10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

(Mark One)

þ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended June 30, 2013

OR

¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                          to                         

Commission file number: 1-7414

NORTHWEST PIPELINE LLC

(Exact name of registrant as specified in its charter)

DELAWARE	26-1157701
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)
295 Chipeta Way Salt Lake City, Utah	84108
(Address of principal executive offices)	(Zip Code)

Registrant’s telephone number, including area code: (801) 583-8800

NORTHWEST PIPELINE GP

(Former name, former address and former fiscal year, if changed since last report)

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  þ    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  þ    No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer,” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer	¨	Accelerated filer	¨
Non-accelerated filer	þ  (Do not check if a smaller reporting company)	Smaller reporting company	¨

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨    No  þ

THE REGISTRANT MEETS THE CONDITIONS SET FORTH IN GENERAL INSTRUCTION (H)(1)(a) AND (b) OF FORM 10-Q AND IS THEREFORE FILING THIS FORM 10-Q WITH THE REDUCED DISCLOSURE FORMAT.

NORTHWEST PIPELINE LLC

FORM 10-Q

INDEX

	Page
PART I. FINANCIAL INFORMATION:
Item 1. Financial Statements -
Statement of Comprehensive Income — Three and Six Months Ended June 30, 2013 and 2012		1
Balance Sheet — June 30, 2013 and December 31, 2012		2
Statement of Cash Flows — Six Months Ended June 30, 2013 and 2012		4
Notes to Financial Statements		5
Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations		9
Item 4. Controls and Procedures		10
PART II. OTHER INFORMATION:
Item 1. Legal Proceedings		11
Item 5. Other Information		11
Item 6. Exhibits		12

Forward Looking Statements

Certain matters contained in this report include “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. These forward-looking statements relate to anticipated financial performance, management’s plans and objectives for future operations, business prospects, outcome of regulatory proceedings, market conditions, and other matters. We make these forward-looking statements in reliance on the safe harbor protections provided under the Private Securities Litigation Reform Act of 1995.

All statements, other than statements of historical facts, included in this report that address activities, events or developments that we expect, believe or anticipate will exist or may occur in the future are forward-looking statements. Forward-looking statements can be identified by various forms of words such as “anticipates,” “believes,” “seeks,” “could,” “may,” “should,” “continues,” “estimates,” “expects,” “assumes,” “forecasts,” “intends,” “might,” “goals,” “objectives,” “targets,” “planned,” “potential,” “projects,” “scheduled,” “will,” “guidance,” “outlook,” “in service date,” or other similar expressions. These statements are based on management’s beliefs and assumptions and on information currently available to management and include, among others, statements regarding:

• Amounts and nature of future capital expenditures;

i

• Expansion and growth of our business and operations;

• Financial condition and liquidity;

• Business strategy;

• Cash flow from operations or results of operations;

• Rate case filings;

• Natural gas prices, supply, and demand; and

• Demand for our services.

Forward-looking statements are based on numerous assumptions, uncertainties, and risks that could cause future events or results to be materially different from those stated or implied in this report. Many of the factors that will determine these results are beyond our ability to control or predict. Specific factors that could cause actual results to differ from results contemplated by the forward-looking statements include, among others, the following:

• Availability of supplies, market demand, and volatility of prices;

• Inflation, interest rates and general economic conditions (including future disruptions and volatility in the global credit markets and the impact of these events on our customers and suppliers);

• The strength and financial resources of our competitors and the effects of competition;

• Development of alternative energy sources;

• The impact of operational and development hazards and unforeseen interruptions;

• Costs of, changes in, or the results of laws, government regulations (including safety and environmental regulations), environmental liabilities, litigation, and rate proceedings;

• Our allocated costs for defined benefit pension plans and other postretirement benefit plans sponsored by our affiliates;

• Changes in maintenance and construction costs;

• Changes in the current geopolitical situation;

• Our exposure to the credit risks of our customers and counterparties;

• Risks related to strategy and financing, including restrictions stemming from our debt agreements, future changes in our credit ratings and the availability and cost of capital;

• Risks associated with weather and natural phenomenon, including climate conditions;

• Acts of terrorism, including cybersecurity threats and related disruptions; and

• Additional risks described in our filings with the Securities and Exchange Commission (SEC).

Given the uncertainties and risk factors that could cause our actual results to differ materially from those contained in any forward-looking statement, we caution investors not to unduly rely on our forward-looking statements. We disclaim any obligations to and do not intend to update the above list or to announce publicly the result of any revisions to any of the forward-looking statements to reflect future events or developments.

ii

In addition to causing our actual results to differ, the factors listed above and referred to below may cause our intentions to change from those statements of intention set forth in this report. Such changes in our intentions may also cause our results to differ. We may change our intentions, at any time and without notice, based upon changes in such factors, our assumptions, or otherwise.

Because forward-looking statements involve risks and uncertainties, we caution that there are important factors, in addition to those listed above, that may cause actual results to differ materially from those contained in the forward-looking statements. For a detailed discussion of those factors, see Part I, Item 1A. Risk Factors in our Annual Report on Form 10-K for the year ended December 31, 2012.

iii

PART I – FINANCIAL INFORMATION

ITEM 1. Financial Statements.

