Summit Midstream Partners (SMLP) 10-Q6 Nov 232023 Q3 Quarterly reportFinancial data

Company Profile

Cover Page

Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2023	Oct. 31, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	001-35666
Entity Registrant Name	Summit Midstream Partners, LP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	45-5200503
Entity Address, Address Line One	910 Louisiana Street
Entity Address, Address Line Two	Suite 4200
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77002
City Area Code	832
Local Phone Number	413-4770
Title of 12(b) Security	Common Units
Trading Symbol	SMLP
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		10,376,189
Entity Central Index Key	0001549922
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3

UNAUDITED CONDENSED CONSOLIDATE

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
ASSETS
Cash and cash equivalents	$ 17,097	$ 11,808
Restricted cash	1,798	1,723
Accounts receivable	78,915	75,287
Other current assets	3,159	8,724
Total current assets	100,969	97,542
Property, plant and equipment, net	1,695,459	1,718,754
Intangible assets, net	182,195	198,718
Investment in equity method investees	491,747	506,677
Other noncurrent assets	39,144	38,273
TOTAL ASSETS	2,509,514	2,559,964
LIABILITIES AND CAPITAL
Trade accounts payable	15,496	14,052
Accrued expenses	31,542	20,601
Deferred revenue	11,262	9,054
Ad valorem taxes payable	7,969	10,245
Accrued compensation and employee benefits	5,269	16,319
Accrued interest	39,468	17,355
Accrued environmental remediation	1,365	1,365
Accrued settlement payable	6,659	6,667
Current portion of long-term debt	14,258	10,507
Other current liabilities	9,313	11,724
Total current liabilities	142,601	117,889
Long-term debt, net of issuance costs	1,440,832	1,479,855
Noncurrent deferred revenue	31,280	37,694
Noncurrent accrued environmental remediation	1,701	2,340
Other noncurrent liabilities	34,546	38,784
TOTAL LIABILITIES	1,650,960	1,676,562
Commitments and contingencies (Note 14)
Mezzanine Capital
Subsidiary Series A Preferred Units (93,039 units issued and outstanding at September 30, 2023 and December 31, 2022)	122,564	118,584
Partners' Capital
Series A Preferred Units (65,508 units issued and outstanding at September 30, 2023 and December 31, 2022)	93,769	85,327
Common limited partner capital (10,376,189 and 10,182,763 units issued and outstanding at September 30, 2023 and December 31, 2022, respectively)	642,221	679,491
Total partners' capital	735,990	764,818
TOTAL LIABILITIES AND CAPITAL	$ 2,509,514	$ 2,559,964

UNAUDITED CONDENSED CONSOLIDA_2

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Sep. 30, 2023	Dec. 31, 2022
Partners' Capital
Common limited partner capital (in shares), issued	10,376,189	10,182,763
Common limited partner capital (in shares), outstanding	10,376,189	10,182,763
Subsidiary Series A Preferred Units
Subsidiary Series A preferred unitholders, issued (in shares)	93,039,000
Preferred units, outstanding (in shares)	93,039,000
Series A Preferred Units
Subsidiary Series A preferred unitholders, issued (in shares)	65,508	65,508
Preferred units, outstanding (in shares)	65,508	65,508

UNAUDITED CONDENSED CONSOLIDA_3

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues:
Total revenues	$ 121,193	$ 88,682	$ 331,585	$ 283,871
Costs and expenses:
Cost of natural gas and NGLs	27,110	15,080	77,967	64,162
Operation and maintenance	26,161	21,877	75,291	61,216
General and administrative	11,098	8,550	31,897	31,983
Depreciation and amortization	30,778	28,841	90,734	89,397
Transaction costs	144	1,517	926	1,750
Acquisition integration costs	171	0	2,396	0
Gain on asset sales, net	(40)	(99)	(183)	(409)
Long-lived asset impairments	0	7,016	455	91,644
Total costs and expenses	95,422	82,782	279,483	339,743
Other income (expense), net	(315)	0	747	(4)
Gain on interest rate swaps	2,856	5,527	4,851	16,491
Loss on sale of business	(9)	(85)	(45)	(85)
Interest expense	(34,568)	(24,932)	(103,966)	(73,982)
Loss before income taxes and equity method investment income	(6,265)	(13,590)	(46,311)	(113,452)
Income tax benefit (expense)	(72)	68	180	(307)
Income from equity method investees	10,211	5,734	22,302	14,162
Net income (loss)	3,874	(7,788)	(23,829)	(99,597)
Net income (loss) attributable to Summit Midstream Partners, LP	$ 251	$ (11,066)	$ (32,694)	$ (111,752)
Net loss per limited partner unit:
Common unit - basic (in dollars per share)	$ (0.27)	$ (1.28)	$ (3.99)	$ (9.68)
Common unit - diluted (in dollars per share)	$ (0.27)	$ (1.28)	$ (3.99)	$ (9.68)
Series A Preferred Units \| Subsidiary
Costs and expenses:
Less: Net income attributable to Subsidiary Series A Preferred Units	$ (3,623)	$ (3,278)	$ (8,865)	$ (12,155)
Common Units
Costs and expenses:
Net loss attributable to common limited partners	$ (2,753)	$ (13,028)	$ (41,136)	$ (96,848)
Weighted-average limited partner units outstanding:
Common units - basic (in shares)	10,376	10,168	10,320	10,003
Common units - diluted (in shares)	10,376	10,168	10,320	10,003
Gathering services and related fees
Revenues:
Total revenues	$ 66,035	$ 61,814	$ 180,492	$ 187,465
Natural gas, NGLs and condensate sales
Revenues:
Total revenues	45,120	16,628	130,365	67,364
Other revenues
Revenues:
Total revenues	$ 10,038	$ 10,240	$ 20,728	$ 29,042

UNAUDITED CONDENSED CONSOLIDA_4

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL - USD ($) $ in Thousands	Total	Common Limited Partners Capital	Common Limited Partners Capital Series A Preferred Units
Beginning balance at Dec. 31, 2021	$ 904,363	$ 734,594	$ 169,769
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(5,718)	(7,938)	2,220
Unit-based compensation	1,690	1,690	0
Tax withholdings and associated payments on vested SMLP LTIP awards	(562)	(562)	0
Tax withholdings on 2022 Preferred Exchange Offer	(2,652)	(2,652)	0
Effect of 2022 Preferred Exchange Offer, inclusive of a $20.9 million deemed contribution to common unit holders (Note 10)	0	92,587	(92,587)
Ending balance at Mar. 31, 2022	897,121	817,719	79,402
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(94,968)	(96,856)	1,888
Unit-based compensation	582	582	0
Tax withholdings and associated payments on vested SMLP LTIP awards	(327)	(327)	0
Ending balance at Jun. 30, 2022	802,408	721,118	81,290
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(11,066)	(13,028)	1,962
Unit-based compensation	692	692	0
Tax withholdings and associated payments on vested SMLP LTIP awards	(213)	(213)	0
Ending balance at Sep. 30, 2022	791,821	708,569	83,252
Beginning balance at Dec. 31, 2022	764,818	679,491	85,327
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(15,909)	(18,548)	2,639
Unit-based compensation	1,929	1,929	0
Tax withholdings and associated payments on vested SMLP LTIP awards	(1,136)	(1,136)	0
Ending balance at Mar. 31, 2023	749,702	661,736	87,966
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(17,036)	(19,835)	2,799
Unit-based compensation	1,833	1,833	0
Tax withholdings and associated payments on vested SMLP LTIP awards	(148)	(148)	0
Ending balance at Jun. 30, 2023	734,351	643,586	90,765
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	251	(2,753)	3,004
Unit-based compensation	1,396	1,396	0
Tax withholdings and associated payments on vested SMLP LTIP awards	(8)	(8)	0
Ending balance at Sep. 30, 2023	$ 735,990	$ 642,221	$ 93,769

UNAUDITED CONDENSED CONSOLIDA_5

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL (Parenthetical) $ in Millions	1 Months Ended
	Jan. 31, 2022 USD ($)
Statement of Partners' Capital [Abstract]
Deemed contribution to common unit holders	$ 20.9

UNAUDITED CONDENSED CONSOLIDA_6

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities:
Net loss	$ (23,829)	$ (99,597)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	91,438	90,101
Noncash lease expense	3,804	675
Amortization of debt issuance costs	9,493	6,642
Unit-based and noncash compensation	5,158	2,964
Income from equity method investees	(22,302)	(14,162)
Distributions from equity method investees	40,732	31,764
Gain on asset sales, net	(183)	(409)
Foreign currency gain	(83)	0
Loss on earn-out	420	0
Loss on sale of business	45	85
Unrealized gain on interest rate swaps	(1,074)	(16,870)
Long-lived asset impairment	455	91,644
Changes in operating assets and liabilities:
Accounts receivable	(3,765)	(1,323)
Trade accounts payable	1,525	4,284
Accrued expenses	6,718	(2,040)
Deferred revenue, net	(4,206)	(4,861)
Ad valorem taxes payable	(2,277)	(1,769)
Accrued interest	22,113	21,448
Accrued environmental remediation, net	(639)	(1,730)
Other, net	(12,784)	(10,041)
Net cash provided by operating activities	110,759	96,805
Cash flows from investing activities:
Capital expenditures	(49,863)	(20,955)
Proceeds from asset sale	128	4,646
Investment in Double E equity method investee	(3,500)	(8,444)
Other, net	(2,611)	0
Net cash provided by (used in) investing activities	(55,846)	87,438
Cash flows from financing activities:
Repayments on Permian Transmission Term Loan	(7,804)	(3,442)
Repayments on ABL Facility	(70,000)	(205,000)
Borrowings on ABL Facility	35,000	23,000
Distributions on Subsidiary Series A Preferred Units	(4,884)	(1,628)
Debt issuance costs	(247)	0
Other, net	(1,614)	(2,781)
Net cash used in financing activities	(49,549)	(189,851)
Net change in cash, cash equivalents and restricted cash	5,364	(5,608)
Cash, cash equivalents and restricted cash, beginning of period	13,531	19,572
Cash, cash equivalents and restricted cash, end of period	18,895	13,964
Lane G&P System
Cash flows from investing activities:
Proceeds from sale of business, net of cash sold in transaction	0	75,520
Bison Midstream, LLC
Cash flows from investing activities:
Proceeds from sale of business, net of cash sold in transaction	$ 0	$ 36,671

