filed with the SEC), until all the common units offered hereby are sold:

•: Our Annual Report on Form 10-K for the year ended December 31, 2014, as filed with the SEC on March 2, 2015;
•: Our Quarterly Report on Form 10-Q for the quarter ended March 31, 2015, as filed with the SEC on May 6, 2015;
•: Our Current Reports on Form 8-K as filed with the SEC on January 5, 2015, March 4, 2015 and May 6, 2015 (excluding any information furnished pursuant to Item 2.02 or Item 7.01 of any such Current Report on Form 8-K); and
•: The description of our common units in our Registration Statement on Form 8-A (File No. 001-35666) as filed with the SEC on September 26, 2012 and any subsequent amendment thereto filed for the purpose of updating such description.

You may request a copy of any document incorporated by reference in this prospectus supplement or the accompanying base prospectus and any exhibit specifically incorporated by reference in those documents, at no cost, by writing or telephoning us at the following address or phone number:

Summit Midstream Partners, LP
1790 Hughes Landing Boulevard, Suite 500
The Woodlands, Texas 77380
Attention: Brock M. Degeyter
Executive Vice President and General Counsel
Telephone: (832) 413-4770

FORWARD-LOOKING STATEMENTS

Investors are cautioned that certain statements contained in this prospectus as well as in periodic press releases and certain oral statements made by our officials during our presentations are "forward-looking" statements. Forward-looking statements include, without limitation, any statement that may project, indicate or imply future results, events, performance or achievements, and may contain the words "expect," "intend," "plan," "anticipate," "estimate," "believe," "will be," "will continue," "will likely result," and similar expressions, or future conditional verbs such as "may," "will," "should," "would," and "could." In addition, any statement concerning future financial performance (including future revenues, earnings or growth rates), ongoing business strategies or prospects, and possible actions taken by us or our subsidiaries, are also forward-looking statements. These forward-looking statements involve external risks and uncertainties, including, but not limited to, those described under the section entitled "Risk Factors" included herein.

Forward-looking statements are based on current expectations and projections about future events and are inherently subject to a variety of risks and uncertainties, many of which are beyond the control of our management team. All forward-looking statements in this prospectus and subsequent written and oral forward-looking statements attributable to us, or to persons acting on our behalf, are expressly qualified in their entirety by the cautionary statements in this paragraph. These risks and uncertainties include, among others:

•: fluctuations in natural gas, NGLs and crude oil prices;
•: the extent and success of drilling efforts, as well as the extent and quality of natural gas and crude oil volumes produced within proximity of our assets;
•: failure or delays by our customers in achieving expected production in their natural gas and crude oil projects;

S-29

Table of Contents

•: competitive conditions in our industry and their impact on our ability to connect hydrocarbon supplies to our gathering and processing assets or systems;
•: actions or inactions taken or non-performance by third parties, including suppliers, contractors, operators, processors, transporters and customers, including the inability or failure of our shipper customers to meet their financial obligations under our gathering agreements;
•: our ability to acquire any assets owned by Summit Investments, which is subject to a number of factors, including Summit Investments deciding, in its sole discretion, to offer us the right to acquire such assets, the ability to reach agreement on acceptable terms, the approval of the conflicts committee of our general partner's board of directors (if appropriate), prevailing conditions and outlook in the natural gas, NGL and crude oil industries and markets, and our ability to obtain financing on acceptable terms from the credit and/or capital markets or other sources;
•: our ability to consummate acquisitions, including the Acquisition, successfully integrate the acquired businesses, realize any cost savings and other synergies from any acquisition;
•: the ability to attract and retain key management personnel;
•: commercial bank and capital market conditions and the potential impact of changes or disruptions in the credit and/or capital markets;
•: changes in the availability and cost of capital, and the results of our financing efforts, including availability of funds in the credit and/or capital markets;
•: restrictions placed on us by the agreements governing our debt instruments;
•: the availability, terms and cost of downstream transportation and processing services;
•: natural disasters, accidents, weather-related delays, casualty losses and other matters beyond our control;
•: operational risks and hazards inherent in the gathering, treating and processing of natural gas;
•: weather conditions and seasonal trends;
•: timely receipt of necessary government approvals and permits, our ability to control the costs of construction, including costs of materials, labor and rights-of-way and other factors that may impact our ability to complete projects within budget and on schedule;
•: the effects of existing and future laws and governmental regulations, including environmental and climate change requirements;
•: the effects of litigation;
•: changes in general economic conditions; and
•: certain factors discussed elsewhere in this prospectus supplement.

Developments in any of these areas could cause actual results to differ materially from those anticipated or projected or cause a significant reduction in the market price of our common units.

The foregoing list of risks and uncertainties may not contain all of the risks and uncertainties that could affect us. In addition, in light of these risks and uncertainties, the matters referred to in the forward-looking statements contained or incorporated by reference in this prospectus may not in fact occur. Accordingly, undue reliance should not be placed on these statements. We undertake no obligation to publicly update or revise any forward-looking statements as a result of new information, future events or otherwise, except as otherwise required by law.

S-30

Table of Contents

PROSPECTUS

Summit Midstream Partners, LP
Summit Midstream Holdings, LLC
Summit Midstream Finance Corp.

Common Units Representing Limited Partner Interests
Debt Securities

Summit Midstream Partners, LP (the "Partnership," "we," "are" or "us") may from time to time, in one or more offerings, offer and sell common units representing limited partner interests in the Partnership (the "Units"). We or Summit Midstream Holdings, LLC, together with Summit Midstream Finance Corp., may offer and sell debt securities described in this prospectus. Summit Midstream Finance Corp. may act as co-issuer of the debt securities, and certain direct or indirect subsidiaries of the Partnership or Summit Midstream Holdings, LLC may guarantee any debt securities offered by this prospectus, if and to the extent identified in the related prospectus supplement. We refer to the Units and the debt securities collectively as the "securities." The aggregate initial offering price of all securities sold by us under this prospectus will not exceed $1,200,000,000.

The selling unitholder named in this prospectus or in any supplement to this prospectus may, from time to time, offer and sell up to 14,691,397 Units on any exchange on which the Units are listed on terms to be negotiated with buyers. The selling unitholder named in this prospectus acquired the Units in connection with our initial public offering in September 2012, its disposition to us of all the outstanding membership interests in Bison Midstream, LLC and to partially fund our acquisition of certain natural gas gathering assets from MarkWest Liberty Midstream & Resources, L.L.C. The selling unitholder will be responsible for its own legal fees and expenses and for any underwriting fees, discounts and commissions due to brokers, dealers or agents. We will be responsible for all other offering expenses.

We or the selling unitholder may offer and sell these securities in amounts, at prices and on terms to be determined by market conditions and other factors at the time of our offerings. We or the selling unitholder may offer and sell these securities to or through one or more underwriters, dealers or agents, or directly to purchasers, on a continuous or delayed basis. This prospectus describes only the general terms of the securities and the general manner in which we or the selling unitholder will offer the securities. The specific terms of any securities we or the selling unitholder offer will be included in a supplement to this prospectus. The prospectus supplement will describe the specific manner in which we or the selling unitholder will offer the securities and also may add, update or change information contained in this prospectus. The names of any underwriters and the specific terms of a plan of distribution will be stated in the prospectus supplement. The selling unitholder, who is an affiliate of Summit Midstream Partners, LP, is an "underwriter" within the meaning of the Securities Act of 1933, as amended, or the Securities Act, and, as a result, will be deemed to be making a primary offering of securities on our behalf. We will not receive any of the proceeds from any sale of our Units by the selling unitholder.

Our common units are traded on the New York Stock Exchange ("NYSE") under the symbol "SMLP."

Investing in our securities involves a high degree of risk. Limited partnerships are inherently different from corporations. You should review carefully the risk factors identified in the documents incorporated by reference herein for a discussion of important risks you should consider before you make an investment in our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is November 8, 2013

Table of Contents

TABLE OF CONTENTS

		PAGE

ABOUT THIS PROSPECTUS			ii
WHERE YOU CAN FIND MORE INFORMATION			ii
FORWARD-LOOKING STATEMENTS			iv
WHO WE ARE			1
RISK FACTORS			2
USE OF PROCEEDS			3
RATIO OF EARNINGS TO FIXED CHARGES			4
DESCRIPTION OF OUR COMMON UNITS			5
DESCRIPTION OF DEBT SECURITIES AND GUARANTEES			7
PROVISIONS OF OUR PARTNERSHIP AGREEMENT RELATING TO CASH DISTRIBUTIONS			15
THE PARTNERSHIP AGREEMENT			29
MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES			43
TAX CONSEQUENCES OF OWNERSHIP OF DEBT SECURITIES			60
SELLING UNITHOLDER			61
INVESTMENT IN SUMMIT MIDSTREAM PARTNERS, LP BY EMPLOYEE BENEFIT PLANS			63
PLAN OF DISTRIBUTION			65
VALIDITY OF THE SECURITIES			67
EXPERTS			67

In making your investment decision, you should rely only on the information contained or incorporated by reference in this prospectus and in any prospectus supplement. We have not authorized any other person to provide you with any other information. If anyone provides you with different or inconsistent information, you should not rely on it.

You should not assume that the information contained in this prospectus or in any prospectus supplement is accurate as of any date other than the date on the front cover of those documents. You should not assume that the information contained in the documents incorporated by reference in this prospectus or in any prospectus supplement is accurate as of any date other than the respective dates of those documents. Our business, financial condition, results of operations and prospects may have changed since those dates. We will disclose any material changes in our affairs in an amendment to this prospectus, a prospectus supplement or a future filing with the Securities and Exchange Commission (the "SEC") incorporated by reference in this prospectus.

Table of Contents

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we have filed with the SEC using a "shelf" registration process. Under this shelf registration process, we may over time, in one or more offerings, offer and sell any combination of the securities described in this prospectus, and the selling unitholder may, over time, in one or more offerings, offer and sell Units.

This prospectus provides you with a general description of Summit Midstream Partners, LP and the securities that are registered hereunder. Each time we sell any securities offered by this prospectus, we will provide a prospectus supplement that will contain specific information about the terms of that offering and the securities being offered. Because the selling unitholder is an "underwriter" under the Securities Act, each time the selling unitholder sells any Units offered by this prospectus, the selling unitholder is required to provide you with this prospectus and the related prospectus supplement containing specific information about the selling unitholder and the terms of the Units being offered in the manner required by the Securities Act. Any prospectus supplement may also add to, update or change information contained in this prospectus. To the extent information in this prospectus is inconsistent with the information contained in a prospectus supplement, you should rely on the information in the prospectus supplement.

Additional information, including our financial statements and the notes thereto, is incorporated in this prospectus by reference to our reports filed with the SEC. Before you invest in our securities, you should carefully read this prospectus, including the information provided under the heading "Risk Factors," any prospectus supplement, the information incorporated by reference in this prospectus and any prospectus supplement (including the documents described under the heading "Where You Can Find More Information" in both this prospectus and any prospectus supplement), and any additional information you may need to make your investment decision.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly, current and other reports with the SEC under the Securities Exchange Act of 1934 (File No. 001-35666). You may read and copy any document we file with the SEC at the SEC's public reference room at 100 F Street, N.E., Room 1580, Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information about the public reference room. Our SEC filings are also available to the public through the SEC's website at www.sec.gov. You can also obtain information about us at the offices of the NYSE, 20 Broad Street, New York, New York 10005.

Our internet address is www.summitmidstream.com. Our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and other filings with the SEC are available, free of charge, through our website, as soon as reasonably practicable after those reports or filings are electronically filed with or furnished to the SEC. Information on our website or any other website is not incorporated by reference into this prospectus and you should not consider information contained on our website as part of this prospectus.

We "incorporate by reference" information into this prospectus, which means that we disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, except for any information superseded by information contained expressly in this prospectus. You should not assume that the information in this prospectus is current as of the date other than the date on the cover page of this prospectus.

We incorporate by reference in this prospectus the documents listed below and any subsequent filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, (excluding information deemed to be furnished and not filed with the SEC) until

Table of Contents

all offerings under the registration statement of which this prospectus forms a part are completed or terminated:

•: Our Annual Report on Form 10-K for the year ended December 31, 2012, as filed with the SEC on March 18, 2013;
•: Our Quarterly Report on Form 10-Q for the three months ended March 31, 2013, as filed with the SEC on May 14, 2013 (except Items 1 and 2 of Part I and Item 1A of Part II, which have been superseded by the Current Report on Form 8-K dated September 20, 2013);
•: Our Quarterly Report on Form 10-Q for the three months ended June 30, 2013, as filed with the SEC on August 13, 2013, as amended and updated by Form 10-Q/A, as filed with the SEC on October 4, 2013;
•: Our Current Reports on Form 8-K as filed with the SEC on June 5, 2013, June 12, 2013, June 17, 2013, June 24, 2013, July 3, 2013, August 9, 2013, September 18, 2013, September 20, 2013 and September 27, 2013 (excluding any information furnished pursuant to Item 2.02 or Item 7.01 of any such Current Report on Form 8-K); and
•: The description of our common units contained in our Registration Statement on Form 8-A (File No. 001-35666) as filed with the SEC on September 26, 2012 and any subsequent amendment thereto filed for the purpose of updating such description.

We are also incorporating by reference all additional documents we may file with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, after the date hereof and prior to the effectiveness of the registration statement of which this prospectus forms a part.

You may request a copy of any document incorporated by reference in this prospectus and any exhibit specifically incorporated by reference in those documents, at no cost, by writing or telephoning us at the following address or phone number:

Summit Midstream Partners, LP
2100 McKinney Avenue, Suite 1250
Dallas, Texas 75201
Attention: Brock M. Degeyter
Senior Vice President and General Counsel
Telephone: (214) 242-1955

iii

Table of Contents

FORWARD-LOOKING STATEMENTS

Investors are cautioned that certain statements contained in this prospectus are "forward-looking" statements. Forward-looking statements include, without limitation, any statement that may project, indicate or imply future results, events, performance or achievements, and may contain the words "expect," "intend," "plan," "anticipate," "estimate," "believe," "will be," "will continue," "will likely result," and similar expressions, or future conditional verbs such as "may," "will," "should," "would," and "could." In addition, any statement concerning future financial performance (including future revenues, earnings or growth rates), ongoing business strategies or prospects, and possible actions taken by us or our subsidiaries, are also forward-looking statements. These forward-looking statements involve external risks and uncertainties, including, but not limited to, those described under the section entitled "Risk Factors" included herein.

•: changes in general economic conditions;
•: fluctuations in crude oil, natural gas and natural gas liquids prices;
•: the extent and success of drilling efforts, as well as the extent and quality of natural gas volumes produced within proximity of our assets;
•: failure or delays by our customers in achieving expected production in their natural gas and crude oil projects;
•: competitive conditions in our industry and their impact on our ability to connect natural gas supplies to our gathering and compression assets or systems;
•: actions or inactions taken or non-performance by third parties, including suppliers, contractors, operators, processors, transporters and customers, including the inability or failure of our shipper customers to meet their financial obligations under our gathering agreements;
•: our ability to consummate acquisitions, successfully integrate the acquired businesses, realize any cost savings and other synergies from any acquisition;
•: the ability to attract and retain key management personnel;
•: commercial bank and capital market conditions and the potential impact of changes or disruptions in the credit and/or capital markets;
•: changes in the availability and cost of capital, and the results of our financing efforts, including availability of funds in the credit and/or capital markets;
•: restrictions placed on us by the agreements governing our debt instruments;
•: the availability, terms and cost of downstream transportation and processing services;
•: operating hazards, natural disasters, accidents, weather-related delays, casualty losses and other matters beyond our control;
•: weather conditions and seasonal trends;

Table of Contents

•: timely receipt of necessary government approvals and permits, our ability to control the costs of construction, including costs of materials, labor and rights-of-way and other factors that may impact our ability to complete projects within budget and on schedule;
•: the effects of existing and future laws and governmental regulations, including environmental and climate change requirements;
•: the effects of litigation; and
•: certain factors discussed elsewhere in this prospectus.

Developments in any of these areas could cause actual results to differ materially from those anticipated or projected.

The foregoing list of risks and uncertainties may not contain all of the risks and uncertainties that could affect us. In addition, in light of these risks and uncertainties, the matters referred to in the forward-looking statements contained in this prospectus may not in fact occur. Accordingly, undue reliance should not be placed on these statements. We undertake no obligation to publicly update or revise any forward-looking statements as a result of new information, future events or otherwise, except as otherwise required by law.

Table of Contents

WHO WE ARE

Unless the context otherwise requires, references in this prospectus to the "Partnership," "we," "our," "us" or like terms, refer to Summit Midstream Partners, LP and its subsidiaries. "Summit Holdings" refers to Summit Midstream Holdings, LLC, a wholly owned subsidiary of the Partnership that may issue any debt securities offered by this prospectus. "Finance Corp." refers to Summit Midstream Finance Corp., a wholly owned subsidiary of Summit Holdings that may act as co-issuer of any debt securities offered by this prospectus. Our "general partner" refers to Summit Midstream GP, LLC.

General

We are a growth-oriented publicly traded Delaware limited partnership formed in 2012. Our common units are listed on the New York Stock Exchange under the trading symbol "SMLP." We are focused on owning and operating midstream energy infrastructure assets that are strategically located in the core producing areas of unconventional resource basins, primarily shale formations, in North America. We currently provide primarily fee-based natural gas gathering and compression services in four unconventional resource basins:

•: the Piceance Basin, which includes the Mesaverde formation and the Mancos and Niobrara shale formations in western Colorado;
•: the Fort Worth Basin, which includes the Barnett Shale formation in north-central Texas;
•: the Williston Basin, which includes the Bakken and Three Forks shale formations in northwestern North Dakota; and
•: the Appalachian Basin, which includes the Marcellus Shale formation in northern West Virginia.

Summit Holdings was formed under the laws of the State of Delaware on March 30, 2011, is wholly owned by the Partnership and indirectly owns all of the Partnership's operating assets.

Finance Corp. was incorporated under the laws of the State of Delaware on May 29, 2013, is wholly owned by Summit Holdings, and has no material assets or any liabilities other than as a co-issuer of debt securities. Its activities are limited to co-issuing debt securities and engaging in other activities incidental thereto.

Our executive offices are located at 2100 McKinney Avenue, Suite 1250, Dallas, Texas 75201 and our telephone number at this address is (214) 242-1955.

Table of Contents

RISK FACTORS

Limited partner interests are inherently different from capital stock of a corporation, although many of the business risks to which we are subject are similar to those that would be faced by a corporation engaged in similar businesses. We urge you to carefully consider the risk factors included in our most recent Annual Report on Form 10-K and Quarterly Reports on Form 10-Q, which are incorporated by reference into this prospectus and the applicable prospectus supplement, together with all of the other information included in this prospectus, the applicable prospectus supplement and the documents we incorporate by reference, in evaluating an investment in our securities. If any of the risks discussed in the foregoing documents were to materialize, our business, financial condition, results of operations and cash flows could be materially adversely affected and you could lose all or part of your investment. Please also read "Forward-Looking Statements."

Table of Contents

USE OF PROCEEDS

The actual application of proceeds to us from the sale of any particular offering of securities using this prospectus will be determined at the time of the offering and will be described in the applicable prospectus supplement relating to such offering. The precise amount and timing of the application of these proceeds will depend upon, among other factors, our funding requirements and the availability and cost of other funds. We will not receive any of the proceeds from any sale of Units by the selling unitholder.

Table of Contents

RATIO OF EARNINGS TO FIXED CHARGES

The following table sets forth our ratio of earnings to fixed charges for the periods indicated on a consolidated historical basis. For purposes of computing the ratio of earnings to fixed charges, "earnings" are defined as income before taxes plus fixed charges less capitalized interest. "Fixed charges" consist of interest expensed and capitalized, amortization of deferred loan costs and an estimate of interest within rent expense.

												Initial Predecessor to Summit Midstream Partners, LP

			Year Ended December 31,									Initial Predecessor to Summit Midstream Partners, LP
	Six Months Ended June 30, 2013		Year Ended December 31,						Period From September 3, 2009 to December 31, 2009			Period From January 1, 2009 to September 3, 2009
	Six Months Ended June 30, 2013		2012		2011		2010		Period From September 3, 2009 to December 31, 2009			Period From January 1, 2009 to September 3, 2009
Ratio of Earnings to Fixed Charges		4.32x		3.51x		6.36x		119.51x		(732.22)x	(1)		(2.36)x	(2)

(1): The ratio of earnings to fixed charges was less than 1:1 for the period from September 3, 2009 to December 31, 2009. In order to achieve a ratio of earnings to fixed charges of 1:1, we would have had to generate an additional $6.6 million of earnings for the period from September 3, 2009 to December 31, 2009.
(2): The ratio of earnings to fixed charges was less than 1:1 for the period from January 1, 2009 to September 3, 2009. In order to achieve a ratio of earnings to fixed charges of 1:1, we would have had to generate an additional $0.8 million of earnings for the period from January 1, 2009 to September 3, 2009.

Table of Contents

DESCRIPTION OF OUR COMMON UNITS

The Units

The common units represent limited partner interests in us. The holders of common units, along with the holders of subordinated units, are entitled to participate in partnership distributions and are entitled to exercise the rights and privileges available to limited partners under our partnership agreement. For a description of the relative rights and preferences of holders of common units and subordinated units in and to partnership distributions, please read this section and "Provisions of Our Partnership Agreement Relating to Cash Distributions." For a description of the rights and privileges of limited partners under our partnership agreement, including voting rights, please read "The Partnership Agreement."

Our outstanding common units are listed on the NYSE under the symbol "SMLP," and any additional common units we issue will also be listed on the NYSE. As of October 25, 2013, there were 29,079,866 common units outstanding. On October 25, 2013, the last reported sales price of our common units on the NYSE was $33.42 per common unit.

Transfer Agent and Registrar

Duties. American Stock Transfer and Trust Company ("AST") serves as the transfer agent, cash distribution paying agent and registrar for the common units. We will pay all fees charged by the transfer agent for transfers of common units except the following that must be paid by unitholders:

•: surety bond premiums to replace lost or stolen certificates, taxes and other governmental charges in connection therewith;
•: special charges for services requested by a common unitholder; and
•: other similar fees or charges.

There will be no charge to unitholders for disbursements of our cash distributions. We will indemnify AST, its agents and each of their respective stockholders, directors, officers and employees against all claims and losses that may arise out of acts performed or omitted for its activities in that capacity, except for any liability due to any gross negligence or intentional misconduct of the indemnified person or entity.

Resignation or Removal. The transfer agent may resign, by notice to us, or be removed by us. The resignation or removal of the transfer agent will become effective upon our appointment of a successor transfer agent, cash distribution paying agent and registrar and its acceptance of the appointment. If no successor has been appointed and has accepted the appointment within 30 days after notice of the resignation or removal, our general partner may act as the transfer agent and registrar until a successor is appointed.