NORTHWEST PIPELINE GP

STATEMENT OF COMPREHENSIVE INCOME

(Thousands of Dollars)

(Unaudited)

	Three months ended						Six months ended
	June 30,						June 30,
	2013			2012			2013			2012
OPERATING REVENUES	$	113,853		$	106,311		$	232,587		$	217,683
OPERATING EXPENSES:
General and administrative		15,773			17,417			31,983			34,231
Operation and maintenance		18,693			19,236			35,488			36,652
Depreciation		23,728			23,225			47,740			46,535
Regulatory debits (credits)		165			(115	)		350			(404	)
Taxes, other than income taxes		4,352			3,737			8,692			8,199
Total operating expenses		62,711			63,500			124,253			125,213
OPERATING INCOME		51,142			42,811			108,334			92,470
OTHER (INCOME) AND OTHER EXPENSES:
Interest expense		11,555			11,587			23,109			23,180
Allowance for equity and borrowed funds used during construction		(371	)		(742	)		(647	)		(1,053	)
Miscellaneous other (income) expenses, net		(67	)		80			209			149
Total other (income) and other expenses		11,117			10,925			22,671			22,276
NET INCOME		40,025			31,886			85,663			70,194
CASH FLOW HEDGES:
Amortization of cash flow hedges into Other interest		(16	)		(15	)		(31	)		(31	)
COMPREHENSIVE INCOME	$	40,009		$	31,871		$	85,632		$	70,163

See accompanying notes.

1

NORTHWEST PIPELINE GP

BALANCE SHEET

(Thousands of Dollars)

(Unaudited)

	June 30, 2013		December 31, 2012
ASSETS
CURRENT ASSETS:
Cash	$	100	$	117
Receivables:
Trade		37,964		39,836
Affiliated companies		2,253		1,683
Advances to affiliate		112,195		29,322
Other		7,977		6,700
Materials and supplies, less reserves of $28 at June 30, 2013 and $81 at December 31, 2012		10,320		10,137
Exchange gas due from others		3,456		3,426
Exchange gas offset		1,069		1,277
Prepayments and other		4,343		3,353
Total current assets		179,677		95,851
PROPERTY, PLANT AND EQUIPMENT, at cost		3,173,360		3,163,489
Less-Accumulated depreciation		1,190,852		1,159,944
Total property, plant and equipment, net		1,982,508		2,003,545
OTHER ASSETS:
Deferred charges		7,474		7,918
Regulatory assets		58,645		60,298
Total other assets		66,119		68,216
Total assets	$	2,228,304	$	2,167,612

See accompanying notes.

2

NORTHWEST PIPELINE GP

BALANCE SHEET

(Thousands of Dollars)

(Unaudited)

	June 30,		December 31,
	2013		2012
LIABILITIES AND OWNER’S EQUITY
CURRENT LIABILITIES:
Payables:
Trade	$	19,076	$	18,383
Affiliated companies		10,163		10,912
Accrued liabilities:
Taxes, other than income taxes		12,354		10,961
Interest		4,045		4,045
Exchange gas due to others		2,925		6,572
Other		5,044		4,467
Total current liabilities		53,607		55,340
LONG-TERM DEBT		694,125		694,027
OTHER NONCURRENT LIABILITIES:
Asset retirement obligations		69,502		67,557
Other		24,200		22,450
Total other noncurrent liabilities		93,702		90,007
CONTINGENT LIABILITIES AND COMMITMENTS (Note 2)
OWNER’S EQUITY:
Owner’s capital		1,060,592		1,060,592
Retained earnings		326,095		267,432
Accumulated other comprehensive income		183		214
Total owner’s equity		1,386,870		1,328,238
Total liabilities and owner’s equity	$	2,228,304	$	2,167,612

See accompanying notes.

3

NORTHWEST PIPELINE GP

STATEMENT OF CASH FLOWS

(Thousands of Dollars)

(Unaudited)

	Six months ended June 30,
	2013			2012
OPERATING ACTIVITIES:
Net income	$	85,663		$	70,194
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation		47,740			46,535
Regulatory debits (credits)		350			(404	)
Amortization of deferred charges and credits		830			795
Allowance for equity funds used during construction		(436	)		(719	)
Changes in current assets and liabilities:
Trade and other accounts receivable		595			2,098
Affiliated receivables		(570	)		2,250
Exchange gas due from others		3,647			2,296
Materials and supplies		(183	)		439
Other current assets		(990	)		(978	)
Trade accounts payable		(2,686	)		(2,465	)
Affiliated payables		(749	)		4,695
Exchange gas due to others		(3,647	)		(2,295	)
Other accrued liabilities		1,974			303
Changes in noncurrent assets and liabilities:
Deferred charges		(3,434	)		(954	)
Noncurrent liabilities		4,193			2,639
Net cash provided by operating activities		132,297			124,429
FINANCING ACTIVITIES:
Capital contributions from parent		—			2,330
Distributions paid		(27,000	)		(73,000	)
Other		(2,194	)		(1,719	)
Net cash used in financing activities		(29,194	)		(72,389	)
INVESTING ACTIVITIES:
Property, plant and equipment:
Capital expenditures*		(21,898	)		(47,147	)
Proceeds from sales		1,651			4,748
Advances to affiliates		(82,873	)		(9,438	)
Net cash used in investing activities		(103,120	)		(51,837	)
NET (DECREASE) INCREASE IN CASH		(17	)		203
CASH AT BEGINNING OF PERIOD		117			37
CASH AT END OF PERIOD	$	100		$	240
* Increases to property, plant and equipment	$	(27,471	)	$	(54,479	)
Changes in related accounts payable and accrued liabilities		5,573			7,332
Capital expenditures	$	(21,898	)	$	(47,147	)

See accompanying notes.