ORGANIZATION, BUSINESS OPERATIO

ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION	1. ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION Organization. Summit Midstream Partners, LP (including its subsidiaries, collectively “SMLP” or the “Partnership”) is a Delaware limited partnership that was formed in May 2012 and began operations in October 2012. SMLP is a value-oriented limited partnership focused on developing, owning and operating midstream energy infrastructure assets that are strategically located in unconventional resource basins, primarily shale formations, in the continental United States. The Partnership’s business activities are primarily conducted through various operating subsidiaries, each of which is owned or controlled by its wholly owned subsidiary holding company, Summit Holdings, a Delaware limited liability company. Business Operations. The Partnership provides natural gas gathering, compression, treating and processing services as well as crude oil and produced water gathering services pursuant to primarily long-term, fee-based agreements with its customers. The Partnership’s results are primarily driven by the volumes of natural gas that it gathers, compresses, treats and/or processes as well as by the volumes of crude oil and produced water that it gathers. Other than the Partnership’s investments in Double E and Ohio Gathering, all of its business activities are conducted through wholly owned operating subsidiaries. Presentation and Consolidation. The Partnership prepares its condensed consolidated financial statements in accordance with GAAP as established by the FASB and pursuant to the rules and regulations of the SEC pertaining to interim financial information. The unaudited condensed consolidated financial statements contained in this report include all normal and recurring material adjustments that, in the opinion of management, are necessary for a fair statement of the financial position, results of operations and cash flows for the interim periods presented herein. These unaudited condensed consolidated financial statements and notes thereto should be read in conjunction with the consolidated financial statements and related notes that are included in the Partnership’s Annual Report on Form 10-K for the year ended December 31, 2022. The Partnership makes estimates and assumptions that affect the reported amounts of assets and liabilities at the balance sheet dates, including fair value measurements, the reported amounts of revenues and expenses and the disclosure of commitments and contingencies. Although management believes these estimates are reasonable, actual results could differ from its estimates. The unaudited condensed consolidated financial statements contained in this report include the assets, liabilities and results of operations of SMLP and its subsidiaries and all intercompany transactions among the consolidated entities have been eliminated in consolidation. Comprehensive income or loss is the same as net income or loss for all periods presented.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENTLY ISSUED ACCOUNTING STANDARDS APPLICABLE TO THE PARTNERSHIP	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENTLY ISSUED ACCOUNTING STANDARDS APPLICABLE TO THE PARTNERSHIP	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENTLY ISSUED ACCOUNTING STANDARDS APPLICABLE TO THE PARTNERSHIP There have been no changes to the Partnership’s significant accounting policies since December 31, 2022. Accounting standards recently implemented. ASU No. 2020-4 Reference Rate Reform (“ASU 2020-4”). ASU 2020-4 provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform on financial reporting. Contract terms that are modified due to the replacement of a reference rate are not required to be remeasured or reassessed under relevant accounting standards. During the quarter ended June 30, 2023, the Partnership amended the terms of its Permian Transmission Credit Facility and Term Loan and interest rate swaps, which replaced its existing LIBOR based terms with SOFR rate terms. The amendments in ASU 2020-4 are effective as of March 12, 2020 through December 31, 2022. In December 2022, the FASB issued ASU 2022-06, which amended Topic 848 to defer the sunset date to apply the practical expedients until December 31, 2024. The impact of the change in reference rate did not have a material impact on the Partnership’s consolidated financial statements. See Note 8 - Debt, for additional information. New accounting standards not yet implemented. ASU No. 2020-6 Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815–40) (“ASU 2020-6”). ASU 2020-6 simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. The ASU is part of the FASB’s simplification initiative, which aims to reduce unnecessary complexity in GAAP. The ASU’s amendments are effective for fiscal years beginning after December 15, 2023, and interim periods within those fiscal years. The Partnership does not expect the provisions of ASU 2020-6 will have a material impact on its consolidated financial statements and disclosures.

ACQUISTIONS AND DIVESTITURES

ACQUISTIONS AND DIVESTITURES	9 Months Ended
ACQUISTIONS AND DIVESTITURES	Sep. 30, 2023
Business Combination and Asset Acquisition [Abstract]
ACQUISITIONS AND DIVESTITURES	3. ACQUISITIONS AND DIVESTITURES Acquisition of Outrigger DJ. On December 1, 2022, the Partnership completed the acquisition of 100% of the equity interests of Outrigger DJ Midstream LLC (“Outrigger DJ”) from Outrigger Energy II LLC. The acquisition of Outrigger DJ constituted a business combination and was accounted for using the acquisition method of accounting. For tax purposes, the acquisition was accounted for as an acquisition of assets. The acquisition significantly increased the Partnership’s gas processing capacity and footprint in the DJ Basin and diversified its customer base. No material changes were made during nine months ended September 30, 2023 to the provisional purchase accounting measurements initially recorded in December 2022 for the Outrigger DJ acquisition. The provisional measurements are subject to change during the measurement period and such changes could be material. The Partnership continues to assess the fair values of the assets acquired and liabilities assumed. Certain data and assessments necessary to complete the purchase price allocation are still under evaluation, including, but not limited to, the final actualization of accrued liabilities and receivable balances and the valuation of property, plant and equipment and intangible assets. The Partnership will finalize the purchase price allocation during the twelve-month period following the acquisition date, during which time the value of the assets and liabilities may be revised as appropriate. Acquisition of Sterling DJ. On December 1, 2022, the Partnership completed the acquisition of 100% of the equity interests in each of Sterling Energy Investments LLC, Grasslands Energy Marketing LLC and Centennial Water Pipelines LLC (collectively, “Sterling DJ”) from Sterling Investment Holdings LLC. The acquisition of Sterling DJ constituted a business combination and was accounted for using the acquisition method of accounting. For tax purposes, the acquisition was accounted for as an acquisition of assets. The acquisition significantly increased the Partnership’s gas processing capacity and footprint in the DJ Basin and diversified its customer base. No material changes were made during nine months ended September 30, 2023 to the provisional purchase accounting measurements initially recorded in December 2022 for the Sterling DJ acquisition. The provisional measurements are subject to change during the measurement period and such changes could be material. The Partnership continues to assess the fair values of the assets acquired and liabilities assumed. Certain data and assessments necessary to complete the purchase price allocation are still under evaluation, including, but not limited to, the final actualization of accrued liabilities and receivable balances and the valuation of property, plant and equipment and intangible assets. The Partnership will finalize the purchase price allocation during the twelve-month period following the acquisition date, during which time the value of the assets and liabilities may be revised as appropriate. Divestiture of Lane G&P System. On June 30, 2022, the Partnership completed the sale of Summit Permian, which owns the Lane Gathering and Processing System (“Lane G&P System”), and Permian Finance to Longwood Gathering and Disposal Systems, LP (“Longwood”), a wholly owned subsidiary of Matador ͏Resources Company (“Matador”). In connection with the transaction, the Partnership released, to a subsidiary of Matador, and Matador agreed to assume, take or-pay firm capacity on the Double E Pipeline. During the quarterly period ended June 30, 2022, the Partnership recognized an impairment of $84.5 million related to the disposition of the Lane G&P System based on total cash proceeds received of $77.5 million, including $2.0 million of cash sold in the transaction, net assets of $160.8 million, and other costs to sell of $1.2 million. Divestiture of Bison Midstream. On September 19, 2022, the Partnership completed the sale of Bison Midstream, LLC (“Bison Midstream”), its gas gathering system in Burke and Mountrail Counties, North Dakota to a subsidiary of Steel Reef Infrastructure Corp. (“Steel Reef”), an integrated owner and operator of associated gas capture, gathering and processing assets in North Dakota and Saskatchewan. During the quarterly period ended September 30, 2022, the Partnership recognized an impairment of $6.9 million related to the disposition of Bison Midstream based on total cash proceeds received of $36.7 million and net assets of $43.6 million. The cash proceeds were used to reduce amounts outstanding under the ABL Facility. Pro Forma Information (Unaudited) The following unaudited supplemental pro forma condensed results of operations for the three and nine months ended September 30, 2022 present consolidated information as though the acquisition of Sterling DJ and Outrigger DJ, and the divestiture of the Lane G&P System and Bison Midstream had occurred on January 1, 2021. The unaudited supplemental pro forma financial information was derived from the historical consolidated and combined statements of operations of the Partnership, Sterling DJ, and Outrigger DJ and modified to include required conforming adjustments. These unaudited supplemental pro forma results of operations are provided for illustrative purposes only and do not purport to be indicative of the actual results that would have been achieved by the combined entities for the periods presented or that may be achieved in the future. Future results may vary significantly from the results reflected in this unaudited pro forma financial information: Three Months Ended Nine Months Ended 2022 2022 Revenues $ 145,465 $ 394,575 Net loss $ (4,712) $ (13,003)

REVENUE

REVENUE	9 Months Ended
REVENUE	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
REVENUE	4. REVENUE The following table presents estimated revenue expected to be recognized during the remainder of 2023 and over the remaining contract period related to performance obligations that are unsatisfied and are comprised of estimated minimum volume commitments. (In thousands) 2023 2024 2025 2026 2027 Thereafter Gathering services and related fees $ 19,180 $ 67,079 $ 46,803 $ 30,527 $ 9,038 $ 6,042 Revenue by category. In the following tables, revenue is disaggregated by geographic area and major products and services. For more detailed information about reportable segments, see Note 15 – Segment Information. Three Months Ended September 30, 2023 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (In thousands) Reportable Segments: Northeast $ 18,157 $ — $ — $ 18,157 Rockies 18,383 43,967 5,541 67,891 Permian — — 893 893 Piceance 20,658 937 1,569 23,164 Barnett 8,837 216 2,035 11,088 Total reportable segments 66,035 45,120 10,038 121,193 Corporate and other — — — — Total $ 66,035 $ 45,120 $ 10,038 $ 121,193 Three Months Ended September 30, 2022 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (In thousands) Reportable Segments: Northeast $ 13,528 $ — $ — $ 13,528 Rockies 17,209 14,111 4,823 36,143 Permian — — 891 891 Piceance 20,406 1,519 1,581 23,506 Barnett 10,671 998 2,622 14,291 Total reportable segments 61,814 16,628 9,917 88,359 Corporate and other — — 323 323 Total $ 61,814 $ 16,628 $ 10,240 $ 88,682 Nine Months Ended September 30, 2023 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (In thousands) Reportable Segments: Northeast $ 43,717 $ — $ — $ 43,717 Rockies 48,595 125,871 8,885 183,351 Permian — — 2,678 2,678 Piceance 59,791 3,913 4,368 68,072 Barnett 28,389 581 4,835 33,805 Total reportable segments 180,492 130,365 20,766 331,623 Corporate and other — — (38) (38) Total $ 180,492 $ 130,365 $ 20,728 $ 331,585 Nine Months Ended September 30, 2022 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (In thousands) Reportable Segments: Northeast $ 41,104 $ — $ — $ 41,104 Rockies 51,508 42,697 14,708 108,913 Permian 3,669 17,381 3,208 24,258 Piceance 60,458 5,481 4,132 70,071 Barnett 30,726 1,784 6,356 38,866 Total reportable segments 187,465 67,343 28,404 283,212 Corporate and other — 21 638 659 Total $ 187,465 $ 67,364 $ 29,042 $ 283,871

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	9 Months Ended
PROPERTY, PLANT AND EQUIPMENT	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	5. PROPERTY, PLANT AND EQUIPMENT Details on the Partnership’s property, plant and equipment follow. September 30, 2023 December 31, 2022 (In thousands) Gathering and processing systems and related equipment $ 2,315,041 $ 2,262,330 Construction in progress 49,412 59,036 Land and line fill 11,990 11,756 Other 63,976 62,222 Total 2,440,419 2,395,344 Less: accumulated depreciation (744,960) (676,590) Property, plant and equipment, net $ 1,695,459 $ 1,718,754 Depreciation expense and capitalized interest for the Partnership follow. Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 (In thousands) Depreciation expense $ 23,926 $ 22,474 $ 70,130 $ 70,235 Capitalized interest 351 128 790 711

EQUITY METHOD INVESTMENTS

EQUITY METHOD INVESTMENTS	9 Months Ended
EQUITY METHOD INVESTMENTS	Sep. 30, 2023
Equity Method Investments and Joint Ventures [Abstract]
EQUITY METHOD INVESTMENTS	6. EQUITY METHOD INVESTMENTS The Partnership has equity method investments in Double E and Ohio Gathering, the balances of which are included in the Investment in equity method investees caption on the unaudited condensed consolidated balance sheets. Details of the Partnership’s equity method investments follow. September 30, 2023 December 31, 2022 (In thousands) Double E $ 277,094 $ 281,640 Ohio Gathering 214,653 225,037 Total $ 491,747 $ 506,677

