X0306 4 2021-03-15 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 2021-03-15 4 M 0 36294 A 36294 D Common Units 2021-03-15 4 F 0 14282 29.00 D 22012 D Phantom Units 2021-03-15 4 M 0 36294 0.00 D Common Units 36294 72588 D Each phantom unit is the economic equivalent of one common unit. Common Units being withheld to pay tax liability. One-third of the phantom units subject to the original award agreement vested on March 15, 2021, with the remaining phantom units subject to vesting on the second and third anniversaries of the March 15, 2020 reference date, subject to continued employment. 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 reference 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. Total excludes phantom units from other tranches with different vesting and expiration 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 2021-03-17