4

NORTHWEST PIPELINE GP

NOTES TO FINANCIAL STATEMENTS

(Unaudited)

1. BASIS OF PRESENTATION

In this report, Northwest Pipeline GP (Northwest) is at times referred to in the first person as “we”, “us” or “our.”

On June 30, 2013, Northwest was indirectly owned by Williams Partners L.P. (WPZ), a publicly traded Delaware limited partnership, which is consolidated by The Williams Companies, Inc. (Williams). At June 30, 2013, Williams holds an approximate 68 percent interest in WPZ, comprised of an approximate 66 percent limited partner interest and all of WPZ’s 2 percent general partner interest.

On July 1, 2013, Northwest converted from a Delaware general partnership to a Delaware limited liability company, Northwest Pipeline LLC (Company). Following the conversion, the sole member of the Company, Williams Partners Operating LLC, a Delaware limited liability company, executed a limited liability company operating agreement. In connection with the conversion of the Company to a limited liability company, the Amended and Restated Partnership Agreement of Northwest was terminated.

General

The accompanying interim financial statements do not include all the notes in our annual financial statements, and therefore, should be read in conjunction with the financial statements and notes thereto in our 2012 Annual Report on Form 10-K. The accompanying unaudited financial statements include all adjustments both normal recurring and others which, in the opinion of our management, are necessary to present fairly our interim financial statements.

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.

Certain prior period amounts reported within Total operating expenses in the Statement of Comprehensive Income have been reclassified to conform to the current presentation. For the three and six months ended June 30, 2012, the effect of the correction increased Operation and maintenance costs $0.7 million and $1.2 million, respectively; increased General and administrative expenses $0.1 million and $0.4 million, respectively; and decreased Taxes, other than income taxes $0.8 million and $1.6 million, respectively; with no net impact on Total operating expenses, Operating Income, or Net Income.

2. CONTINGENT LIABILITIES AND COMMITMENTS

Environmental Matters

We are subject to the National Environmental Policy Act and other federal and state legislation regulating the environmental aspects of our business. Except as discussed below, our management believes that we are in substantial compliance with existing environmental requirements. Environmental expenditures are expensed or capitalized depending on their future economic benefit and potential for rate recovery. We believe that, with respect to any expenditures required to meet applicable standards and regulations, the Federal Energy Regulatory Commission (FERC) would grant the requisite rate relief so that substantially all of such expenditures would be permitted to be recovered through rates. We believe that compliance with applicable environmental requirements is not likely to have a material adverse effect upon our financial position or results of operations.

5

NORTHWEST PIPELINE GP

NOTES TO FINANCIAL STATEMENTS

(Unaudited)

Beginning in the mid-1980s, we evaluated many of our facilities for the presence of toxic and hazardous substances to determine to what extent, if any, remediation might be necessary. We identified polychlorinated biphenyl (PCB) contamination in air compressor systems, soils and related properties at certain compressor station sites. Similarly, we identified hydrocarbon impacts at these facilities due to the former use of earthen pits and mercury contamination at certain natural gas metering sites. The PCBs were remediated pursuant to a Consent Decree with the U.S. Environmental Protection Agency (EPA) in the late 1980s, and we conducted a voluntary clean-up of the hydrocarbon and mercury impacts in the early 1990s. In 2005, the Washington Department of Ecology required us to re-evaluate our previous mercury clean-ups in Washington. Currently, we are conducting assessment and remediation activities for mercury and other constituents to bring the sites up to Washington’s current environmental standards. At June 30, 2013, we had accrued liabilities totaling approximately $7.5 million for these costs which are expected to be incurred through 2017. We are conducting environmental assessments and implementing a variety of remedial measures that may result in increases or decreases in the total estimated costs.

In March 2008, the EPA promulgated a new, lower National Ambient Air Quality Standard (NAAQS) for ground-level ozone. However, in September 2009, the EPA announced it would reconsider the 2008 NAAQS for ground-level ozone to ensure that the standards were clearly grounded in science, and were protective of both public health and the environment. As a result, the EPA delayed designation of new eight-hour ozone non-attainment areas under the 2008 standards until the reconsideration was complete. In January 2010, the EPA proposed to further reduce the ground-level ozone NAAQS from the March 2008 levels. In September 2011, the EPA announced that it was proceeding with required actions to implement the 2008 ozone standard and area designations. In May 2012, the EPA completed designation of new eight-hour ozone non-attainment areas. Based on the published designations, no Northwest facilities are located within the non-attainment areas. At this time, it is unknown whether future state regulatory actions associated with implementation of the 2008 ozone standard will impact our operations and increase the cost of additions to property, plant and equipment. Until any additional state regulatory actions are proposed, we are unable to estimate the cost of additions that may be required to meet any such new regulation.

Additionally, in August 2010, the EPA promulgated National Emission Standards for hazardous air pollutants (NESHAP) regulations that will impact our operations. The emission control additions required to comply with the hazardous air pollutant regulations are estimated to include capital costs in the range of $500 thousand to $1 million through 2013, the compliance date.