DEFERRED REVENUE

DEFERRED REVENUE	9 Months Ended
DEFERRED REVENUE	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
DEFERRED REVENUE	7. DEFERRED REVENUE Certain of the Partnership’s gathering and/or processing agreements provide for monthly or annual MVCs. The amount of the shortfall payment is based on the difference between the actual throughput volume shipped and/or processed for the applicable period and the MVC for the applicable period, multiplied by the applicable gathering or processing fee. Many of the Partnership’s gas gathering agreements contain provisions that can reduce or delay the cash flows that it expects to receive from MVCs to the extent that a customer's actual throughput volumes are above or below its MVC for the applicable contracted measurement period. The balances in deferred revenue as of September 30, 2023 and December 31, 2022 are primarily related to contributions in aid of construction which will be recognized as revenue over the life of the contract. An update of current deferred revenue follows. Total (In thousands) Current deferred revenue, December 31, 2022 $ 9,054 Add: additions 8,940 Less: revenue recognized and other (6,732) Current deferred revenue, September 30, 2023 $ 11,262 An update of noncurrent deferred revenue follows. Total (In thousands) Noncurrent deferred revenue, December 31, 2022 $ 37,694 Add: additions 2,215 Less: reclassification to current deferred revenue and other (8,629) Noncurrent deferred revenue, September 30, 2023 $ 31,280

DEBT

DEBT	9 Months Ended
DEBT	Sep. 30, 2023
Debt Disclosure [Abstract]
DEBT	8. DEBT Debt for the Partnership at September 30, 2023 and December 31, 2022, follows: September 30, 2023 December 31, 2022 (In thousands) ABL Facility : Summit Holdings' asset based credit facility due May 1, 2026 $ 295,000 $ 330,000 Permian Transmission Term Loan : Permian Transmission's variable rate senior secured term loan due January 2028 147,549 155,353 2025 Senior Notes : Summit Holdings' 5.75% senior unsecured notes due April 15, 2025 259,463 259,463 2026 Secured Notes : Summit Holdings' and Finance Corp's 8.50% senior second lien notes due October 15, 2026 785,000 785,000 Less: unamortized debt discount and debt issuance costs (31,922) (39,454) Total debt 1,455,090 1,490,362 Less: current portion of Permian Transmission Credit Facility (14,258) (10,507) Total long-term debt $ 1,440,832 $ 1,479,855 ABL Facility. On November 2, 2021, the Partnership, the Partnership’s subsidiary, Summit Holdings, and the subsidiaries of Summit Holdings party thereto entered into a first-lien, senior secured credit facility, consisting of a $400.0 million asset-based revolving credit facility (the “ABL Facility”), subject to a borrowing base comprised of a percentage of eligible accounts receivable of Summit Holdings and its subsidiaries that guarantee the ABL Facility (collectively, the “ABL Facility Subsidiary Guarantors”) and a percentage of eligible above-ground fixed assets including eligible compression units, processing plants, compression stations and related equipment of Summit Holdings and the ABL Facility Subsidiary Guarantors. As of September 30, 2023, the most recent borrowing base determination of eligible assets totaled $715.2 million, an amount greater than the $400.0 million of aggregate commitments. The ABL Facility will mature on May 1, 2026; provided that, (a) if the outstanding amount of the 2025 Senior Notes (or any permitted refinancing indebtedness in respect thereof that has a final maturity, scheduled amortization or any other scheduled repayment, mandatory prepayment, mandatory redemption or sinking fund obligation prior to the date that is 120 days after the Termination Date (as defined in the ABL Agreement)) on such date equals or exceeds $50.0 million, then the ABL Facility will mature on December 13, 2024 and (b) if both (i) any amount of the 2025 Senior Notes (or any permitted refinancing indebtedness in respect thereof that has a final maturity, scheduled amortization or any other scheduled repayment, mandatory prepayment, mandatory redemption or sinking fund obligation prior to the date that is 120 days after the Termination Date) is outstanding on such date and (ii) Liquidity (as defined in the ABL Agreement) is less than an amount equal to the sum of the then aggregate outstanding principal amount of the 2025 Senior Notes (or any permitted refinancing indebtedness in respect thereof that has a final maturity, scheduled amortization or any other scheduled repayment, mandatory prepayment, mandatory redemption or sinking fund obligation prior to the date that is 120 days after the Termination Date) plus the Threshold Amount (as defined in the ABL Agreement) on such date, then the ABL Facility will mature on January 14, 2025. The Partnership is actively pursuing opportunities to refinance parts or the entirety of its capital structure, including the 2025 Senior Notes. If the outstanding amount of the 2025 Senior Notes is expected to equal or exceed $50.0 million by December 13, 2024, then the Partnership will include a December 13, 2024 maturity of the ABL Facility in its going concern assessment under FASB ASC 205-40, Going Concern , starting with the release of the 2023 annual financial statements. As of September 30, 2023, the applicable margin under the adjusted SOFR borrowings was 3.50%, the interest rate was 8.93% and the available borrowing capacity of the ABL Facility totaled $100.7 million after giving effect to the issuance of $4.3 million in outstanding but undrawn irrevocable standby letters of credit. The ABL Facility requires that Summit Holdings not permit (i) the First Lien Net Leverage Ratio (as defined in the ABL Agreement) as of the last day of any fiscal quarter to be greater than 2.50:1.00, or (ii) the Interest Coverage Ratio (as defined in the ABL Agreement) as of the last day of any fiscal quarter to be less than 2.00:1.00. As of September 30, 2023, the First Lien Net Leverage Ratio was 1.16:1.00 and the Interest Coverage Ratio was 2.21:1.00 As of September 30, 2023, the Partnership was in compliance with the financial covenants of the ABL Facility. Permian Transmission Credit Facility. On March 8, 2021, the Partnership’s unrestricted subsidiary, Permian Transmission, entered into a Credit Agreement which allows for $175.0 million of senior secured credit facilities (the “Permian Transmission Credit Facilities”), including a $160.0 million Term Loan Facility and a $15.0 million working capital facility. The Permian Transmission Credit Facilities can be used to finance Permian Transmission’s capital calls associated with its investment in Double E, debt service and other general corporate purposes. Unexpended proceeds from draws on the Permian Transmission Credit Facilities are classified as restricted cash on the accompanying unaudited condensed consolidated balance sheets. As of September 30, 2023, the applicable margin under adjusted SOFR borrowings was 2.475%, the average interest rate was 7.69% and the unused portion of the Permian Transmission Credit Facilities totaled $4.5 million, subject to a commitment fee of 0.7% after giving effect to the issuance of $10.5 million in outstanding but undrawn irrevocable standby letters of credit. Summit Permian Transmission, LLC entered into interest rate hedges with notional amounts representing approximately 90% of the Permian Term Loan facility. As of September 30, 2023, the interest rate hedges were at a fixed SOFR rate of 1.23%. As of September 30, 2023, the Partnership was in compliance with the financial covenants of the Permian Transmission Credit Facilities. Permian Transmission Term Loan. In accordance with the terms of the Permian Transmission Credit Facilities, in January 2022, the Permian Term Loan Facility was converted into a Term Loan (the “Permian Transmission Term Loan”). The Permian Transmission Term Loan is due January 2028. As of September 30, 2023, the applicable margin under adjusted SOFR borrowings was 2.475% and the average interest rate was 7.69%. As of September 30, 2023, the Partnership was in compliance with the financial covenants governing the Permian Transmission Term Loan. In accordance with the terms of the Permian Transmission Term Loan, Permian Transmission is required to make mandatory principal repayments. Below is a summary of the remaining mandatory principal repayments as of September 30, 2023: (In thousands) Total 2023 2024 2025 2026 2027 Thereafter Amortizing principal repayments $ 147,549 $ 2,703 $ 15,524 $ 16,580 $ 16,967 $ 17,769 $ 78,006 2026 Secured Notes. In 2021, the Co-Issuers issued $700.0 million of 8.500% Senior Secured Second Lien Notes due 2026 to eligible purchasers pursuant to Rule 144A and Regulation S of the Securities Act, at a price of 98.5% of their face value. Additionally, in November 2022, in connection with the 2022 DJ Acquisitions, the Co-Issuers issued an additional $85.0 million of 2026 Secured Notes at a price of 99.26% of their face value. The Co-Issuers pay interest on the 2026 Secured Notes semi-annually in cash in arrears on April 15 and October 15 of each year, and will be jointly and severally guaranteed, on a senior second-priority secured basis (subject to permitted liens), by the Partnership and each restricted subsidiary of the Partnership (other than the Co-Issuers) that is an obligor under the ABL Agreement, or under the Co-Issuers’ 2025 Senior Notes on the issue date of the 2026 Secured Notes. The 2026 Secured Notes are effectively subordinated to any of our or the guarantors’ current and future secured first lien indebtedness, including indebtedness incurred under the ABL Facility, to the extent of the value of the collateral securing such indebtedness, and our and the guarantors’ current and future debt that is secured by liens on assets other than the collateral, to the extent of the value of such assets. The 2026 Secured Notes are structurally subordinated to all indebtedness and other liabilities of our subsidiaries that do not guarantee the 2026 Secured Notes. The 2026 Secured Notes are effectively equal to our and the guarantors’ obligations under any future second lien indebtedness and effectively senior to all of our future junior lien indebtedness and existing and future unsecured indebtedness, including our outstanding senior unsecured notes, to the extent of the value of the collateral, and senior to any of our future subordinated indebtedness. The 2026 Secured Notes will mature on October 15, 2026. Before October 15, 2023, the Co-Issuers could have redeemed the 2026 Secured Notes, in whole or in part, at a price equal to 100% of their principal amount, plus a make-whole premium, together with accrued and unpaid interest to, but not including the redemption date. On and after October 15, 2023, the Co-Issuers may redeem all or part of the 2026 Secured Notes at redemption prices (expressed as percentages of principal amount) equal to: (a) 104.250% for the twelve-month period beginning October 15, 2023; (b) 102.125% for the twelve-month period beginning October 15, 2024; and (c) 100.000% for the twelve-month period beginning on October 15, 2025 and at any time thereafter, in each case plus accrued and unpaid interest, if any, to, but not including, the redemption date. As of September 30, 2023, the Partnership was in compliance with the financial covenants governing its 2026 Secured Notes. Starting in the first quarter of 2023 with respect to the fiscal year ended 2022, and continuing annually through the fiscal year ended 2025, the Partnership is required under the terms of the 2026 Secured Notes Indenture to, if it has Excess Cash Flow (as defined in the 2026 Secured Notes Indenture), and subject to its ability to make such an offer under the ABL Facility, offer to purchase an amount of the 2026 Secured Notes, at 100% of the principal amount plus accrued and unpaid interest, equal to 100% of the Excess Cash Flow generated in the prior year. Excess Cash Flow is generally defined as consolidated cash flow minus the sum of capital expenditures and cash payments in respect of permitted investments and permitted restricted payments. Generally, if the Partnership does not offer to purchase designated annual amounts of its 2026 Secured Notes or reduce its first lien capacity under the 2026 Secured Notes Indenture per annum from 2023 through 2025, the interest rate on the 2026 Secured Notes is subject to certain rate escalations. Per the terms of the 2026 Secured Notes Indenture, the designated amounts are to offer to purchase $50.0 million aggregate principal amount of the 2026 Secured Notes by April 1, 2023, otherwise the interest rate shall automatically increase by 50 basis points per annum; $100.0 million aggregate principal amount of the 2026 Secured Notes by April 1, 2024, otherwise the interest rate shall automatically increase by 100 basis points per annum (minus any amount previously increased); and $200.0 million aggregate principal amount of the 2026 Secured Notes by April 1, 2025, otherwise the interest rate shall automatically increase by 200 basis points per annum (minus any amount previously increased). Based on the amount of the Partnership’s Excess Cash Flow for the fiscal year ended 2022, the Partnership was not able to make offers to purchase in the designated amount for the fiscal year ended 2022; as a result, the interest rate on the 2026 Secured Notes increased 50 basis points to 9.00% effective with the first payment on April 1, 2023. To the extent the Partnership makes an offer to purchase, and the offer is not fully accepted by the holders of the 2026 Secured Notes, the Partnership may use any remaining amount not accepted for any purpose not prohibited by the 2026 Secured Notes Indenture or the ABL Facility. 2025 Senior Notes. In February 2017, the Co-Issuers co-issued the 2025 Senior Notes. The Partnership pays interest on the 2025 Senior Notes semi-annually in cash in arrears on April 15 and October 15 of each year. The 2025 Senior Notes are senior, unsecured obligations and rank equally in right of payment with all of the Partnership’s existing and future senior obligations. The 2025 Senior Notes are effectively subordinated in right of payment to all of the Partnership’s secured indebtedness, to the extent of the collateral securing such indebtedness. The Co-Issuers have the right to redeem all or part of the 2025 Senior Notes at a redemption price of 100.00%, plus accrued and unpaid interest, if any, to, but not including the redemption date. As of September 30, 2023, the Partnership was in compliance with the financial covenants governing its 2025 Senior Notes.

