X0306 4 2023-03-15 0 0001549922 Summit Midstream Partners, LP SMLP 0001555671 Deneke J Heath C/O SUMMIT MIDSTREAM PARTNERS, LP 910 LOUISIANA STREET, SUITE 4200 HOUSTON TX 77002 1 1 0 0 See remarks below. Common Units 2023-03-15 4 M 0 36294 A 133454 D Common Units 2023-03-15 4 F 0 14282 16.00 D 119172 D Common Units 2023-03-15 4 M 0 25000 A 144172 D Common Units 2023-03-15 4 F 0 9838 16.00 D 134334 D Common Units 2023-03-15 4 M 0 17934 A 152268 D Common Units 2023-03-15 4 F 0 7058 16.00 D 145210 D Common Units 2023-03-15 4 M 0 6556 A 151766 D Common Units 2023-03-15 4 F 0 2580 16.00 D 149186 D Common Units 2023-03-15 4 M 0 19456 A 168642 D Common Units 2023-03-15 4 F 0 7656 16.00 D 160986 D Common Units 2023-03-15 4 M 0 25993 A 186979 D Common Units 2023-03-15 4 F 0 10229 16.00 D 176750 D Phantom Units 2023-03-15 4 A 0 90045 0.00 A Common Units 90045 90045 D Phantom Units 2023-03-15 4 A 0 60030 0.00 A Common Units 60030 60030 D Phantom Units 2023-03-15 4 M 0 36294 0.00 D Common Units 36294 0 D Phantom Units 2023-03-15 4 M 0 25000 0.00 D Common Units 25000 25000 D Phantom Units 2023-03-15 4 M 0 17934 0.00 D Common Units 17934 35868 D Phantom Units 2023-03-15 4 M 0 6556 0.00 D Common Units 6556 0 D Phantom Units 2023-03-15 4 M 0 19456 0.00 D Common Units 19456 19456 D Phantom Units 2023-03-15 4 M 0 25993 0.00 D Common Units 25993 103973 D Each phantom unit is the economic equivalent of one common unit. On November 9, 2020, the Issuer effected a 1-for-15 reverse unit split (the "Reverse Unit Split"). Pursuant to the Reverse Unit Split, common unitholders received one common unit for every 15 common units owned at the close of business on November 9, 2020. All fractional units created by the Reverse Unit Split were rounded to the nearest whole unit. The common units began trading on a split-adjusted basis on November 10, 2020. After giving effect to the Reverse Unit Split, the number of issued and outstanding common units decreased to 3,774,992. Common units being withheld to pay tax liability. One-third of the phantom units (rounded down to the nearest whole number of units, except in the case of the final vesting date) shall vest on each of the first, second and third anniversaries of the March 15, 2023 Reference Date, subject to continued employment and accelerated vesting as provided in the applicable award agreement. The Reporting Person will receive distribution equivalent rights ("DERs") for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units The phantom units and associated DERs do not expire. The phantom units are settled upon vesting in common units (on a one-for-one basis) or in cash, at the discretion of the Issuer. The phantom units shall vest if and to the extent that the phantom units are earned during the performance period from January 1, 2023 through December 31, 2025, which will depend on whether the performance criteria are achieved as determined by the committee as soon as reasonably practicable, but no later than Friday, March 6, 2026. The vesting of the phantom units is subject to continued employment and accelerated vesting as provided in the applicable award agreement. The Reporting Person will receive DERs for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. The final one-third of the phantom units (rounded down to the nearest whole number of units, except in the case of the final vesting date) subject to the original award agreement vested on March 15, 2023, on the third anniversary of the March 15, 2020 reference date. The Reporting Person received DERs for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. One-third of the phantom units subject to the original award agreement vested on March 15, 2023, with the final one-third of the phantom units subject to vesting on the third anniversary of the March 15, 2021 reference date, subject to continued employment. The Reporting Person received DERs for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. One-third of the phantom units subject to the original award agreement vested on March 15, 2023, with the remaining phantom units subject to vesting on the second and third anniversaries of the March 15, 2022 reference date, subject to continued employment. The Reporting Person received DERs for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. The phantom units (rounded down to the nearest whole number of units) vested on March 15, 2023, subject to continued employment and accelerated vesting as provided in the applicable award agreement. The Reporting Person received DERs for each phantom unit, if applicable, providing for payment on the vesting date of a lump sum of cash equal to any accrued distributions from and after the grant date of the phantom units. One-half of the phantom units (rounded down to the nearest whole number of units, except in the case of the final vesting date) vested on March 15, 2023, and the other half shall vest on March 15, 2024, subject to continued employment and accelerated vesting as provided in the applicable award agreement. The Reporting Person received DERs for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. Twenty percent of the phantom units (rounded down to the nearest whole number of units, except in the case of the final vesting date) vested on March 15, 2023 and sixty percent and twenty percent of the phantom unites shall respectively vest on the second and third anniversaries of the March 15, 2022, the reference date, subject to continued employment and accelerated vesting as provided in the applicable award agreement. The Reporting Person received DERs for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. After giving effect to the transactions reported in this Report, the Reporting Person holds an aggregate 334,372 phantom units. This total includes phantom units from other tranches with different vesting dates. The Reporting Person is President and Chief Executive Officer of Summit Midstream GP, LLC, the general partner of the Issuer (the "General Partner"). The Issuer is managed by the directors and executive officers of the General Partner. /s/ James D. Johnston, Attorney-in-Fact for J. Heath Deneke 2023-03-17