On January 22, 2010, the EPA set a new one-hour nitrogen dioxide (NO₂) NAAQS. The effective date of the new NO₂ standard was April 12, 2010. This standard is subject to challenges in federal court. On January 20, 2012, the EPA determined pursuant to available information that no area in the country is violating the 2010 NO₂ NAAQS, and thus, designated all areas of the country as “unclassifiable/attainment.” Also, at that time, the EPA noted its plan to deploy an expanded NO₂ monitoring network beginning in 2013. However, on October 5, 2012, the EPA proposed a graduated implementation of the monitoring network between January 1, 2014 and January 1, 2017. Once three years of data is collected from the new monitoring network, the EPA will reassess attainment status with the one-hour NO₂ NAAQS. Until that time, the EPA or states may require ambient air quality modeling on a case by case basis to demonstrate compliance with the NO₂ standard. Because we are unable to predict the outcome of the EPA’s or states’ future assessment using the new monitoring network, we are unable to estimate the cost of additions that may be required to meet this regulation.

Other Matters

Various other proceedings are pending against us and are considered incidental to our operations.

Summary

We estimate that for all matters for which we are able to reasonably estimate a range of loss, including those noted above and others that are not individually significant, our aggregate reasonably possible losses beyond amounts accrued for all of our contingent liabilities are immaterial to our expected

6

NORTHWEST PIPELINE GP

NOTES TO FINANCIAL STATEMENTS

(Unaudited)

future annual results of operations, liquidity and financial position. These calculations have been made without consideration of any potential recovery from third-parties. We have disclosed all significant matters for which we are unable to reasonably estimate a range of possible loss.

3. DEBT AND FINANCING ARRANGEMENT

Credit Facility

Total letter of credit capacity available to WPZ under the $2.4 billion credit facility is $1.3 billion. At June 30, 2013, no letters of credit have been issued and no loans are outstanding under the credit facility. We may borrow up to $400 million under the credit facility to the extent not otherwise utilized by WPZ and Transcontinental Gas Pipe Line Company, LLC (Transco). At June 30, 2013, the full $400 million under the credit facility was available to us.

On July 31, 2013, WPZ amended the $2.4 billion credit facility to increase the aggregate commitments to $2.5 billion and extend the maturity date to July 31, 2018. The amended credit facility may also, under certain conditions, be increased by up to an additional $500 million. We may borrow up to $500 million under the amended credit facility to the extent not otherwise utilized by WPZ and Transco.

WPZ participates in a commercial paper program, and WPZ management considers amounts outstanding under this program to be a reduction of available capacity under the credit facility. At June 30, 2013, WPZ had $710 million in outstanding commercial paper.

4. FINANCIAL INSTRUMENTS

Fair Value of Financial Instruments

The following methods and assumptions were used to estimate the fair value of each class of financial instruments for which it is practicable to estimate that value:

Cash and advances to affiliate—The carrying amounts approximate fair value because of the short-term nature of these instruments.

Long-term debt—The disclosed fair value of our long-term debt, which we consider as a level 2 measurement, is determined by a market approach using broker quoted indicative period-end bond prices. The quoted prices are based on observable transactions in less active markets for our debt or similar instruments. The carrying amount and estimated fair value of our long-term debt, including current maturities, were $694.1 million and $817.4 million, respectively, at June 30, 2013, and $694.0 million and $840.2 million, respectively, at December 31, 2012.

5. TRANSACTIONS WITH AFFILIATES

We are a participant in WPZ’s cash management program. At June 30, 2013 and December 31, 2012, our advances to WPZ totaled approximately $112.2 million and $29.3 million, respectively. These advances are represented by demand notes and are classified as Current Assets in the accompanying Balance Sheet. The interest rate on these intercompany demand notes is based upon the daily overnight investment rate paid on WPZ’s excess cash at the end of each month, which was approximately 0.01 percent at June 30, 2013. The interest income from these advances was minimal during the six months ended June 30, 2013 and June 30, 2012. Such interest income is included in Other (Income) and Other Expenses – Miscellaneous other (income) expenses, net on the accompanying Statement of Comprehensive Income.

7

We have no employees. Services necessary to operate our business are provided to us by Williams and certain affiliates of Williams. We reimburse Williams and its affiliates for all direct and indirect expenses incurred or payments made (including salary, bonus, incentive compensation, and benefits) in connection with these services. Employees of Williams also provide general administrative and management services to us, and we are charged for certain administrative expenses incurred by Williams. These charges are either directly identifiable or allocated to our assets. Direct charges are for goods and services provided by Williams at our request. Allocated charges are based on a three-factor formula, which considers revenues; property, plant, and equipment; and payroll. In management’s estimation, the allocation methodologies used are reasonable and result in a reasonable allocation to us of our costs of doing business incurred by Williams. We were billed $27.9 million and $54.3 million in the three and six months ended June 30, 2013, respectively, and $28.8 million and $55.0 million in the three and six months ended June 30, 2012, respectively, for these services. Such expenses are primarily included in General and administrative and Operation and maintenance expenses on the accompanying Statement of Comprehensive Income.

During the six months ended June 30, 2013 and 2012, we declared and paid equity distributions to our parent of $27.0 million and $73.0 million, respectively. During July 2013, we declared and paid equity distributions of $35.0 million to our parent.

During the six months ended June 30, 2012, we received contributions of $2.3 million from our parent to fund a portion of our expansion related expenditures for additions to property, plant, and equipment. No contributions were received from our parent during the six months ended June 30, 2013. In July 2013, our parent authorized an additional $1.9 million capital contribution to us to fund a portion of our expenditures for additions to property, plant and equipment.

We have entered into various other transactions with certain related parties, the amounts of which were not significant. These transactions and the above-described transactions are made on the basis of commercial relationships and prevailing market prices or general industry practices.