Transfer of Common Units

By transfer of common units in accordance with our partnership agreement, each transferee of common units shall be admitted as a limited partner with respect to the common units transferred when such transfer and admission are reflected in our books and records. Each transferee:

•: automatically agrees to be bound by the terms and conditions of, and is deemed to have executed, our partnership agreement;
•: represents and warrants that the transferee has the right, power, authority and capacity to enter into our partnership agreement; and
•: gives the consents, waivers and approvals contained in our partnership agreement.

Table of Contents

Our general partner will cause any transfers to be recorded on our books and records no less frequently than quarterly.

We may, at our discretion, treat the nominee holder of a common unit as the absolute owner. In that case, the beneficial holder's rights are limited solely to those that it has against the nominee holder as a result of any agreement between the beneficial owner and the nominee holder.

Common units are securities and any transfers are subject to the laws governing the transfer of securities.

Until a common unit has been transferred on our books, we and the transfer agent may treat the record holder of the unit as the absolute owner for all purposes, except as otherwise required by law or stock exchange regulations.

Table of Contents

DESCRIPTION OF DEBT SECURITIES AND GUARANTEES

The following description, together with the additional information we include in any applicable prospectus supplement, summarizes certain general terms and provisions of the debt securities that we may offer under this prospectus. When we offer to sell a particular series of debt securities, we will describe the specific terms of the series in a supplement to this prospectus. We will also indicate in the supplement to what extent the general terms and provisions described in this prospectus apply to a particular series of debt securities.

As used in this section only, (i) the term "Company" refers only to Summit Midstream Holdings, LLC and not to any of its subsidiaries, (ii) the term "Finance Corp." refers to Summit Midstream Finance Corp., (iii) the term "Parent" refers to Summit Midstream Partners, LP and not to any of its subsidiaries, and (iv) the terms "we," "our," "us" or "Issuers" refer to the Company and Finance Corp., unless expressly stated or the context otherwise requires.

We may issue debt securities either separately, or together with, or upon the conversion or exercise of or in exchange for, other securities described in this prospectus. Debt securities may be our senior, senior subordinated or subordinated obligations and, unless otherwise specified in a supplement to this prospectus, the debt securities will be our direct, unsecured obligations and may be issued in one or more series.

The debt securities will be issued under an indenture between us and U.S. Bank National Association, as trustee. We have summarized select portions of the indenture below. The summary is not complete. The form of the indenture has been filed as an exhibit to the registration statement and you should read the indenture for provisions that may be important to you. In the summary below, we have included references to the section numbers of the indenture so that you can easily locate these provisions. Capitalized terms used in the summary and not defined herein have the meanings specified in the indenture.

General

The terms of each series of debt securities will be established by or pursuant to a resolution of the board of directors of our general partner and set forth or determined in the manner provided in a resolution of the board of directors of our general partner, in an officer's certificate or by a supplemental indenture. (Section 2.2) The particular terms of each series of debt securities will be described in a prospectus supplement relating to such series (including any pricing supplement or term sheet).

We can issue an unlimited amount of debt securities under the indenture that may be in one or more series with the same or various maturities, at par, at a premium, or at a discount. (Section 2.1) We will set forth in a prospectus supplement (including any pricing supplement or term sheet) relating to any series of debt securities being offered, the aggregate principal amount and the following terms of the debt securities, if applicable:

•: the title and ranking of the debt securities (including the terms of any subordination provisions);
•: the price or prices (expressed as a percentage of the principal amount) at which we will sell the debt securities;
•: any limit on the aggregate principal amount of the debt securities;
•: the date or dates on which the principal of the securities of the series is payable;
•: the rate or rates (which may be fixed or variable) per annum or the method used to determine the rate or rates (including any commodity, commodity index, stock exchange index or financial index) at which the debt securities will bear interest, the date or dates from which interest will

Table of Contents

accrue, the date or dates on which interest will commence and be payable and any regular record date for the interest payable on any interest payment date;

•: the place or places where principal of, and interest, if any, on the debt securities will be payable (and the method of such payment), where the securities of such series may be surrendered for registration of transfer or exchange, and where notices and demands to us in respect of the debt securities may be delivered;
•: the period or periods within which, the price or prices at which and the terms and conditions upon which we may redeem the debt securities;
•: any obligation we have to redeem or purchase the debt securities pursuant to any sinking fund or analogous provisions or at the option of a holder of debt securities and the period or periods within which, the price or prices at which and in the terms and conditions upon which securities of the series shall be redeemed or purchased, in whole or in part, pursuant to such obligation;
•: the dates on which and the price or prices at which we will repurchase debt securities at the option of the holders of debt securities and other detailed terms and provisions of these repurchase obligations;
•: the denominations in which the debt securities will be issued, if other than denominations of $1,000, and any integral multiple thereof;
•: whether the debt securities will be issued in the form of certificated debt securities or global debt securities;
•: the portion of principal amount of the debt securities payable upon declaration of acceleration of the maturity date, if other than the principal amount;
•: the currency of denomination of the debt securities, which may be U.S. Dollars or any foreign currency, and if such currency of denomination is a composite currency, the agency or organization, if any, responsible for overseeing such composite currency;
•: the designation of the currency, currencies or currency units in which payment of principal of, premium and interest on the debt securities will be made;
•: if payments of principal of, premium or interest on the debt securities will be made in one or more currencies or currency units other than that or those in which the debt securities are denominated, the manner in which the exchange rate with respect to these payments will be determined;
•: the manner in which the amounts of payment of principal of, premium, if any, or interest on the debt securities will be determined, if these amounts may be determined by reference to an index based on a currency or currencies other than that in which the debt securities are denominated or designated to be payable or by reference to a commodity, commodity index, stock exchange index or financial index;
•: any provisions relating to any security provided for the debt securities;
•: any addition to, deletion of or change in the Events of Default described in this prospectus or in the indenture with respect to the debt securities and any change in the acceleration provisions described in this prospectus or in the indenture with respect to the debt securities;
•: any addition to, deletion of or change in the covenants described in this prospectus or in the indenture with respect to the debt securities;
•: any depositaries, interest rate calculation agents, exchange rate calculation agents or other agents with respect to the debt securities;

Table of Contents

•: the provisions, if any, relating to conversion or exchange of any debt securities of such series, including if applicable, the conversion or exchange price and period, provisions as to whether conversion or exchange will be mandatory, the events requiring an adjustment of the conversion or exchange price and provisions affecting conversion or exchange;
•: any other terms of the debt securities, which may supplement, modify or delete any provision of the indenture as it applies to that series, including any terms that may be required under applicable law or regulations or advisable in connection with the marketing of the securities; and
•: whether any of our Parent's or any of our direct or indirect subsidiaries will guarantee the debt securities of that series, including the terms of subordination, if any, of such guarantees. (Section 2.2)

We may issue debt securities that provide for an amount less than their stated principal amount to be due and payable upon declaration of acceleration of their maturity pursuant to the terms of the indenture. We will provide you with information on the federal income tax considerations and other special considerations applicable to any of these debt securities in the applicable prospectus supplement.

If we denominate the purchase price of any of the debt securities in a foreign currency or currencies or a foreign currency unit or units, or if the principal of and any premium and interest on any series of debt securities is payable in a foreign currency or currencies or a foreign currency unit or units, we will provide you with information on the restrictions, elections, general tax considerations, specific terms and other information with respect to that issue of debt securities and such foreign currency or currencies or foreign currency unit or units in the applicable prospectus supplement.

Transfer and Exchange

Each debt security will be represented by either one or more global securities registered in the name of The Depository Trust Company (the "Depositary"), or a nominee of the Depositary (we will refer to any debt security represented by a global debt security as a "book-entry debt security"), or a certificate issued in definitive registered form (we will refer to any debt security represented by a certificated security as a "certificated debt security") as set forth in the applicable prospectus supplement. Except as set forth under the heading "Global Debt Securities and Book-Entry System" below, book-entry debt securities will not be issuable in certificated form.

Certificated Debt Securities. You may transfer or exchange certificated debt securities at any office we maintain in accordance with the terms of the indenture. (Section 2.4) No service charge will be made for any transfer or exchange of certificated debt securities, but we may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection with a transfer or exchange. (Section 2.7)

You may effect the transfer of certificated debt securities and the right to receive the principal of, premium and interest on certificated debt securities only by surrendering the certificate representing those certificated debt securities and either reissuance by us or the trustee of the certificate to the new holder or the issuance by us or the trustee of a new certificate to the new holder.

Global Debt Securities and Book-Entry System. Each global debt security representing book-entry debt securities will be deposited with, or on behalf of, the Depositary, and registered in the name of the Depositary or a nominee of the Depositary.

Covenants

We will set forth in the applicable prospectus supplement any restrictive covenants applicable to any issue of debt securities. (Article IV)

Table of Contents

No Protection in the Event of a Change of Control

Unless we state otherwise in the applicable prospectus supplement, the debt securities will not contain any provisions which may afford holders of the debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction (whether or not such transaction results in a change in control) which could adversely affect holders of debt securities.

Consolidation, Merger and Sale of Assets

The Company may not consolidate with or merge with or into, or convey, transfer or lease all or substantially all of our properties and assets to any person (a "successor person") unless:

•: we are the surviving entity or the successor person (if other than the Company) is an entity organized and validly existing under the laws of any U.S. domestic jurisdiction and expressly assumes our obligations on the debt securities and under the indenture; and
•: immediately after giving effect to the transaction, no Default (as defined in the indenture) or Event of Default, shall have occurred and be continuing.

Notwithstanding the above, any of our subsidiaries may consolidate with, merge into or transfer all or part of its properties to us or our Parent, and we may consolidate with, merge into or transfer all or part of our properties to our Parent. (Section 5.1)

Events of Default

"Event of Default" means with respect to any series of debt securities, any of the following:

•: default in the payment of any interest upon any debt security of that series when it becomes due and payable, and continuance of such default for a period of 30 days (unless the entire amount of the payment is deposited by us with the trustee or with a paying agent prior to the expiration of the 30-day period);
•: default in the payment of principal of any debt security of that series at its maturity;
•: default in the performance or breach of any other covenant or warranty by us in the indenture (other than a covenant or warranty that has been included in the indenture solely for the benefit of a series of debt securities other than that series), which default continues uncured for a period of 60 days after (i) we receive written notice from the trustee or (ii) the Issuers and the trustee receive written notice from the holders of not less than 25% in principal amount of the outstanding debt securities of that series as provided in the indenture;
•: certain voluntary or involuntary events of bankruptcy, insolvency or reorganization of the Issuers; and
•: any other Event of Default provided with respect to debt securities of that series that is described in the applicable prospectus supplement. (Section 6.1).

No Event of Default with respect to a particular series of debt securities (except as to certain events of bankruptcy, insolvency or reorganization) necessarily constitutes an Event of Default with respect to any other series of debt securities. (Section 6.1) The occurrence of certain Events of Default or an acceleration under the indenture may constitute an event of default under certain indebtedness of ours or our subsidiaries outstanding from time to time.

We will provide the trustee written notice of any Default or Event of Default within 30 days of becoming aware of the occurrence of such Default or Event of Default, which notice will describe in reasonable detail the status of such Default or Event of Default and what action we are taking or propose to take in respect thereof. (Section 6.1)

Table of Contents

If an Event of Default with respect to debt securities of any series at the time outstanding occurs and is continuing, then the trustee or the holders of not less than 25% in principal amount of the outstanding debt securities of that series may, by a notice in writing to us (and to the trustee if given by the holders), declare to be due and payable immediately the principal of (or, if the debt securities of that series are discount securities, that portion of the principal amount as may be specified in the terms of that series) and accrued and unpaid interest, if any, on all debt securities of that series. In the case of an Event of Default resulting from certain events of bankruptcy, insolvency or reorganization, the principal (or such specified amount) of and accrued and unpaid interest, if any, on all outstanding debt securities will become and be immediately due and payable without any declaration or other act on the part of the trustee or any holder of outstanding debt securities. At any time after a declaration of acceleration with respect to debt securities of any series has been made, but before a judgment or decree for payment of the money due has been obtained by the trustee, the holders of a majority in principal amount of the outstanding debt securities of that series may rescind and annul the acceleration if all Events of Default, other than the non-payment of accelerated principal and interest, if any, with respect to debt securities of that series, have been cured or waived as provided in the indenture. (Section 6.2) We refer you to the prospectus supplement relating to any series of debt securities that are discount securities for the particular provisions relating to acceleration of a portion of the principal amount of such discount securities upon the occurrence of an Event of Default.

The indenture provides that the trustee will be under no obligation to exercise any of its rights or powers under the indenture unless the trustee receives indemnity satisfactory to it against any cost, liability or expense which might be incurred by it in exercising such right or power. (Section 7.1(e)) Subject to certain rights of the trustee, the holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee with respect to the debt securities of that series. (Section 6.12)

No holder of any debt security of any series will have any right to institute any proceeding, judicial or otherwise, with respect to the indenture or for the appointment of a receiver or trustee, or for any remedy under the indenture, unless:

•: that holder has previously given to the trustee written notice of a continuing Event of Default with respect to debt securities of that series; and
•: the holders of not less than 25% in principal amount of the outstanding debt securities of that series have made written request, and offered reasonable indemnity or security, to the trustee to institute the proceeding as trustee, and the trustee has not received from the holders of not less than a majority in principal amount of the outstanding debt securities of that series a direction inconsistent with that request and has failed to institute the proceeding within 60 days. (Section 6.7)

Notwithstanding any other provision in the indenture, the holder of any debt security will have an absolute and unconditional right to receive payment of the principal of, premium and any interest on that debt security on or after the due dates expressed in that debt security and to institute suit for the enforcement of payment. (Section 6.8)

The indenture requires us, within 120 days after the end of our fiscal year, to furnish to the trustee a statement as to compliance with the indenture. (Section 4.3) If a Default or Event of Default occurs and is continuing with respect to the securities of any series and if it is known to a responsible officer of the trustee, the trustee shall mail to each securityholder of the debt securities of that series notice of a Default or Event of Default within 90 days after it occurs. The indenture provides that the trustee may withhold notice to the holders of debt securities of any series of any Default or Event of Default (except in payment on any debt securities of that series) with respect to debt securities of that series if

Table of Contents

the trustee determines in good faith that withholding notice is in the interest of the holders of those debt securities. (Section 7.5)

Modification and Waiver

We and the trustee may modify and amend the indenture or the debt securities of any series without the consent of any holder of any debt security:

•: to cure any ambiguity, defect or inconsistency;
•: to comply with covenants in the indenture described above under the heading "Consolidation, Merger and Sale of Assets";
•: to provide for uncertificated debt securities in addition to or in place of certificated debt securities;
•: to add guarantees with respect to debt securities of any series or secure debt securities of any series;
•: to surrender any of our rights or powers under the indenture;
•: to add covenants or events of default for the benefit of the holders of debt securities of any series;
•: to comply with the applicable procedures of the applicable depositary;
•: to make any change that does not adversely affect the rights of any holder of debt securities;
•: to provide for the issuance of and establish the form and terms and conditions of debt securities of any series as permitted by the indenture;
•: to effect the appointment of a successor trustee with respect to the debt securities of any series and to add to or change any of the provisions of the indenture to provide for or facilitate administration by more than one trustee; or
•: to comply with requirements of the SEC in order to effect or maintain the qualification of the indenture under the Trust Indenture Act of 1939. (Section 9.1)

We may also modify and amend the indenture with the consent of the holders of at least a majority in principal amount of the outstanding debt securities of each series affected by the modifications or amendments. We may not make any modification or amendment without the consent of the holders of each affected debt security then outstanding if that amendment will:

•: reduce the amount of debt securities whose holders must consent to an amendment, supplement or waiver;
•: reduce the rate of or extend the time for payment of interest (including default interest) on any debt security;
•: reduce the principal of or premium on or change the fixed maturity of any debt security or reduce the amount of, or postpone the date fixed for, the payment of any sinking fund or analogous obligation with respect to any series of debt securities;
•: reduce the principal amount of discount securities payable upon acceleration of maturity;
•: waive a default in the payment of the principal, premium or interest on any debt security (except a rescission of acceleration of the debt securities of any series by the holders of at least a majority in aggregate principal amount of the then outstanding debt securities of that series and a waiver of the payment default that resulted from such acceleration);

Table of Contents

•: make the principal of or premium or interest on any debt security payable in currency other than that stated in the debt security;
•: make any change to certain provisions of the indenture relating to, among other things, the right of holders of debt securities to receive payment of the principal of, premium and interest on those debt securities and to institute suit for the enforcement of any such payment and to waivers or amendments; or
•: waive a redemption payment with respect to any debt security. (Section 9.3)

Except for certain specified provisions, the holders of at least a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all debt securities of that series waive our compliance with provisions of the indenture. (Section 9.2) The holders of a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all the debt securities of such series waive any past default under the indenture with respect to that series and its consequences, except a default in the payment of the principal of, premium or any interest on any debt security of that series; provided, however, that the holders of a majority in principal amount of the outstanding debt securities of any series may rescind an acceleration and its consequences, including any related payment default that resulted from the acceleration. (Section 6.13)

Defeasance of Debt Securities and Certain Covenants in Certain Circumstances

Legal Defeasance. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, we may be discharged from any and all obligations in respect of the debt securities of any series (subject to certain exceptions). We will be so discharged upon the deposit with the trustee, in trust, of money and/or U.S. government obligations or, in the case of debt securities denominated in a single currency other than U.S. Dollars, government obligations of the government that issued or caused to be issued such currency, that, through the payment of interest and principal in accordance with their terms, will provide money or U.S. government obligations in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants or investment bank to pay and discharge each installment of principal, premium and interest on and any mandatory sinking fund payments in respect of the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities.

This discharge may occur only if, among other things, we have delivered to the trustee an opinion of counsel stating that we have received from, or there has been published by, the United States Internal Revenue Service a ruling or, since the date of execution of the indenture, there has been a change in the applicable United States federal income tax law, in either case to the effect that, and based thereon such opinion shall confirm that, the holders of the debt securities of that series will not recognize income, gain or loss for United States federal income tax purposes as a result of the deposit, defeasance and discharge and will be subject to United States federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit, defeasance and discharge had not occurred. (Section 8.3)

Defeasance of Certain Covenants. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, upon compliance with certain conditions:

•: we may omit to comply with the covenant described under the heading "Consolidation, Merger and Sale of Assets" and certain other covenants set forth in the indenture, as well as any additional covenants which may be set forth in the applicable prospectus supplement; and
•: any omission to comply with those covenants will not constitute a Default or an Event of Default with respect to the debt securities of that series ("covenant defeasance").

Table of Contents

The conditions include:

•: depositing with the trustee money and/or U.S. government obligations or, in the case of debt securities denominated in a single currency other than U.S. Dollars, government obligations of the government that issued or caused to be issued such currency, that, through the payment of interest and principal in accordance with their terms, will provide money in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants or investment bank to pay and discharge each installment of principal of, premium and interest on and any mandatory sinking fund payments in respect of the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities; and
•: delivering to the trustee an opinion of counsel to the effect that the holders of the debt securities of that series will not recognize income, gain or loss for United States federal income tax purposes as a result of the deposit and related covenant defeasance and will be subject to United States federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit and related covenant defeasance had not occurred. (Section 8.4)

Covenant Defeasance and Events of Default. In the event we exercise our option to effect covenant defeasance with respect to any series of debt securities and the debt securities of that series are declared due and payable because of the occurrence of any Event of Default, the amount of money and/or U.S. government obligations or foreign government obligations on deposit with the trustee will be sufficient to pay amounts due on the debt securities of that series at the time of their stated maturity but may not be sufficient to pay amounts due on the debt securities of that series at the time of the acceleration resulting from the Event of Default. However, we shall remain liable for those payments. (Section 8.4)

No Personal Liability of Directors, Officers, Employees or Unitholders

None of our past, present or future directors, officers, employees or unitholders, as such, will have any liability for any of our obligations under the debt securities or the indenture or for any claim based on, or in respect or by reason of, such obligations or their creation. By accepting a debt security, each holder waives and releases all such liability. This waiver and release is part of the consideration for the issue of the debt securities. However, this waiver and release may not be effective to waive liabilities under U.S. federal securities laws, and it is the view of the SEC that such a waiver is against public policy.

Governing Law

The indenture and the debt securities, including any claim or controversy arising out of or relating to the indenture or the debt securities, will be governed by the laws of the State of New York (without regard to the conflicts of laws provisions thereof other than Section 5-1401 of the General Obligations Law). (Section 10.10)

Table of Contents

PROVISIONS OF OUR PARTNERSHIP AGREEMENT RELATING TO CASH DISTRIBUTIONS

Set forth below is a summary of the significant provisions of our partnership agreement that relate to cash distributions.

Distributions of Available Cash

General. Our partnership agreement requires that, within 45 days after the end of each quarter, we distribute all of our available cash to unitholders of record on the applicable record date.

Definition of Available Cash. Available cash generally means, for any quarter, all cash on hand at the end of that quarter:

•

less the amount of cash reserves established by our general partner at the date of determination of available cash for the quarter to:

•: provide for the proper conduct of our business (including reserves for our future capital expenditures and anticipated future debt service requirements);
•: comply with applicable law, any of our debt instruments or other agreements; or
•: provide funds for distributions to our unitholders and to our general partner for any one or more of the next four quarters (provided that our general partner may not establish cash reserves for distributions unless it determines that the establishment of reserves will not prevent us from distributing the minimum quarterly distribution on all common units and any cumulative arrearages on such common units for the current quarter);

•

plus, if our general partner so determines, all or any portion of the cash on hand on the date of determination of available cash for the quarter resulting from working capital borrowings made subsequent to the end of such quarter.

The purpose and effect of the last bullet point above is to allow our general partner, if it so decides, to use cash from working capital borrowings made after the end of the quarter but on or before the date of determination of available cash for that quarter to pay distributions to unitholders. Under our partnership agreement, working capital borrowings are generally borrowings that are made under a credit facility, commercial paper facility or similar financing arrangement, and in all cases are used solely for working capital purposes or to pay distributions to partners, and with the intent of the borrower to repay such borrowings within 12 months with funds other than from additional working capital borrowings. The proceeds of working capital borrowings increase operating surplus and repayments of working capital borrowings are generally operating expenditures (as described below) and thus reduce operating surplus when repayments are made. However, if working capital borrowings, which increase operating surplus, are not repaid during the 12-month period following the borrowing, they will be deemed repaid at the end of such period, thus decreasing operating surplus at such time. When such working capital borrowings are in fact repaid, they will not be treated as a further reduction in operating surplus because operating surplus will have been previously reduced by the deemed repayment.