FINANCIAL INSTRUMENTS

FINANCIAL INSTRUMENTS	9 Months Ended
FINANCIAL INSTRUMENTS	Sep. 30, 2023
Fair Value Disclosures [Abstract]
FINANCIAL INSTRUMENTS	9. FINANCIAL INSTRUMENTS Fair Value. A summary of the estimated fair value of our debt financial instruments follows. September 30, 2023 December 31, 2022 Carrying Value (1) Estimated Carrying Value (1) Estimated (In thousands) 2025 Senior Notes $ 259,463 $ 242,814 $ 259,463 $ 221,733 2026 Secured Notes 785,000 754,581 785,000 750,983 ________ (1) Excludes applicable unamortized debt issuance costs and debt discounts. The carrying values on the balance sheets of the ABL Facility and Permian Transmission Term Loan represents their fair value due to their floating interest rates. The fair values of the 2026 Secured Notes and 2025 Senior Notes are based on an average of nonbinding broker quotes as of September 30, 2023 and December 31, 2022. The use of different market assumptions or valuation methodologies may have a material effect on their estimated fair value. Deferred earn-out. As a result of the acquisition of Sterling DJ, the Partnership assumed a deferred earn-out liability, which is remeasured each reporting period. As of September 30, 2023 and December 31, 2022, the estimated fair value of the deferred earn-out liability was $4.9 million and $5.2 million, respectively, and was estimated using a discounted cash flow technique based on estimated future fresh water deliveries and appropriate discount rates. Given the unobservable nature of the inputs, the fair value measurement of the deferred earn-out is deemed to use Level 3 inputs. The deferred earn-out sits within Centennial Water Pipelines LLC, one of the Partnership’s unrestricted subsidiaries. Interest Rate Swaps. In connection with the Permian Transmission Term Loan, formerly the Permian Transmission Credit Facility, the Partnership entered into amortizing interest rate swap agreements. As of September 30, 2023 and December 31, 2022, the outstanding notional amounts of interest rate swaps were $132.8 million and $139.8 million, respectively. These interest rate swaps manage exposure to variability in expected cash flows attributable to interest rate risk. Interest rate swaps convert a portion of the Partnership’s variable rate debt to fixed rate debt. The Partnership chooses counterparties for its derivative instruments that it believes are creditworthy at the time the transactions are entered into, and the Partnership actively monitors the creditworthiness where applicable. However, there can be no assurance that a counterparty will be able to meet its obligations to the Partnership. The Partnership presents its derivative positions on a gross basis and does not net the asset and liability positions. During the quarter ended June 30, 2023, the Partnership amended its interest rate swap agreements to, among other things, replace its LIBOR based terms with a SOFR rate terms.

PARTNERS' CAPITAL AND MEZZANINE

PARTNERS' CAPITAL AND MEZZANINE CAPITAL	9 Months Ended
PARTNERS' CAPITAL AND MEZZANINE CAPITAL	Sep. 30, 2023
Equity [Abstract]
PARTNERS' CAPITAL AND MEZZANINE CAPITAL	10. PARTNERS' CAPITAL AND MEZZANINE CAPITAL Common Units. An update of the number of issued and outstanding common limited partner units is as follows for the period from December 31, 2022 to September 30, 2023. Common Units Units, December 31, 2022 10,182,763 Common units issued for SMLP LTIP, net 193,426 Units, September 30, 2023 10,376,189 Series A Preferred Units. As of September 30, 2023, the Partnership had 65,508 Series A Preferred Units outstanding and $29.9 million of accrued and unpaid distributions on its Series A Preferred Units. Series A Preferred Unit Exchange Offers. In January 2022, the Partnership completed an offer to exchange its Series A Preferred Units for newly issued common units (the “2022 Preferred Exchange Offer”), whereby it issued 2,853,875 SMLP common units, net of units withheld for withholding taxes, in exchange for 77,939 Series A Preferred Units. As a result of the transaction, the Partnership recognized a deemed contribution of $20.9 million from the Series A Preferred Unit holders to the common unit holders. Subsidiary Series A Preferred Units. The Partnership records its Subsidiary Series A Preferred Units at fair value upon issuance, net of issuance costs, and subsequently records an effective interest method accretion amount each reporting period to accrete the carrying value to a most probable redemption value that is based on a predetermined internal rate of return measure. If the Partnership elects to make payment-in-kind (“PIK”) distributions to holders of its Subsidiary Series A Preferred Units, these PIK distributions increase the liquidation preference on each Subsidiary Series A Preferred Unit. Net Income (Loss) attributable to our common units includes adjustments for PIK distributions and redemption accretion. As of September 30, 2023, the Partnership had 93,039 Subsidiary Series A Preferred Units issued and outstanding. If the Subsidiary Series A Preferred Units were redeemed on September 30, 2023, the redemption amount would be $123.9 million when considering the applicable multiple of invested capital metric and make-whole amount provisions contained in the Subsidiary Series A Preferred Unit agreement. The following table shows the change in our Subsidiary Series A Preferred Unit balance from January 1, 2023 to September 30, 2023, net of $1.8 million and $2.2 million of unamortized issuance costs at September 30, 2023 and December 31, 2022, respectively: (In thousands) Balance at December 31, 2022 $ 118,584 Redemption accretion, net of issuance cost amortization 8,865 Cash distribution (includes a $1.6 million distribution payable as of September 30, 2023) (4,885) Balance at September 30, 2023 $ 122,564 Cash Distribution Policy. The Partnership suspended its cash distributions to holders of its common units, commencing with respect to the quarter ended March 31, 2020. Upon the resumption of distributions, the Partnership Agreement requires that it distribute all available cash, subject to reserves established by its General Partner, within 45 days after the end of each quarter

EARNINGS PER UNIT

EARNINGS PER UNIT	9 Months Ended
EARNINGS PER UNIT	Sep. 30, 2023
Earnings Per Share [Abstract]
EARNINGS PER UNIT	11. EARNINGS PER UNIT The following table details the components of EPU. Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 (In thousands, except per-unit amounts) Numerator for basic and diluted EPU: Allocation of net loss among limited partner interests: Net income (loss) $ 3,874 $ (7,788) $ (23,829) $ (99,597) Less: Net income attributable to Subsidiary Series A Preferred Units (3,623) (3,278) (8,865) (12,155) Net income (loss) attributable to Summit Midstream Partners, LP $ 251 $ (11,066) $ (32,694) (111,752) Less: Net income attributable to Series A Preferred Units $ (3,004) $ (1,962) $ (8,442) (6,070) Add: Deemed capital contribution from 2022 Preferred Exchange Offer — — — 20,974 Net loss attributable to common limited partners $ (2,753) $ (13,028) $ (41,136) $ (96,848) Denominator for basic and diluted EPU: Weighted-average common units outstanding – basic 10,376 10,168 10,320 10,003 Effect of nonvested phantom units — — — — Weighted-average common units outstanding – diluted 10,376 10,168 10,320 10,003 Net income per limited partner unit: Common unit – basic $ (0.27) $ (1.28) $ (3.99) $ (9.68) Common unit – diluted $ (0.27) $ (1.28) $ (3.99) $ (9.68) Nonvested anti-dilutive phantom units excluded from the calculation of diluted EPU 160 — 221 —

SUPPLEMENTAL CASH FLOW INFORMAT

SUPPLEMENTAL CASH FLOW INFORMATION	9 Months Ended
SUPPLEMENTAL CASH FLOW INFORMATION	Sep. 30, 2023
Supplemental Cash Flow Elements [Abstract]
SUPPLEMENTAL CASH FLOW INFORMATION	12. SUPPLEMENTAL CASH FLOW INFORMATION Nine Months Ended September 30, 2023 2022 (In thousands) Supplemental cash flow information: Cash interest paid $ 72,749 $ 46,093 Cash paid for taxes $ 15 $ 149 Noncash investing and financing activities: Capital expenditures in trade accounts payable (period-end accruals) $ 7,354 $ 4,102 Accretion of Subsidiary Series A Preferred Units, net of issuance cost amortization $ 8,865 $ 10,554 2022 Preferred Exchange Offer $ — $ 92,587

