We are regulated by the Federal Energy Regulatory Commission (FERC). Accounting Standards Codification (ASC) Topic 980, “Regulated Operations,” (Topic 980), provides that certain costs that would otherwise be charged to expense should be deferred as regulatory assets, based on the expected recovery from customers in future rates. Likewise, certain actual or anticipated credits that would otherwise reduce expense should be deferred as regulatory liabilities, based on the expected return to customers in future rates. Management's expected recovery of deferred costs and return of deferred credits generally results from specific decisions by regulators granting such ratemaking treatment. We record certain incurred costs and obligations as regulatory assets or liabilities if, based on regulatory orders or other available evidence, it is probable that the costs or obligations will be included in amounts allowable for recovery or refunded in future rates. Accounting for businesses that are regulated and apply the provisions of Topic 980 can differ from the accounting requirements for non-regulated businesses. Transactions that are recorded differently as a result of regulatory accounting requirements include the capitalization of an equity return component on regulated capital projects, capitalization of other project costs, retirements of general plant assets, levelized cost of service, negative salvage, asset retirement obligations (ARO), employee-related benefits, environmental costs, and other costs and taxes included in, or expected to be included in, future rates. As a rate-regulated entity, our management has determined that it is appropriate to apply the accounting prescribed by Topic 980, and, accordingly, the

Certain customers reimburse us for costs we incur associated with construction of property, plant, and equipment utilized in our operations. As a rate-regulated entity applying Topic 980, we follow FERC guidelines with respect to reimbursement of construction costs. FERC tariffs only allow for cost reimbursement and are non-negotiable in nature; thus, in our judgment, the construction activities do not represent an ongoing major and central operation of our gas pipeline business and are not within the scope of ASC Topic 606, “Revenues from Contracts with Customers.” Accordingly, cost reimbursements are treated as a reduction to the cost of the constructed asset.

We are subject to regulation by certain state and federal authorities, including the FERC, with revenue derived from both firm and interruptible transportation and storage contracts. Firm transportation and storage agreements provide for a fixed reservation charge based on the pipeline or storage capacity reserved, and a commodity charge based on the volume of natural gas delivered/stored, each at rates specified in our FERC tariffs or as negotiated with our customers, with contract terms that are generally long-term in nature. Most of our long-term contracts contain an evergreen provision, which allows the contracts to be extended for periods primarily up to one year in length an indefinite number of times following the specified contract term and until terminated generally by either us or the customer, but in certain cases unilaterally by the customer, with advance notice of termination ranging from one to five years. Interruptible transportation and storage agreements provide for a volumetric charge based on actual commodity transportation or storage utilized in the period in which those services are provided, and the contracts are generally limited to one-month periods or less. Our performance obligations include the following:

In situations where, in our judgment, we consider the integrated package of services as a single performance obligation, which represents a majority of our contracts with customers, we do not consider there to be multiple performance obligations because the nature of the overall promise in the contract is to stand ready (with regard to firm transportation and storage contracts), receive, transport or store, and redeliver natural gas to the customer; therefore, revenue is recognized over time upon satisfaction of our daily stand ready performance obligation.

We recognize revenues for reservation charges over the performance obligation period, which is the contract term, regardless of the volume of natural gas that is transported or stored. Revenues for commodity charges from both firm and interruptible transportation services and storage services are recognized when natural gas is delivered at the agreed upon point or when natural gas is injected or withdrawn from the storage facility because they specifically relate to our efforts to provide these distinct services. Generally, reservation charges and commodity charges are recognized as revenue in the same period they are invoiced to our customers. As a result of the ratemaking process, certain amounts collected by us may be subject to refunds upon the issuance of final orders by the FERC in pending rate proceedings. We use judgment to record estimates of rate refund liabilities considering our and other third-party regulatory proceedings, advice of counsel, and other risks. At December 31, 2023 and 2022, we had no such rate refund liabilities.

customer imbalances are typically settled through the receipt or delivery of gas in the future based on the timelines outlined in Northwest’s tariff, whereas the over/under recovery of fuel is cleared up through Northwest’s semi-annual fuel tracker. Customer imbalances to be repaid or recovered in-kind are recorded as Exchange gas receivables or Exchange gas payables in our Balance Sheet. The under recovery of fuel is recorded as a Regulatory Asset and the over recovery is recorded as a Regulatory Liability. These imbalances are valued at published spot rates.