Intent to Distribute the Minimum Quarterly Distribution. We intend to make a minimum quarterly distribution to the holders of our common and subordinated units of $0.40 per unit, or $1.60 on an annualized basis, to the extent we have sufficient cash from our operations after the establishment of cash reserves and payment of costs and expenses, including reimbursements of expenses to our general partner. Our most recent quarterly distribution was $0.435 per unit, or $1.74 annualized. However, there is no guarantee that we will pay the minimum quarterly distribution on our units in any quarter. Even if our cash distribution policy is not modified or revoked, the amount of distributions paid under our policy and the decision to make any distribution is determined by our general partner, taking into consideration the terms of our partnership agreement.

Table of Contents

General Partner Interest and Incentive Distribution Rights. Our general partner is entitled to 2.0% of all distributions that we make prior to our liquidation. Our general partner has the right, but not the obligation, to contribute a proportionate amount of capital to us to maintain its current general partner interest. Our general partner's 2.0% interest in our distributions will be reduced if we issue additional units in the future and our general partner does not contribute a proportionate amount of capital to us to maintain its 2.0% general partner interest.

Our general partner also currently holds incentive distribution rights that entitle it to receive increasing percentages, up to a maximum of 50.0%, of the cash we distribute from operating surplus (as defined below) in excess of $0.46 per unit per quarter. The maximum distribution of 50.0% includes distributions paid to our general partner on its 2.0% general partner interest and assumes that our general partner maintains its general partner interest at 2.0%. The maximum distribution of 50.0% does not include any distributions that our general partner may receive on any common or subordinated units that it owns.

Operating Surplus and Capital Surplus

General. All cash distributed to unitholders will be characterized as either being paid from "operating surplus" or "capital surplus." We treat distributions of available cash from operating surplus differently than distributions of available cash from capital surplus.

Operating Surplus. We define operating surplus as:

•: $50.0 million (as described below); plus
•: all of our cash receipts after the closing of our initial public offering, excluding cash from interim capital transactions (as defined below), provided that cash receipts from the termination of a commodity hedge or interest rate hedge prior to its specified termination date shall be included in operating surplus in equal quarterly installments over the remaining scheduled life of such commodity hedge or interest rate hedge; plus
•: working capital borrowings made after the end of a quarter but on or before the date of determination of operating surplus for that quarter; plus
•: cash distributions (including incremental distributions on incentive distribution rights) paid on equity issued, other than equity issued in our initial public offering, to finance all or a portion of the construction, acquisition, development or improvement of a capital improvement or replacement of a capital asset (such as equipment or facilities) in respect of the period beginning on the date that we enter into a binding obligation to commence the construction, acquisition, development or improvement of a capital improvement or replacement of a capital asset and ending on the earlier to occur of the date the capital improvement or capital asset commences commercial service and the date that it is abandoned or disposed of; plus
•: cash distributions (including incremental distributions on incentive distribution rights) paid on equity issued, other than equity issued in our initial public offering, to pay the construction-period interest on debt incurred, or to pay construction-period distributions on equity issued, to finance the capital improvements or capital assets referred to above; less
•: all of our operating expenditures (as defined below) after the closing of our initial public offering; less
•: the amount of cash reserves established by our general partner to provide funds for future operating expenditures; less
•: all working capital borrowings not repaid within 12 months after having been incurred or repaid within such 12-month period with the proceeds of additional working capital borrowings.

Table of Contents

As described above, operating surplus does not reflect actual cash on hand that is available for distribution to our unitholders and is not limited to cash generated by operations. For example, it includes a provision that will enable us, if we choose, to distribute as operating surplus up to $50.0 million of cash we receive in the future from non-operating sources such as asset sales, issuances of securities and long-term borrowings that would otherwise be distributed as capital surplus. In addition, the effect of including, as described above, certain cash distributions on equity interests in operating surplus is to increase operating surplus by the amount of any such cash distributions. As a result, we may also distribute as operating surplus up to the amount of any such cash that we receive from non-operating sources.

We define interim capital transactions as (i) borrowings, refinancings or refundings of indebtedness (other than working capital borrowings and items purchased on open account in the ordinary course of business) and sales of debt securities, (ii) sales of equity securities, (iii) sales or other dispositions of assets, other than sales or other dispositions of inventory, accounts receivable and other assets in the ordinary course of business and sales or other dispositions of assets as part of ordinary course asset retirements or replacements and (iv) capital contributions received.

We define operating expenditures as all of our cash expenditures, including, but not limited to, taxes, compensation of employees, officers and directors of our general partner, reimbursements of expenses to our general partner and its affiliates, interest payments, payments made in the ordinary course of business under interest rate hedge contracts and commodity hedge contracts (provided that (i) with respect to amounts paid in connection with the initial purchase of an interest rate hedge contract or a commodity hedge contract, such amounts will be amortized over the life of the applicable interest rate hedge contract or commodity hedge contract and (ii) payments made in connection with the termination of any interest rate hedge contract or commodity hedge contract prior to the expiration of its stipulated settlement or termination date will be included in operating expenditures in equal quarterly installments over the remaining scheduled life of such interest rate hedge contract or commodity hedge contract), and repayment of working capital borrowings; provided, however, that operating expenditures do not include:

•: repayment of working capital borrowings where such borrowings have previously been deemed to have been repaid (as described above);
•: payments (including prepayments and prepayment penalties) of principal of and premium on indebtedness other than working capital borrowings;
•: expansion capital expenditures;
•: payment of transaction expenses (including, but not limited to, taxes) relating to interim capital transactions;
•: distributions to our partners; or
•: repurchases of our units, other than repurchases to satisfy obligations under employee benefit plans or reimbursement of expenses of our general partner for purchases of units to satisfy obligations under employee benefit plans.

Capital Surplus. Capital surplus is defined in our partnership agreement as any distribution of available cash in excess of our cumulative operating surplus. Accordingly, except as described above, capital surplus would generally be generated by:

•: borrowings other than working capital borrowings;
•: sales of our equity and debt securities; and
•: sales or other dispositions of assets, other than inventory, accounts receivable and other assets sold in the ordinary course of business or as part of ordinary course retirement or replacement of assets.

Table of Contents

Characterization of Cash Distributions. Our partnership agreement requires that we treat all available cash distributed as coming from operating surplus until the sum of all available cash distributed since the closing of our initial public offering equals the operating surplus from the closing of our initial public offering through the end of the quarter immediately preceding that distribution. Our partnership agreement requires that we treat any amount distributed in excess of operating surplus, regardless of its source, as capital surplus. We do not anticipate that we will make any distributions from capital surplus.

Capital Expenditures

Maintenance capital expenditures are cash expenditures (including expenditures for the addition or improvement to, or the replacement of, our capital assets or for the acquisition of existing, or the construction or development of new, capital assets) made to maintain our operating income or operating capacity over the long term. We expect that a primary component of maintenance capital expenditures will include expenditures to connect additional wells to our gathering systems to offset natural declines in production over time and for routine equipment and pipeline maintenance or replacement due to obsolescence.

Expansion capital expenditures are cash expenditures incurred for acquisitions or capital improvements that we expect will increase our operating income or operating capacity over the long term. Expansion capital expenditures include interest payments (and related fees) on debt incurred and issued to finance the construction of such capital improvement and paid in respect of the period beginning on the date that we enter into a binding obligation to commence construction of the capital improvement and ending on the earlier to occur of the date that such capital improvement commences commercial service and the date that such capital improvement is abandoned or disposed of. Examples of expansion capital expenditures include the acquisition of equipment, or the construction, development or acquisition of additional pipeline or treating capacity or new compression capacity, to the extent such capital expenditures are expected to expand our long-term operating capacity or operating income.

Capital expenditures that are made in part for maintenance capital purposes and in part for expansion capital purposes will be allocated between maintenance capital expenditures and expansion capital expenditures by our general partner.

Subordination Period

General. Our partnership agreement provides that, during the subordination period (which we define below), the common units have the right to receive distributions of available cash from operating surplus each quarter in an amount equal to $0.40 per common unit, which amount is defined in our partnership agreement as the minimum quarterly distribution, plus any arrearages in the payment of the minimum quarterly distribution on the common units from prior quarters, before any distributions of available cash from operating surplus is made on the subordinated units. These units are deemed "subordinated" because for a period of time, referred to as the subordination period, the subordinated units are not entitled to receive any distributions until the common units have received the minimum quarterly distribution plus any arrearages from prior quarters. Furthermore, no arrearages are paid on the subordinated units. The practical effect of the subordinated units is to increase the likelihood that during the subordination period there will be available cash to be distributed on the common units.

Subordination Period. Except as described below, the subordination period will extend until the first business day of any quarter, beginning after December 31, 2015, that each of the following tests are met:

•: distributions of available cash from operating surplus on each of the outstanding common units and subordinated units and the related distribution on the general partner interest equaled or

Table of Contents

exceeded $1.60 (the annualized minimum quarterly distribution) for each of the three consecutive, non-overlapping four-quarter periods immediately preceding that date;

•: the adjusted operating surplus (as defined below) generated during each of the three consecutive, non-overlapping four-quarter periods immediately preceding that date equaled or exceeded (i) the sum of $1.60 (the annualized minimum quarterly distribution) on all of the outstanding common and subordinated units during those periods on a fully diluted weighted-average basis and (ii) the corresponding distribution on our 2.0% general partner interest; and
•: there are no arrearages in payment of the minimum quarterly distribution on the common units.

Early Termination of Subordination Period. Notwithstanding the foregoing, the subordination period will automatically terminate on the first business day of any quarter beginning after December 31, 2013, that each of the following tests are met:

•: distributions of available cash from operating surplus on each of the outstanding common units and subordinated units and the related distribution on the general partner interest equaled or exceeded $2.40 (150.0% of the annualized minimum quarterly distribution), plus the related distributions on the incentive distribution rights, for the four-quarter period immediately preceding that date;
•: the adjusted operating surplus (as defined below) generated during the four-quarter period immediately preceding that date equaled or exceeded the sum of (i) $2.40 (150.0% of the annualized minimum quarterly distribution) on all of the outstanding common units and subordinated units during that period on a fully diluted weighted average basis and (ii) the distributions made on our 2.0% general partner interest and the incentive distribution rights; and
•: there are no arrearages in payment of the minimum quarterly distributions on the common units.

Expiration of the Subordination Period. When the subordination period ends, each outstanding subordinated unit will convert into one common unit and will thereafter participate pro rata with the other common units in distributions of available cash. In addition, if the unitholders remove our general partner other than for cause and no units held by our general partner and its affiliates are voted in favor of such removal:

•: the subordination period will end and each subordinated unit will immediately and automatically convert into one common unit;
•: any existing arrearages in payment of the minimum quarterly distribution on the common units will be extinguished; and
•: our general partner will have the right to convert its general partner interest and its incentive distribution rights into common units or to receive cash in exchange for those interests.

Definition of Adjusted Operating Surplus. Adjusted operating surplus is intended to reflect the cash generated from operations during a particular period and therefore excludes net increases in working capital borrowings and net drawdowns of reserves of cash established in prior periods. Adjusted operating surplus for a period consists of:

•: operating surplus generated with respect to that period (excluding any amounts attributable to the item described in the first bullet point under the caption "—Operating Surplus and Capital Surplus—Operating Surplus" above); less
•: any net increase in working capital borrowings with respect to that period; less

Table of Contents

•: any net decrease in cash reserves for operating expenditures with respect to that period not relating to an operating expenditure made with respect to that period; plus
•: any net decrease in working capital borrowings with respect to that period; plus
•: any net decrease made in subsequent periods to cash reserves for operating expenditures initially established with respect to that period to the extent such decrease results in a reduction in adjusted operating surplus in subsequent periods pursuant to the third bullet point above; plus
•: any net increase in cash reserves for operating expenditures with respect to that period required by any debt instrument for the repayment of principal, interest or premium.

Distributions of Available Cash from Operating Surplus during the Subordination Period

We will make distributions of available cash from operating surplus for any quarter during the subordination period in the following manner:

•: first, 98.0% to the common unitholders, pro rata, and 2.0% to our general partner, until we distribute for each outstanding common unit an amount equal to the minimum quarterly distribution for that quarter;
•: second, 98.0% to the common unitholders, pro rata, and 2.0% to our general partner, until we distribute for each outstanding common unit an amount equal to any arrearages in payment of the minimum quarterly distribution on the common units for any prior quarters during the subordination period;
•: third, 98.0% to the subordinated unitholders, pro rata, and 2.0% to our general partner, until we distribute for each outstanding subordinated unit an amount equal to the minimum quarterly distribution for that quarter; and
•: thereafter, in the manner described in "—General Partner Interest and Incentive Distribution Rights" below.

The preceding discussion is based on the assumptions that our general partner maintains its 2.0% general partner interest and that we do not issue additional classes of equity securities.

Distributions of Available Cash from Operating Surplus after the Subordination Period

We will make distributions of available cash from operating surplus for any quarter after the subordination period in the following manner:

•: first, 98.0% to all unitholders, pro rata, and 2.0% to our general partner, until we distribute for each outstanding unit an amount equal to the minimum quarterly distribution for that quarter; and
•: thereafter, in the manner described in "—General Partner Interest and Incentive Distribution Rights" below.

The preceding discussion is based on the assumptions that our general partner maintains its 2.0% general partner interest and that we do not issue additional classes of equity securities.

General Partner Interest and Incentive Distribution Rights

Our general partner is currently entitled to 2.0% of all distributions that we make prior to our liquidation. Our general partner has the right, but not the obligation, to contribute a proportionate amount of capital to us in order to maintain its 2.0% general partner interest if we issue additional units. Our general partner's 2.0% interest, and the percentage of our cash distributions to which it is entitled from such 2.0% interest, will be proportionately reduced if we issue additional units in the

Table of Contents

future (other than the issuance of common units upon conversion of outstanding subordinated units or the issuance of common units upon a reset of the incentive distribution rights) and our general partner does not contribute a proportionate amount of capital to us in order to maintain its 2.0% general partner interest. Our partnership agreement does not require that our general partner fund its capital contribution with cash. It may instead fund its capital contribution by the contribution to us of common units or other property.

Incentive distribution rights represent the right to receive an increasing percentage (13.0%, 23.0% and 48.0%) of quarterly distributions of available cash from operating surplus after the minimum quarterly distribution and the target distribution levels have been achieved. Our general partner currently holds the incentive distribution rights, but may transfer these rights separately from its general partner interest at any time without the approval of any person.

The following discussion assumes that our general partner maintains its 2.0% general partner interest, that there are no arrearages on common units and that our general partner continues to own the incentive distribution rights.

If for any quarter:

•: we have distributed available cash from operating surplus to the common and subordinated unitholders in an amount equal to the minimum quarterly distribution; and
•: we have distributed available cash from operating surplus on outstanding common units in an amount necessary to eliminate any cumulative arrearages in payment of the minimum quarterly distribution;

then, we will distribute any additional available cash from operating surplus for that quarter among the unitholders and the general partner in the following manner:

•: first, 98.0% to all unitholders, pro rata, and 2.0% to our general partner, until each unitholder receives a total of $0.46 per unit for that quarter (the "first target distribution");
•: second, 85.0% to all unitholders, pro rata, and 15.0% to our general partner, until each unitholder receives a total of $0.50 per unit for that quarter (the "second target distribution");
•: third, 75.0% to all unitholders, pro rata, and 25.0% to our general partner, until each unitholder receives a total of $0.60 per unit for that quarter (the "third target distribution"); and
•: thereafter, 50.0% to all unitholders, pro rata, and 50.0% to our general partner.

Percentage Allocations of Available Cash from Operating Surplus

The following table illustrates the percentage allocations of available cash from operating surplus between the unitholders and our general partner based on the specified target distribution levels. The amounts set forth under "Marginal Percentage Interest in Distributions" are the percentage interests of our general partner and the unitholders in any available cash from operating surplus we distribute up to and including the corresponding amount in the column "Total Quarterly Distribution Per Unit Target Amount." The percentage interests shown for our unitholders and our general partner for the minimum quarterly distribution are also applicable to quarterly distribution amounts that are less than the minimum quarterly distribution. The percentage interests set forth below for our general partner include its 2.0% general partner interest and assume that our general partner has contributed any

Table of Contents

additional capital necessary to maintain its 2.0% general partner interest, our general partner has not transferred its incentive distribution rights and that there are no arrearages on common units.

		Marginal Percentage Interest in Distributions

	Total Quarterly Distribution Per Unit Target Amount	Unitholders			General partner
Minimum Quarterly Distribution	$0.40		98.0	%		2.0	%
First Target Distribution	$0.40 up to $0.46		98.0	%		2.0	%
Second Target Distribution	above $0.46 up to $0.50		85.0	%		15.0	%
Third Target Distribution	above $0.50 up to $0.60		75.0	%		25.0	%
Thereafter	above $0.60		50.0	%		50.0	%

General Partner's Right to Reset Incentive Distribution Levels

Our general partner, as the initial holder of our incentive distribution rights, has the right under our partnership agreement to elect to relinquish the right to receive incentive distribution payments based on the initial target distribution levels and to reset, at higher levels, the minimum quarterly distribution amount and target distribution levels upon which the incentive distribution payments to our general partner would be set. If our general partner transfers all or a portion of our incentive distribution rights in the future, then the holder or holders of a majority of our incentive distribution rights will be entitled to exercise this right. The following discussion assumes that our general partner holds all of the incentive distribution rights at the time that a reset election is made. Our general partner's right to reset the minimum quarterly distribution amount and the target distribution levels upon which the incentive distributions payable to our general partner are based may be exercised, without approval of our unitholders or the conflicts committee of our general partner, at any time when there are no subordinated units outstanding and we have made cash distributions to the holders of the incentive distribution rights at the highest level of incentive distribution for each of the four consecutive fiscal quarters immediately preceding such time and the amount of each such distribution did not exceed adjusted operating surplus for such quarter, respectively. If our general partner and its affiliates are not the holders of a majority of the incentive distribution rights at the time an election is made to reset the minimum quarterly distribution amount and the target distribution levels, then the proposed reset will be subject to the prior written concurrence of the general partner that the conditions described above have been satisfied. The reset minimum quarterly distribution amount and target distribution levels will be higher than the minimum quarterly distribution amount and the target distribution levels prior to the reset such that our general partner will not receive any incentive distributions under the reset target distribution levels until cash distributions per unit following this event increase as described below. We anticipate that our general partner would exercise this reset right in order to facilitate acquisitions or internal growth projects that would otherwise not be sufficiently accretive to cash distributions per common unit, taking into account the existing levels of incentive distribution payments being made to our general partner.

In connection with the resetting of the minimum quarterly distribution amount and the target distribution levels and the corresponding relinquishment by our general partner of incentive distribution payments based on the target distributions prior to the reset, our general partner will be entitled to receive a number of newly issued common units and general partner units based on a predetermined formula described below that takes into account the "cash parity" value of the average cash distributions related to the incentive distribution rights received by our general partner for the two quarters immediately preceding the reset event as compared to the average cash distributions per common unit during that two-quarter period. Our general partner will be issued the number of general partner units necessary to maintain our general partner's interest in us immediately prior to the reset election.

Table of Contents

The number of common units that our general partner would be entitled to receive from us in connection with a resetting of the minimum quarterly distribution amount and the target distribution levels then in effect would be equal to the quotient determined by dividing (x) the average aggregate amount of cash distributions received by our general partner in respect of its incentive distribution rights during the two consecutive fiscal quarters ended immediately prior to the date of such reset election by (y) the average of the aggregate amount of cash distributed per common unit during each of these two quarters.

Following a reset election, the minimum quarterly distribution amount will be reset to an amount equal to the average cash distribution amount per unit for the two fiscal quarters immediately preceding the reset election (which amount we refer to as the "reset minimum quarterly distribution") and the target distribution levels will be reset to be correspondingly higher such that we would distribute all of our available cash from operating surplus for each quarter thereafter as follows:

•: first, 98.0% to all unitholders, pro rata, and 2.0% to our general partner, until each unitholder receives an amount per unit equal to 115.0% of the reset minimum quarterly distribution for that quarter;
•: second, 85.0% to all unitholders, pro rata, and 15.0% to our general partner, until each unitholder receives an amount per unit equal to 125.0% of the reset minimum quarterly distribution for the quarter;
•: third, 75.0% to all unitholders, pro rata, and 25.0% to our general partner, until each unitholder receives an amount per unit equal to 150.0% of the reset minimum quarterly distribution for the quarter; and
•: thereafter, 50.0% to all unitholders, pro rata, and 50.0% to our general partner.

The following table illustrates the percentage allocation of available cash from operating surplus between the unitholders and our general partner at various cash distribution levels (i) pursuant to the cash distribution provisions of our partnership agreement, as well as (ii) following a hypothetical reset of the minimum quarterly distribution and target distribution levels based on the assumption that the average quarterly cash distribution amount per common unit during the two fiscal quarters immediately preceding the reset election was $0.65.

		Marginal Percentage Interest In Distributions

	Quarterly Distribution per Unit Prior to Reset	Unitholders			2% General Partner Interest			Incentive Distribution Rights			Quarterly Distributions per Unit Following Hypothetical Reset
Minimum Quarterly Distribution	$0.400		98.0	%		2.0	%		—		$0.650
First Target Distribution	above $0.400 up to $0.460		98.0	%		2.0	%		—		above $0.650 up to $0.748(1)
Second Target Distribution	above $0.460 up to $0.500		85.0	%		2.0	%		13.0	%	above $0.748(1) up to $0.813(2)
Third Target Distribution	above $0.500 up to $0.600		75.0	%		2.0	%		23.0	%	above $0.813(2) up to $0.975(3)
Thereafter	above $0.600		50.0	%		2.0	%		48.0	%	above $0.975(3)

(1): This amount is 115.0% of the hypothetical reset minimum quarterly distribution.
(2): This amount is 125.0% of the hypothetical reset minimum quarterly distribution.
(3): This amount is 150.0% of the hypothetical reset minimum quarterly distribution.

Table of Contents

rights, based on an average of the amounts distributed each quarter for the two quarters immediately prior to the reset. The table assumes that immediately prior to the reset there would be 53,489,716 common units outstanding, our general partner has maintained its 2.0% general partner interest and the average distribution to each common unit would be $0.65 for the two quarters prior to the reset. For the purpose of the following table, the 283,682 phantom and restricted units with distribution equivalent rights that have been granted will be treated as common units.

