X0306 4 2022-03-14 0 0001549922 Summit Midstream Partners, LP SMLP 0001911802 Sicinski Matthew B. C/O SUMMIT MIDSTREAM PARTNERS, LP 910 LOUISIANA STREET, SUITE 4200 HOUSTON TX 77002 0 1 0 0 See remarks below. Common Units 2022-03-15 4 M 0 2933 A 5151 D Common Units 2022-03-15 4 F 0 715 14.83 D 4436 D Common Units 2022-03-15 4 M 0 867 A 5303 D Common Units 2022-03-15 4 F 0 212 14.83 D 5091 D Phantom Units 2022-03-14 4 A 0 5240 0.00 A Common Units 5240 5240 D Phantom Units 2022-03-15 4 M 0 2933 0.00 D Common Units 2933 2933 D Phantom Units 2022-03-15 4 M 0 867 0.00 D Common Units 867 1733 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, 2022 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. After giving effect to the transactions reported in this Report, the Reporting Person holds an aggregate 9,906 phantom units. 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, 2022, with the final one-third of the phantom units subject to vesting on the third anniversary of the March 15, 2020 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 (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, 2022, with the remaining phantom units subject to vesting on the second and third anniversaries 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. The Reporting Person is Senior Vice President, Chief Accounting 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 Matthew B. Sicinski 2022-03-16