X0306 4 2018-12-01 0 0001549922 Summit Midstream Partners, LP SMLP 0001235281 MALLETT LEONARD WAYNE C/O SUMMIT MIDSTREAM PARTNERS, LP 1790 HUGHES LANDING BLVD., SUITE 500 THE WOODLANDS TX 77380 0 1 0 0 See remarks below. Common Units 2018-12-01 4 M 0 28658 A 110608 D Phantom Units 2018-12-01 4 M 0 28658 0.00 D Common Units 28658 0 D Distribution Equivalent Rights 6.90 2018-12-01 4 D 0 28658 0.00 D Common Units 28658 0 D Each phantom unit is the economic equivalent of one common unit. The final one-third of the phantom units subject to the original award agreement vested on December 1, 2018, on the third anniversary of the December 1, 2015 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. The Reporting Person is Executive Vice President and Chief Operations 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/ Brock M. Degeyter, Attorney-in-Fact for Leonard W. Mallett 2018-12-04