				Cash distributions to general partner prior to reset

		Cash Distributions to Common Unitholders Prior to Reset		Cash distributions to general partner prior to reset
	Quarterly Distribution per Unit Prior to Reset	Cash Distributions to Common Unitholders Prior to Reset		2.0% General Partner Interest		Incentive Distribution Rights		Total		Total Distributions
Minimum Quarterly Distribution	$0.400	$	21,509,359	$	438,967	$	—	$	438,967	$	21,948,326
First Target Distribution	above $0.400 up to $0.460		3,226,404		65,845		—		65,845		3,292,249
Second Target Distribution	above $0.460 up to $0.500		2,150,936		50,610		328,967		379,577		2,530,513
Third Target Distribution	above $0.500 up to $0.600		5,377,340		143,396		1,649,051		1,792,447		7,169,786
Thereafter	above $0.600		2,688,670		107,547		2,581,123		2,688,670		5,377,340

		$	34,952,709	$	806,364	$	4,559,141	$	5,365,505	$	40,318,214

The following table illustrates the total amount of available cash from operating surplus that would be distributed to the unitholders and our general partner, including in respect of incentive distribution rights, with respect to the quarter in which the reset occurs. The table reflects that, as a result of the reset, there would be 60,503,779 common units outstanding, our general partner's 2.0% interest has been maintained, and the average distribution to each common unit would be $0.65. The number of common units to be issued to our general partner upon the reset was calculated by dividing (i) the average of the amounts received by our general partner in respect of its incentive distribution rights for the two quarters prior to the reset as shown in the table above, or $4,559,141, by (ii) the average available cash distributed on each common unit for the two quarters prior to the reset as shown in the table above, or $0.65. For the purpose of the following table, the 283,682 phantom and restricted units with distribution equivalent rights that have been granted will be treated as common units.

						Cash Distribution to General Partner After Reset

		Cash Distributions to Common Unitholders After Reset				Cash Distribution to General Partner After Reset
	Quarterly Distribution per Unit After Reset	Cash Distributions to Common Unitholders After Reset		Common Units Issued as a Result of the Reset		2.0% General Partner Interest		Incentive Distribution Rights		Total		Total Distributions
Minimum Quarterly Distribution	$0.650	$	39,511,849		7,014,063	$	806,364	$	—	$	806,364	$	40,318,214
First Target Distribution	above $0.650 up to $0.748		—		—		—		—		—		—
Second Target Distribution	above $0.748 up to $0.813		—		—		—		—		—		—
Third Target Distribution	above $0.813 up to $0.975		—		—		—		—		—		—
Thereafter	above $0.975		—		—		—		—		—		—

		$	39,511,849		7,014,063	$	806,364	$	—	$	806,364	$	40,318,214

Our general partner will be entitled to cause the minimum quarterly distribution amount and the target distribution levels to be reset on more than one occasion, provided that it may not make a reset election except at a time when it has received incentive distributions for the immediately preceding four consecutive fiscal quarters based on the highest level of incentive distributions that it is entitled to receive under our partnership agreement.

Table of Contents

Distributions From Capital Surplus

How Distributions from Capital Surplus Will Be Made. We will make distributions of available cash from capital surplus, if any, in the following manner:

•: first, 98.0% to all unitholders, pro rata, and 2.0% to our general partner, until we distribute for each common unit that was issued in our initial public offering, an amount of available cash from capital surplus equal to the initial public offering price of our initial public offering;
•: second, 98.0% to the common unitholders, pro rata, and 2.0% to our general partner, until we distribute for each outstanding common unit, an amount of available cash from capital surplus equal to any unpaid arrearages in payment of the minimum quarterly distribution on the common units; and
•: thereafter, as if they were distributions from operating surplus.

The preceding discussion is based on the assumption that our general partner maintains its 2.0% general partner interest and that we do not issue additional classes of equity securities.

Effect of a Distribution from Capital Surplus. Our partnership agreement treats a distribution of capital surplus as the repayment of the initial unit price from our initial public offering, which is a return of capital. The initial public offering price less any distributions of capital surplus per unit is referred to as the "unrecovered initial unit price." Each time a distribution of capital surplus is made, the minimum quarterly distribution and the target distribution levels will be reduced in the same proportion as the corresponding reduction in the unrecovered initial unit price. Because distributions of capital surplus will reduce the minimum quarterly distribution and target distribution levels after any of these distributions are made, it may be easier for our general partner to receive incentive distributions and for the subordinated units to convert into common units. However, any distribution of capital surplus before the unrecovered initial unit price is reduced to zero cannot be applied to the payment of the minimum quarterly distribution or any arrearages.

Once we distribute capital surplus on a unit issued in our initial public offering in an amount equal to the initial unit price, we will reduce the minimum quarterly distribution and the target distribution levels to zero. We will then make all future distributions from operating surplus, with 50.0% being paid to the unitholders, pro rata, and 50.0% to our general partner. The percentage interests shown for our general partner include its 2.0% general partner interest and assume that our general partner has not transferred the incentive distribution rights. Adjustment to the Minimum Quarterly Distribution and Target Distribution Levels.

Adjustment to the Minimum Quarterly Distribution and Target Distribution Levels

In addition to adjusting the minimum quarterly distribution and target distribution levels to reflect a distribution of capital surplus, if we combine our units into fewer units or subdivide our units into a greater number of units, we will proportionately adjust:

•: the minimum quarterly distribution;
•: the target distribution levels;
•: the unrecovered initial unit price;
•: the number of general partner units comprising the general partner interest; and
•: the per unit arrearage in payment of the minimum quarterly distribution on the common units.

For example, if a two-for-one split of the common units should occur, the minimum quarterly distribution, the target distribution levels and the unrecovered initial unit price would each be reduced

Table of Contents

to 50% of its initial level, and each subordinated unit would be split into two common units. We will not make any adjustment by reason of the issuance of additional units for cash or property.

In addition, if legislation is enacted or if existing law is modified or interpreted by a governmental authority, so that we become taxable as a corporation or otherwise subject to taxation as an entity for federal, state or local income tax purposes, our partnership agreement specifies that the minimum quarterly distribution and the target distribution levels for each quarter may be reduced by multiplying each distribution level by a fraction, the numerator of which is available cash for that quarter (reduced by the amount of the estimated tax liability for such quarter payable by reason of such legislation or interpretation) and the denominator of which is the sum of available cash for that quarter (reduced by the amount of the estimated tax liability for such quarter payable by reason of such legislation or interpretation) plus our general partner's estimate of our aggregate liability for the quarter for such income taxes payable by reason of such legislation or interpretation. To the extent that the actual tax liability differs from the estimated tax liability for any quarter, the difference will be accounted for in subsequent quarters.

Distributions of Cash Upon Liquidation

General. If we dissolve in accordance with our partnership agreement, we will sell or otherwise dispose of our assets in a process called liquidation. We will first apply the proceeds of liquidation to the payment of our creditors. We will distribute any remaining proceeds to the unitholders and our general partner, in accordance with their capital account balances, as adjusted to reflect any gain or loss upon the sale or other disposition of our assets in liquidation.

The allocations of gain and loss upon liquidation are intended, to the extent possible, to entitle the holders of outstanding common units to a preference over the holders of outstanding subordinated units upon our liquidation, to the extent required to permit common unitholders to receive their unrecovered initial unit price plus the minimum quarterly distribution for the quarter during which liquidation occurs plus any unpaid arrearages in payment of the minimum quarterly distribution on the common units. However, there may not be sufficient gain upon our liquidation to enable the holders of common units to fully recover all of these amounts, even though there may be cash available for distribution to the holders of subordinated units. Any further net gain recognized upon liquidation will be allocated in a manner that takes into account the incentive distribution rights of our general partner.

Manner of Adjustments for Gain. The manner of the adjustment for gain is set forth in our partnership agreement. If our liquidation occurs before the end of the subordination period, we will allocate any gain to our partners in the following manner:

•: first, to our general partner and the holders of units who have negative balances in their capital accounts to the extent of and in proportion to those negative balances;
•: second, 98.0% to the common unitholders, pro rata, and 2.0% to our general partner, until the capital account for each common unit is equal to the sum of: (1) the unrecovered initial unit price; (2) the amount of the minimum quarterly distribution for the quarter during which our liquidation occurs; and (3) any unpaid arrearages in payment of the minimum quarterly distribution;
•: third, 98.0% to the subordinated unitholders, pro rata, and 2.0% to our general partner, until the capital account for each subordinated unit is equal to the sum of: (1) the unrecovered initial unit price; and (2) the amount of the minimum quarterly distribution for the quarter during which our liquidation occurs;
•: fourth, 98.0% to all unitholders, pro rata, and 2.0% to our general partner, until we allocate under this paragraph an amount per unit equal to: (1) the sum of the excess of the first target distribution per unit over the minimum quarterly distribution per unit for each quarter of our

Table of Contents

existence; less (2) the cumulative amount per unit of any distributions of available cash from operating surplus in excess of the minimum quarterly distribution per unit that we distributed 98.0% to the unitholders, pro rata, and 2.0% to our general partner, for each quarter of our existence;

•: fifth, 85.0% to all unitholders, pro rata, and 15.0% to our general partner, until we allocate under this paragraph an amount per unit equal to: (1) the sum of the excess of the second target distribution per unit over the first target distribution per unit for each quarter of our existence; less (2) the cumulative amount per unit of any distributions of available cash from operating surplus in excess of the first target distribution per unit that we distributed 85.0% to the unitholders, pro rata, and 15.0% to our general partner for each quarter of our existence;
•: sixth, 75.0% to all unitholders, pro rata, and 25.0% to our general partner, until we allocate under this paragraph an amount per unit equal to: (1) the sum of the excess of the third target distribution per unit over the second target distribution per unit for each quarter of our existence;less (2) the cumulative amount per unit of any distributions of available cash from operating surplus in excess of the second target distribution per unit that we distributed 75.0% to the unitholders, pro rata, and 25.0% to our general partner for each quarter of our existence; and
•: thereafter, 50.0% to all unitholders, pro rata, and 50.0% to our general partner.

The percentages set forth above are based on the assumption that our general partner has not transferred its incentive distribution rights and that we do not issue additional classes of equity securities.

If the liquidation occurs after the end of the subordination period, the distinction between common units and subordinated units will disappear, so that clause (3) of the second bullet point above and all of the fourth bullet point above will no longer be applicable.

Manner of Adjustments for Losses. If our liquidation occurs before the end of the subordination period, after making allocations of loss to the general partner and the unitholders in a manner intended to offset in reverse order the allocations of gains that have previously been allocated, we will generally allocate any loss to our general partner and the unitholders in the following manner:

•: first, 98.0% to the holders of subordinated units in proportion to the positive balances in their capital accounts and 2.0% to our general partner, until the capital accounts of the subordinated unitholders have been reduced to zero;
•: second, 98.0% to the holders of common units in proportion to the positive balances in their capital accounts and 2.0% to our general partner, until the capital accounts of the common unitholders have been reduced to zero; and
•: thereafter, 100.0% to our general partner.

If the liquidation occurs after the end of the subordination period, the distinction between common units and subordinated units will disappear, so that all of the first bullet point above will no longer be applicable.

Adjustments to Capital Accounts. Our partnership agreement requires that we make adjustments to capital accounts upon the issuance of additional units. In this regard, our partnership agreement specifies that we allocate any unrealized and, for tax purposes, unrecognized gain resulting from the adjustments to the unitholders and the general partner in the same manner as we allocate gain upon liquidation. In the event that we make positive adjustments to the capital accounts upon the issuance of additional units, our partnership agreement requires that we generally allocate any later negative adjustments to the capital accounts resulting from the issuance of additional units or upon our

Table of Contents

liquidation in a manner which results, to the extent possible, in the partners' capital account balances equaling the amount which they would have been if no earlier positive adjustments to the capital accounts had been made. In contrast to the allocations of gain, and except as provided above, we generally will allocate any unrealized and unrecognized loss resulting from the adjustments to capital accounts upon the issuance of additional units to the unitholders and our general partner based on their respective percentage ownership of us. In this manner, prior to the end of the subordination period, we generally will allocate any such loss equally with respect to our common and subordinated units. If we make negative adjustments to the capital accounts as a result of such loss, future positive adjustments resulting from the issuance of additional units will be allocated in a manner designed to reverse the prior negative adjustments, and special allocations will be made upon liquidation in a manner that results, to the extent possible, in our unitholders' capital account balances equaling the amounts they would have been if no earlier adjustments for loss had been made.

Table of Contents

THE PARTNERSHIP AGREEMENT

The following is a summary of the material provisions of our partnership agreement. We will provide prospective investors with a copy of our partnership agreement upon request at no charge.

We summarize the following provisions of our partnership agreement elsewhere in this prospectus:

•: with regard to distributions of available cash, please read "Provisions of our Partnership Agreement Relating to Cash Distributions;"
•: with regard to the transfer of common units, please read "Description of Our Common Units—Transfer of Common Units;" and
•: with regard to allocations of taxable income and taxable loss, please read "Material U.S. Federal Income Tax Consequences."

Organization and Duration

We were organized in Delaware in May 2012 and have a perpetual existence.

Purpose

Our purpose under our partnership agreement is limited to any business activities that are approved by our general partner and in any event that lawfully may be conducted by a limited partnership organized under Delaware law; provided that our general partner may not cause us to engage, directly or indirectly, in any business activity that our general partner determines would be reasonably likely to cause us to be treated as an association taxable as a corporation or otherwise taxable as an entity for federal income tax purposes.

Although our general partner has the power to cause us, our operating company and its subsidiaries to engage in activities other than the business of gathering, compressing and transporting natural gas, our general partner has no current plans to do so and may decline to do so free of any duty or obligation whatsoever to us or our unitholders, other than the implied contractual covenant of good faith and fair dealing. Our general partner is generally authorized to perform all acts it determines to be necessary or appropriate to carry out our purposes and to conduct our business.

Cash Distributions

Our partnership agreement specifies the manner in which we will make cash distributions to holders of our common units and other partnership interests as well as to our general partner in respect of its general partner interest and its incentive distribution rights. For a description of these cash distribution provisions, please read "Provisions of Our Partnership Agreement Relating to Cash Distributions."

Capital Contributions

Unitholders are not obligated to make additional capital contributions, except as described below under "—Limited Liability."

For a discussion of our general partner's right to contribute capital to maintain its 2.0% general partner interest if we issue additional units, please read "—Issuance of Additional Partnership Interests."

Table of Contents

Voting Rights

The following is a summary of the unitholder vote required for approval of the matters specified below. Matters that require the approval of a "unit majority" require:

•: during the subordination period, the approval of a majority of the common units, excluding those common units held by our general partner and its affiliates, and a majority of the outstanding subordinated units, voting as separate classes; and
•: after the subordination period, the approval of a majority of the common units.

By virtue of the exclusion of those common units held by our general partner and its affiliates from the required vote, and by their ownership of all of the subordinated units, during the subordination period our general partner and its affiliates do not have the ability to ensure passage of, but do have the ability to ensure defeat of, any amendment that requires a unit majority.

In voting their common and subordinated units, our general partner and its affiliates will have no fiduciary duty or obligation whatsoever to us or our unitholders, including any duty to act in the best

Table of Contents

interests of us or our unitholders, other than the implied contractual covenant of good faith and fair dealing.


Issuance of additional units		No approval right.
Amendment of our partnership agreement		Certain amendments may be made by our general partner without the approval of the unitholders. Other amendments generally require the approval of a unit majority. Please read "—Amendment of Our Partnership Agreement."
Merger of our partnership or the sale of all or substantially all of our assets		Unit majority in certain circumstances. Please read "—Merger, Sale or Other Disposition of Assets."
Dissolution of our partnership		Unit majority. Please read "—Termination and Dissolution."
Continuation of our business upon dissolution		Unit majority. Please read "—Termination and Dissolution."
Withdrawal of our general partner		Under most circumstances, the approval of a majority of the common units, excluding common units held by our general partner and its affiliates, is required for the withdrawal of our general partner prior to December 31, 2022 in a manner that would cause a dissolution of our partnership. Please read "—Withdrawal or Removal of Our General Partner."
Removal of our general partner		Not less than 66²/3% of the outstanding units, voting as a single class, including units held by our general partner and its affiliates. Please read "— Withdrawal or Removal of Our General Partner."
Transfer of our general partner interest		Our general partner may transfer all, but not less than all, of its general partner interest in us without a vote of our unitholders to an affiliate or another person in connection with its merger or consolidation with or into, or sale of all or substantially all of its assets to, such person. The approval of a majority of the outstanding common units, excluding common units held by our general partner and its affiliates, is required in other circumstances for a transfer of the general partner interest to a third party prior to December 31, 2022. Please read "—Transfer of General Partner Interest."
Transfer of incentive distribution rights		Our general partner may transfer any or all of the incentive distribution rights to an affiliate or a third party without the consent of our unitholders. Please read "—Transfer of Incentive Distribution Rights."
Transfer of ownership interests in our general partner		No approval required at any time. Please read "—Transfer of Ownership Interests in Our General Partner."

Table of Contents

Limited Liability

Assuming that a limited partner does not participate in the control of our business within the meaning of the Delaware Revised Uniform Limited Partnership Act (the "Delaware Act") and that it otherwise acts in conformity with the provisions of our partnership agreement, its liability under the Delaware Act will be limited, subject to possible exceptions, to the amount of capital it is obligated to contribute to us for its common units plus its share of any undistributed profits and assets. If it were determined, however, that the right of, or exercise of the right by, the limited partners as a group:

•: to remove or replace our general partner;
•: to approve some amendments to our partnership agreement; or
•: to take other action under our partnership agreement;

constituted "participation in the control" of our business for the purposes of the Delaware Act, then the limited partners could be held personally liable for our obligations under the laws of Delaware, to the same extent as our general partner. This liability would extend to persons who transact business with us who reasonably believe that a limited partner is a general partner. Neither our partnership agreement nor the Delaware Act specifically provides for legal recourse against our general partner if a limited partner were to lose limited liability through any fault of our general partner. While this does not mean that a limited partner could not seek legal recourse, we know of no precedent for such a claim in Delaware case law.

Under the Delaware Act, a limited partnership may not make a distribution to a partner if, after the distribution, all liabilities of the limited partnership, other than liabilities to partners on account of their partnership interests and liabilities for which the recourse of creditors is limited to specific property of the partnership, would exceed the fair value of the assets of the limited partnership, except that the fair value of property that is subject to a liability for which the recourse of creditors is limited is included in the assets of the limited partnership only to the extent that the fair value of that property exceeds that liability. For the purpose of determining the fair value of the assets of a limited partnership, the Delaware Act provides that the fair value of property subject to liability for which recourse of creditors is limited shall be included in the assets of the limited partnership only to the extent that the fair value of that property exceeds the nonrecourse liability. The Delaware Act provides that a limited partner who receives a distribution and knew at the time of the distribution that the distribution was in violation of the Delaware Act shall be liable to the limited partnership for the amount of the distribution for three years. Under the Delaware Act, a substituted limited partner of a limited partnership is liable for the obligations of its assignor to make contributions to the partnership, except that such person is not obligated for liabilities unknown to it at the time it became a limited partner and that could not be ascertained from the partnership agreement.

Our subsidiaries conduct business in four states and we may have subsidiaries that conduct business in other states in the future. Maintenance of our limited liability as a member of our primary operating subsidiary, Summit Holdings, which we refer to as our "operating company," may require compliance with legal requirements in the jurisdictions in which the operating company conducts business, including qualifying our subsidiaries to do business there.

Limitations on the liability of members or limited partners for the obligations of a limited liability company or limited partnership have not been clearly established in many jurisdictions. If, by virtue of our ownership interest in our operating company or otherwise, it were determined that we were conducting business in any state without compliance with the applicable limited partnership or limited liability company statute, or that the right or exercise of the right by the limited partners as a group to remove or replace our general partner, to approve some amendments to our partnership agreement, or to take other action under our partnership agreement constituted "participation in the control" of our business for purposes of the statutes of any relevant jurisdiction, then the limited partners could be

Table of Contents

held personally liable for our obligations under the law of that jurisdiction to the same extent as our general partner under the circumstances. We will operate in a manner that our general partner considers reasonable and necessary or appropriate to preserve the limited liability of the limited partners.

Issuance of Additional Partnership Interests

Our partnership agreement authorizes us to issue an unlimited number of additional partnership interests for the consideration and on the terms and conditions determined by our general partner without the approval of our limited partners.

It is possible that we will fund acquisitions through the issuance of additional common units, subordinated units or other partnership interests. Holders of any additional common units we issue will be entitled to share equally with the then-existing holders of common units in our distributions of available cash. In addition, the issuance of additional common units or other partnership interests may dilute the value of the interests of the then-existing holders of common units in our net assets.

In accordance with Delaware law and the provisions of our partnership agreement, we may also issue additional partnership interests that, as determined by our general partner, may have rights to distributions or special voting rights to which the common units are not entitled. In addition, our partnership agreement does not prohibit our subsidiaries from issuing equity securities, which may effectively rank senior to the common units.

Upon issuance of additional partnership interests (other than the issuance of common units upon conversion of outstanding subordinated units or the issuance of common units upon a reset of the incentive distribution rights) our general partner will be entitled, but not required, to make additional capital contributions to the extent necessary to maintain its 2.0% general partner interest in us. Our general partner's 2.0% interest in us will be reduced if we issue additional units in the future (other than in those circumstances described above) and our general partner does not contribute a proportionate amount of capital to us to maintain its 2.0% general partner interest. Moreover, our general partner has the right, which it may from time to time assign in whole or in part to any of its affiliates, to purchase common units, subordinated units or other partnership interests whenever, and on the same terms that, we issue those interests to persons other than our general partner and its affiliates, to the extent necessary to maintain the percentage interest of the general partner and its affiliates, including such interest represented by common and subordinated units, that existed immediately prior to each issuance. The holders of common units do not have preemptive rights under our partnership agreement to acquire additional common units or other partnership interests.

Amendment of Our Partnership Agreement

General. Amendments to our partnership agreement may be proposed only by our general partner. However, our general partner has no duty or obligation to propose any amendment and may decline to do so free of any duty or obligation whatsoever to us or our unitholders, including any duty to act in the best interests of our partnership or our unitholders, other than the implied contractual covenants of good faith and fair dealing. In order to adopt a proposed amendment, other than the amendments discussed below, our general partner must seek written approval of the holders of the number of units required to approve the amendment or call a meeting of the limited partners to consider and vote upon the proposed amendment. Except as described below, an amendment must be approved by a unit majority.

Prohibited Amendments. No amendment may be made that would:

•: enlarge the obligations of any limited partner without its consent, unless approved by at least a majority of the type or class of limited partner interests so affected; or

Table of Contents

•: enlarge the obligations of, restrict in any way any action by or rights of, or reduce in any way the amounts distributable, reimbursable or otherwise payable by us to our general partner or any of its affiliates without the consent of our general partner, which consent may be given or withheld in its sole discretion.

The provision of our partnership agreement preventing the amendments having the effects described in the clauses above can be amended upon the approval of the holders of at least 90.0% of the outstanding units, voting as a single class (including units owned by our general partner and its affiliates). As of October 25, 2013, our general partner and its affiliates beneficially owned approximately 73.2% of the outstanding common and subordinated units.