UNIT-BASED AND NONCASH COMPENSA

UNIT-BASED AND NONCASH COMPENSATION	9 Months Ended
UNIT-BASED AND NONCASH COMPENSATION	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
UNIT-BASED AND NONCASH COMPENSATION	13. UNIT-BASED AND NONCASH COMPENSATION SMLP Long-Term Incentive Plan. The Partnership’s Long-Term Incentive Plan (“SMLP LTIP”) provides for equity awards to eligible officers, employees, consultants and directors of the Partnership, thereby linking the recipients’ compensation directly to SMLP’s performance. Significant items to note: • For the nine-month period ended September 30, 2023, the Partnership granted 212,893 time-based phantom units and associated distribution equivalent rights to employees in connection with the Partnership’s annual incentive compensation award cycle. These awards had a grant date fair value of $16.00 per common unit and vest ratably over a 3-year period. • For the nine-month period ended September 30, 2023, the Partnership granted 110,478 performance-based phantom units and associated distribution equivalent rights to certain members of management in connection with the Partnership’s annual incentive compensation award cycle. The grant date fair value of these awards total $2.2 million. • For the nine-month period ended September 30, 2023, the Partnership issued 38,100 common units to the Partnership’s six independent directors in connection with their annual compensation plan. These awards had a grant date fair value of $16.00 per common unit and vested immediately. • As of September 30, 2023, approximately 0.5 million common units remained available for future issuance under the SMLP LTIP, which includes the impact of 0.7 million granted but unvested phantom units.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	14. COMMITMENTS AND CONTINGENCIES Environmental Matters. Although the Partnership believes that it is in material compliance with applicable environmental regulations, the risk of environmental remediation costs and liabilities are inherent in pipeline ownership and operation. Furthermore, the Partnership can provide no assurances that significant environmental remediation costs and liabilities will not be incurred in the future. The Partnership is currently not aware of any material contingent liabilities that exist with respect to environmental matters, except as noted below. As of September 30, 2023, the Partnership has recognized (i) a current liability for remediation effort expenditures expected to be incurred within the next 12 months and (ii) a noncurrent liability for estimated remediation expenditures expected to be incurred subsequent to September 30, 2024. Each of these amounts represent the Partnership’s best estimate for costs expected to be incurred. Neither of these amounts have been discounted to their present value. An update of the Partnership’s undiscounted accrued environmental remediation is as follows and is primarily related to the 2015 Blacktail Release and other environmental remediation activities, as detailed below. (In thousands) Accrued environmental remediation, December 31, 2022 $ 3,705 Payments made (579) Changes in estimates (60) Accrued environmental remediation, September 30, 2023 $ 3,066 In 2015, the Partnership learned of the rupture of a four-inch produced water gathering pipeline on the Meadowlark Midstream system near Williston, North Dakota (“2015 Blacktail Release”). On August 4, 2021, subsidiaries of the Partnership entered into the following agreements to resolve the U.S. federal and North Dakota state governments’ environmental claims with respect to the 2015 Blacktail Release: (i) a Consent Decree with the U.S. Department of Justice (“DOJ”), the U.S. Environmental Protection Agency (“EPA”), and the State of North Dakota (“Consent Decree”); (ii) a Plea Agreement with the United States (“Plea Agreement”); and (iii) a Consent Agreement with the North Dakota Industrial Commission (“Consent Agreement” together with the Consent Decree and Plea Agreement, the “Global Settlement”). As of September 30, 2023 and December 31, 2022, the accrued loss liability for the 2015 Blacktail Release were $25.5 million and $28.3 million, respectively and are recorded within Other noncurrent liabilities and Accrued settlement payable within the unaudited condensed consolidated balance sheets. Key terms of the Global Settlement included (i) payment of penalties and fines totaling $36.3 million, consisting of $1.25 million in natural resource damages payable to federal and state governments, a $25.0 million payable to the federal government over 5 years, and a $10.0 million payable to state governments over, for the federal and state civil amounts, six years and, for the federal criminal amounts, five years, with interest applied to unpaid amounts accruing at, for the federal and state civil amounts, a fixed rate of 3.25% and, for the federal criminal amounts, a variable rate set by statute, and of which $6.7 million is expected to be paid within the next twelve months; (ii) continuation of remediation efforts at the site of the 2015 Blacktail Release; (iii) other injunctive relief including but not limited to control room management, environmental management system audit, training, and reporting; (iv) guilty pleas by Defendant subsidiary for (a) one charge of negligent discharge of a harmful quantity of oil and (b) one charge of knowing failure to immediately report a discharge of oil; and (v) organizational probation for a minimum period of three years from sentencing on December 6, 2021, including payment in full of certain components of the fines and penalty amounts. The agreements comprising the Global Settlement were subject to the approval of the U.S. District Court for the District of North Dakota (the “U.S. District Court”). The U.S. District Court entered an order making the civil components of the Global Settlement effective on September 28, 2021 and accepted the sentencing in the Plea Agreement on December 6, 2021, completing approval of the Global Settlement. Subsidiaries of the Partnership are also participating in two proceedings before the EPA as a result of the Plea Agreement becoming effective. Following the U.S. District Court’s entering judgment on Defendant subsidiary’s guilty plea to one count of negligent discharge of produced water in violation of the Clean Water Act, Defendant subsidiary was statutorily debarred by operation of law pursuant to 33 U.S.C. § 1368(a) to participate in federal awards performed at the “violating facility,” which EPA determined to be the Marmon subsystem of the produced water gathering system in North Dakota. The scope and effect of the debarment as defined do not materially affect our operations. Defendant has submitted a petition for reinstatement, which was denied by the EPA’s suspension and debarment office (“SDO”) on July 11, 2022. The SDO determined that the term of probation in the Plea Agreement was the appropriate period of time to demonstrate Defendant subsidiary’s change of corporate attitude, policies, practices, and procedures. The Partnership and certain subsidiaries have also received a show cause notice from the EPA requesting us to “show cause” why SDO should not issue a Notice of Proposed Debarment to the Defendant subsidiary and certain affiliates under 2 C.F.R. § 180.800(d), to which we have responded, and in which proceeding no further developments have occurred. Legal Proceedings. The Partnership is involved in various litigation and administrative proceedings arising in the ordinary course of business. In the opinion of management, any liabilities, which include insured claims, would not individually or in the aggregate have a material adverse effect on the Partnership's financial position or results of operations.

SEGMENT INFORMATION

SEGMENT INFORMATION	9 Months Ended
SEGMENT INFORMATION	Sep. 30, 2023
Segment Reporting [Abstract]
SEGMENT INFORMATION	15. SEGMENT INFORMATION As of September 30, 2023, the Partnership’s reportable segments are: • Rockies – Includes the Partnership’s wholly owned midstream assets located in the Williston Basin and the DJ Basin. In September 2022, the Partnership completed the sale of Bison Midstream and its gas gathering system in Burke and Mountrail Counties, North Dakota to a subsidiary of Steel Reef. Additionally, in December 2022 the Partnership completed the acquisitions of Sterling DJ and Outrigger DJ and their related midstream infrastructure. For additional information regarding these acquisitions and divestitures, see Note 3 - Acquisitions and Divestitures. • Permian – Includes the Partnership’s equity method investment in Double E and its wholly owned Lane G&P System, which was sold on June 30, 2022 to Matador. For additional information regarding the sale of the Lane G&P System, see Note 3 - Acquisitions and Divestitures. • Northeast – Includes the Partnership’s wholly owned midstream assets located in the Utica and Marcellus shale plays and the equity method investment in Ohio Gathering that is focused on the Utica Shale. • Piceance – Includes the Partnership’s wholly owned midstream assets located in the Piceance Basin. • Barnett – Includes the Partnership’s wholly owned midstream assets located in the Barnett Shale. Corporate and Other represents those results that: (i) are not specifically attributable to a reportable segment; (ii) are not individually reportable; or (iii) have not been allocated to a reportable segment for the purpose of evaluating their performance, including certain general and administrative expense items and transaction costs. Assets by reportable segment follow. September 30, 2023 December 31, 2022 (In thousands) Assets: Rockies $ 896,333 $ 886,629 Permian 295,375 298,906 Northeast 577,572 591,091 Piceance 445,302 475,719 Barnett 283,702 295,473 Total reportable segment assets 2,498,284 2,547,818 Corporate and Other 11,230 12,146 Total assets $ 2,509,514 $ 2,559,964 Segment adjusted EBITDA by reportable segment follows. Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 (In thousands) Reportable segment adjusted EBITDA Rockies $ 24,998 $ 14,262 $ 64,986 $ 43,991 Permian 5,840 4,882 16,283 13,848 Northeast 27,751 19,353 65,806 57,989 Piceance 15,292 14,249 43,640 45,367 Barnett 6,084 7,864 20,380 24,397 Total of reportable segments' measures of profit $ 79,965 $ 60,610 $ 211,095 $ 185,592 A reconciliation of income or loss before income taxes and income from equity method investees to total of reportable segments' measures of profit follows. Three Months Ended Nine Months Ended 2023 2022 2023 2022 (In thousands) Reconciliation of loss before income taxes and income from equity method investees to total of reportable segments' measures of profit: Loss before income taxes and income from equity method investees $ (6,265) $ (13,590) $ (46,311) $ (113,452) Add: Corporate and Other expense 5,487 2,151 20,695 11,778 Interest expense 34,568 24,932 103,966 73,982 Depreciation and amortization (1) 31,013 29,076 91,438 90,101 Proportional adjusted EBITDA for equity method investees 16,917 11,949 42,655 33,807 Adjustments related to capital reimbursement activity (3,111) (1,517) (6,778) (4,823) Unit-based and noncash compensation 1,396 692 5,158 2,964 Gain on asset sales, net (40) (99) (183) (409) Long-lived asset impairment — 7,016 455 91,644 Total of reportable segments' measures of profit $ 79,965 $ 60,610 $ 211,095 $ 185,592 ________ (1) Includes the amortization expense associated with our favorable gas gathering contracts as reported in other revenues.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENTLY ISSUED ACCOUNTING STANDARDS APPLICABLE TO THE PARTNERSHIP (Policies)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation	The Partnership prepares its condensed consolidated financial statements in accordance with GAAP as established by the FASB and pursuant to the rules and regulations of the SEC pertaining to interim financial information. The unaudited condensed consolidated financial statements contained in this report include all normal and recurring material adjustments that, in the opinion of management, are necessary for a fair statement of the financial position, results of operations and cash flows for the interim periods presented herein.
Use of Estimates	The Partnership makes estimates and assumptions that affect the reported amounts of assets and liabilities at the balance sheet dates, including fair value measurements, the reported amounts of revenues and expenses and the disclosure of commitments and contingencies. Although management believes these estimates are reasonable, actual results could differ from its estimates.
Consolidation	The unaudited condensed consolidated financial statements contained in this report include the assets, liabilities and results of operations of SMLP and its subsidiaries and all intercompany transactions among the consolidated entities have been eliminated in consolidation. Comprehensive income or loss is the same as net income or loss for all periods presented.
Accounting standards recently implemented and New accounting standards not yet implemented	Accounting standards recently implemented. ASU No. 2020-4 Reference Rate Reform (“ASU 2020-4”). ASU 2020-4 provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform on financial reporting. Contract terms that are modified due to the replacement of a reference rate are not required to be remeasured or reassessed under relevant accounting standards. During the quarter ended June 30, 2023, the Partnership amended the terms of its Permian Transmission Credit Facility and Term Loan and interest rate swaps, which replaced its existing LIBOR based terms with SOFR rate terms. The amendments in ASU 2020-4 are effective as of March 12, 2020 through December 31, 2022. In December 2022, the FASB issued ASU 2022-06, which amended Topic 848 to defer the sunset date to apply the practical expedients until December 31, 2024. The impact of the change in reference rate did not have a material impact on the Partnership’s consolidated financial statements. See Note 8 - Debt, for additional information. New accounting standards not yet implemented. ASU No. 2020-6 Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815–40) (“ASU 2020-6”). ASU 2020-6 simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. The ASU is part of the FASB’s simplification initiative, which aims to reduce unnecessary complexity in GAAP. The ASU’s amendments are effective for fiscal years beginning after December 15, 2023, and interim periods within those fiscal years. The Partnership does not expect the provisions of ASU 2020-6 will have a material impact on its consolidated financial statements and disclosures.

ACQUISTIONS AND DIVESTITURES (T

ACQUISTIONS AND DIVESTITURES (Tables)	9 Months Ended
ACQUISTIONS AND DIVESTITURES (Tables)	Sep. 30, 2023
Business Combination and Asset Acquisition [Abstract]
Schedule of Pro Forma Information	The following unaudited supplemental pro forma condensed results of operations for the three and nine months ended September 30, 2022 present consolidated information as though the acquisition of Sterling DJ and Outrigger DJ, and the divestiture of the Lane G&P System and Bison Midstream had occurred on January 1, 2021. The unaudited supplemental pro forma financial information was derived from the historical consolidated and combined statements of operations of the Partnership, Sterling DJ, and Outrigger DJ and modified to include required conforming adjustments. These unaudited supplemental pro forma results of operations are provided for illustrative purposes only and do not purport to be indicative of the actual results that would have been achieved by the combined entities for the periods presented or that may be achieved in the future. Future results may vary significantly from the results reflected in this unaudited pro forma financial information: Three Months Ended Nine Months Ended 2022 2022 Revenues $ 145,465 $ 394,575 Net loss $ (4,712) $ (13,003)

REVENUE (Tables)