Our contract liabilities consist of a fixed rate facility charge billed to customers that declines annually as specified per the tariff. These liabilities are classified as current or non-current according to when such amounts are expected to be recognized. Current and non-current liabilities are included within Accrued Liabilities and Other Long-Term Liabilities, respectively, on our Balance Sheet.

We are a lessee through noncancellable lease agreements for property and equipment consisting primarily of buildings, land, vehicles, and equipment used in both our operations and administrative functions. We recognize a lease liability with an offsetting right-of-use asset in our Balance Sheet for operating leases based on the present value of the future lease payments. We have elected to combine lease and nonlease components for all classes of leased assets in our calculation of the lease liability and the offsetting right-of-use asset.

Our lease agreements require both fixed and variable periodic payments, with initial terms typically ranging from one year to 30 years. Payment provisions in certain of our lease agreements contain escalation factors which may be based on stated rates or a change in a published index at a future time. The amount by which a lease escalates based on the change in a published index, which is not known at lease commencement, is considered a variable payment and is not included in the present value of the future lease payments, which only includes those that are stated or can be calculated based on the lease agreement at lease commencement. In addition to the noncancellable periods, many of our lease agreements provide for one or more extensions of the lease agreement for periods ranging from one year in length to an indefinite number of times following the specified contract term. Other lease agreements provide for extension terms that allow us to utilize the identified leased asset for an indefinite period of time so long as the asset continues to be utilized in our operations. In consideration of these renewal features, we assess the term of the lease agreements, which includes using judgment in the determination of which renewal periods and termination provisions, when at our sole election, will be reasonably certain of being exercised. Periods after the initial term or extension terms that allow for either party to the lease to cancel the lease are not considered in the assessment of the lease term. Additionally, we have elected to exclude leases with an original term of one year or less, including renewal periods, from the calculation of the lease liability and the offsetting right-of-use asset.

We are subject to federal, state, and local environmental laws and regulations. Environmental expenditures are expensed or capitalized depending on their economic benefit and potential for rate recovery. We believe that expenditures required to meet applicable environmental laws and regulations are prudently incurred in the ordinary course of business and such expenditures would be permitted to be recovered through rates.

In accordance with the Climate Commitment Act of the state of Washington, which established a market-based cap-and-invest program, we are required to obtain emission allowances for the carbon emissions from nine of our thirteen compressor stations within the state of Washington whose annual carbon emissions exceed 25,000 metric tons of carbon dioxide equivalent. We record the purchased emission allowances at cost and the associated accumulated interest to a regulatory asset. The difference between the allowances held and the allowances required based on actual emissions for the period are measured using an estimate based on our most recent cost of allowances and accrued to a current liability and to a regulatory asset. Our Settlement allows us to recover the costs of purchasing allowances under the program in our next rate case.

Property, plant and equipment, consisting principally of natural gas transmission facilities, is recorded at cost. The FERC identifies installation, construction and replacement costs that are to be capitalized and included in our asset base for recovery in rates. Routine maintenance, repairs, and renewal costs are charged to income as incurred. Gains or losses from the ordinary sale or retirement of property, plant and equipment are charged or credited to accumulated depreciation; certain other gains or losses are recorded in operating income.

We provide for depreciation under the composite (group) method at straight-line FERC prescribed rates that are applied to the cost of the group for transmission and storage facilities. Under this method, assets with similar lives and characteristics are grouped and depreciated as one asset. Included in our depreciation rates is a negative salvage component (net cost of removal) that we currently collect in rates. Our depreciation rates are subject to change each time we file a general rate case with the FERC.