8

Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations

GENERAL

The following discussion should be read in conjunction with the Financial Statements, Notes, and Management’s Discussion and Analysis contained in Items 7 and 8 of our 2012 Annual Report on Form 10-K and with the Financial Statements and Notes contained in this Form 10-Q.

RESULTS OF OPERATIONS

ANALYSIS OF FINANCIAL RESULTS

This analysis discusses financial results of our operations for the six-month periods ended June 30, 2013 and 2012. Variances due to changes in natural gas prices and transportation volumes have little impact on revenues, because under our rate design methodology, the majority of overall cost of service is recovered through firm capacity reservation charges in our transportation rates.

Our operating revenues increased $14.9 million, or 7 percent, as compared to the first six months of 2012. This increase is primarily attributed to new rates, which became effective January 1, 2013.

Transportation service and gas storage service accounted for 98 percent and 2 percent, respectively, of our operating revenues for the period ended June 30, 2013, and 97 percent and 3 percent, respectively, of our operating revenues for the period ended June 30, 2012.

Operating expenses decreased $1.0 million, or 1 percent, due primarily to lower employee incentive compensation expense of $2.2 million and lower labor costs of $1.0 million, partially offset by higher depreciation of $1.2 million, primarily attributed to property additions.

The increase in our net income for the first six months of 2013, as compared to the comparable period in 2012, is primarily due to the increase in operating revenues associated with our new rates.

CAPITAL EXPENDITURES

Our capital expenditures were $21.9 million and $47.1 million for the six months ended June 30, 2013 and 2012, respectively. Our capital expenditures estimate for 2013 is discussed in our 2012 Annual Report on Form 10-K. This estimate includes the following new capital project proposed by us:

South Seattle Lateral Delivery Expansion

We have executed an agreement with Puget Sound Energy to expand the South Seattle Lateral to provide an additional 64 MDth per day of capacity. The project is on schedule for a November 2013 in-service date, and is estimated to cost between $19 million and $21 million.

9

Item 4. Controls and Procedures

Our management, including our Senior Vice President—West and our Vice President and Chief Accounting Officer, does not expect that our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) of the Securities Exchange Act) (Disclosure Controls) or our internal controls over financial reporting (Internal Controls) will prevent all errors and all fraud. A control system, no matter how well conceived and operated, can provide only reasonable, not absolute, assurance that the objectives of the control system are met. Further, the design of a control system must reflect the fact that there are resource constraints, and the benefits of controls must be considered relative to their costs. Because of the inherent limitations in all control systems, no evaluation of controls can provide absolute assurance that all control issues and instances of fraud, if any, within Northwest have been detected. These inherent limitations include the realities that judgments in decision-making can be faulty and that breakdowns can occur because of simple error or mistake. Additionally, controls can be circumvented by the individual acts of some persons, by collusion of two or more people, or by management override of the control. The design of any system of controls also is based in part upon certain assumptions about the likelihood of future events, and there can be no assurance that any design will succeed in achieving its stated goals under all potential future conditions. Because of the inherent limitations in a cost-effective control system, misstatements due to error or fraud may occur and not be detected. We monitor our Disclosure Controls and Internal Controls and make modifications as necessary; our intent in this regard is that the Disclosure Controls and Internal Controls will be modified as systems change and conditions warrant.

Evaluation of Disclosure Controls and Procedures

An evaluation of the effectiveness of the design and operation of our Disclosure Controls was performed as of the end of the period covered by this report. This evaluation was performed under the supervision and with the participation of our management, including our Senior Vice President—West and our Vice President and Chief Accounting Officer. Based upon that evaluation, our Senior Vice President—West and our Vice President and Chief Accounting Officer concluded that these Disclosure Controls are effective at a reasonable assurance level.

Second-Quarter 2013 Changes in Internal Controls

There have been no changes during the second quarter of 2013 that have materially affected, or are reasonably likely to materially affect, our Internal Controls.

10

PART II. OTHER INFORMATION

Item 1. Legal Proceedings

The information called for by this item is provided in Note 2. Contingent Liabilities and Commitments, included in the Notes to Financial Statements included under Part 1, Item 1. Financial Statements of this Form 10-Q, which information is incorporated by reference into this item.

Item 5. Other Information

Entry Into a Material Definitive Agreement & Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

First Amended & Restated Credit Agreement

On July 31, 2013, Williams Partners L.P. (WPZ), Northwest Pipeline LLC (Northwest) and Transcontinental Gas Pipe Line Company, LLC (Transco and, together with WPZ and Northwest, collectively the “Borrowers”) entered into a First Amended & Restated Credit Agreement (the “Restated Credit Agreement”), with Citibank, N.A. (Citi), as administrative agent, and the lenders named therein. The Restated Credit Agreement amends and restates that certain Credit Agreement, dated as of June 3, 2011 (as amended prior to July 31, 2013, the “Existing Credit Agreement”), among the Borrowers, Citi, as administrative agent and the lenders named therein. Capitalized terms used in this Item 5 and not otherwise defined herein have the meaning given to them in the Restated Credit Agreement.