No Unitholder Approval. Our general partner may generally make amendments to our partnership agreement without the approval of any limited partner to reflect:

•: a change in our name, the location of our principal place of business, our registered agent or our registered office;
•: the admission, substitution, withdrawal or removal of partners in accordance with our partnership agreement;
•: a change that our general partner determines to be necessary or appropriate for us to qualify or to continue our qualification as a limited partnership or a partnership in which the limited partners have limited liability under the laws of any state or to ensure that neither we, our operating company nor its subsidiaries will be treated as an association taxable as a corporation or otherwise taxed as an entity for federal income tax purposes;
•: a change in our fiscal year or taxable year and related changes;
•: an amendment that is necessary, in the opinion of our counsel, to prevent us or our general partner or its directors, officers, agents or trustees from in any manner being subjected to the provisions of the Investment Company Act of 1940, the Investment Advisers Act of 1940 or "plan asset" regulations adopted under the Employee Retirement Income Security Act of 1974, or ERISA, whether or not substantially similar to plan asset regulations currently applied or proposed by the United States Department of Labor;
•: an amendment that our general partner determines to be necessary or appropriate in connection with the authorization or issuance of additional partnership interests or rights to acquire partnership interests;
•: any amendment expressly permitted in our partnership agreement to be made by our general partner acting alone;
•: an amendment effected, necessitated or contemplated by a merger agreement that has been approved under the terms of our partnership agreement;
•: any amendment that our general partner determines to be necessary or appropriate for the formation by us of, or our investment in, any corporation, partnership, joint venture, limited liability company or other entity, as otherwise permitted by our partnership agreement;
•: mergers with, conveyances to or conversions into another limited liability entity that is newly formed and has no assets, liabilities or operations at the time of the merger, conveyance or conversion other than those it receives by way of the merger, conveyance or conversion; or
•: any other amendments substantially similar to any of the matters described above.

Table of Contents

In addition, our general partner may make amendments to our partnership agreement, without the approval of any limited partner, if our general partner determines that those amendments:

•: do not adversely affect in any material respect the limited partners considered as a whole or any particular class of partnership interests as compared to other classes of partnership interests;
•: are necessary or appropriate to satisfy any requirements, conditions or guidelines contained in any opinion, directive, order, ruling or regulation of any federal or state agency or judicial authority or contained in any federal or state statute;
•: are necessary or appropriate to facilitate the trading of units or to comply with any rule, regulation, guideline or requirement of any securities exchange on which the units are or will be listed for trading;
•: are necessary or appropriate for any action taken by our general partner relating to splits or combinations of units under the provisions of our partnership agreement; or
•: are required to effect the intent expressed in this prospectus or the intent of the provisions of our partnership agreement or are otherwise contemplated by our partnership agreement.

Opinion of Counsel and Limited Partner Approval. Our general partner will not be required to obtain an opinion of counsel that an amendment will not result in a loss of limited liability to the limited partners or result in our being treated as an entity for federal income tax purposes in connection with any of the amendments described above under "—No Unitholder Approval." No other amendments to our partnership agreement will become effective without the approval of holders of at least 90.0% of the outstanding units voting as a single class unless we first obtain an opinion of counsel to the effect that the amendment will not affect the limited liability under applicable law of any of our limited partners.

In addition to the above restrictions, any amendment that would have a material adverse effect on the rights or preferences of any type or class of outstanding units in relation to other classes of units will require the approval of at least a majority of the type or class of units so affected. Any amendment that reduces the voting percentage required to take any action must be approved by the affirmative vote of limited partners whose aggregate outstanding units constitute not less than the percentage sought to be reduced. Any amendment that would increase the percentage of units required to remove our general partner must be approved by the affirmative vote of limited partners whose aggregate outstanding units constitute not less than 90.0% of outstanding units. Any amendment that would increase the percentage of units required to call a meeting of unitholders must be approved by the affirmative vote of unitholders whose aggregate outstanding units constitute at least a majority of the outstanding units.

Merger, Sale or Other Disposition of Assets

A merger or consolidation of us requires the prior consent of our general partner. However, our general partner has no duty or obligation to consent to any merger or consolidation and may decline to do so free of any duty or obligation whatsoever to us or the limited partners, including any duty to act in the best interests of our partnership or our unitholders, other than the implied contractual covenant of good faith and fair dealing.

In addition, our partnership agreement generally prohibits our general partner, without the prior approval of the holders of a unit majority, from causing us to, among other things, sell, exchange or otherwise dispose of all or substantially all of our and our subsidiaries' assets in a single transaction or a series of related transactions, including by way of merger, consolidation, other combination or sale of ownership interests of our subsidiaries. Our general partner may, however, mortgage, pledge, hypothecate, or grant a security interest in all or substantially all of our and our subsidiaries' assets

Table of Contents

without that approval. Our general partner may also sell all or substantially all of our and our subsidiaries' assets under a foreclosure or other realization upon those encumbrances without that approval. Finally, our general partner may consummate any merger without the prior approval of our unitholders if we are the surviving entity in the transaction, our general partner has received an opinion of counsel regarding limited liability and tax matters, the transaction would not result in a material amendment to the partnership agreement (other than an amendment that the general partner could adopt without the consent of the limited partners), each of our units will be an identical unit of our partnership following the transaction and the partnership interests to be issued do not exceed 20.0% of our outstanding partnership interests immediately prior to the transaction.

If the conditions specified in our partnership agreement are satisfied, our general partner may convert us or any of our subsidiaries into a new limited liability entity or merge us or any of our subsidiaries into, or convey all of our assets to, a newly formed limited liability entity, if the sole purpose of that conversion, merger or conveyance is to effect a mere change in our legal form into another limited liability entity, our general partner has received an opinion of counsel regarding limited liability and tax matters and the governing instruments of the new entity provide the limited partners and our general partner with the same rights and obligations as contained in our partnership agreement. Our unitholders are not entitled to dissenters' rights of appraisal under our partnership agreement or applicable Delaware law in the event of a conversion, merger or consolidation, a sale of substantially all of our assets or any other similar transaction or event.

Termination and Dissolution

We will continue as a limited partnership until dissolved under our partnership agreement. We will dissolve upon:

•: the withdrawal or removal of our general partner or any other event that results in its ceasing to be our general partner other than by reason of a transfer of its general partner interest in accordance with our partnership agreement or its withdrawal or removal following the approval and admission of a successor;
•: the election of our general partner to dissolve us, if approved by the holders of units representing a unit majority;
•: the entry of a decree of judicial dissolution of our partnership; or
•: there being no limited partners, unless we are continued without dissolution in accordance with the Delaware Act;

Upon a dissolution under the first clause above, the holders of a unit majority may also elect, within specific time limitations, to continue our business on the same terms and conditions described in our partnership agreement and appoint as a successor general partner an entity approved by the holders of units representing a unit majority, subject to our receipt of an opinion of counsel to the effect that:

•: the action would not result in the loss of limited liability of any limited partner; and
•: neither we nor any of our subsidiaries would be treated as an association taxable as a corporation or otherwise be taxable as an entity for federal income tax purposes upon the exercise of that right to continue (to the extent not already so treated or taxed).

Liquidation and Distribution of Proceeds

Upon our dissolution, unless we are continued as a limited partnership, the liquidator authorized to wind up our affairs will, acting with all of the powers of our general partner that are necessary or appropriate, liquidate our assets and apply the proceeds of the liquidation as described in "Provisions

Table of Contents

of Our Partnership Agreement Relating to Cash Distributions—Distributions of Cash Upon Liquidation." The liquidator may defer liquidation or distribution of our assets for a reasonable period of time if it determines that an immediate sale or distribution would be impractical or would cause undue loss to our partners. The liquidator may distribute our assets, in whole or in part, in kind if it determines that a sale would be impractical or would cause undue loss to the partners.

Withdrawal or Removal of Our General Partner

Except as described below, our general partner has agreed not to withdraw voluntarily as our general partner prior to December 31, 2022 without obtaining the approval of the holders of at least a majority of the outstanding common units, excluding common units held by the general partner and its affiliates, and furnishing an opinion of counsel regarding limited liability and tax matters. On or after December 31, 2022, our general partner may withdraw as general partner without first obtaining approval of any unitholder by giving at least 90 days' written notice, and that withdrawal will not constitute a violation of our partnership agreement. Notwithstanding the information above, our general partner may withdraw without unitholder approval upon 90 days' notice to the limited partners if at least 50.0% of the outstanding common units are held or controlled by one person and its affiliates, other than our general partner and its affiliates. In addition, our partnership agreement permits our general partner in some instances to sell or otherwise transfer all of its general partner interest in us without the approval of the unitholders. Please read "—Transfer of General Partner Interest" and "—Transfer of Incentive Distribution Rights."

Upon withdrawal of our general partner under any circumstances, other than as a result of a transfer by our general partner of all or a part of its general partner interest in us, the holders of a unit majority may select a successor to that withdrawing general partner. If a successor is not elected, or is elected but an opinion of counsel regarding limited liability and tax matters cannot be obtained, we will be dissolved, wound up and liquidated, unless within a specified period of time after that withdrawal, the holders of a unit majority agree in writing to continue our business and to appoint a successor general partner. Please read "—Termination and Dissolution."

Our general partner may not be removed unless that removal is approved by the vote of the holders of not less than 66²/3% of all outstanding units, voting together as a single class, including units held by our general partner and its affiliates, and we receive an opinion of counsel regarding limited liability and tax matters. Any removal of our general partner is also subject to the approval of a successor general partner by the vote of the holders of a majority of the outstanding common units and a majority of the outstanding subordinated units, voting as a single class. The ownership of more than 33¹/3% of the outstanding units by our general partner and its affiliates gives them the ability to prevent our general partner's removal.

Our partnership agreement also provides that if our general partner is removed as our general partner under circumstances where cause does not exist and units held by the general partner and its affiliates are not voted in favor of that removal:

•: the subordination period will end, and all subordinated units will immediately and automatically convert into common units on a one-for-one basis;
•: all cumulative arrearages in payment of the minimum quarterly distribution on the common units will be extinguished; and
•: our general partner will have the right to convert its general partner interest and its incentive distribution rights into common units or receive cash in exchange for those interests based on the fair market value of those interests as of the effective date of its removal.

In the event of removal of our general partner under circumstances where cause exists or withdrawal of our general partner where that withdrawal violates our partnership agreement, a

Table of Contents

successor general partner will have the option to purchase the general partner interest and incentive distribution rights of the departing general partner for a cash payment equal to the fair market value of those interests. Under all other circumstances where our general partner withdraws or is removed by the limited partners, the departing general partner will have the option to require the successor general partner to purchase the general partner interest of the departing general partner and its incentive distribution rights for their fair market value. In each case, this fair market value will be determined by agreement between the departing general partner and the successor general partner. If no agreement is reached, an independent investment banking firm or other independent expert selected by the departing general partner and the successor general partner will determine the fair market value. Or, if the departing general partner and the successor general partner cannot agree upon an expert, then an expert chosen by agreement of the experts selected by each of them will determine the fair market value.

If the option described above is not exercised by either the departing general partner or the successor general partner, the departing general partner's general partner interest and its incentive distribution rights will automatically convert into common units equal to the fair market value of those interests as determined by an investment banking firm or other independent expert selected in the manner described in the preceding paragraph.

In addition, we will be required to reimburse the departing general partner for all amounts due to it, including, without limitation, all employee-related liabilities, including severance liabilities, incurred in connection with the termination of any employees employed by the departing general partner or its affiliates for our benefit.

Transfer of General Partner Interest

Except for transfer by our general partner of all, but not less than all, of its general partner interest to:

•: an affiliate of our general partner (other than an individual); or
•: another entity as part of the merger or consolidation of our general partner with or into another entity or the transfer by our general partner of all or substantially all of its assets to such entity,

our general partner may not transfer all or any of its general partner interest to another person prior to December 31, 2022 without the approval of the holders of at least a majority of the outstanding common units, excluding common units held by our general partner and its affiliates. As a condition of this transfer, the transferee must, among other things, assume the rights and duties of our general partner, agree to be bound by the provisions of our partnership agreement and furnish an opinion of counsel regarding limited liability and tax matters.

Our general partner and its affiliates may, at any time, transfer units to one or more persons, without unitholder approval, except that they may not transfer subordinated units to us.

Transfer of Ownership Interests in Our General Partner

At any time, the owners of our general partner may sell or transfer all or part of their ownership interests in our general partner to an affiliate or a third party without the approval of our unitholders.

Transfer of Incentive Distribution Rights

Our general partner may transfer any or all of its incentive distribution rights to an affiliate or a third party without unitholder approval.

Table of Contents

Change of Management Provisions

Our partnership agreement contains specific provisions that are intended to discourage a person or group from attempting to remove our general partner or otherwise change our management. Please read "—Withdrawal or Removal of Our General Partner" for a discussion of certain consequences of the removal of our general partner. If any person or group, other than our general partner and its affiliates, acquires beneficial ownership of 20.0% or more of any class of units, that person or group loses voting rights on all of its units. This loss of voting rights does not apply to any person or group that acquires the units directly from our general partner or its affiliates or any transferee of that person or group that is approved by our general partner or to any person or group who acquires the units with the prior approval of the board of directors of our general partner. Please read "—Meetings; Voting."

Limited Call Right

If at any time our general partner and its affiliates own more than 80.0% of the then-issued and outstanding limited partner interests of any class, our general partner will have the right, which it may assign in whole or in part to any of its affiliates or to us, to acquire all, but not less than all, of the remaining limited partner interests of the class held by unaffiliated persons as of a record date to be selected by our general partner, on at least 10, but not more than 60, days' notice. The purchase price in the event of this purchase is the greater of:

•: the highest price paid by our general partner or any of its affiliates for any limited partner interests of the class purchased within the 90 days preceding the date on which our general partner first mails notice of its election to purchase those limited partner interests; and
•: the average of the daily closing prices of the partnership interests of such class for the 20 consecutive trading days preceding the date three days before the date the notice is mailed.

As a result of our general partner's right to purchase outstanding limited partner interests, a holder of limited partner interests may have his limited partner interests purchased at an undesirable time or price. The tax consequences to a unitholder of the exercise of this call right are the same as a sale by that unitholder of his common units in the market. Please read "Material U.S. Federal Income Tax Consequences—Disposition of Common Units."

Meetings; Voting

Except as described below regarding a person or group owning 20.0% or more of any class of units then outstanding, unitholders who are record holders of units on the record date will be entitled to notice of, and to vote at, meetings of our limited partners and to act upon matters for which approvals may be solicited.

Our general partner does not anticipate that any meeting of unitholders will be called in the foreseeable future. Any action that is required or permitted to be taken by the unitholders may be taken either at a meeting of the unitholders or without a meeting if consents in writing describing the action so taken are signed by holders of the number of units necessary to authorize or take that action at a meeting. Meetings of the unitholders may be called by our general partner or by unitholders owning at least 20.0% of the outstanding units of the class for which a meeting is proposed. Unitholders may vote either in person or by proxy at meetings. The holders of a majority of the outstanding units of the class or classes for which a meeting has been called, represented in person or by proxy, will constitute a quorum unless any action by the unitholders requires approval by holders of a greater percentage of the units, in which case the quorum will be the greater percentage. The units representing the general partner interest are units for distribution and allocation purposes, but do not entitle our general partner to any vote other than its rights as general partner under our partnership agreement, will not be entitled to vote on any action required or permitted to be taken by the

Table of Contents

unitholders and will not count toward or be considered outstanding when calculating required votes, determining the presence of a quorum, or for similar purposes.

Each record holder of a unit has a vote according to its percentage interest in us, although additional limited partner interests having special voting rights could be issued. Please read "—Issuance of Additional Partnership Interests." However, if at any time any person or group, other than our general partner and its affiliates, or a direct or subsequently approved transferee of our general partner or its affiliates, acquires, in the aggregate, beneficial ownership of 20.0% or more of any class of units then outstanding, that person or group will lose voting rights on all of its units and the units may not be voted on any matter and will not be considered to be outstanding when sending notices of a meeting of unitholders, calculating required votes, determining the presence of a quorum or for other similar purposes. Common units held in nominee or street name account will be voted by the broker or other nominee in accordance with the instruction of the beneficial owner unless the arrangement between the beneficial owner and its nominee provides otherwise. Except as our partnership agreement otherwise provides, subordinated units will vote together with common units as a single class.

Any notice, demand, request, report or proxy material required or permitted to be given or made to record holders of common units under our partnership agreement will be delivered to the record holder by us or by the transfer agent.

Status as Limited Partner

By transfer of common units in accordance with our partnership agreement, each transferee of common units will be admitted as a limited partner with respect to the common units transferred when such transfer and admission are reflected in our books and records. Except as described above under "—Limited Liability," the common units will be fully paid, and unitholders will not be required to make additional contributions.

Redemption of Ineligible Holders

In order to avoid any material adverse effect on the maximum applicable rates that can be charged to customers by our subsidiaries on assets that may be subject to rate regulation by the Federal Energy Regulatory Commission or an analogous regulatory body in the future, each transferee of common units, upon becoming the record holder of such common units, will automatically certify, and the general partner at any time can request such unitholder to re-certify:

•: that the transferee or unitholder is an individual or an entity subject to United States federal income taxation on the income generated by us; or
•: that, if the transferee unitholder is an entity not subject to United States federal income taxation on the income generated by us, as in the case, for example, of a mutual fund taxed as a regulated investment company or a partnership, all the entity's owners are subject to United States federal income taxation on the income generated by us.

Furthermore, in order to avoid a substantial risk of cancellation or forfeiture of any property, including any governmental permit, endorsement or other authorization, in which we have an interest as the result of any federal, state or local law or regulation concerning the nationality, citizenship or other related status of any unitholder, our general partner may at any time request unitholders to certify as to, or provide other information with respect to, their nationality, citizenship or other related status.

The certifications as to taxpayer status and nationality, citizenship or other related status can be changed in any manner our general partner determines is necessary or appropriate to implement its original purpose.

Table of Contents

If a unitholder fails to furnish the certification or other requested information with 30 days or if our general partner determines, with the advice of counsel, upon review of such certification or other information that a unitholder does not meet the status set forth in the certification, we will have the right to redeem all of the units held by such unitholder at the market price as of the date three days before the date the notice of redemption is mailed.

The purchase price will be paid in cash or by delivery of a promissory note, as determined by our general partner. Any such promissory note will bear interest at the rate of 5.0% annually and be payable in three equal annual installments of principal and accrued interest, commencing one year after the redemption date. Further, the units will not be entitled to any allocations of income or loss, distributions or voting rights while held by such unitholder.

Indemnification

Under our partnership agreement we will indemnify the following persons, in most circumstances, to the fullest extent permitted by law, from and against all losses, claims, damages or similar events:

•: our general partner;
•: any departing general partner;
•: any person who is or was an affiliate of our general partner or any departing general partner;
•: any person who is or was a director, officer, managing member, manager, general partner, fiduciary or trustee of our subsidiaries, us or any entity set forth in the preceding three bullet points;
•: any person who is or was serving at the request of the general partner or any departing general partner or any of their affiliates as an officer, director, managing member, manager, general partner, fiduciary or trustee of another person owing a fiduciary duty to us or our subsidiaries; and
•: any person designated by our general partner.

Any indemnification under these provisions will only be out of our assets. Unless it otherwise agrees, our general partner will not be personally liable for, or have any obligation to contribute or lend funds or assets to us to enable us to effectuate, indemnification. We may purchase insurance against liabilities asserted against and expenses incurred by persons for our activities, regardless of whether we would have the power to indemnify the person against liabilities under our partnership agreement.

Reimbursement of Expenses

Our partnership agreement requires us to reimburse our general partner for all direct and indirect expenses it incurs or payments it makes on our behalf and all other expenses allocable to us or otherwise incurred by our general partner in connection with operating our business. These expenses include salary, bonus, incentive compensation and other amounts paid to persons who perform services for us or on our behalf and expenses allocated to our general partner by its affiliates. Our general partner is entitled to determine in good faith the expenses that are allocable to us.

Books and Reports

Our general partner is required to keep or cause to be kept appropriate books and records of our business at our principal offices. The books will be maintained for both tax and financial reporting purposes on an accrual basis. For fiscal and tax reporting purposes, we use the calendar year.

Table of Contents

We will furnish or make available to record holders of common units, within 105 days after the close of each fiscal year, an annual report containing audited financial statements and a report on those financial statements by our independent public accountants, including a balance sheet and statements of operations, and our equity and cash flows. Except for our fourth quarter, we will also furnish or make available summary financial information within 50 days after the close of each quarter. We will be deemed to have made any such report available if we file such report with the SEC on the Electronic Data Gathering, Analysis and Retrieval system ("EDGAR") or make the report available on a publicly available website that we maintain.

We will furnish each record holder with information reasonably required for federal and state tax reporting purposes within 90 days after the close of each calendar year. This information is expected to be furnished in summary form so that some complex calculations normally required of partners can be avoided. Our ability to furnish this summary information to unitholders will depend on the cooperation of unitholders in supplying us with specific information. Every unitholder will receive information to assist him in determining its federal and state tax liability and filing its federal and state income tax returns, regardless of whether he supplies us with the necessary information.

Right to Inspect Our Books and Records

Our partnership agreement provides that a limited partner can, for a purpose reasonably related to its interest as a limited partner, upon reasonable written demand stating the purpose of such demand and at its own expense, have furnished to him:

•: a current list of the name and last known address of each record holder;
•: copies of our partnership agreement and our certificate of limited partnership and all amendments thereto; and
•: certain information regarding the status of our business and financial condition.

Our general partner may, and intends to, keep confidential from the limited partners any information that our general partner reasonably believes to be in the nature of trade secrets or other information the disclosure of which our general partner in good faith believes is not in our best interests or could damage us or our business or that we are required by law or by agreements with third parties to keep confidential. Our partnership agreement limits the right to information that a limited partner would otherwise have under Delaware law.

Registration Rights

Under our partnership agreement, we have agreed to register for resale under the Securities Act and applicable state securities laws any common units, subordinated units, or other partnership interests proposed to be sold by our general partner or any of its affiliates, other than individuals, or their assignees if an exemption from the registration requirements is not otherwise available. These registration rights continue for two years following any withdrawal or removal of Summit Midstream GP, LLC as our general partner. We are obligated to pay all expenses incidental to the registration, excluding underwriting discounts and commissions.

Operating Agreement of Summit Midstream Holdings, LLC

We conduct all of our operations through Summit Holdings and its operating subsidiaries. Under the amended and restated limited liability company agreement of Summit Holdings, the management of Summit Holdings is vested in us. As the sole member, we have the authority to cause Summit Holdings to make distributions to us, among other things, as required.

