Schedule Pages: 114 line 2 column c and 309 line 22 column b :

Total Reported Operating Revenues of $55.7 Million includes $21.8 Million attributable to Leased Transportation capacity that is not part of Overthrust’s system pursuant to 119 FERC ¶ 61,069, at P 40 (2007). In addition, approximately 21% of Overthrust’s overall costs are allocable to the Leased Transportation capacity.

Schedule Page: 114 line 2 column d :

Total Reported Operating Revenues of $56.7 Million includes $21.8 Million attributable to Leased Transportation capacity that is not part of Overthrust’s system pursuant to 119 FERC ¶ 61,069, at P 40 (2007). In addition, approximately 21% of Overthrust’s overall costs are allocable to the Leased Transportation capacity.

Schedule Page: 118 line 20 column d:

Certain reclassifications have been made to the prior year presentation to conform to the current year presentation. These reclassifications had no impact on total assets, liabilities or equity, total net income or cash flows.

Schedule Page: 278 Line No.: 1 Column: a

FERC GAS TARIFF SECTION 33

Schedule Page: 278 Line No.: 2 Column: a

FERC GAS TARIFF SECTION 33

Schedule Page: 278 Line No.: 3 Column: a

FERC GAS TARIFF SECTION 14.6

Schedule Page: 278 Line No.: 4 Column: a

Account 254 predominately reflects MountainWest Overthrust Pipeline's estimate of amounts probable of refund to customers for excess deferred income taxes (EDIT) resulting from the reduction in the corporate income tax rate to 21% under the 2017 Tax Reform Act. Refer to Overthrust's FERC Form No. 2, Note 2 to Financial Statements for the year ending December 31, 2024 for further discussion.

Schedule Page: 309 Line No.: 11 Column: b

Schedule Page: 309 Line No.: 11 Column: c

Of the total reported volumes, 6,558,584 Dth is attributable to Leased Capacity

Schedule Page: 520 Line No.: 29 Column: c and d

Footnote to Instruction 5:

Overthrust does not bundle sales and transportation services.

Footnote to Instruction 7:

All quantities of gas were subject to Commission regulation.

Footnote to Instruction 9:

Overthrust does not have gas storage.

Schedule Page: 520 Line No.: 20 Column: c

This amount includes 6,558,584 Dth of Leased Capacity volumes which are not subject to the Annual Charge Adjustment (ACA). The total volume subject to the ACA is 279,431,472 Dth.

Schedule Page: 520 Line No.: 20 Column: d

This amount includes 810,042 Dth of Leased Capacity volumes which are not subject to the ACA. The total volume subject to the ACA is 104,114,646 Dth.

Schedule Page: 520 Line No.: 29 Column: c and d

Gas used for Meter and Regulator M&R Fuel. Applies to column (d) also.

Schedule Page: 521 Line No.: 4 Column: e

Allocation method was based on throughput. Applies to lines 11, 18, and 26 also.

Schedule Page: 521 Line No.: 4 Column: i

Shipper Supplied Gas, Gas Consumed in Pipeline Operations, and Net Excess or (Deficiency) balances are valued based on the "Inside FERC’s Gas Market Report" first-of-the-month posting for Northwest Pipeline Corp., Rocky Mountains, published for the first of the month following gas flow. Applies to lines 11, 18, and 26 also.

Schedule Page: 521 Line No.: 4 Column: n

In accordance with FERC Order No. 581, Shipper Supplied Gas is not directly charged to an account. Any excess or deficiency in net Shipper Supplied Gas (line 37) is recorded as “Other Regulatory Assets/Liabilities” (Accounts 182.3 / 254) with offsetting entries booked to “Regulatory Debits/Credits”, (Accounts 407.3 / .4). Applies to month 2 & 3 also.

Schedule Page: 521 Line No.: 18 Column: e

Gas used for M&R Fuel. Applies to all other columns on this line.

Schedule Page: 521 Line No.: 34 Column: e

“Net excess or (deficiency)” balances are refunded or collected in-kind through Overthrust’s “Gas Use, Lost or Gained and Unaccounted-for Gas-Reimbursement and Tracking” provision (§33) of the General Terms and Conditions of Overthrust's FERC Gas Tariff. Applies to month 2 & 3 also.