REVENUE (Tables)	9 Months Ended
REVENUE (Tables)	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Schedule of Estimated Revenue Expected to be Recognized and MVC Shortfall Payments	The following table presents estimated revenue expected to be recognized during the remainder of 2023 and over the remaining contract period related to performance obligations that are unsatisfied and are comprised of estimated minimum volume commitments. (In thousands) 2023 2024 2025 2026 2027 Thereafter Gathering services and related fees $ 19,180 $ 67,079 $ 46,803 $ 30,527 $ 9,038 $ 6,042
Schedule of Disaggregated Revenue by Geographic Area and Major Products and Services Reportable Segments	Revenue by category. In the following tables, revenue is disaggregated by geographic area and major products and services. For more detailed information about reportable segments, see Note 15 – Segment Information. Three Months Ended September 30, 2023 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (In thousands) Reportable Segments: Northeast $ 18,157 $ — $ — $ 18,157 Rockies 18,383 43,967 5,541 67,891 Permian — — 893 893 Piceance 20,658 937 1,569 23,164 Barnett 8,837 216 2,035 11,088 Total reportable segments 66,035 45,120 10,038 121,193 Corporate and other — — — — Total $ 66,035 $ 45,120 $ 10,038 $ 121,193 Three Months Ended September 30, 2022 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (In thousands) Reportable Segments: Northeast $ 13,528 $ — $ — $ 13,528 Rockies 17,209 14,111 4,823 36,143 Permian — — 891 891 Piceance 20,406 1,519 1,581 23,506 Barnett 10,671 998 2,622 14,291 Total reportable segments 61,814 16,628 9,917 88,359 Corporate and other — — 323 323 Total $ 61,814 $ 16,628 $ 10,240 $ 88,682 Nine Months Ended September 30, 2023 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (In thousands) Reportable Segments: Northeast $ 43,717 $ — $ — $ 43,717 Rockies 48,595 125,871 8,885 183,351 Permian — — 2,678 2,678 Piceance 59,791 3,913 4,368 68,072 Barnett 28,389 581 4,835 33,805 Total reportable segments 180,492 130,365 20,766 331,623 Corporate and other — — (38) (38) Total $ 180,492 $ 130,365 $ 20,728 $ 331,585 Nine Months Ended September 30, 2022 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (In thousands) Reportable Segments: Northeast $ 41,104 $ — $ — $ 41,104 Rockies 51,508 42,697 14,708 108,913 Permian 3,669 17,381 3,208 24,258 Piceance 60,458 5,481 4,132 70,071 Barnett 30,726 1,784 6,356 38,866 Total reportable segments 187,465 67,343 28,404 283,212 Corporate and other — 21 638 659 Total $ 187,465 $ 67,364 $ 29,042 $ 283,871

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	9 Months Ended
PROPERTY, PLANT AND EQUIPMENT (Tables)	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	Details on the Partnership’s property, plant and equipment follow. September 30, 2023 December 31, 2022 (In thousands) Gathering and processing systems and related equipment $ 2,315,041 $ 2,262,330 Construction in progress 49,412 59,036 Land and line fill 11,990 11,756 Other 63,976 62,222 Total 2,440,419 2,395,344 Less: accumulated depreciation (744,960) (676,590) Property, plant and equipment, net $ 1,695,459 $ 1,718,754
Schedule Of Depreciation Expense And Capitalized Interest Costs	Depreciation expense and capitalized interest for the Partnership follow. Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 (In thousands) Depreciation expense $ 23,926 $ 22,474 $ 70,130 $ 70,235 Capitalized interest 351 128 790 711

EQUITY METHOD INVESTMENTS (Tabl

EQUITY METHOD INVESTMENTS (Tables)	9 Months Ended
EQUITY METHOD INVESTMENTS (Tables)	Sep. 30, 2023
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Equity Method Investments	Details of the Partnership’s equity method investments follow. September 30, 2023 December 31, 2022 (In thousands) Double E $ 277,094 $ 281,640 Ohio Gathering 214,653 225,037 Total $ 491,747 $ 506,677

DEFERRED REVENUE (Tables)

DEFERRED REVENUE (Tables)	9 Months Ended
DEFERRED REVENUE (Tables)	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Schedule of Contract with Customer, Contract Asset, Contract Liability, and Receivable	An update of current deferred revenue follows. Total (In thousands) Current deferred revenue, December 31, 2022 $ 9,054 Add: additions 8,940 Less: revenue recognized and other (6,732) Current deferred revenue, September 30, 2023 $ 11,262 An update of noncurrent deferred revenue follows. Total (In thousands) Noncurrent deferred revenue, December 31, 2022 $ 37,694 Add: additions 2,215 Less: reclassification to current deferred revenue and other (8,629) Noncurrent deferred revenue, September 30, 2023 $ 31,280

DEBT (Tables)

DEBT (Tables)	9 Months Ended
DEBT (Tables)	Sep. 30, 2023
Debt Disclosure [Abstract]
Schedule of Debt	Debt for the Partnership at September 30, 2023 and December 31, 2022, follows: September 30, 2023 December 31, 2022 (In thousands) ABL Facility : Summit Holdings' asset based credit facility due May 1, 2026 $ 295,000 $ 330,000 Permian Transmission Term Loan : Permian Transmission's variable rate senior secured term loan due January 2028 147,549 155,353 2025 Senior Notes : Summit Holdings' 5.75% senior unsecured notes due April 15, 2025 259,463 259,463 2026 Secured Notes : Summit Holdings' and Finance Corp's 8.50% senior second lien notes due October 15, 2026 785,000 785,000 Less: unamortized debt discount and debt issuance costs (31,922) (39,454) Total debt 1,455,090 1,490,362 Less: current portion of Permian Transmission Credit Facility (14,258) (10,507) Total long-term debt $ 1,440,832 $ 1,479,855
Schedule of Maturities of Long-term Debt	Below is a summary of the remaining mandatory principal repayments as of September 30, 2023: (In thousands) Total 2023 2024 2025 2026 2027 Thereafter Amortizing principal repayments $ 147,549 $ 2,703 $ 15,524 $ 16,580 $ 16,967 $ 17,769 $ 78,006

FINANCIAL INSTRUMENTS (Tables)

FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
FINANCIAL INSTRUMENTS (Tables)	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments	A summary of the estimated fair value of our debt financial instruments follows. September 30, 2023 December 31, 2022 Carrying Value (1) Estimated Carrying Value (1) Estimated (In thousands) 2025 Senior Notes $ 259,463 $ 242,814 $ 259,463 $ 221,733 2026 Secured Notes 785,000 754,581 785,000 750,983 ________ (1) Excludes applicable unamortized debt issuance costs and debt discounts.

PARTNERS' CAPITAL AND MEZZANI_2

PARTNERS' CAPITAL AND MEZZANINE CAPITAL (Tables)	9 Months Ended
PARTNERS' CAPITAL AND MEZZANINE CAPITAL (Tables)	Sep. 30, 2023
Equity [Abstract]
Schedule Of Partner Units Activity	An update of the number of issued and outstanding common limited partner units is as follows for the period from December 31, 2022 to September 30, 2023. Common Units Units, December 31, 2022 10,182,763 Common units issued for SMLP LTIP, net 193,426 Units, September 30, 2023 10,376,189
Schedule of Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net	The following table shows the change in our Subsidiary Series A Preferred Unit balance from January 1, 2023 to September 30, 2023, net of $1.8 million and $2.2 million of unamortized issuance costs at September 30, 2023 and December 31, 2022, respectively: (In thousands) Balance at December 31, 2022 $ 118,584 Redemption accretion, net of issuance cost amortization 8,865 Cash distribution (includes a $1.6 million distribution payable as of September 30, 2023) (4,885) Balance at September 30, 2023 $ 122,564

EARNINGS PER UNIT (Tables)

EARNINGS PER UNIT (Tables)	9 Months Ended
EARNINGS PER UNIT (Tables)	Sep. 30, 2023
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table details the components of EPU. Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 (In thousands, except per-unit amounts) Numerator for basic and diluted EPU: Allocation of net loss among limited partner interests: Net income (loss) $ 3,874 $ (7,788) $ (23,829) $ (99,597) Less: Net income attributable to Subsidiary Series A Preferred Units (3,623) (3,278) (8,865) (12,155) Net income (loss) attributable to Summit Midstream Partners, LP $ 251 $ (11,066) $ (32,694) (111,752) Less: Net income attributable to Series A Preferred Units $ (3,004) $ (1,962) $ (8,442) (6,070) Add: Deemed capital contribution from 2022 Preferred Exchange Offer — — — 20,974 Net loss attributable to common limited partners $ (2,753) $ (13,028) $ (41,136) $ (96,848) Denominator for basic and diluted EPU: Weighted-average common units outstanding – basic 10,376 10,168 10,320 10,003 Effect of nonvested phantom units — — — — Weighted-average common units outstanding – diluted 10,376 10,168 10,320 10,003 Net income per limited partner unit: Common unit – basic $ (0.27) $ (1.28) $ (3.99) $ (9.68) Common unit – diluted $ (0.27) $ (1.28) $ (3.99) $ (9.68) Nonvested anti-dilutive phantom units excluded from the calculation of diluted EPU 160 — 221 —

SUPPLEMENTAL CASH FLOW INFORM_2

SUPPLEMENTAL CASH FLOW INFORMATION (Tables)	9 Months Ended
SUPPLEMENTAL CASH FLOW INFORMATION (Tables)	Sep. 30, 2023
Supplemental Cash Flow Elements [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Nine Months Ended September 30, 2023 2022 (In thousands) Supplemental cash flow information: Cash interest paid $ 72,749 $ 46,093 Cash paid for taxes $ 15 $ 149 Noncash investing and financing activities: Capital expenditures in trade accounts payable (period-end accruals) $ 7,354 $ 4,102 Accretion of Subsidiary Series A Preferred Units, net of issuance cost amortization $ 8,865 $ 10,554 2022 Preferred Exchange Offer $ — $ 92,587

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	9 Months Ended
COMMITMENTS AND CONTINGENCIES (Tables)	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Schedule of Accrued Environmental Remediation	An update of the Partnership’s undiscounted accrued environmental remediation is as follows and is primarily related to the 2015 Blacktail Release and other environmental remediation activities, as detailed below. (In thousands) Accrued environmental remediation, December 31, 2022 $ 3,705 Payments made (579) Changes in estimates (60) Accrued environmental remediation, September 30, 2023 $ 3,066

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	9 Months Ended
SEGMENT INFORMATION (Tables)	Sep. 30, 2023
Segment Reporting [Abstract]
Schedule of Reconciliation of Assets from Segment to Consolidated	Assets by reportable segment follow. September 30, 2023 December 31, 2022 (In thousands) Assets: Rockies $ 896,333 $ 886,629 Permian 295,375 298,906 Northeast 577,572 591,091 Piceance 445,302 475,719 Barnett 283,702 295,473 Total reportable segment assets 2,498,284 2,547,818 Corporate and Other 11,230 12,146 Total assets $ 2,509,514 $ 2,559,964
Schedule of Reconciliation of Revenue from Segments to Consolidated	Segment adjusted EBITDA by reportable segment follows. Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 (In thousands) Reportable segment adjusted EBITDA Rockies $ 24,998 $ 14,262 $ 64,986 $ 43,991 Permian 5,840 4,882 16,283 13,848 Northeast 27,751 19,353 65,806 57,989 Piceance 15,292 14,249 43,640 45,367 Barnett 6,084 7,864 20,380 24,397 Total of reportable segments' measures of profit $ 79,965 $ 60,610 $ 211,095 $ 185,592
Schedule of Reconciliation of Net Income to Adjusted EBITDA	A reconciliation of income or loss before income taxes and income from equity method investees to total of reportable segments' measures of profit follows. Three Months Ended Nine Months Ended 2023 2022 2023 2022 (In thousands) Reconciliation of loss before income taxes and income from equity method investees to total of reportable segments' measures of profit: Loss before income taxes and income from equity method investees $ (6,265) $ (13,590) $ (46,311) $ (113,452) Add: Corporate and Other expense 5,487 2,151 20,695 11,778 Interest expense 34,568 24,932 103,966 73,982 Depreciation and amortization (1) 31,013 29,076 91,438 90,101 Proportional adjusted EBITDA for equity method investees 16,917 11,949 42,655 33,807 Adjustments related to capital reimbursement activity (3,111) (1,517) (6,778) (4,823) Unit-based and noncash compensation 1,396 692 5,158 2,964 Gain on asset sales, net (40) (99) (183) (409) Long-lived asset impairment — 7,016 455 91,644 Total of reportable segments' measures of profit $ 79,965 $ 60,610 $ 211,095 $ 185,592 ________ (1) Includes the amortization expense associated with our favorable gas gathering contracts as reported in other revenues.