The Restated Credit Agreement increases the Aggregate Commitments available to the Borrowers by $100 million (the “Incremental Commitments”) and extends the Maturity Date to July 31, 2018. Additionally, the Restated Credit Agreement lowers, in certain cases, the applicable margin and commitment fees payable by each Borrower based on such Borrower’s senior unsecured debt ratings. The Incremental Commitments are increased Commitments from lenders named in the Existing Credit Agreement as well as a new Commitment from an institution party to the Restated Credit Agreement. After giving effect to the Restated Credit Amendment, the Borrowers may borrow, in the aggregate, up to $2.5 billion under the Restated Credit Agreement. Northwest and Transco are each subject to a $500 million borrowing sublimit. In addition, WPZ may request an increase of up to an additional $500 million in Commitments from either new lenders or increased Commitments from existing lenders named in the Restated Credit Agreement. However, at no time may the Aggregate Commitments under the Restated Credit Agreement exceed $3.0 billion.

The foregoing description of the Restated Credit Amendment does not purport to be complete and is qualified in its entirety by reference to the Restated Credit Amendment, a copy of which has been filed as Exhibit 10 to WPZ’s Quarterly Report on Form 10-Q, filed on July 31, 2013 (File No. 001-32599) and incorporated into this Item 5 by reference.

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ITEM 6. EXHIBITS

The following instruments are included as exhibits to this report.

Exhibit	Description
3(a)	Certificate of Conversion of Northwest Pipeline GP (Exhibit 2.1 to our report on Form 8-K, filed July 3, 2013 (File No. 001-07414)) and incorporated herein by reference.
3(b)	Certificate of Formation of Northwest Pipeline LLC (Exhibit 2.2 to our report on Form 8-K, filed July 3, 2013 (File No. 001-07414)) and incorporated herein by reference.
3(c)	Operating Agreement of Northwest Pipeline LLC (Exhibit 3.1 to our report on Form 8-K, filed July 3, 2013 (File No. 001-07414)) and incorporated herein by reference.
10(a)	First Amended & Restated Credit Agreement, dated as of July 31, 2013, by and among Williams Partners L.P., Northwest Pipeline LLC, and Transcontinental Gas Pipe Line Company, LLC, as co-borrowers, the lenders named therein, and Citibank N.A., as Administrative Agent (filed on July 31, 2013 as Exhibit 10 to Williams Partners L.P.’s Quarterly Report on Form 10-Q (File No. 001-32599)) and incorporated herein by reference.
31(a)*	Certification of Principal Executive Officer pursuant to Rules 13a-14(a) and 15d-14(a) promulgated under the Securities Exchange Act of 1934, as amended and Item 601(b)(31) of Regulation S-K, as adopted pursuant to Section 302 of The Sarbanes-Oxley Act of 2002.
31(b)*	Certification of Principal Financial Officer pursuant to Rules 13a-14(a) and 15d-14(a) promulgated under the Securities Exchange Act of 1934, as amended, and Item 601(b)(31) of Regulation S-K, as adopted pursuant to Section 302 of The Sarbanes-Oxley Act of 2002.
32(a)**	Certification of Principal Executive Officer and Principal Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.
101.INS**	XBRL Instance Document.
101.SCH**	XBRL Taxonomy Extension Schema.
101.CAL**	XBRL Taxonomy Extension Calculation Linkbase.

12

101.DEF**	XBRL Taxonomy Definition Linkbase.
101.LAB**	XBRL Taxonomy Extension Label Linkbase.
101.PRE**	XBRL Taxonomy Extension Presentation Linkbase.

* Filed herewith.

** Furnished herewith.

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SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	NORTHWEST PIPELINE LLC
	Registrant
By:	/s/ Jeffrey P. Heinrichs
	Jeffrey P. Heinrichs Controller (Duly Authorized Officer and Principal Accounting Officer)

Date: July 31, 2013

EXHIBIT INDEX

Exhibit	Description
3(a)	Certificate of Conversion of Northwest Pipeline GP (Exhibit 2.1 to our report on Form 8-K, filed July 3, 2013 (File No. 001-07414)) and incorporated herein by reference.
3(b)	Certificate of Formation of Northwest Pipeline LLC (Exhibit 2.2 to our report on Form 8-K, filed July 3, 2013 (File No. 001-07414)) and incorporated herein by reference.
3(c)	Operating Agreement of Northwest Pipeline LLC (Exhibit 3.1 to our report on Form 8-K, filed July 3, 2013 (File No. 001-07414)) and incorporated herein by reference.
10(a)	First Amended & Restated Credit Agreement, dated as of July 31, 2013, by and among Williams Partners L.P., Northwest Pipeline LLC, and Transcontinental Gas Pipe Line Company, LLC, as co-borrowers, the lenders named therein, and Citibank N.A., as Administrative Agent (filed on July 31, 2013 as Exhibit 10 to Williams Partners L.P.’s Quarterly Report on Form 10-Q (File No. 001-32599)) and incorporated herein by reference.
31(a)*	Certification of Principal Executive Officer pursuant to Rules 13a-14(a) and 15d-14(a) promulgated under the Securities Exchange Act of 1934, as amended and Item 601(b)(31) of Regulation S-K, as adopted pursuant to Section 302 of The Sarbanes-Oxley Act of 2002.
31(b)*	Certification of Principal Financial Officer pursuant to Rules 13a-14(a) and 15d-14(a) promulgated under the Securities Exchange Act of 1934, as amended, and Item 601(b)(31) of Regulation S-K, as adopted pursuant to Section 302 of The Sarbanes-Oxley Act of 2002.
32(a)**	Certification of Principal Executive Officer and Principal Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.
101.INS**	XBRL Instance Document.
101.SCH**	XBRL Taxonomy Extension Schema.
101.CAL**	XBRL Taxonomy Extension Calculation Linkbase.
101.DEF**	XBRL Taxonomy Definition Linkbase.