Table of Contents

MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES

This section is a summary of the material tax considerations that may be relevant to prospective unitholders who are individual citizens or residents of the U.S. and, unless otherwise noted in the following discussion, is the opinion of Latham & Watkins LLP, counsel to our general partner and us, insofar as it relates to legal conclusions with respect to matters of U.S. federal income tax law. This section is based upon current provisions of the Internal Revenue Code of 1986, as amended (the "Internal Revenue Code"), existing and proposed Treasury regulations promulgated under the Internal Revenue Code (the "Treasury Regulations") and current administrative rulings and court decisions, all of which are subject to change. Later changes in these authorities may cause the tax consequences to vary substantially from the consequences described below. Unless the context otherwise requires, references in this section to "us" or "we" are references to Summit Midstream Partners, LP and our operating subsidiaries.

The following discussion does not comment on all federal income tax matters affecting us or our unitholders. Moreover, the discussion focuses on unitholders who are individual citizens or residents of the U.S. and has only limited application to corporations, estates, entities treated as partnerships for U.S. federal income tax purposes, trusts, nonresident aliens, U.S. expatriates and former citizens or long-term residents of the United States or other unitholders subject to specialized tax treatment, such as banks, insurance companies and other financial institutions, tax-exempt institutions, foreign persons (including, without limitation, controlled foreign corporations, passive foreign investment companies and non-U.S. persons eligible for the benefits of an applicable income tax treaty with the United States), individual retirement accounts ("IRAs"), real estate investment trusts (REITs) or mutual funds, dealers in securities or currencies, traders in securities, U.S. persons whose "functional currency" is not the U.S. dollar, persons holding their units as part of a "straddle," "hedge," "conversion transaction" or other risk reduction transaction, and persons deemed to sell their units under the constructive sale provisions of the Code.

In addition, the discussion only comments to a limited extent on state, local, and foreign tax consequences. Accordingly, we encourage each prospective unitholder to consult his own tax advisor in analyzing the state, local and foreign tax consequences particular to him of the ownership or disposition of common units and potential changes in applicable tax laws.

No ruling has been requested from the IRS regarding our characterization as a partnership for tax purposes. Instead, we will rely on opinions of Latham & Watkins LLP. Unlike a ruling, an opinion of counsel represents only that counsel's best legal judgment and does not bind the IRS or the courts. Accordingly, the opinions and statements made herein may not be sustained by a court if contested by the IRS. Any contest of this sort with the IRS may materially and adversely impact the market for the common units and the prices at which common units trade. In addition, the costs of any contest with the IRS, principally legal, accounting and related fees, will result in a reduction in cash available for distribution to our unitholders and our general partner and thus will be borne indirectly by our unitholders and our general partner. Furthermore, the tax treatment of us, or of an investment in us, may be significantly modified by future legislative or administrative changes or court decisions. Any modifications may or may not be retroactively applied.

All statements as to matters of federal income tax law and legal conclusions with respect thereto, but not as to factual matters, contained in this section, unless otherwise noted, are the opinion of Latham & Watkins LLP and are based on the accuracy of the representations made by us.

For the reasons described below, Latham & Watkins LLP has not rendered an opinion with respect to the following specific federal income tax issues: (i) the treatment of a unitholder whose common units are loaned to a short seller to cover a short sale of common units (please read "—Tax Consequences of Unit Ownership—Treatment of Short Sales"); (ii) whether our monthly convention for allocating taxable income and losses is permitted by existing Treasury Regulations (please read

Table of Contents

"—Disposition of Common Units—Allocations Between Transferors and Transferees"); and (iii) whether our method for taking into account Section 743 adjustments is sustainable in certain cases (please read "—Tax Consequences of Unit Ownership—Section 754 Election" and "—Uniformity of Units").

Partnership Status

A partnership is not a taxable entity and incurs no federal income tax liability. Instead, each partner of a partnership is required to take into account his share of items of income, gain, loss and deduction of the partnership in computing his federal income tax liability, regardless of whether cash distributions are made to him by the partnership. Distributions by a partnership to a partner are generally not taxable to the partnership or the partner unless the amount of cash distributed to him is in excess of the partner's adjusted basis in his partnership interest. Section 7704 of the Internal Revenue Code provides that publicly traded partnerships will, as a general rule, be taxed as corporations. However, an exception, referred to as the "Qualifying Income Exception," exists with respect to publicly traded partnerships of which 90% or more of the gross income for every taxable year consists of "qualifying income." Qualifying income includes income and gains derived from the transportation, processing, storage and marketing of crude oil, natural gas and products thereof. Other types of qualifying income include interest (other than from a financial business), dividends, gains from the sale of real property and gains from the sale or other disposition of capital assets held for the production of income that otherwise constitutes qualifying income. We estimate that less than 1.0% of our current gross income is not qualifying income; however, this estimate could change from time to time. Based upon and subject to this estimate, the factual representations made by us and our general partner and a review of the applicable legal authorities, Latham & Watkins LLP is of the opinion that at least 90% of our current gross income constitutes qualifying income. The portion of our income that is qualifying income may change from time to time.

The IRS has made no determination as to our status or the status of our operating subsidiaries for federal income tax purposes. Instead, we will rely on the opinion of Latham & Watkins LLP on such matters. It is the opinion of Latham & Watkins LLP that, based upon the Internal Revenue Code, its regulations, published revenue rulings and court decisions and the representations described below that:

•: We will be classified as a partnership for federal income tax purposes; and
•: Each of our operating subsidiaries will be treated as a partnership or will be disregarded as an entity separate from us for federal income tax purposes.

In rendering its opinion, Latham & Watkins LLP has relied on factual representations made by us and our general partner. The representations made by us and our general partner upon which Latham & Watkins LLP has relied include:

•: Neither we nor the operating subsidiaries has elected or will elect to be treated, or is otherwise treated, as a corporation for federal income tax purposes; and
•: For each taxable year, more than 90% of our gross income has been and will be income of the type that Latham & Watkins LLP has opined or will opine is "qualifying income" within the meaning of Section 7704(d) of the Internal Revenue Code.

We believe that these representations have been true in the past and expect that these representations will continue to be true in the future.

If we fail to meet the Qualifying Income Exception, other than a failure that is determined by the IRS to be inadvertent and that is cured within a reasonable time after discovery (in which case the IRS may also require us to make adjustments with respect to our unitholders or pay other amounts), we will be treated as if we had transferred all of our assets, subject to liabilities, to a newly formed

Table of Contents

corporation, on the first day of the year in which we fail to meet the Qualifying Income Exception, in return for stock in that corporation, and then distributed that stock to the unitholders in liquidation of their interests in us. This deemed contribution and liquidation should be tax-free to unitholders and us so long as we, at that time, do not have liabilities in excess of the tax basis of our assets. Thereafter, we would be treated as a corporation for federal income tax purposes.

If we were treated as an association taxable as a corporation in any taxable year, either as a result of a failure to meet the Qualifying Income Exception or otherwise, our items of income, gain, loss and deduction would be reflected only on our tax return rather than being passed through to our unitholders, and our net income would be taxed to us at corporate rates. In addition, any distribution made to a unitholder would be treated as taxable dividend income, to the extent of our current and accumulated earnings and profits, or, in the absence of earnings and profits, a nontaxable return of capital, to the extent of the unitholder's tax basis in his common units, or taxable capital gain, after the unitholder's tax basis in his common units is reduced to zero. Accordingly, taxation as a corporation would result in a material reduction in a unitholder's cash flow and after-tax return and thus would likely result in a substantial reduction of the value of the units.

The discussion below is based on Latham & Watkins LLP's opinion that we will be classified as a partnership for federal income tax purposes.

Limited Partner Status

Unitholders of Summit Midstream Partners, LP will be treated as partners of Summit Midstream Partners, LP for federal income tax purposes. Also, unitholders whose common units are held in street name or by a nominee and who have the right to direct the nominee in the exercise of all substantive rights attendant to the ownership of their common units will be treated as partners of Summit Midstream Partners, LP for federal income tax purposes.

A beneficial owner of common units whose units have been transferred to a short seller to complete a short sale would appear to lose his status as a partner with respect to those units for federal income tax purposes. Please read "—Tax Consequences of Unit Ownership—Treatment of Short Sales."

Income, gains, losses or deductions would not appear to be reportable by a unitholder who is not a partner for federal income tax purposes, and any cash distributions received by a unitholder who is not a partner for federal income tax purposes would therefore appear to be fully taxable as ordinary income. These holders are urged to consult their tax advisors with respect to the tax consequences to them of holding common units in Summit Midstream Partners, LP. The references to "unitholders" in the discussion that follows are to persons who are treated as partners in Summit Midstream Partners, LP for federal income tax purposes.

Tax Consequences of Unit Ownership

Flow-Through of Taxable Income

Subject to the discussion below under "—Entity-Level Collections." we will not pay any federal income tax. Instead, each unitholder will be required to report on his income tax return his share of our income, gains, losses and deductions without regard to whether we make cash distributions to him. Consequently, we may allocate income to a unitholder even if he has not received a cash distribution. Each unitholder will be required to include in income his allocable share of our income, gains, losses and deductions for our taxable year ending with or within his taxable year. Our taxable year ends on December 31.

Table of Contents

Treatment of Distributions

Distributions by us to a unitholder generally will not be taxable to the unitholder for federal income tax purposes, except to the extent the amount of any such cash distribution exceeds his tax basis in his common units immediately before the distribution. Our cash distributions in excess of a unitholder's tax basis generally will be considered to be gain from the sale or exchange of the common units, taxable in accordance with the rules described under "—Disposition of Common Units." Any reduction in a unitholder's share of our liabilities for which no partner, including the general partner, bears the economic risk of loss, known as "nonrecourse liabilities," will be treated as a distribution by us of cash to that unitholder. To the extent our distributions cause a unitholder's "at-risk" amount to be less than zero at the end of any taxable year, he must recapture any losses deducted in previous years. Please read "—Limitations on Deductibility of Losses."

A decrease in a unitholder's percentage interest in us because of our issuance of additional common units will decrease his share of our nonrecourse liabilities, and thus will result in a corresponding deemed distribution of cash. This deemed distribution may constitute a non-pro rata distribution. A non-pro rata distribution of money or property may result in ordinary income to a unitholder, regardless of his tax basis in his common units, if the distribution reduces the unitholder's share of our "unrealized receivables," including depreciation recapture and/or substantially appreciated "inventory items," each as defined in the Internal Revenue Code, and collectively, "Section 751 Assets." To that extent, the unitholder will be treated as having been distributed his proportionate share of the Section 751 Assets and then having exchanged those assets with us in return for the non-pro rata portion of the actual distribution made to him. This latter deemed exchange will generally result in the unitholder's realization of ordinary income, which will equal the excess of (i) the non-pro rata portion of that distribution over (ii) the unitholder's tax basis (often zero) for the share of Section 751 Assets deemed relinquished in the exchange.

Basis of Common Units

A unitholder's initial tax basis for his common units will be the amount he paid for the common units plus his share of our nonrecourse liabilities. That basis will be increased by his share of our income and by any increases in his share of our nonrecourse liabilities. That basis will be decreased, but not below zero, by distributions from us, by the unitholder's share of our losses, by any decreases in his share of our nonrecourse liabilities and by his share of our expenditures that are not deductible in computing taxable income and are not required to be capitalized. A unitholder will have no share of our debt that is recourse to our general partner to the extent of the general partner's "net value" as defined in regulations under Section 752 of the Internal Revenue Code, but will have a share, generally based on his share of profits, of our nonrecourse liabilities. Please read "—Disposition of Common Units—Recognition of Gain or Loss."

Limitations on Deductibility of Losses

The deduction by a unitholder of his share of our losses will be limited to the tax basis in his units and, in the case of an individual unitholder, estate, trust, or corporate unitholder (if more than 50% of the value of the corporate unitholder's stock is owned directly or indirectly by or for five or fewer individuals or some tax-exempt organizations) to the amount for which the unitholder is considered to be "at risk" with respect to our activities, if that is less than his tax basis. A common unitholder subject to these limitations must recapture losses deducted in previous years to the extent that distributions cause his at-risk amount to be less than zero at the end of any taxable year. Losses disallowed to a unitholder or recaptured as a result of these limitations will carry forward and will be allowable as a deduction to the extent that his at-risk amount is subsequently increased, provided such losses do not exceed such common unitholder's tax basis in his common units. Upon the taxable disposition of a unit, any gain recognized by a unitholder can be offset by losses that were previously suspended by the

Table of Contents

at-risk limitation but may not be offset by losses suspended by the basis limitation. Any loss previously suspended by the at-risk limitation in excess of that gain would no longer be utilizable.

In general, a unitholder will be at risk to the extent of the tax basis of his units, excluding any portion of that basis attributable to his share of our nonrecourse liabilities, reduced by (i) any portion of that basis representing amounts otherwise protected against loss because of a guarantee, stop loss agreement or other similar arrangement and (ii) any amount of money he borrows to acquire or hold his units, if the lender of those borrowed funds owns an interest in us, is related to the unitholder or can look only to the units for repayment. A unitholder's at-risk amount will increase or decrease as the tax basis of the unitholder's units increases or decreases, other than tax basis increases or decreases attributable to increases or decreases in his share of our nonrecourse liabilities.

In addition to the basis and at-risk limitations on the deductibility of losses, the passive loss limitations generally provide that individuals, estates, trusts and some closely-held corporations and personal service corporations can deduct losses from passive activities, which are generally trade or business activities in which the taxpayer does not materially participate, only to the extent of the taxpayer's income from those passive activities. The passive loss limitations are applied separately with respect to each publicly traded partnership. Consequently, any passive losses we generate will only be available to offset our passive income generated in the future and will not be available to offset income from other passive activities or investments, including our investments or a unitholder's investments in other publicly traded partnerships, or the unitholder's salary, active business or other income. Passive losses that are not deductible because they exceed a unitholder's share of income we generate may be deducted in full when he disposes of his entire investment in us in a fully taxable transaction with an unrelated party. The passive loss limitations are applied after other applicable limitations on deductions, including the at-risk rules and the basis limitation.

A unitholder's share of our net income may be offset by any of our suspended passive losses, but it may not be offset by any other current or carryover losses from other passive activities, including those attributable to other publicly traded partnerships.

Limitations on Interest Deductions

The deductibility of a non-corporate taxpayer's "investment interest expense" is generally limited to the amount of that taxpayer's "net investment income." Investment interest expense includes:

•: interest on indebtedness properly allocable to property held for investment;
•: our interest expense attributed to portfolio income; and
•: the portion of interest expense incurred to purchase or carry an interest in a passive activity to the extent attributable to portfolio income.

The computation of a unitholder's investment interest expense will take into account interest on any margin account borrowing or other loan incurred to purchase or carry a unit. Net investment income includes gross income from property held for investment and amounts treated as portfolio income under the passive loss rules, less deductible expenses, other than interest, directly connected with the production of investment income, but generally does not include gains attributable to the disposition of property held for investment or (if applicable) qualified dividend income. The IRS has indicated that the net passive income earned by a publicly traded partnership will be treated as investment income to its unitholders. In addition, the unitholder's share of our portfolio income will be treated as investment income.

Table of Contents

Entity-Level Collections

If we are required or elect under applicable law to pay any federal, state, local or foreign income tax on behalf of any unitholder or our general partner or any former unitholder, we are authorized to pay those taxes from our funds. That payment, if made, will be treated as a distribution of cash to the unitholder on whose behalf the payment was made. If the payment is made on behalf of a person whose identity cannot be determined, we are authorized to treat the payment as a distribution to all current unitholders. We are authorized to amend our partnership agreement in the manner necessary to maintain uniformity of intrinsic tax characteristics of units and to adjust later distributions, so that after giving effect to these distributions, the priority and characterization of distributions otherwise applicable under our partnership agreement is maintained as nearly as is practicable. Payments by us as described above could give rise to an overpayment of tax on behalf of an individual unitholder in which event the unitholder would be required to file a claim in order to obtain a credit or refund.

Allocation of Income, Gain, Loss and Deduction

In general, if we have a net profit, our items of income, gain, loss and deduction will be allocated among our general partner and the unitholders in accordance with their percentage interests in us. At any time that distributions are made to the common units in excess of distributions to the subordinated units, or incentive distributions are made to our general partner, gross income will be allocated to the recipients to the extent of these distributions. If we have a net loss, that loss will be allocated first to our general partner and the unitholders in accordance with their percentage interests in us to the extent of their positive capital accounts, as adjusted for certain items in accordance with applicable Treasury Regulations and, second, to our general partner.

Specified items of our income, gain, loss and deduction will be allocated to account for (i) any difference between the tax basis and fair market value of our assets at the time of an offering and (ii) any difference between the tax basis and fair market value of any property contributed to us by the general partner and its affiliates (or by a third party) that exists at the time of such contribution, together referred to in this discussion as the "Contributed Property." The effect of these allocations, referred to as Section 704(c) Allocations, to a unitholder purchasing common units from us in an offering will be essentially the same as if the tax bases of our assets were equal to their fair market values at the time of the offering. In the event we issue additional common units or engage in certain other transactions in the future, "reverse Section 704(c) Allocations," similar to the Section 704(c) Allocations described above, will be made to the general partner and all of our unitholders immediately prior to such issuance or other transactions to account for the difference between the "book" basis for purposes of maintaining capital accounts and the fair market value of all property held by us at the time of such issuance or future transaction. In addition, items of recapture income will be allocated to the extent possible to the unitholder who was allocated the deduction giving rise to the treatment of that gain as recapture income in order to minimize the recognition of ordinary income by some unitholders. Finally, although we do not expect that our operations will result in the creation of negative capital accounts, if negative capital accounts nevertheless result, items of our income and gain will be allocated in an amount and manner sufficient to eliminate the negative balance as quickly as possible.

An allocation of items of our income, gain, loss or deduction, other than an allocation required by the Internal Revenue Code to eliminate the difference between a partner's "book" capital account, credited with the fair market value of Contributed Property, and "tax" capital account, credited with the tax basis of Contributed Property, referred to in this discussion as the "Book-Tax Disparity," will generally be given effect for federal income tax purposes in determining a partner's share of an item of income, gain, loss or deduction only if the allocation has "substantial economic effect." In any other

Table of Contents

case, a partner's share of an item will be determined on the basis of his interest in us, which will be determined by taking into account all the facts and circumstances, including:

•: his relative contributions to us;
•: the interests of all the partners in profits and losses;
•: the interest of all the partners in cash flow; and
•: the rights of all the partners to distributions of capital upon liquidation.

Latham & Watkins LLP is of the opinion that, with the exception of the issues described in "—Section 754 Election" and "—Disposition of Common Units—Allocations Between Transferors and Transferees," allocations under our partnership agreement will be given effect for federal income tax purposes in determining a partner's share of an item of income, gain, loss or deduction.

Treatment of Short Sales

A unitholder whose units are loaned to a "short seller" to cover a short sale of units may be considered as having disposed of those units. If so, he would no longer be treated for tax purposes as a partner with respect to those units during the period of the loan and may recognize gain or loss from the disposition. As a result, during this period:

•: any of our income, gain, loss or deduction with respect to those units would not be reportable by the unitholder;
•: any cash distributions received by the unitholder as to those units would be fully taxable; and
•: while not entirely free from doubt, all of these distributions would appear to be ordinary income.

Because there is no direct or indirect controlling authority on the issue relating to partnership interests, Latham & Watkins LLP has not rendered an opinion regarding the tax treatment of a unitholder whose common units are loaned to a short seller to effect a short sale of common units; therefore, unitholders desiring to assure their status as partners and avoid the risk of gain recognition from a loan to a short seller are urged to consult a tax advisor to discuss whether it is advisable to modify any applicable brokerage account agreements to prohibit their brokers from borrowing and loaning their units. The IRS has previously announced that it is studying issues relating to the tax treatment of short sales of partnership interests. Please also read "—Disposition of Common Units—Recognition of Gain or Loss."

Alternative Minimum Tax

Each unitholder will be required to take into account his distributive share of any items of our income, gain, loss or deduction for purposes of the alternative minimum tax. The current minimum tax rate for noncorporate taxpayers is 26% on the first $179,500 of alternative minimum taxable income in excess of the exemption amount and 28% on any additional alternative minimum taxable income. Prospective unitholders are urged to consult with their tax advisors as to the impact of an investment in units on their liability for the alternative minimum tax.

Tax Rates

Beginning on January 1, 2013, the highest marginal U.S. federal income tax rate applicable to ordinary income of individuals is 39.6% and the highest marginal U.S. federal income tax rate applicable to long-term capital gains (generally, capital gains on certain assets held for more than twelve months) of individuals is 20%. Such rates are subject to change by new legislation at any time.

Table of Contents

In addition, a 3.8% Medicare tax, or NIIT, on certain net investment income earned by individuals, estates and trusts applies for taxable years beginning after December 31, 2012. For these purposes, net investment income generally includes a unitholder's allocable share of our income and gain realized by a unitholder from a sale of units. In the case of an individual, the tax will be imposed on the lesser of (i) the unitholder's net investment income and (ii) the amount by which the unitholder's modified adjusted gross income exceeds $250,000 (if the unitholder is married and filing jointly or a surviving spouse), $125,000 (if the unitholder is married and filing separately) or $200,000 (in any other case). In the case of an estate or trust, the tax will be imposed on the lesser of (i) undistributed net investment income and (ii) the excess adjusted gross income over the dollar amount at which the highest income tax bracket applicable to an estate or trust begins. Recently, the Department of the Treasury and the IRS issued proposed Treasury Regulations that provide guidance regarding the NIIT. Although the proposed Treasury Regulations are effective for taxable years beginning after December 31, 2013, taxpayers may rely on the proposed Treasury Regulations for purposes of compliance until the effective date of the final regulations. Prospective unitholders are urged to consult with their tax advisors as to the impact of the NIIT on an investment in our common units.

Section 754 Election

We have made the election permitted by Section 754 of the Internal Revenue Code. That election is irrevocable without the consent of the IRS unless there is a constructive termination of the partnership. Please read "—Disposition of Common Units—Constructive Termination." The election will generally permit us to adjust a common unit purchaser's tax basis in our assets ("inside basis") under Section 743(b) of the Internal Revenue Code to reflect his purchase price. This election does not apply with respect to a person who purchases common units directly from us. The Section 743(b) adjustment belongs to the purchaser and not to other unitholders. For purposes of this discussion, the inside basis in our assets with respect to a unitholder will be considered to have two components: (i) his share of our tax basis in our assets ("common basis") and (ii) his Section 743(b) adjustment to that basis.

We have adopted the remedial allocation method as to all our properties. Where the remedial allocation method is adopted, the Treasury Regulations under Section 743 of the Internal Revenue Code require a portion of the Section 743(b) adjustment that is attributable to recovery property that is subject to depreciation under Section 168 of the Internal Revenue Code and whose book basis is in excess of its tax basis to be depreciated over the remaining cost recovery period for the property's unamortized Book-Tax Disparity. Under Treasury Regulation Section 1.167(c)-1(a)(6), a Section 743(b) adjustment attributable to property subject to depreciation under Section 167 of the Internal Revenue Code, rather than cost recovery deductions under Section 168, is generally required to be depreciated using either the straight-line method or the 150% declining balance method.

