Overthrust is indirectly owned by the MountainWest Pipelines Holding Company which is in turn 100% owned by The WIlliams Companies, Inc

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.

In 2024, Total Reported Revenues includes $29.1 Millions 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.

In 2023, Total Reported Revenues includes $29.1 Millions 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. 1

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

404.3 Amortization Expense - Utility Plant			$	550

Contributions from Dominion Energy Questar Pipeline, LLC			$	4,161,000

Reconciliation of Plant and Provision Accounts:
Includes Book Retirements - 101 (page 204, line 129, col. d)			$	(140,000)

Inventory in account 164.1 represents the balance of pipeline owned gas which the pipeline intends to sell or transport. Pipeline owned gas is reported under the inventory method.

			DEF
CTD			TAX			12/31/2024
DESCRIPTION			ACCT			Balance
PROPERTY, PLANT, & EQUIPMENT			190			5,449
REGULATORY LIABILITIES			190			3,178,141
OTHER ACCRUED LIABILITIES			190			1,223,489
190 TOTAL						4,407,079

Corporate federal income taxes related to previous ownership (SouthWest Gas Holdings, Inc.) that were written off

			DEF
CTD			TAX			12/31/2024
DESCRIPTION			ACCT			Balance
PROPERTY, PLANT, & EQUIPMENT			282			(3,856,313)
282 TOTAL						(3,856,313)

			DEF
CTD			TAX			45,657
DESCRIPTION			ACCT			Balance
REGULATORY ASSETS			283			(148,317)
DEFERRED CHARGES & OTHER ASSETS			283			(181,243)
283 TOTAL						(329,560)

Docket RP08-71-000

Docket RP24-928

Docket RP10-1085-000

Balance predominately reflects Overthrust'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. See Note 2 to the Financial Statements for further discussion.

In 2024, Total Reported Operating Revenues of $75.4 million includes $29.065 MM 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.

In 2023, Total Reported Operating Revenues of $72.9 million includes $29.065 MM 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.

Does not include 3,321,229 Dth Leased Capacity

Capacity leased to Rockies Express Pipeline as noted on page 213

Does not include 3,321,229 Dth Leased Capacity

All Transmission Plant except for Electronic Flow Measurement (EFM) and Intangible is depreciated at 2.25%

EFM is depreciated at 8.33%

Intangible is amortized at 20.0%

Enterprise shared services are charged to Overthrust and other franchises via specific allocations based on a relationship with the delivery of services, as in the case of some human resource services costs are allocated based on employee headcount, or via general allocations using the modified Massachusetts formula for residual overhead costs that are not readily assignable to a particular operating area or franchise via specific allocation

Enterprise shared services are charged to Overthrust and other franchises for fleet leasing and other fleet costs via specific allocations based on labor costs assigned to capital work orders.

Payroll and non-payroll charges for the benefit of the Transmission & Gulf of America Operating Area that are not specific to a franchise are allocated to franchises included in the Transmission & Gulf of America Operating Area, including Overthrust, via specific allocations based on a relationship with the delivery of services, as in the case of some human resource services costs are allocated based on employee headcount, or via general allocations using the modified Massachusetts formula for residual overhead costs that are not readily assignable to a particular franchise via specific allocation. The Transmission & Gulf of America Operating Area includes certain non-regulated franchises, MountainWest Overthrust Pipeline, LLC, MountainWest Pipeline, LLC, Northwest Pipeline LLC, and Transcontinental Gas Pipe Line Company, LLC. Allocation to Williams Partners Operating LLC is for the non-regulated franchises in the operating area.

Houston, Texas Williams tower building rent is allocated based on employee labor costs.

Employees' direct assignment payroll and non-payroll charges for the benefit of the Transmission & Gulf of America Operating Area that are not specific to a franchise are allocated to franchises included in the Transmission & Gulf of America Operating Area based on the modified Massachusetts formula. The Transmission

& Gulf of America Operating Area includes certain non-regulated franchises, MountainWest Overthrust Pipeline, LLC, MountainWest Pipeline, LLC, Northwest Pipeline LLC, and Transcontinental Gas Pipe Line Company, LLC.

Salt Lake City, Utah building rent is allocated based on employee labor costs.

Operator Balancing Agreement allocations

Operator Balancing Agreement allocations

12/3/2024 represents the first day of the three day peak ranging from 12/3/24 - 12/5/24.

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.

This amount includes 3,495,582 Dth of Leased Capacity volumes which are not subject to the Annual Charge Adjustment (ACA). The total volume subject to the ACA is 559,274,738 Dth.

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

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.

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 months 2 & 3 also.

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

“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 months 2 & 3 also.