101.LAB**	XBRL Taxonomy Extension Label Linkbase.
101.PRE**	XBRL Taxonomy Extension Presentation Linkbase.

* Filed herewith.

** Furnished herewith.

EX-31.A

Exhibit 31(a)

SECTION 302 CERTIFICATION

I, Allison G. Bridges, certify that:

1. I have reviewed this Quarterly Report on Form 10-Q of Northwest Pipeline LLC;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: July 31, 2013

By:	/s/ Allison G. Bridges
	Allison G. Bridges Sr. Vice President—West (Principal Executive Officer)

EX-31.B

Exhibit 31(b)

SECTION 302 CERTIFICATION

I, Ted T. Timmermans, certify that:

1. I have reviewed this Quarterly Report on Form 10-Q of Northwest Pipeline LLC;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: July 31, 2013

By:	/s/ Ted T. Timmermans
	Ted T. Timmermans Vice President and Chief Accounting Officer (Principal Financial Officer)

EX-32.A

Exhibit 32(a)

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Northwest Pipeline LLC (the “Company”) on Form 10-Q for the period ending June 30, 2013 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), each of the undersigned hereby certifies, in his capacity as an officer of the Company, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that to his knowledge:

(1) The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ Allison G. Bridges

Allison G. Bridges

Senior Vice President—West

July 31, 2013

/s/ Ted T. Timmermans

Ted T. Timmermans

Vice President and Chief Accounting Officer

July 31, 2013

A signed original of this written statement required by Section 906 has been provided to, and will be retained by, the Company and furnished to the Securities and Exchange Commission or its staff upon request.

The foregoing certification is being furnished to the Securities and Exchange Commission as an exhibit to the Report and shall not be considered filed as part of the Report.

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Balance Sheet (Unaudited) (Parenthetical) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
ASSETS
Reserves, materials and supplies	$ 28	$ 81

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Financial Instruments

6 Months Ended

Jun. 30, 2013

Financial Instruments [Abstract]

FINANCIAL INSTRUMENTS

4. FINANCIAL INSTRUMENTS

Fair Value of Financial Instruments

The following methods and assumptions were used to estimate the fair value of each class of financial instruments for which it is practicable to estimate that value:

Cashand advances to affiliate - The carrying amounts approximate fair value because of the short-term nature of these instruments.

Long-term debt - The disclosed fair value of our long-term debt, which we consider as a level 2 measurement, is determined by a market approach using broker quoted indicative period-end bond prices. The quoted prices are based on observable transactions in less active markets for our debt or similar instruments. The carrying amount and estimated fair value of our long-term debt, including current maturities, were $694.1 million and $817.4 million, respectively, at June 30,2013, and $694.0 million and $840.2 million, respectively, at December 31, 2012.

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Statement of Cash Flows (Unaudited) (Parenthetical) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Statement of Cash Flows [Abstract]
Increases to property, plant and equipment	$ (27,471)	$ (54,479)
Changes in related accounts payable and accrued liabilities	5,573	7,332
Capital expenditures	$ (21,898)	$ (47,147)

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Contingent Liabilities and Commitments

6 Months Ended

Jun. 30, 2013

Contingent Liabilities and Commitments [Abstract]

CONTINGENT LIABILITIES AND COMMITMENTS

2. CONTINGENT LIABILITIES AND COMMITMENTS

Environmental Matters

We are subject to the National Environmental Policy Act and other federal and state legislation regulating the environmental aspects of our business. Except as discussed below, our management believes that we are in substantial compliance with existing environmental requirements. Environmental expenditures are expensed or capitalized depending on their future economic benefit and potential for rate recovery. We believe that, with respect to any expenditures required to meet applicable standards and regulations, the Federal Energy Regulatory Commission (FERC) would grant the requisite rate relief so that substantially all of such expenditures would be permitted to be recovered through rates. We believe that compliance with applicable environmental requirements is not likely to have a material adverse effect upon our financial position or results of operations.

Beginning in the mid-1980s, we evaluated many of our facilities for the presence of toxic and hazardous substances to determine to what extent, if any, remediation might be necessary. We identified polychlorinated biphenyl (PCB) contamination in air compressor systems, soils and related properties at certain compressor station sites. Similarly, we identified hydrocarbon impacts at these facilities due to the former use of earthen pits and mercury contamination at certain natural gas metering sites. The PCBs were remediated pursuant to a Consent Decree with the U.S. Environmental Protection Agency (EPA) in the late 1980s, and we conducted a voluntary clean-up of the hydrocarbon and mercury impacts in the early 1990s. In 2005, the Washington Department of Ecology required us to re-evaluate our previous mercury clean-ups in Washington. Currently, we are conducting assessment and remediation activities for mercury and other constituents to bring the sites up to Washington's current environmental standards. At June 30, 2013, we had accrued liabilities totaling approximately $7.5 million for these costs which are expected to be incurred through 2017. We are conducting environmental assessments and implementing a variety of remedial measures that may result in increases or decreases in the total estimated costs.

