X0306 4 2019-03-15 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 2019-03-15 4 M 0 37526 A 148134 D Phantom Units 2019-03-15 4 M 0 13495 0.00 D Common Units 13495 0 D Distribution Equivalent Rights 6.90 2019-03-15 4 D 0 13495 0.00 D Common Units 13495 0 D Phantom Units 2019-03-15 4 M 0 10370 0.00 D Common Units 10370 10370 D Distribution Equivalent Rights 4.60 2019-03-15 4 D 0 10370 0.00 D Common Units 10370 0 D Phantom Units 2019-03-15 4 M 0 13661 0.00 D Common Units 13661 27322 D Distribution Equivalent Rights 2.30 2019-03-15 4 D 0 13661 0.00 D Common Units 13661 0 D Phantom Units 2019-03-15 4 A 0 66462 0.00 A Common Units 66462 66462 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 March 15, 2019, on the third anniversary of the March 15, 2016 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. One-third of the phantom units subject to the original award agreement vested on March 15, 2019, with the final one-third of the phantom units subject to vesting on the third anniversary of the March 15, 2017 grant 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, 2019, with the remaining phantom units subject to vesting on the second and third anniversaries of the March 15, 2018 grant 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) shall vest on each of the first, second and third anniversaries of the Grant Date (March 15, 2019), 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 Reporting Person is President, Chief Executive Officer, 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 2019-03-18