Under our partnership agreement, our general partner is authorized to take a position to preserve the uniformity of units even if that position is not consistent with these and any other Treasury Regulations. Please read "—Uniformity of Units." We depreciate the portion of a Section 743(b) adjustment attributable to unrealized appreciation in the value of Contributed Property, to the extent of any unamortized Book-Tax Disparity, using a rate of depreciation or amortization derived from the depreciation or amortization method and useful life applied to the property's unamortized Book-Tax Disparity, or treat that portion as non-amortizable to the extent attributable to property which is not amortizable. This method is consistent with the methods employed by other publicly traded partnerships but is arguably inconsistent with Treasury Regulation Section 1.167(c)-1(a)(6), which is not expected to directly apply to a material portion of our assets. To the extent this Section 743(b) adjustment is attributable to appreciation in value in excess of the unamortized Book-Tax Disparity, we will apply the rules described in the Treasury Regulations and legislative history. If we determine that this position cannot reasonably be taken, we may take a depreciation or amortization position under which all purchasers acquiring units in the same month would receive depreciation or amortization,

Table of Contents

whether attributable to common basis or a Section 743(b) adjustment, based upon the same applicable rate as if they had purchased a direct interest in our assets. This kind of aggregate approach may result in lower annual depreciation or amortization deductions than would otherwise be allowable to some unitholders. Please read "—Uniformity of Units." A unitholder's tax basis for his common units is reduced by his share of our deductions (whether or not such deductions were claimed on an individual's income tax return) so that any position we take that understates deductions will overstate the common unitholder's basis in his common units, which may cause the unitholder to understate gain or overstate loss on any sale of such units. Please read "—Disposition of Common Units—Recognition of Gain or Loss." Latham & Watkins LLP is unable to opine as to whether our method for taking into account Section 743 adjustments is sustainable for property subject to depreciation under Section 167 of the Internal Revenue Code or if we use an aggregate approach as described above, as there is no direct or indirect controlling authority addressing the validity of these positions. Moreover, the IRS may challenge our position with respect to depreciating or amortizing the Section 743(b) adjustment we take to preserve the uniformity of the units. If such a challenge were sustained, the gain from the sale of units might be increased without the benefit of additional deductions.

A Section 754 election is advantageous if the transferee's tax basis in his units is higher than the units' share of the aggregate tax basis of our assets immediately prior to the transfer. In that case, as a result of the election, the transferee would have, among other items, a greater amount of depreciation deductions and his share of any gain or loss on a sale of our assets would be less. Conversely, a Section 754 election is disadvantageous if the transferee's tax basis in his units is lower than those units' share of the aggregate tax basis of our assets immediately prior to the transfer. Thus, the fair market value of the units may be affected either favorably or unfavorably by the election. A basis adjustment is required regardless of whether a Section 754 election is made in the case of a transfer of an interest in us if we have a substantial built-in loss immediately after the transfer, or if we distribute property and have a substantial basis reduction. Generally, a built-in loss or a basis reduction is substantial if it exceeds $250,000.

The calculations involved in the Section 754 election are complex and will be made on the basis of assumptions as to the value of our assets and other matters. For example, the allocation of the Section 743(b) adjustment among our assets must be made in accordance with the Internal Revenue Code. The IRS could seek to reallocate some or all of any Section 743(b) adjustment allocated by us to our tangible assets to goodwill instead. Goodwill, as an intangible asset, is generally nonamortizable or amortizable over a longer period of time or under a less accelerated method than our tangible assets. We cannot assure you that the determinations we make will not be successfully challenged by the IRS and that the deductions resulting from them will not be reduced or disallowed altogether. Should the IRS require a different basis adjustment to be made, and should, in our opinion, the expense of compliance exceed the benefit of the election, we may seek permission from the IRS to revoke our Section 754 election. If permission is granted, a subsequent purchaser of units may be allocated more income than he would have been allocated had the election not been revoked.

Tax Treatment of Operations

Accounting Method and Taxable Year

We use the year ending December 31 as our taxable year and the accrual method of accounting for federal income tax purposes. Each unitholder will be required to include in income his share of our income, gain, loss and deduction for our taxable year ending within or with his taxable year. In addition, a unitholder who has a taxable year ending on a date other than December 31 and who disposes of all of his units following the close of our taxable year but before the close of his taxable year must include his share of our income, gain, loss and deduction in income for his taxable year, with the result that he will be required to include in income for his taxable year his share of more than twelve months of our income, gain, loss and deduction. Please read "—Disposition of Common Units—Allocations Between Transferors and Transferees."

Table of Contents

Tax Basis, Depreciation and Amortization

The tax basis of our assets will be used for purposes of computing depreciation and cost recovery deductions and, ultimately, gain or loss on the disposition of these assets. The federal income tax burden associated with the difference between the fair market value of our assets and their tax basis immediately prior to an offering will be borne by our unitholders holding interests in us prior to any such offering. Please read "—Tax Consequences of Unit Ownership—Allocation of Income, Gain, Loss and Deduction."

To the extent allowable, we may elect to use the depreciation and cost recovery methods, including bonus depreciation to the extent available, that will result in the largest deductions being taken in the early years after assets subject to these allowances are placed in service. Please read "—Uniformity of Units." Property we subsequently acquire or construct may be depreciated using accelerated methods permitted by the Internal Revenue Code.

If we dispose of depreciable property by sale, foreclosure or otherwise, all or a portion of any gain, determined by reference to the amount of depreciation previously deducted and the nature of the property, may be subject to the recapture rules and taxed as ordinary income rather than capital gain. Similarly, a unitholder who has taken cost recovery or depreciation deductions with respect to property we own will likely be required to recapture some or all of those deductions as ordinary income upon a sale of his interest in us. Please read "—Tax Consequences of Unit Ownership—Allocation of Income, Gain, Loss and Deduction" and "—Disposition of Common Units—Recognition of Gain or Loss."

The costs we incur in selling our units (called "syndication expenses") must be capitalized and cannot be deducted currently, ratably or upon our termination. There are uncertainties regarding the classification of costs as organization expenses, which may be amortized by us, and as syndication expenses, which may not be amortized by us. The underwriting discounts and commissions we incur will be treated as syndication expenses.

Valuation and Tax Basis of Our Properties

The federal income tax consequences of the ownership and disposition of units will depend in part on our estimates of the relative fair market values, and the initial tax bases, of our assets. Although we may from time to time consult with professional appraisers regarding valuation matters, we will make many of the relative fair market value estimates ourselves. These estimates and determinations of basis are subject to challenge and will not be binding on the IRS or the courts. If the estimates of fair market value or basis are later found to be incorrect, the character and amount of items of income, gain, loss or deductions previously reported by unitholders might change, and unitholders might be required to adjust their tax liability for prior years and incur interest and penalties with respect to those adjustments.

Disposition of Common Units

Recognition of Gain or Loss

Gain or loss will be recognized on a sale of units equal to the difference between the amount realized and the unitholder's tax basis for the units sold. A unitholder's amount realized will be measured by the sum of the cash or the fair market value of other property received by him plus his share of our nonrecourse liabilities. Because the amount realized includes a unitholder's share of our nonrecourse liabilities, the gain recognized on the sale of units could result in a tax liability in excess of any cash received from the sale.

Prior distributions from us that in the aggregate were in excess of cumulative net taxable income for a common unit and, therefore, decreased a unitholder's tax basis in that common unit will, in effect,

Table of Contents

become taxable income if the common unit is sold at a price greater than the unitholder's tax basis in that common unit, even if the price received is less than his original cost.

Except as noted below, gain or loss recognized by a unitholder, other than a "dealer" in units, on the sale or exchange of a unit will generally be taxable as capital gain or loss. Capital gain recognized by an individual on the sale of units held for more than twelve months will generally be taxed at the U.S. federal income tax rate applicable to long-term capital gains. However, a portion of this gain or loss, which will likely be substantial, will be separately computed and taxed as ordinary income or loss under Section 751 of the Internal Revenue Code to the extent attributable to assets giving rise to depreciation recapture or other "unrealized receivables" or to "inventory items" we own. The term "unrealized receivables" includes potential recapture items, including depreciation recapture. Ordinary income attributable to unrealized receivables, inventory items and depreciation recapture may exceed net taxable gain realized upon the sale of a unit and may be recognized even if there is a net taxable loss realized on the sale of a unit. Thus, a unitholder may recognize both ordinary income and a capital loss upon a sale of units. Capital losses may offset capital gains and no more than $3,000 of ordinary income, in the case of individuals, and may only be used to offset capital gains in the case of corporations. Both ordinary income and capital gain recognized on a sale of units may be subject to the NIIT in certain circumstances. Please read "—Tax Consequences of Unit Ownership—Tax Rates."

The IRS has ruled that a partner who acquires interests in a partnership in separate transactions must combine those interests and maintain a single adjusted tax basis for all those interests. Upon a sale or other disposition of less than all of those interests, a portion of that tax basis must be allocated to the interests sold using an "equitable apportionment" method, which generally means that the tax basis allocated to the interest sold equals an amount that bears the same relation to the partner's tax basis in his entire interest in the partnership as the value of the interest sold bears to the value of the partner's entire interest in the partnership. Treasury Regulations under Section 1223 of the Internal Revenue Code allow a selling unitholder who can identify common units transferred with an ascertainable holding period to elect to use the actual holding period of the common units transferred. Thus, according to the ruling discussed above, a common unitholder will be unable to select high or low basis common units to sell as would be the case with corporate stock, but, according to the Treasury Regulations, he may designate specific common units sold for purposes of determining the holding period of units transferred. A unitholder electing to use the actual holding period of common units transferred must consistently use that identification method for all subsequent sales or exchanges of common units. A unitholder considering the purchase of additional units or a sale of common units purchased in separate transactions is urged to consult his tax advisor as to the possible consequences of this ruling and application of the Treasury Regulations.

Specific provisions of the Internal Revenue Code affect the taxation of some financial products and securities, including partnership interests, by treating a taxpayer as having sold an "appreciated" partnership interest, one in which gain would be recognized if it were sold, assigned or terminated at its fair market value, if the taxpayer or related persons enter(s) into:

•: a short sale;
•: an offsetting notional principal contract; or
•: a futures or forward contract;

in each case, with respect to the partnership interest or substantially identical property.

Moreover, if a taxpayer has previously entered into a short sale, an offsetting notional principal contract or a futures or forward contract with respect to the partnership interest, the taxpayer will be treated as having sold that position if the taxpayer or a related person then acquires the partnership interest or substantially identical property. The Secretary of the Treasury is also authorized to issue

Table of Contents

regulations that treat a taxpayer that enters into transactions or positions that have substantially the same effect as the preceding transactions as having constructively sold the financial position.

Allocations Between Transferors and Transferees

In general, our taxable income and losses will be determined annually, will be prorated on a monthly basis and will be subsequently apportioned among the unitholders in proportion to the number of units owned by each of them as of the opening of the applicable exchange on the first business day of the month, which we refer to in this prospectus as the "Allocation Date." However, gain or loss realized on a sale or other disposition of our assets other than in the ordinary course of business will be allocated among the unitholders on the Allocation Date in the month in which that gain or loss is recognized. As a result, a unitholder transferring units may be allocated income, gain, loss and deduction realized after the date of transfer.

Although simplifying conventions are contemplated by the Internal Revenue Code and most publicly traded partnerships use similar simplifying conventions, the use of this method may not be permitted under existing Treasury Regulations as there is no direct or indirect controlling authority on this issue. Recently, the Department of the Treasury and the IRS issued proposed Treasury Regulations that provide a safe harbor pursuant to which a publicly traded partnership may use a similar monthly simplifying convention to allocate tax items among transferor and transferee unitholders, although such tax items must be prorated on a daily basis. Existing publicly traded partnerships are entitled to rely on these proposed Treasury Regulations; however, they are not binding on the IRS and are subject to change until final Treasury Regulations are issued. Accordingly, Latham & Watkins LLP is unable to opine on the validity of this method of allocating income and deductions between transferor and transferee unitholders because the issue has not been finally resolved by the IRS or the courts. If this method is not allowed under the Treasury Regulations, or only applies to transfers of less than all of the unitholder's interest, our taxable income or losses might be reallocated among the unitholders. We are authorized to revise our method of allocation between transferor and transferee unitholders, as well as unitholders whose interests vary during a taxable year, to conform to a method permitted under future Treasury Regulations. A unitholder who owns units at any time during a quarter and who disposes of them prior to the record date set for a cash distribution for that quarter will be allocated items of our income, gain, loss and deductions attributable to that quarter through the month of disposition but will not be entitled to receive that cash distribution.

Notification Requirements

A unitholder who sells any of his units is generally required to notify us in writing of that sale within 30 days after the sale (or, if earlier, January 15 of the year following the sale). A purchaser of units who purchases units from another unitholder is also generally required to notify us in writing of that purchase within 30 days after the purchase. Upon receiving such notifications, we are required to notify the IRS of that transaction and to furnish specified information to the transferor and transferee. Failure to notify us of a purchase may, in some cases, lead to the imposition of penalties. However, these reporting requirements do not apply to a sale by an individual who is a citizen of the U.S. and who effects the sale or exchange through a broker who will satisfy such requirements.

Constructive Termination

We will be considered to have technically terminated for federal income tax purposes if there is a sale or exchange of 50 percent or more of the total interests in our capital and profits within a twelve-month period. For purposes of determining whether the 50 percent threshold has been met, multiple sales of the same unit will be counted only once. While we would continue our existence as a Delaware limited partnership, our technical termination would, among other things, result in the closing of our taxable year for all unitholders, which would result in us filing two tax returns (and our unitholders

Table of Contents

could receive two Schedules K-1 if relief was not available, as described below) for one fiscal year. Our termination could also result in a significant deferral of depreciation deductions allowable in computing our taxable income. In the case of a unitholder reporting on a taxable year other than a calendar year, the closing of our taxable year may also result in more than twelve months of our taxable income or loss being includable in his taxable income for the year of termination. Our termination currently would not affect our classification as a partnership for federal income tax purposes, but instead, we would be treated as a new partnership for federal income tax purposes. If treated as a new partnership, we must make new tax elections, including a new election under Section 754 of the Internal Revenue Code, and could be subject to penalties if we are unable to determine that a technical termination occurred. The IRS has announced a relief procedure whereby if a publicly traded partnership that has technically terminated requests and the IRS grants special relief, among other things, the partnership may be permitted to provide only a single Schedule K-1 to unitholders for the tax years in which the termination occurs.

Uniformity of Units

Because we cannot match transferors and transferees of units, we must maintain uniformity of the economic and tax characteristics of the units to a purchaser of these units. In the absence of uniformity, we may be unable to completely comply with a number of federal income tax requirements, both statutory and regulatory. A lack of uniformity can result from a literal application of Treasury Regulation Section 1.167(c)-1(a)(6). Any non-uniformity could have a negative impact on the value of the units. Please read "—Tax Consequences of Unit Ownership—Section 754 Election." We take into account the portion of a Section 743(b) adjustment attributable to unrealized appreciation in the value of Contributed Property, to the extent of any unamortized Book-Tax Disparity, using a rate of depreciation or amortization derived from the depreciation or amortization method and useful life applied to the property's unamortized Book-Tax Disparity, or treat that portion as nonamortizable, to the extent attributable to property the common basis of which is not amortizable, consistent with the regulations under Section 743 of the Internal Revenue Code, even though that position may be inconsistent with Treasury Regulation Section 1.167(c)-1(a)(6), which is not expected to directly apply to a material portion of our assets. Please read "—Tax Consequences of Unit Ownership—Section 754 Election." To the extent that the Section 743(b) adjustment is attributable to appreciation in value in excess of the unamortized Book-Tax Disparity, we will apply the rules described in the Treasury Regulations and legislative history. If we determine that this position cannot reasonably be taken, we may adopt a depreciation and amortization position under which all purchasers acquiring units in the same month would receive depreciation and amortization deductions, whether attributable to common basis or a Section 743(b) adjustment, based upon the same applicable rate as if they had purchased a direct interest in our assets. If this position is adopted, it may result in lower annual depreciation and amortization deductions than would otherwise be allowable to some unitholders and risk the loss of depreciation and amortization deductions not taken in the year that these deductions are otherwise allowable. This position will not be adopted if we determine that the loss of depreciation and amortization deductions will have a material adverse effect on the unitholders. If we choose not to utilize this aggregate method, we may use any other reasonable depreciation and amortization method to preserve the uniformity of the intrinsic tax characteristics of any units that would not have a material adverse effect on the unitholders. In either case, and as stated above under "—Tax Consequences of Unit Ownership—Section 754 Election," Latham & Watkins LLP has not rendered an opinion with respect to these methods. Moreover, the IRS may challenge any method of depreciating the Section 743(b) adjustment described in this paragraph. If this challenge were sustained, the uniformity of units might be affected, and the gain from the sale of units might be increased without the benefit of additional deductions. Please read "—Disposition of Common Units—Recognition of Gain or Loss."

Table of Contents

Tax-Exempt Organizations and Other Investors

Ownership of units by employee benefit plans, other tax-exempt organizations, non-resident aliens, foreign corporations and other foreign persons raises issues unique to those investors and, as described below to a limited extent, may have substantially adverse tax consequences to them. If you are a tax-exempt entity or a non-U.S. person, you should consult your tax advisor before investing in our common units. Employee benefit plans and most other organizations exempt from federal income tax, including individual retirement accounts and other retirement plans, are subject to federal income tax on unrelated business taxable income. Virtually all of our income allocated to a unitholder that is a tax-exempt organization will be unrelated business taxable income and will be taxable to it.

Non-resident aliens and foreign corporations, trusts or estates that own units will be considered to be engaged in business in the U.S. because of the ownership of units. As a consequence, they will be required to file federal tax returns to report their share of our income, gain, loss or deduction and pay federal income tax at regular rates on their share of our net income or gain. Moreover, under rules applicable to publicly traded partnerships, our quarterly distribution to foreign unitholders will be subject to withholding at the highest applicable effective tax rate. Each foreign unitholder must obtain a taxpayer identification number from the IRS and submit that number to our transfer agent on a Form W-8BEN or applicable substitute form in order to obtain credit for these withholding taxes. A change in applicable law may require us to change these procedures.

In addition, because a foreign corporation that owns units will be treated as engaged in a U.S. trade or business, that corporation may be subject to the U.S. branch profits tax at a rate of 30%, in addition to regular federal income tax, on its share of our earnings and profits, as adjusted for changes in the foreign corporation's "U.S. net equity," that is effectively connected with the conduct of a U.S. trade or business. That tax may be reduced or eliminated by an income tax treaty between the U.S. and the country in which the foreign corporate unitholder is a "qualified resident." In addition, this type of unitholder is subject to special information reporting requirements under Section 6038C of the Internal Revenue Code.

A foreign unitholder who sells or otherwise disposes of a common unit will be subject to U.S. federal income tax on gain realized from the sale or disposition of that unit to the extent the gain is effectively connected with a U.S. trade or business of the foreign unitholder. Under a ruling published by the IRS, interpreting the scope of "effectively connected income," a foreign unitholder would be considered to be engaged in a trade or business in the U.S. by virtue of the U.S. activities of the partnership, and part or all of that unitholder's gain would be effectively connected with that unitholder's indirect U.S. trade or business. Moreover, under the Foreign Investment in Real Property Tax Act, a foreign common unitholder generally will be subject to U.S. federal income tax upon the sale or disposition of a common unit if (i) he owned (directly or constructively applying certain attribution rules) more than 5% of our common units at any time during the five-year period ending on the date of such disposition and (ii) 50% or more of the fair market value of all of our assets consisted of U.S. real property interests at any time during the shorter of the period during which such unitholder held the common units or the five-year period ending on the date of disposition.

Administrative Matters

Information Returns and Audit Procedures

We intend to furnish to each unitholder, within 90 days after the close of each calendar year, specific tax information, including a Schedule K-1, which describes his share of our income, gain, loss and deduction for our preceding taxable year. In preparing this information, which will not be reviewed by counsel, we will take various accounting and reporting positions, some of which have been mentioned earlier, to determine each unitholder's share of income, gain, loss and deduction. We cannot assure you that those positions will yield a result that conforms to the requirements of the Internal

Table of Contents

Revenue Code, Treasury Regulations or administrative interpretations of the IRS. Neither we nor Latham & Watkins LLP can assure prospective unitholders that the IRS will not successfully contend in court that those positions are impermissible. Any challenge by the IRS could negatively affect the value of the units.

The IRS may audit our federal income tax information returns. Adjustments resulting from an IRS audit may require each unitholder to adjust a prior year's tax liability, and possibly may result in an audit of his return. Any audit of a unitholder's return could result in adjustments not related to our returns as well as those related to our returns.

Partnerships generally are treated as separate entities for purposes of federal tax audits, judicial review of administrative adjustments by the IRS and tax settlement proceedings. The tax treatment of partnership items of income, gain, loss and deduction are determined in a partnership proceeding rather than in separate proceedings with the partners. The Internal Revenue Code requires that one partner be designated as the "Tax Matters Partner" for these purposes. Our partnership agreement names our general partner as our Tax Matters Partner.

The Tax Matters Partner has made and will make some elections on our behalf and on behalf of unitholders. In addition, the Tax Matters Partner can extend the statute of limitations for assessment of tax deficiencies against unitholders for items in our returns. The Tax Matters Partner may bind a unitholder with less than a 1% profits interest in us to a settlement with the IRS unless that unitholder elects, by filing a statement with the IRS, not to give that authority to the Tax Matters Partner. The Tax Matters Partner may seek judicial review, by which all the unitholders are bound, of a final partnership administrative adjustment and, if the Tax Matters Partner fails to seek judicial review, judicial review may be sought by any unitholder having at least a 1% interest in profits or by any group of unitholders having in the aggregate at least a 5% interest in profits. However, only one action for judicial review will go forward, and each unitholder with an interest in the outcome may participate.

A unitholder must file a statement with the IRS identifying the treatment of any item on his federal income tax return that is not consistent with the treatment of the item on our return. Intentional or negligent disregard of this consistency requirement may subject a unitholder to substantial penalties.