ACQUISTIONS AND DIVESTITURES -

ACQUISTIONS AND DIVESTITURES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 01, 2022
Lane G&P System
Business Acquisition [Line Items]
Proceeds from sale of business, net of cash sold in transaction			$ 0	$ 75,520
Bison Midstream, LLC
Business Acquisition [Line Items]
Proceeds from sale of business, net of cash sold in transaction			$ 0	36,671
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Lane G&P System
Business Acquisition [Line Items]
Impairment on disposition		$ 84,500
Proceeds from sale of business, net of cash sold in transaction		77,500
Cash sold, working capital and other miscellaneous adjustments		2,000
Net book value of assets and liabilities divested		160,800
Other costs to sell		$ 1,200
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Bison Midstream, LLC
Business Acquisition [Line Items]
Impairment on disposition	$ 6,900
Proceeds from sale of business, net of cash sold in transaction	36,700
Net book value of assets and liabilities divested	$ 43,600			$ 43,600
Outrigger DJ
Business Acquisition [Line Items]
Ownership interest (as a percent)					100%
Sterling DJ
Business Acquisition [Line Items]
Ownership interest (as a percent)					100%

ACQUISTIONS AND DIVESTITURES _2

ACQUISTIONS AND DIVESTITURES - Schedule of Pro Forma Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022
Business Combination and Asset Acquisition [Abstract]
Revenues	$ 145,465	$ 394,575
Net loss	$ (4,712)	$ (13,003)

REVENUE - Schedule of Estimated

REVENUE - Schedule of Estimated Revenue Expected to be Recognized (Details) - Gathering services and related fees $ in Thousands	Sep. 30, 2023 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 19,180
Revenue, remaining performance obligation, expected timing of satisfaction	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 67,079
Revenue, remaining performance obligation, expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 46,803
Revenue, remaining performance obligation, expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 30,527
Revenue, remaining performance obligation, expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 9,038
Revenue, remaining performance obligation, expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 6,042
Revenue, remaining performance obligation, expected timing of satisfaction	1 year

REVENUE - Schedule of Disaggreg

REVENUE - Schedule of Disaggregated Revenue by Geographic Area and Major Products and Services Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Total revenues	$ 121,193	$ 88,682	$ 331,585	$ 283,871
Reportable Segments
Disaggregation of Revenue [Line Items]
Total revenues	121,193	88,359	331,623	283,212
Reportable Segments \| Northeast
Disaggregation of Revenue [Line Items]
Total revenues	18,157	13,528	43,717	41,104
Reportable Segments \| Rockies
Disaggregation of Revenue [Line Items]
Total revenues	67,891	36,143	183,351	108,913
Reportable Segments \| Permian
Disaggregation of Revenue [Line Items]
Total revenues	893	891	2,678	24,258
Reportable Segments \| Piceance
Disaggregation of Revenue [Line Items]
Total revenues	23,164	23,506	68,072	70,071
Reportable Segments \| Barnett
Disaggregation of Revenue [Line Items]
Total revenues	11,088	14,291	33,805	38,866
Segment Reconciling Items
Disaggregation of Revenue [Line Items]
Total revenues	0	323	(38)	659
Gathering services and related fees
Disaggregation of Revenue [Line Items]
Total revenues	66,035	61,814	180,492	187,465
Gathering services and related fees \| Reportable Segments
Disaggregation of Revenue [Line Items]
Total revenues	66,035	61,814	180,492	187,465
Gathering services and related fees \| Reportable Segments \| Northeast
Disaggregation of Revenue [Line Items]
Total revenues	18,157	13,528	43,717	41,104
Gathering services and related fees \| Reportable Segments \| Rockies
Disaggregation of Revenue [Line Items]
Total revenues	18,383	17,209	48,595	51,508
Gathering services and related fees \| Reportable Segments \| Permian
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	3,669
Gathering services and related fees \| Reportable Segments \| Piceance
Disaggregation of Revenue [Line Items]
Total revenues	20,658	20,406	59,791	60,458
Gathering services and related fees \| Reportable Segments \| Barnett
Disaggregation of Revenue [Line Items]
Total revenues	8,837	10,671	28,389	30,726
Gathering services and related fees \| Segment Reconciling Items
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Natural gas, NGLs and condensate sales
Disaggregation of Revenue [Line Items]
Total revenues	45,120	16,628	130,365	67,364
Natural gas, NGLs and condensate sales \| Reportable Segments
Disaggregation of Revenue [Line Items]
Total revenues	45,120	16,628	130,365	67,343
Natural gas, NGLs and condensate sales \| Reportable Segments \| Northeast
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Natural gas, NGLs and condensate sales \| Reportable Segments \| Rockies
Disaggregation of Revenue [Line Items]
Total revenues	43,967	14,111	125,871	42,697
Natural gas, NGLs and condensate sales \| Reportable Segments \| Permian
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	17,381
Natural gas, NGLs and condensate sales \| Reportable Segments \| Piceance
Disaggregation of Revenue [Line Items]
Total revenues	937	1,519	3,913	5,481
Natural gas, NGLs and condensate sales \| Reportable Segments \| Barnett
Disaggregation of Revenue [Line Items]
Total revenues	216	998	581	1,784
Natural gas, NGLs and condensate sales \| Segment Reconciling Items
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	21
Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	10,038	10,240	20,728	29,042
Other revenues \| Reportable Segments
Disaggregation of Revenue [Line Items]
Total revenues	10,038	9,917	20,766	28,404
Other revenues \| Reportable Segments \| Northeast
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Other revenues \| Reportable Segments \| Rockies
Disaggregation of Revenue [Line Items]
Total revenues	5,541	4,823	8,885	14,708
Other revenues \| Reportable Segments \| Permian
Disaggregation of Revenue [Line Items]
Total revenues	893	891	2,678	3,208
Other revenues \| Reportable Segments \| Piceance
Disaggregation of Revenue [Line Items]
Total revenues	1,569	1,581	4,368	4,132
Other revenues \| Reportable Segments \| Barnett
Disaggregation of Revenue [Line Items]
Total revenues	2,035	2,622	4,835	6,356
Other revenues \| Segment Reconciling Items
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 323	$ (38)	$ 638

PROPERTY, PLANT AND EQUIPMENT -

PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant, and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total	$ 2,440,419	$ 2,395,344
Less: accumulated depreciation	(744,960)	(676,590)
Property, plant and equipment, net	1,695,459	1,718,754
Gathering and processing systems and related equipment
Property, Plant and Equipment [Line Items]
Total	2,315,041	2,262,330
Construction in progress
Property, Plant and Equipment [Line Items]
Total	49,412	59,036
Land and line fill
Property, Plant and Equipment [Line Items]
Total	11,990	11,756
Other
Property, Plant and Equipment [Line Items]
Total	$ 63,976	$ 62,222

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT - Schedule of Depreciation Expense and Capitalized Interest (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 23,926	$ 22,474	$ 70,130	$ 70,235
Capitalized interest	$ 351	$ 128	$ 790	$ 711

EQUITY METHOD INVESTMENTS - Sch

EQUITY METHOD INVESTMENTS - Schedule of Equity Method Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Investment in equity method investees	$ 491,747	$ 506,677
Double E
Schedule of Equity Method Investments [Line Items]
Investment in equity method investees	277,094	281,640
Ohio Gathering
Schedule of Equity Method Investments [Line Items]
Investment in equity method investees	$ 214,653	$ 225,037

DEFERRED REVENUE (Details)

DEFERRED REVENUE (Details) $ in Thousands	9 Months Ended
DEFERRED REVENUE (Details) $ in Thousands	Sep. 30, 2023 USD ($)
Change in Contract with Customer, Liability, Current [Roll Forward]
Current deferred revenue, beginning balance	$ 9,054
Add: additions	8,940
Less: revenue recognized and other	(6,732)
Current deferred revenue, ending balance	11,262
Change in Contract with Customer, Liability, Noncurrent [Roll Forward]
Noncurrent deferred revenue, beginning balance	37,694
Add: additions	2,215
Less: reclassification to current deferred revenue and other	(8,629)
Noncurrent deferred revenue, ending balance	$ 31,280

DEBT - Components of Long-Term

DEBT - Components of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Line of Credit Facility [Line Items]
Less: unamortized debt discount and debt issuance costs	$ (31,922)	$ (39,454)
Total debt	1,455,090	1,490,362
Less: current portion of Permian Transmission Credit Facility	(14,258)	(10,507)
Total long-term debt	1,440,832	1,479,855
ABL Facility: Summit Holdings' asset based credit facility due May 1, 2026 \| Line of Credit
Line of Credit Facility [Line Items]
Secured notes	295,000	330,000
Permian Transmission Term Loan: Permian Transmission's variable rate senior secured term loan due January 2028
Line of Credit Facility [Line Items]
Term loan	147,549
Permian Transmission Term Loan: Permian Transmission's variable rate senior secured term loan due January 2028 \| Line of Credit
Line of Credit Facility [Line Items]
Term loan	$ 147,549	$ 155,353
2025 Senior Notes: Summit Holdings' 5.75% senior unsecured notes due April 15, 2025
Line of Credit Facility [Line Items]
Stated interest rate (as a percent)	5.75%	5.75%
2025 Senior Notes: Summit Holdings' 5.75% senior unsecured notes due April 15, 2025 \| Senior Notes
Line of Credit Facility [Line Items]
Unsecured notes	$ 259,463	$ 259,463
2026 Secured Notes: Summit Holdings' and Finance Corp's 8.50% senior second lien notes due October 15, 2026
Line of Credit Facility [Line Items]
Stated interest rate (as a percent)	8.50%	8.50%
2026 Secured Notes: Summit Holdings' and Finance Corp's 8.50% senior second lien notes due October 15, 2026 \| Secured Debt
Line of Credit Facility [Line Items]
Unsecured notes	$ 785,000	$ 785,000

DEBT - Narrative (Details)

DEBT - Narrative (Details)	1 Months Ended		9 Months Ended	12 Months Ended
DEBT - Narrative (Details)	Nov. 30, 2021 USD ($)	Feb. 28, 2017	Sep. 30, 2023 USD ($)	Dec. 31, 2022	Nov. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Nov. 02, 2021 USD ($)	Mar. 08, 2021 USD ($)
Revolving Credit Facility \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
Applicable margin (as a percent)			3.50%
ABL Facility
Debt Instrument [Line Items]
Borrowing capacity			$ 400,000,000				$ 400,000,000
Borrowing base capacity			$ 715,200,000
Mandatory redemption period			120 days
Maximum amount of debt outstanding for maturity to occur			$ 50,000,000
Debt instrument, interest rate			8.93%
Unused portion under the facility			$ 100,700,000
First lien net leverage ratio (as a percent)			1.16				2.50
Interest coverage ratio			2.21				2
ABL Facility \| Standby Letters of Credit
Debt Instrument [Line Items]
Secured notes			$ 4,300,000
Credit Agreement
Debt Instrument [Line Items]
Borrowing capacity								$ 175,000,000
Interest rate during period (as a percent)			7.69%
Unused portion of the permian transmission credit facility			$ 4,500,000
Percentage of debt instrument			90%
Credit Agreement \| Standby Letters of Credit
Debt Instrument [Line Items]
Unused portion of the permian transmission credit facility			$ 10,500,000
Credit Agreement \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
Applicable margin (as a percent)			2.475%
Commitment fee (as a percent)			0.70%
Credit Agreement \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Summit Permian Transmissions, LLC
Debt Instrument [Line Items]
Applicable margin (as a percent)			1.23%
Credit Agreement \| Term Loan Credit Facility
Debt Instrument [Line Items]
Borrowing capacity								160,000,000
Credit Agreement \| Working Capital Credit Facility
Debt Instrument [Line Items]
Borrowing capacity								$ 15,000,000
Permian Transmission Term Loan: Permian Transmission's variable rate senior secured term loan due January 2028
Debt Instrument [Line Items]
Interest rate during period (as a percent)			7.69%
Permian Transmission Term Loan: Permian Transmission's variable rate senior secured term loan due January 2028 \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
Applicable margin (as a percent)			2.475%
Senior Secured Second Lien Notes Due 2026
Debt Instrument [Line Items]
Debt offering						$ 700,000,000
Stated interest rate (as a percent)						8.50%
2026 Secured Notes: Summit Holdings' and Finance Corp's 8.50% senior second lien notes due October 15, 2026
Debt Instrument [Line Items]
Debt offering					$ 85,000,000
Stated interest rate (as a percent)			8.50%	8.50%
Debt issued as a percent of face value					99.26%	98.50%
Secured Notes Indenture, 2026
Debt Instrument [Line Items]
Debt instrument, interest rate				9%
Redemption price, expressed as percentage of principal amount	100%
Debt instrument, principal interest rate	100%
Debt instrument, covenant, excess cash flow offer to purchase, period one	$ 50,000,000
Debt instrument, covenant, excess cash flow offer to purchase, basis point increase, period one	0.50%			0.50%
Debt instrument, covenant, excess cash flow offer to purchase, period two	$ 100,000,000
Debt instrument, covenant, excess cash flow offer to purchase, basis point increase, period two	1%
Debt instrument, covenant, excess cash flow offer to purchase, period three	$ 200,000,000
Debt instrument, covenant, excess cash flow offer to purchase, basis point increase, period three	2%
Secured Notes Indenture, 2026 \| Beginning October 15, 2023
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount	104.25%
Secured Notes Indenture, 2026 \| Beginning October 15, 2024
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount	102.125%
Secured Notes Indenture, 2026 \| Beginning October 15, 2025
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount	100%
2025 Senior Notes \| Beginning October 15, 2025 \| Summit Holdings And Finance Corporation
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount		100%

