Term Marketing Dated: December 14, 2015 Dated: December 14, 2015 Source: TC PIPELINES LP, 10-K, 2/26/2016 APPENDIX A Contract Identification FT18150 Date: November 01, 2016 Supersedes Appendix Dated: November 01, 2015 Shipper: ANR PIPELINE COMPANY Maximum Daily Quantity (Dth/Day) per Location: Begin Date End Date Point(s) of Primary Receipt Point(s) of Primary Delivery MDQ Maximum Allowable Operating Pressure (MAOP) 11/01/2014 03/31/2015 SOUTH CHESTER 101,300 974 11/01/2014 03/31/2015 DEWARD 101,300 974 04/01/2015 10/31/2015 SOUTH CHESTER 0 974 11/01/2015 03/31/2016 SOUTH CHESTER 101,300 974 11/01/2015 03/31/2016 DEWARD 101,300 974 04/01/2016 10/31/2016 SOUTH CHESTER 0 974 11/01/2016 03/31/2017 SOUTH CHESTER 101,300 974 11/01/2016 03/31/2017 DEWARD 101,300 974 04/01/2017 10/31/2017 SOUTH CHESTER 0 974 11/01/2014 03/31/2015 FARWELL 101,300 974 04/01/2015 10/31/2015 FARWELL 0 974 11/01/2015 03/31/2016 FARWELL 101,300 974 04/01/2016 10/31/2016 FARWELL 0 974 11/01/2016 03/31/2017 FARWELL 101,300 974 04/01/2017 10/31/2017 FARWELL 0 974 Source: TC PIPELINES LP, 10-K, 2/26/2016 QuickLinks Exhibit 99.12 TRANSPORTATION SERVICE AGREEMENT Contract Identification FT18150 APPENDIX A Contract Identification FT18150 Source: TC PIPELINES LP, 10-K, 2/26/2016