X0306 4 2022-09-16 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 2022-09-16 4 M 0 17160 A 103913 D Common Units 2022-09-16 4 F 0 6753 15.79 D 97160 D Phantom Units 2022-09-16 4 M 0 17160 0.00 D Common Units 17160 0 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. The final one-third of the phantom units subject to the original award agreement vested on September 16, 2022, on the third anniversary of the September 16, 2019 grant date. The Reporting Person received 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. After giving effect to the transactions reported in this Report, the Reporting Person holds an aggregate 140,096 phantom units. 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 2022-09-20