	Depreciation Rate	December 31,
		2023		2022
		(Thousands)
Transmission facilities	2.70% - 10.20%	$	3,569,545	$	3,490,141
Storage facilities	1.60% - 2.76%	155,433		142,326
Construction in progress	Not applicable	84,945		44,702
Other	0% - 33.33%	164,977		159,085
Property, plant and equipment		3,974,900		3,836,254
Less-Accumulated depreciation and amortization		2,026,007		1,941,806
Total property, plant and equipment, net		$	1,948,893	$	1,894,448

We record a liability and increase the basis in the underlying asset for the present value of each expected future ARO at the time the liability is initially incurred, typically when the asset is acquired or constructed. Measurement of ARO includes, as a component of future expected costs, an estimate of the price that a third party would demand, and could expect to receive, for bearing the uncertainties inherent in the obligations, sometimes referred to as market-risk premium. We measure changes in the liability due to passage of time by applying an interest method of allocation. This amount is recognized as an increase in the carrying amount of the liability and is offset by a regulatory asset. The gross regulatory asset balances associated with ARO as of December 31, 2023 and 2022 were $116.2 million and $109.0 million, respectively. The regulatory asset is expected to be fully recovered through the negative salvage component of depreciation included in our rates; as such, that amount of the negative salvage component of accumulated depreciation has been reclassified and netted against the amount of the ARO regulatory asset to result in a regulatory liability of $30.7 million and $30.6 million at December 31, 2023 and 2022, respectively.

constitutes an actual cost of construction under established regulatory practices. The FERC has prescribed a formula to be used in computing separate allowances for borrowed and equity AFUDC. The allowance for borrowed funds used during construction was $0.7 million for 2023, $0.7 million for 2022, and $0.2 million for 2021. The allowance for equity funds was $3.1 million, $2.3 million, and $1.4 million for 2023, 2022, and 2021, respectively.

We are a natural gas company organized as a pass-through entity and our taxable income or loss is consolidated on the federal income tax return of our parent, Williams. We generally are treated as a pass-through entity for state and local income tax purposes, and those taxes are generally borne on a consolidated basis by Williams. Net income for financial statement purposes may differ significantly from taxable income of Williams as a result of differences between the tax basis and financial reporting basis of assets and liabilities.

Accounts receivable are carried on a gross basis less an allowance for doubtful accounts. We estimate the allowance for doubtful accounts, considering current expected credit losses using a forward-looking “expected loss” model, the financial condition of our customers, and the age of past due accounts. The majority of our trade receivable balances are due within 30 days. We monitor the credit quality of our counterparties through review of collection trends, credit ratings, and other analyses, such as bankruptcy monitoring, if applicable. Financial assets are evaluated as one pool. Changes in counterparty risk factors could lead to reassessment of the composition of our financial assets as one pool. We calculate our allowance for credit losses incorporating an aging method. In estimating our expected credit losses, we utilized historical loss rates over many years. Our expected credit loss estimate considered both internal and external forward-looking commodity price expectations, as well as counterparty credit ratings, and factors impacting their near-term liquidity.

We do not offer extended payment terms and typically receive payment within one month. We consider receivables past due if full payment is not received by the contractual due date. Past due accounts are generally written off against the allowance for doubtful accounts only after all collection attempts have been exhausted. We do not have a material amount of significantly aged receivables at December 31, 2023 and 2022.

All materials and supplies inventory is stated at average cost. We perform an annual review of materials and supplies inventories, including a quarterly analysis of parts that may no longer be useful due to planned replacements of compressor engines and other components on our system. Based on this assessment, we record a reserve for the value of the inventory which can no longer be used for maintenance and repairs on our pipeline. The reserve for inventory was $1.0 million at December 31, 2023, and there was a minimal reserve at December 31, 2022.

We record liabilities for estimated loss contingencies, including environmental matters, when we assess that a loss is probable and the amount of the loss can be reasonably estimated. These liabilities are calculated based upon our assumptions and estimates with respect to the likelihood or amount of loss and upon advice of legal counsel, engineers, or other third-parties regarding the probable outcomes of the matters. These calculations are made without consideration of any potential recovery from third-parties. We recognize insurance recoveries or reimbursements from others when realizable. Revisions to these liabilities are generally reflected in income when new or different facts or information become known or circumstances change that affect the previous assumptions or estimates.

We do not have employees. Certain of the costs charged to us by Williams associated with employees who directly support us include costs related to Williams’ pension and other postretirement benefit plans (see Note 7 – Benefit Plans). Although the underlying benefit plans of Williams are single-employer plans, we follow multiemployer plan accounting whereby the amount charged to us, and thus paid by us, is based on our share of net periodic benefit cost.