X0306 4 2019-07-23 1 0001513965 Third Coast Midstream, LLC AMID 0001502553 ARCLIGHT ENERGY PARTNERS FUND V, L.P. C/O ARCLIGHT CAPITAL PARTNERS, LLC 200 CLARENDON STREET, 55TH FLOOR BOSTON MA 02117 1 0 1 1 SEE REMARKS 0001673060 Magnolia Infrastructure Holdings, LLC C/O ARCLIGHT CAPITAL PARTNERS, LLC 200 CLARENDON STREET, 55TH FLOOR BOSTON MA 02117 1 0 1 0 0001638285 Magnolia Infrastructure Partners, LLC C/O ARCLIGHT CAPITAL PARTNERS, LLC 200 CLARENDON STREET, 55TH FLOOR BOSTON MA 02117 1 0 1 0 0001526603 American Midstream GP, LLC C/O ARCLIGHT CAPITAL PARTNERS, LLC 200 CLARENDON STREET, 55TH FLOOR BOSTON, MA 02117 1 0 1 0 0001575227 High Point Infrastructure Partners, LLC C/O ARCLIGHT CAPITAL PARTNERS, LLC 200 CLARENDON STREET, 55TH FLOOR BOSTON MA 02117 1 0 1 0 0001715051 AMID GP Holdings, LLC C/O ARCLIGHT CAPITAL PARTNERS, LLC 200 CLARENDON STREET, 55TH FLOOR BOSTON MA 02117 1 0 1 0 0001441290 ArcLight Capital Holdings, LLC C/O ARCLIGHT CAPITAL PARTNERS, LLC 200 CLARENDON STREET, 55TH FLOOR BOSTON MA 02117 1 0 1 0 0001502945 ArcLight Capital Partners, LLC 200 CLARENDON STREET, 55TH FLOOR BOSTON MA 02117 1 0 1 0 0001405456 Revers Daniel R C/O ARCLIGHT CAPITAL PARTNERS, LLC 200 CLARENDON STREET, 55TH FLOOR BOSTON MA 02117 1 0 1 0 Common Units (limited partner interests) 2019-07-23 4 D 0 42514126 0.00 D 0 I See footnote Represents common units representing limited partnership interests (the "Common Units") of Third Coast Midstream, LLC (f/k/a American Midstream Partners, LP), a Delaware limited liability company (the "Issuer"). Pursuant to that certain Master Contribution Agreement, dated July 22, 2019, by and among Anchor Midstream Acquisition, LLC, a Delaware limited liability company ("Anchor Acquisition"), 3CM Holdings, LLC (f/k/a High Point Infrastructure Partners, LLC), a Delaware limited liability company ("3CM"), Third Coast Midstream Holdings, LLC (f/k/a/ American Midstream GP, LLC), a Delaware limited liability company (the "General Partner"), Magnolia Infrastructure Holdings, LLC, a Delaware limited liability company ("Magnolia Holdings"), Magnolia Infrastructure Partners, LLC, a Delaware limited liability company ("Magnolia"), AMID GP Holdings, LLC, a Delaware limited liability company ("AMID GP"), JP Energy Development, L.P., a Delaware limited partnership ("JP Energy"), Busbar II, LLC, a Delaware limited liability company ("Busbar"), High Point Energy, LLC, a Texas limited liability company, ArcLight Energy Partners Fund V, L.P., (continued from footnote 2) a Delaware limited partnership ("Fund V"), Stephen W. Bergstrom, individually ("Bergstrom") and Daniel C. Campbell, individually, (i) JP Energy, as holder of 422,805 Common Units, transferred all of its Common Units to Magnolia Holdings, (ii) Magnolia Holdings, as holder of 20,372,720 Common Units, transferred all of its Common Units to the General Partner, (iii) Magnolia, as holder of 5,108,669 Common Units, transferred all of its Common Units to the General Partner, (iv) Busbar, as holder of 2,853,482 Common Units, transferred all of its Common Units to the General Partner and (v) Bergstrom, as holder of 64,221 Common Units, transferred all of his Common Units to the General Partner. Immediately following the preceding transactions, the General Partner, as holder of 41,209,117 Common Units, transferred all of its Common Units to Anchor Acquisition. On July 23, 2019, pursuant to a Plan of Conversion adopted by the Issuer, the Issuer converted into a Delaware limited liability company named "Third Coast Midstream, LLC" ("Third Coast Midstream" and, such conversion, the "AMID Conversion"). In connection with the AMID Conversion, each Common Unit issued and outstanding immediately prior to the AMID Conversion was converted into one limited liability company unit of Third Coast Midstream. Magnolia Holdings also beneficially owns 1,369,230 Common Units issuable upon exercise of the warrants issued to Magnolia Holdings by the Issuer, dated July 18, 2019. After the AMID Conversion, all of the outstanding warrants converted into the right to receive 1,369,230 limited liability company units of Third Coast Midstream. As a result of the AMID Conversion, all Common Units were cancelled and ceased to be outstanding and none of JP Energy, Magnolia Holdings, Magnolia and Busbar beneficially own any Common Units. (A) ArcLight Capital Holdings, LLC ("ArcLight Holdings") is the sole manager and member of ArcLight Capital Partners, LLC ("ArcLight Partners" and, together with ArcLight Holdings and Fund V, the "ArcLight Entities"). ArcLight Partners is the investment adviser to Fund V. ArcLight Holdings is the manager of the general partner of Fund V. Mr. Revers is a manager of ArcLight Holdings, and a managing partner of ArcLight Partners and has certain voting and dispositive rights as a member of ArcLight Partners' investment committee. Fund V directly owns Busbar and Magnolia Holdings, which owns Magnolia. Fund V, through Magnolia, also owns approximately 90% of the ownership interest in 3CM. 3CM and AMID GP, a subsidiary of Magnolia Holdings, own respectively, approximately 86% and 14% of the General Partner. (B) Some of the entity names in the signature blocks have been abbreviated due to the limitations of the electronic filing system. Please refer to the text above for the complete legal names of such entities. /s/ Daniel R. Revers FUND V By: ArcLight PEF GP V, LLC, its General Partner By: ArcLight Capital Holdings, LLC, its Manager By: ACHP II, L.P., its Managing Member By: ACH GP, LLC, its General Partner By: Daniel R. Revers, Manager 2019-07-24 /s/ Daniel R. Revers, President MAGNOLIA INFRASTRUCTURE HOLDINGS, LLC By: Daniel R. Revers, President 2019-07-24 /s/ Daniel R. Revers MAGNOLIA INFRASTRUCTURE PARTNERS, LLC By: Daniel R. Revers, President 2019-07-24 /s/ Daniel R. Revers THIRD COAST MIDSTREAM HOLDINGS, LLC By: its Class A Member, 3CM Holdings, LLC By: Daniel R. Revers, President 2019-07-24 /s/ Daniel R. Revers 3CM HOLDINGS, LLC By: Daniel R. Revers, President 2019-07-24 /s/ Daniel R. Revers AMID GP HOLDINGS, LLC By: Daniel R. Revers, President 2019-07-24 /s/ Daniel R. Revers ARCLIGHT CAPITAL HOLDINGS, LLC By: ACHP II, L.P., its Managing Member By: ACH GP, LLC, its General Partner By: Daniel Revers, Manager 2019-07-24 /s/ Daniel R. Revers ARCLIGHT CAPITAL PARTNERS, LLC By: Daniel R. Revers, Managing Partner 2019-07-24 /s/ Daniel R. Revers 2019-07-24