Additional Withholding Requirements

Withholding taxes may apply to certain types of payments made to "foreign financial institutions" (as specially defined in the Internal Revenue Code) and certain other non-U.S. entities. Specifically, a 30% withholding tax may be imposed on interest, dividends and other fixed or determinable annual or periodical gains, profits and income from sources within the United States ("FDAP Income"), or gross proceeds from the sale or other disposition of any property of a type which can produce interest or dividends from sources within the United States ("Gross Proceeds") paid to a foreign financial institution or to a "non-financial foreign entity" (as specially defined in the Internal Revenue Code), unless (i) the foreign financial institution undertakes certain diligence and reporting, (ii) the non-financial foreign entity either certifies it does not have any substantial U.S. owners or furnishes identifying information regarding each substantial U.S. owner or (iii) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules. If the payee is a foreign financial institution and is subject to the diligence and reporting requirements in clause (i) above, it must enter into an agreement with the U.S. Treasury requiring, among other things, that it undertake to identify accounts held by certain U.S. persons or U.S.-owned foreign entities, annually report certain information about such accounts, and withhold 30% on payments to noncompliant foreign financial institutions and certain other account holders.

These rules generally will apply to payments of FDAP Income made on or after July 1, 2014 and to payments of relevant Gross Proceeds made on or after January 1, 2017. Thus, to the extent we have

Table of Contents

FDAP Income or Gross Proceeds after these dates that are not treated as effectively connected with a U.S. trade or business (please read "—Tax-Exempt Organizations and Other Investors"), unitholders who are foreign financial institutions or certain other non-US entities may be subject to withholding on distributions they receive from us, or their distributive share of our income, pursuant to the rules described above.

Prospective investors should consult their own tax advisors regarding the potential application of these withholding provisions to their investment in our common units.

Nominee Reporting

Persons who hold an interest in us as a nominee for another person are required to furnish to us:

•

the name, address and taxpayer identification number of the beneficial owner and the nominee;

•

whether the beneficial owner is:

•: a person that is not a U.S. person;
•: a foreign government, an international organization or any wholly owned agency or instrumentality of either of the foregoing; or
•: a tax-exempt entity;

•

the amount and description of units held, acquired or transferred for the beneficial owner; and

•

specific information including the dates of acquisitions and transfers, means of acquisitions and transfers, and acquisition cost for purchases, as well as the amount of net proceeds from dispositions.

Brokers and financial institutions are required to furnish additional information, including whether they are U.S. persons and specific information on units they acquire, hold or transfer for their own account. A penalty of $100 per failure, up to a maximum of $1,500,000 per calendar year, is imposed by the Internal Revenue Code for failure to report that information to us. The nominee is required to supply the beneficial owner of the units with the information furnished to us.

Accuracy-Related Penalties

An additional tax equal to 20% of the amount of any portion of an underpayment of tax that is attributable to one or more specified causes, including negligence or disregard of rules or regulations, substantial understatements of income tax and substantial valuation misstatements, is imposed by the Internal Revenue Code. No penalty will be imposed, however, for any portion of an underpayment if it is shown that there was a reasonable cause for that portion and that the taxpayer acted in good faith regarding that portion.

For individuals, a substantial understatement of income tax in any taxable year exists if the amount of the understatement exceeds the greater of 10% of the tax required to be shown on the return for the taxable year or $5,000 ($10,000 for most corporations). The amount of any understatement subject to penalty generally is reduced if any portion is attributable to a position adopted on the return:

•: for which there is, or was, "substantial authority"; or
•: as to which there is a reasonable basis and the pertinent facts of that position are disclosed on the return.

If any item of income, gain, loss or deduction included in the distributive shares of unitholders might result in that kind of an "understatement" of income for which no "substantial authority" exists, we must disclose the pertinent facts on our return. In addition, we will make a reasonable effort to

Table of Contents

furnish sufficient information for unitholders to make adequate disclosure on their returns and to take other actions as may be appropriate to permit unitholders to avoid liability for this penalty. More stringent rules apply to "tax shelters," which we do not believe includes us, or any of our investments, plans or arrangements.

A substantial valuation misstatement exists if (a) the value of any property, or the adjusted basis of any property, claimed on a tax return is 150% or more of the amount determined to be the correct amount of the valuation or adjusted basis, (b) the price for any property or services (or for the use of property) claimed on any such return with respect to any transaction between persons described in Internal Revenue Code Section 482 is 200% or more (or 50% or less) of the amount determined under Section 482 to be the correct amount of such price, or (c) the net Internal Revenue Code Section 482 transfer price adjustment for the taxable year exceeds the lesser of $5 million or 10% of the taxpayer's gross receipts. No penalty is imposed unless the portion of the underpayment attributable to a substantial valuation misstatement exceeds $5,000 ($10,000 for most corporations). If the valuation claimed on a return is 200% or more than the correct valuation or certain other thresholds are met, the penalty imposed increases to 40%. We do not anticipate making any valuation misstatements.

In addition, the 20% accuracy-related penalty also applies to any portion of an underpayment of tax that is attributable to transactions lacking economic substance. To the extent that such transactions are not disclosed, the penalty imposed is increased to 40%. Additionally, there is no reasonable cause defense to the imposition of this penalty to such transactions.

Reportable Transactions

If we were to engage in a "reportable transaction," we (and possibly you and others) would be required to make a detailed disclosure of the transaction to the IRS. A transaction may be a reportable transaction based upon any of several factors, including the fact that it is a type of tax avoidance transaction publicly identified by the IRS as a "listed transaction" or that it produces certain kinds of losses for partnerships, individuals, S corporations, and trusts in excess of $2 million in any single year, or $4 million in any combination of six successive tax years. Our participation in a reportable transaction could increase the likelihood that our federal income tax information return (and possibly your tax return) would be audited by the IRS. Please read "—Information Returns and Audit Procedures."

Moreover, if we were to participate in a reportable transaction with a significant purpose to avoid or evade tax, or in any listed transaction, you may be subject to the following additional consequences:

•: accuracy-related penalties with a broader scope, significantly narrower exceptions, and potentially greater amounts than described above at "—Accuracy-Related Penalties";
•: for those persons otherwise entitled to deduct interest on federal tax deficiencies, nondeductibility of interest on any resulting tax liability; and
•: in the case of a listed transaction, an extended statute of limitations.

We do not expect to engage in any "reportable transactions."

Recent Legislative Developments

Table of Contents

partnership for federal income tax purposes. Please read "—Partnership Status." We are unable to predict whether any such changes will ultimately be enacted. However, it is possible that a change in law could affect us, and any such changes could negatively impact the value of an investment in our common units.

State, Local, Foreign and Other Tax Considerations

In addition to federal income taxes, you likely will be subject to other taxes, such as state, local and foreign income taxes, unincorporated business taxes, and estate, inheritance or intangible taxes that may be imposed by the various jurisdictions in which we do business or own property or in which you are a resident. Although an analysis of those various taxes is not presented here, each prospective unitholder should consider their potential impact on his investment in us. We currently own property or do business in Colorado, North Dakota, Texas and West Virginia. Several of these states impose a personal income tax on individuals; certain of these states also impose an income tax on corporations and other entities. We may also own property or do business in other jurisdictions in the future. Although you may not be required to file a return and pay taxes in some jurisdictions because your income from that jurisdiction falls below the filing and payment requirement, you will be required to file income tax returns and to pay income taxes in many of these jurisdictions in which we do business or own property and may be subject to penalties for failure to comply with those requirements. In some jurisdictions, tax losses may not produce a tax benefit in the year incurred and may not be available to offset income in subsequent taxable years. Some of the jurisdictions may require us, or we may elect, to withhold a percentage of income from amounts to be distributed to a unitholder who is not a resident of the jurisdiction. Withholding, the amount of which may be greater or less than a particular unitholder's income tax liability to the jurisdiction, generally does not relieve a nonresident unitholder from the obligation to file an income tax return. Amounts withheld will be treated as if distributed to unitholders for purposes of determining the amounts distributed by us. Please read "—Tax Consequences of Unit Ownership—Entity-Level Collections." Based on current law and our estimate of our future operations, our general partner anticipates that any amounts required to be withheld will not be material.

It is the responsibility of each unitholder to investigate the legal and tax consequences, under the laws of pertinent states, localities and foreign jurisdictions, of his investment in us. Accordingly, each prospective unitholder is urged to consult his own tax counsel or other advisor with regard to those matters. Further, it is the responsibility of each unitholder to file all state, local and foreign, as well as U.S. federal tax returns, that may be required of him. Latham & Watkins LLP has not rendered an opinion on the state, local or foreign tax consequences of an investment in us.

TAX CONSEQUENCES OF OWNERSHIP OF DEBT SECURITIES

A description of the material federal income tax consequences of the acquisition, ownership and disposition of debt securities will be set forth in a prospectus supplement relating to the offering of debt securities.

Table of Contents

SELLING UNITHOLDER

This prospectus covers the offering for resale from time to time, in one or more offerings, of common units owned by a selling unitholder. As of October 25, 2013, the selling unitholder owns 14,691,397 of our common units and all of the ownership interests in our general partner, which owns our incentive distribution rights, all of which were issued in connection with our initial public offering.

The selling unitholder may sell all, some or none of the common units covered by this prospectus. Please read "Plan of Distribution." We will bear all costs, fees and expenses incurred in connection with the registration of the Units offered by this prospectus, other than brokerage commissions and similar selling expenses, if any, attributable to the sale of common units, which will be borne by the selling unitholder.

The selling unitholder is neither a broker-dealer registered under Section 15 of the Exchange Act, nor an affiliate of a broker-dealer registered under Section 15 of the Exchange Act.

The following table sets forth information relating to the selling unitholder as of October 25, 2013 based on information supplied to us by the selling unitholder on or prior to that date. We have not sought to verify such information. Information concerning the selling unitholder may change over time, including by addition of additional selling unitholders, and if necessary, we will supplement this prospectus accordingly. The selling unitholder may hold or acquire at any time common units in addition to those offered by this prospectus and may have acquired additional common units since the date on which the information reflected herein was provided to us. Additionally, the selling unitholder may have sold, transferred or otherwise disposed of some or all of the units listed below in exempt or non-exempt transactions since the date on which the information was provided to us and may in the future sell, transfer or otherwise dispose of some or all of their common units in private placement transactions exempt from or not subject to the registration requirements of the Securities Act.

	Common units beneficially owned prior to the offering					Common units being offered(1)		Total units beneficially owned after the offering(1)

Name of Selling Unitholder	Number		Percentage(2)			Number		Number		Percentage
Summit Midstream Partners Holdings, LLC		14,691,397		50.5	%		14,691,397		—		—

(1): Assumes the sale of all common units held by the selling unitholder.
(2): Based on 29,079,866 common units outstanding as of October 25, 2013.

Any determination with respect to the disposition of common units by Summit Midstream Partners Holdings, LLC pursuant to this prospectus will be made by the board of managers of Summit Midstream Partners, LLC, the sole member of Summit Midstream Partners Holdings, LLC. As of October 29, 2013, the members of the board of managers of Summit Midstream Partners, LLC were Steven J. Newby, Thomas K. Lane, Jeffrey R. Spinner and Curtis A. Morgan.

Each time the selling unitholder sells any common units offered by this prospectus, the selling unitholder is required to provide you with this prospectus and the related prospectus supplement containing specific information about such selling unitholder and the terms of the common units being offered in the manner required by the Securities Act. The prospectus supplement will set forth the following information with respect to the selling unitholder:

•: the name of the selling unitholder;
•: the nature of any position, office or other material relationship that the selling unitholder has had within the last three years with us, our predecessors or any of our affiliates;
•: the number of common units owned by the selling unitholder prior to the offering;

Table of Contents

•: the amount of common units to be offered for the selling unitholder's account; and
•: the amount and (if one percent or more) the percentage of common units to be beneficially owned by the selling unitholder after the completion of the offering.

No offer or sale may occur unless the registration statement that includes this prospectus has been declared effective by the SEC and remains effective at the time the selling unitholder offers or sells common units. We are required, under certain circumstances, to update, supplement or amend this prospectus to reflect material developments in our business, financial position and results of operations and may do so by an amendment to this prospectus, a prospectus supplement or a future filing with the SEC incorporated by reference in this prospectus.

The selling unitholder, which is an affiliate of Summit Midstream Partners, LP, is an "underwriter" within the meaning of the Securities Act, and, as a result, will be deemed to be making a primary offering of securities on our behalf.

Table of Contents

INVESTMENT IN SUMMIT MIDSTREAM PARTNERS, LP BY EMPLOYEE BENEFIT PLANS

An investment in us by an employee benefit plan is subject to additional considerations because the investments of these plans are subject to the fiduciary responsibility and prohibited transaction provisions of ERISA and the restrictions imposed by Section 4975 of the Internal Revenue Code and provisions under any federal, state, local, non-U.S. or other laws or regulations that are similar to such provisions of the Internal Revenue Code or ERISA (collectively, "Similar Laws"). For these purposes the term "employee benefit plan" includes, but is not limited to, qualified pension, profit-sharing and stock bonus plans, Keogh plans, simplified employee pension plans and tax deferred annuities or IRAs or annuities established or maintained by an employer or employee organization, and entities whose underlying assets are considered to include "plan assets" of such plans, accounts and arrangements, collectively, "Employee Benefit Plans." Among other things, consideration should be given to:

•: whether the investment is prudent under Section 404(a)(1)(B) of ERISA and any other applicable Similar Laws;
•: whether in making the investment, the plan will satisfy the diversification requirements of Section 404(a)(1)(C) of ERISA and any other applicable Similar Laws;
•: whether the investment will result in recognition of unrelated business taxable income by the plan and, if so, the potential after-tax investment return. Please read "Material U.S. Federal Tax Consequences—Tax-Exempt Organizations and Other Investors"; and
•: whether making such an investment will comply with the delegation of control and prohibited transaction provisions of ERISA, the Internal Revenue Code and any other applicable Similar Laws.

The person with investment discretion with respect to the assets of an Employee Benefit Plan, often called a fiduciary, should determine whether an investment in us is authorized by the appropriate governing instrument and is a proper investment for the plan.

Section 406 of ERISA and Section 4975 of the Internal Revenue Code prohibit Employee Benefit Plans from engaging, either directly or indirectly, in specified transactions involving "plan assets" with parties that, with respect to the Employee Benefit Plan, are "parties in interest" under ERISA or "disqualified persons" under the Internal Revenue Code unless an exemption is available. A party in interest or disqualified person who engages in a non-exempt prohibited transaction may be subject to excise taxes and other penalties and liabilities under ERISA and the Internal Revenue Code. In addition, the fiduciary of the ERISA plan that engaged in such a non-exempt prohibited transaction may be subject to penalties and liabilities under ERISA and the Internal Revenue Code.

In addition to considering whether the purchase of common units is a prohibited transaction, a fiduciary should consider whether the Employee Benefit Plan will, by investing in us, be deemed to be an undivided interest in our assets, with the result that the general partner would also be a fiduciary of such Employee Benefit Plan and our operations would be subject to the regulatory restrictions of ERISA, including its prohibited transaction rules, as well as the prohibited transaction rules of the Internal Revenue Code, ERISA and any other applicable Similar Laws.

Table of Contents

In addition to considering whether the purchase of common units is a prohibited transaction, a fiduciary should consider whether the Employee Benefit Plan will, by investing in us, be deemed to own an undivided interest in our assets, with the result that our general partner would also be a fiduciary of such Employee Benefit Plan and our operations would be subject to the regulatory restrictions of ERISA, including its prohibited transaction rules, as well as the prohibited transaction rules of the Internal Revenue Code, ERISA and any other applicable Similar Laws.

The Department of Labor regulations and Section 3(42) of ERISA provide guidance with respect to whether, in certain circumstances, the assets of an entity in which Employee Benefit Plans acquire equity interests would be deemed "plan assets." Under these regulations, an entity's assets would not be considered to be "plan assets" if, among other things:

(a) the equity interests acquired by the Employee Benefit Plan are publicly offered securities—i.e., the equity interests are widely held by 100 or more investors independent of the issuer and each other, are "freely transferable" (as defined in the regulations) and are registered under certain provisions of the federal securities laws;

(b) the entity is an "operating company,"—i.e., it is primarily engaged in the production or sale of a product or service, other than the investment of capital, either directly or through a majority-owned subsidiary or subsidiaries; or

(c) there is no significant investment by "benefit plan investors," which is defined to mean that less than 25% of the value of each class of equity interest, disregarding certain interests held by our general partner, its affiliates and certain other persons, is held generally by Employee Benefit Plans.

Our assets should not be considered "plan assets" under these regulations because it is expected that the investment will satisfy the requirements in (a) and (b) above.

In light of the serious penalties imposed on persons who engage in prohibited transactions or other violations, plan fiduciaries contemplating a purchase of common units should consult with their own counsel regarding the consequences under ERISA, the Internal Revenue Code and other Similar Laws.

Table of Contents

PLAN OF DISTRIBUTION

The securities offered pursuant to this prospectus and any accompanying prospectus supplement may be sold in any of the following ways:

•: directly to one or more purchasers;
•: through agents;
•: through underwriters, brokers or dealers; or
•: through a combination of any of these methods of sale.

In addition, we or the selling unitholder may from time to time sell securities in compliance with Rule 144 under the Securities Act, if available, or pursuant to other available exemptions from the registration requirements under the Securities Act, rather than pursuant to this prospectus. In such event, we and the selling unitholder, if applicable, may be required by the securities laws of certain states to offer and sell securities only through registered or licensed brokers or dealers.

We will fix a price or prices of our securities at:

•: market prices prevailing at the time of any sale under this registration statement;
•: prices related to market prices; or
•: negotiated prices.

We may change the price of the securities offered from time to time.

The selling unitholder may act independently of us in making decisions with respect to the timing, manner and size of each of its sales. The selling unitholder may make sales of the common units on the NYSE or otherwise at prices and under terms prevailing at the time of the sale, or at prices related to the then-current market price, at fixed prices, or in privately negotiated transactions.

Offers to purchase securities may be solicited directly by us and the sale thereof may be made by us directly to institutional investors or others. In this case, no underwriters or agents would be involved. We may use electronic media, including the Internet, to sell offered securities directly.

We, or agents designated by us, may directly solicit, from time to time, offers to purchase the securities. Any such agent may be deemed to be an underwriter as that term is defined in the Securities Act. We will name any agents involved in the offer or sale of the securities and describe any commissions payable by us to these agents in the prospectus supplement. Unless otherwise indicated in the prospectus supplement, these agents will be acting on a best efforts basis for the period of their appointment. The agents may be entitled under agreements which may be entered into with us to indemnification by us against specific civil liabilities, including liabilities under the Securities Act. The agents may also be our customers or may engage in transactions with or perform services for us in the ordinary course of business.

If we or the selling unitholder utilize any underwriters in the sale of the securities in respect of which this prospectus is delivered, we and, if applicable, the selling unitholder, will enter into an underwriting agreement with those underwriters at the time of sale to them. We will set forth the names of these underwriters and the terms of the transaction in the prospectus supplement, which will be used by the underwriters to make resales of the securities in respect of which this prospectus is delivered to the public. We or the selling unitholder may indemnify the underwriters under the relevant underwriting agreement against specific liabilities, including liabilities under the Securities Act. The underwriters or their affiliates may be customers of, may engage in transactions with and may perform services for us or our affiliates in the ordinary course of business.

Table of Contents

If we or the selling unitholder utilize a dealer in the sale of the securities in respect of which this prospectus is delivered, we or the selling unitholder, as applicable, will sell those securities to the dealer, as principal. The dealer may then resell those securities to the public at varying prices to be determined by the dealer at the time of resale. We or the selling unitholder may indemnify the dealers against specific liabilities, including liabilities under the Securities Act. The dealers or their affiliates may also be our customers or may engage in transactions with, or perform services for us in the ordinary course of business.

We or the selling unitholder may offer the common units covered by this prospectus into an existing trading market on the terms described in the prospectus supplement relating thereto. Underwriters, dealers and agents who participate in any at—the—market offerings will be described in the prospectus supplement relating thereto.

A prospectus and accompanying prospectus supplement in electronic form may be made available on the web sites maintained by the underwriters. The underwriters may agree to allocate a number of securities for sale to their online brokerage account holders. Such allocations of securities for internet distributions will be made on the same basis as other allocations. In addition, securities may be sold by the underwriters to securities dealers who resell securities to online brokerage account holders.

Because the Financial Industry Regulatory Authority, Inc., or FINRA, views our common units as interests in a direct participation program, any offering of common units under the registration statement of which this prospectus forms a part will be made in compliance with Rule 2310 of the FINRA Conduct Rules.

The maximum commission or discount to be received by any FINRA member or independent broker/dealer may not be greater than 8% of the gross proceeds received by us for the sale of any securities being registered pursuant to Rule 415 under the Securities Act.

To the extent required, this prospectus may be amended or supplemented from time to time to describe a specific plan of distribution. The place and time of delivery for the securities in respect of which this prospectus is delivered will be set forth in the accompanying prospectus supplement.

In connection with offerings of securities under the registration statement of which this prospectus forms a part and in compliance with applicable law, underwriters, brokers or dealers may engage in transactions that stabilize or maintain the market price of the securities at levels above those that might otherwise prevail in the open market. Specifically, underwriters, brokers or dealers may over—allot in connection with offerings, creating a short position in the securities for their own accounts. For the purpose of covering a syndicate short position or stabilizing the price of the securities, the underwriters, brokers or dealers may place bids for the securities or effect purchases of the securities in the open market. Finally, the underwriters may impose a penalty whereby selling concessions allowed to syndicate members or other brokers or dealers for distribution of the securities in offerings may be reclaimed by the syndicate if the syndicate repurchases previously distributed securities in transactions to cover short positions, in stabilization transactions or otherwise. These activities may stabilize, maintain or otherwise affect the market price of the securities, which may be higher than the price that might otherwise prevail in the open market, and, if commenced, may be discontinued at any time.

Table of Contents

VALIDITY OF THE SECURITIES

In connection with particular offerings of the securities offered in this prospectus in the future, and if stated in the applicable prospectus supplements, the validity of the issuance of the securities and certain other legal matters will be passed upon for us by Latham & Watkins LLP, Houston, Texas. Legal counsel to any underwriters may pass upon legal matters for such underwriters and will be named in the applicable prospectus supplement.

EXPERTS

The consolidated financial statements of Summit Midstream Partners, LP incorporated in this prospectus by reference from the Partnership's Annual Report on Form 10-K have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report, which is incorporated herein by reference. Such consolidated financial statements have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

The carve-out financial statements of Bison Gas Gathering System of Bear Tracker Energy, LLC (subsequently acquired by Bison Midstream, LLC) as of and for the year ended December 31, 2012 incorporated in this prospectus by reference from the Partnership's Current Report on Form 8-K dated June 5, 2013 have been audited by Anton Collins Mitchell LLP, independent auditors, as stated in their report, which is incorporated herein by reference. Such financial statements have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

Table of Contents

Summit Midstream Partners, LP
6,500,000 Common Units
Representing Limited Partner Interests

Prospectus Supplement

May 7, 2015

Barclays

BofA Merrill Lynch

Goldman, Sachs & Co.

Morgan Stanley

Wells Fargo Securities

Baird

Citigroup

Deutsche Bank Securities

RBC Capital Markets

BB&T Capital Markets

U.S. Capital Advisors