DEBT - Schedule of Maturities (

DEBT - Schedule of Maturities (Details) - Permian Transmission Term Loan: Permian Transmission's variable rate senior secured term loan due January 2028 $ in Thousands	Sep. 30, 2023 USD ($)
Debt
Amortizing principal repayments	$ 147,549
2023	2,703
2024	15,524
2025	16,580
2026	16,967
2027	17,769
Thereafter	$ 78,006

FINANCIAL INSTRUMENTS - Fair Va

FINANCIAL INSTRUMENTS - Fair Value of Debt Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
2025 Senior Notes \| Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 259,463	$ 259,463
2025 Senior Notes \| Fair Value \| Estimated Fair Value (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	242,814	221,733
2026 Secured Notes \| Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	785,000	785,000
2026 Secured Notes \| Fair Value \| Estimated Fair Value (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 754,581	$ 750,983

FINANCIAL INSTRUMENTS - Narrati

FINANCIAL INSTRUMENTS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Concentration Risk [Line Items]
Loss on interest rate swaps	$ (2,856)	$ (5,527)	$ (4,851)	$ (16,491)
Fair Value, Inputs, Level 3 \| Sterling DJ
Concentration Risk [Line Items]
Deferred earn-out liability	4,900		4,900		$ 5,200
Interest Rate Swap
Concentration Risk [Line Items]
Derivative liability, notional amount	132,800		132,800		139,800
Fair value, other assets	16,300		16,300		$ 15,200
Loss on interest rate swaps	$ (2,900)		$ 4,900

PARTNERS' CAPITAL AND MEZZANI_3

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Partners' Capital and Schedule of Units (Details) - Common Units	9 Months Ended
	Sep. 30, 2023 shares
Increase (Decrease) in Partners' Capital [Roll Forward]
Units, beginning balance (in shares)	10,182,763
Common units issued for SMLP LTIP, net (in shares)	193,426
Units, ending balance (in shares)	10,376,189

PARTNERS' CAPITAL AND MEZZANI_4

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2022	Mar. 31, 2020	Sep. 30, 2023	Dec. 31, 2022
Partners Capital [Line Items]
Contributed capital from preferred units exchange	$ 20.9
Maximum period following end of quarter to distribute all available cash		45 days
Common Units
Partners Capital [Line Items]
Series A preferred unit exchange offer, net of shares withheld for taxes (in shares)	2,853,875
Series A Preferred Units
Partners Capital [Line Items]
Subsidiary Series A preferred unitholders, outstanding (in shares)			65,508	65,508
Preferred units issued (in shares)			65,508	65,508
Subsidiary Series A Preferred Units
Partners Capital [Line Items]
Subsidiary Series A preferred unitholders, outstanding (in shares)			93,039,000
Preferred units issued (in shares)			93,039,000
Series A Preferred Units
Partners Capital [Line Items]
Accrued and unpaid distributions			$ 29.9
Preferred units issued (in shares)	77,939
Redemption amount			123.9
Issuance costs			$ 1.8	$ 2.2

PARTNERS' CAPITAL AND MEZZANI_5

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Change in Subsidiary (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Increase (Decrease) in Partners' Capital [Roll Forward]
Distribution payable	$ 1,600
Series A Preferred Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Redemption accretion, net of issuance cost amortization	8,865	$ 10,554
Series A Preferred Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance	118,584
Cash distribution (includes a $1.6 million distribution payable as of September 30, 2023)	(4,885)
Ending balance	$ 122,564

EARNINGS PER UNIT (Details)

EARNINGS PER UNIT (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss)	$ 3,874	$ (7,788)	$ (23,829)	$ (99,597)
Net income (loss) attributable to Summit Midstream Partners, LP	$ 251	$ (11,066)	$ (32,694)	$ (111,752)
Common unit - basic (in dollars per share)	$ (0.27)	$ (1.28)	$ (3.99)	$ (9.68)
Common unit - diluted (in dollars per share)	$ (0.27)	$ (1.28)	$ (3.99)	$ (9.68)
Nonvested anti-dilutive phantom units excluded from the calculation of diluted EPU (in shares)	160	0	221	0
Parent Company
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Add: Deemed capital contribution from 2022 Preferred Exchange Offer	$ 0	$ 0	$ 0	$ 20,974
Series A Preferred Units \| Subsidiaries
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Less: Net income attributable to Subsidiary Series A Preferred Units	(3,623)	(3,278)	(8,865)	(12,155)
Series A Preferred Units \| Parent Company
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Less: Net income attributable to Subsidiary Series A Preferred Units	(3,004)	(1,962)	(8,442)	(6,070)
Common Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss attributable to common limited partners	$ (2,753)	$ (13,028)	$ (41,136)	$ (96,848)
Weighted-average common units outstanding – basic (in shares)	10,376,000	10,168,000	10,320,000	10,003,000
Effect of nonvested phantom units (in shares)	0	0	0	0
Weighted-average common units outstanding – diluted (in shares)	10,376,000	10,168,000	10,320,000	10,003,000
Common Units \| Parent Company
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss attributable to common limited partners	$ (2,753)	$ (13,028)	$ (41,136)	$ (96,848)

SUPPLEMENTAL CASH FLOW INFORM_3

SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Supplemental cash flow information:
Cash interest paid	$ 72,749	$ 46,093
Cash paid for taxes	15	149
Noncash investing and financing activities:
Capital expenditures in trade accounts payable (period-end accruals)	7,354	4,102
2022 Preferred Exchange Offer	0	92,587
Series A Preferred Units
Noncash investing and financing activities:
Accretion of Subsidiary Series A Preferred Units, net of issuance cost amortization	$ 8,865	$ 10,554

UNIT-BASED AND NONCASH COMPEN_2

UNIT-BASED AND NONCASH COMPENSATION (Details) - SMLP LTIP $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($) director $ / shares shares
Phantom Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted units (in shares)	212,893
Grant date fair value (in dollars per share) \| $ / shares	$ 16
Vesting period	3 years
Unvested phantom units granted (in shares)	700,000
Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted units (in shares)	110,478
Grant date fair value \| $	$ 2.2
Common Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issued units (in shares)	38,100
Number of directors \| director	6
Grant date fair value (in dollars per share) \| $ / shares	$ 16
Units remaining available (in shares)	500,000

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Schedule of Environmental Matters (Details) - Meadowlark Midstream Gathering System $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Accrued environmental remediation, beginning balance	$ 3,705
Payments made	(579)
Changes in estimates	(60)
Accrued environmental remediation, ending balance	$ 3,066

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Narrative (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($) claim	Dec. 31, 2022 USD ($)
Loss Contingencies [Line Items]
Legal fines and other fees	$ 36,300
Claims settled \| claim	1
2015 Blacktail Release
Loss Contingencies [Line Items]
Loss contingency accrual	$ 25,500	$ 28,300
Unpaid penalties and fines, fixed rate (as a percent)	3.25%
Expected payment	$ 6,700
Claims settled \| claim	1
Pending claims \| claim	2
Natural Resource Damages To Federal and State Governments \| 2015 Blacktail Release
Loss Contingencies [Line Items]
Legal fines and other fees	$ 1,250
Penalties and fines, payment period	5 years
Damages Payable To Federal Government over Five Years \| 2015 Blacktail Release
Loss Contingencies [Line Items]
Legal fines and other fees	$ 25,000
Damages Payable To State Governments Over Six Years \| 2015 Blacktail Release
Loss Contingencies [Line Items]
Legal fines and other fees	$ 10,000
Penalties and fines, payment period	6 years
Damages Payable To Federal Criminal Over Five Years \| 2015 Blacktail Release
Loss Contingencies [Line Items]
Penalties and fines, payment period	5 years

SEGMENT INFORMATION - Assets, R

SEGMENT INFORMATION - Assets, Revenues, Depreciation and Amortization, and Capital Expenditures by Reportable Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Assets	$ 2,509,514	$ 2,559,964
Reportable Segments
Segment Reporting Information [Line Items]
Assets	2,498,284	2,547,818
Reportable Segments \| Rockies
Segment Reporting Information [Line Items]
Assets	896,333	886,629
Reportable Segments \| Permian
Segment Reporting Information [Line Items]
Assets	295,375	298,906
Reportable Segments \| Northeast
Segment Reporting Information [Line Items]
Assets	577,572	591,091
Reportable Segments \| Piceance
Segment Reporting Information [Line Items]
Assets	445,302	475,719
Reportable Segments \| Barnett
Segment Reporting Information [Line Items]
Assets	283,702	295,473
Corporate and Other
Segment Reporting Information [Line Items]
Assets	$ 11,230	$ 12,146

SEGMENT INFORMATION - Adjusted

SEGMENT INFORMATION - Adjusted EBITDA by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 79,965	$ 60,610	$ 211,095	$ 185,592
Rockies
Segment Reporting Information [Line Items]
Adjusted EBITDA	24,998	14,262	64,986	43,991
Permian
Segment Reporting Information [Line Items]
Adjusted EBITDA	5,840	4,882	16,283	13,848
Northeast
Segment Reporting Information [Line Items]
Adjusted EBITDA	27,751	19,353	65,806	57,989
Piceance
Segment Reporting Information [Line Items]
Adjusted EBITDA	15,292	14,249	43,640	45,367
Barnett
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 6,084	$ 7,864	$ 20,380	$ 24,397

SEGMENT INFORMATION - Reconcili

SEGMENT INFORMATION - Reconciliation of Net Income (Loss) to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting [Abstract]
Loss before income taxes and equity method investment income	$ (6,265)	$ (13,590)	$ (46,311)	$ (113,452)
Add:
Corporate and Other expense	5,487	2,151	20,695	11,778
Interest expense	34,568	24,932	103,966	73,982
Depreciation and amortization	31,013	29,076	91,438	90,101
Proportional adjusted EBITDA for equity method investees	16,917	11,949	42,655	33,807
Adjustments related to capital reimbursement activity	(3,111)	(1,517)	(6,778)	(4,823)
Unit-based and noncash compensation	1,396	692	5,158	2,964
Gain on asset sales, net	(40)	(99)	(183)	(409)
Long-lived asset impairments	0	7,016	455	91,644
Total of reportable segments' measures of profit	$ 79,965	$ 60,610	$ 211,095	$ 185,592