In March 2008, the EPA promulgated a new, lower National Ambient Air Quality Standard (NAAQS) for ground-level ozone. However, in September 2009, the EPA announced it would reconsider the 2008 NAAQS for ground-level ozone to ensure that the standards were clearly grounded in science, and were protective of both public health and the environment. As a result, the EPA delayed designation of new eight-hour ozone non-attainment areas under the 2008 standards until the reconsideration was complete. In January 2010, the EPA proposed to further reduce the ground-level ozone NAAQS from the March 2008 levels. In September 2011, the EPA announced that it was proceeding with required actions to implement the 2008 ozone standard and area designations. In May 2012, the EPA completed designation of new eight-hour ozone non-attainment areas. Based on the published designations, no Northwest facilities are located within the non-attainment areas. At this time, it is unknown whether future state regulatory actions associated with implementation of the 2008 ozone standard will impact our operations and increase the cost of additions to property, plant and equipment. Until any additional state regulatory actions are proposed, we are unable to estimate the cost of additions that may be required to meet any such new regulation.

Additionally, in August 2010, the EPA promulgated National Emission Standards for hazardous air pollutants (NESHAP) regulations that will impact our operations. The emission control additions required to comply with the hazardous air pollutant regulations are estimated to include capital costs in the range of $500 thousand to $1 million through 2013, the compliance date.

On January 22, 2010, the EPA set a new one-hour nitrogen dioxide (NO2) NAAQS. The effective date of the new NO2 standard was April 12, 2010. This standard is subject to challenges in federal court. On January 20, 2012, the EPA determined pursuant to available information that no area in the country is violating the 2010 NO2 NAAQS, and thus, designated all areas of the country as “unclassifiable/attainment.” Also, at that time, the EPA noted its plan to deploy an expanded NO2 monitoring network beginning in 2013. However, on October 5, 2012, the EPA proposed a graduated implementation of the monitoring network between January 1, 2014 and January 1, 2017. Once three years of data is collected from the new monitoring network, the EPA will reassess attainment status with the one-hour NO2 NAAQS. Until that time, the EPA or states may require ambient air quality modeling on a case by case basis to demonstrate compliance with the NO2 standard. Because we are unable to predict the outcome of the EPA's or states' future assessment using the new monitoring network, we are unable to estimate the cost of additions that may be required to meet this regulation.

Other Matters

Various other proceedings are pending against us and are considered incidental to our operations.

Summary

We estimate that for all matters for which we are able to reasonably estimate a range of loss, including those noted above and others that are not individually significant, our aggregate reasonably possible losses beyond amounts accrued for all of our contingent liabilities are immaterial to our expected future annual results of operations, liquidity and financial position.  These calculations have been made without consideration of any potential recovery from third-parties.  We have disclosed all significant matters for which we are unable to reasonably estimate a range of possible loss.

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Transactions with Affiliates

6 Months Ended

Jun. 30, 2013

Transactions with Affiliates [Abstract]

TRANSACTIONS WITH AFFILIATES

5. TRANSACTIONS WITH AFFILIATES

We are a participant in WPZ's cash management program. At June 30,2013 and December 31, 2012, our advances toWPZ totaled approximately $112.2 million and $29.3 million, respectively. These advances are represented by demand notes and are classified as Current Assets in the accompanying Balance Sheet. The interest rate on these intercompany demand notes is based upon the daily overnight investment rate paid on WPZ's excess cash at the end of each month, which was approximately 0.01 percent at June 30,2013. The interest income from these advances was minimal during the six months ended June 30,2013and June 30, 2012. Such interest income is included in Other (Income) and Other Expenses– Miscellaneous other (income) expenses, net on the accompanying Statement of Comprehensive Income.

We have no employees. Services necessary to operate our business are provided to us by Williams and certain affiliates of Williams. We reimburse Williams and its affiliates for all direct and indirect expenses incurred or payments made (including salary, bonus, incentive compensation, and benefits) in connection with these services. Employees of Williams also provide general administrative and management services to us, and we are charged for certain administrative expenses incurred by Williams. These charges are either directly identifiable or allocated to our assets. Direct charges are for goods and services provided by Williams at our request. Allocated charges are based on a three-factor formula, which considers revenues; property, plant, and equipment; and payroll. In management's estimation, the allocation methodologies used are reasonable and result in a reasonable allocation to us of our costs of doing business incurred by Williams. We were billed $27.9 million and $54.3 million in the three and six months ended June 30, 2013, respectively, and $28.8 million and $55.0 million in the three and six months ended June 30,2012, respectively, for these services. Such expenses are primarily included in General and administrative and Operation and maintenance expenses on the accompanying Statement of Comprehensive Income.

During the six months ended June 30,2013 and 2012, we declared and paid equity distributions to our parent of $27.0 million and $73.0 million, respectively. During July2013, we declared and paid equity distributions of $35.0 million to our parent.

During the six months ended June 30, 2012, we received contributions of $2.3 million from our parent to fund a portion of our expansion related expenditures for additions to property, plant, and equipment. No contributions were received from our parent during the six months ended June 30, 2013. In July 2013, our parent authorized an additional $1.9 million capital contribution to us to fund a portion of our expenditures for additions to property, plant and equipment.

       We have entered into various other transactions with certain related parties, the amounts of which were not significant. These transactions and the above-described transactions are made on the basis of commercial relationships and prevailing market prices or general industry practices.

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Debt and Financing Arrangements

6 Months Ended

Jun. 30, 2013

Debt and Financing Arrangement [Abstract]

DEBT AND FINANCING ARRANGEMENT

3. DEBT AND FINANCING ARRANGEMENT

Credit Facility

Total letter of credit capacity available to WPZ under the$2.4 billion credit facility is $1.3 billion. At June 30,2013, no letters of credit have been issued and no loans are outstanding under the credit facility. We may borrow up to $400 million under the credit facility to the extent not otherwise utilized by WPZ and Transcontinental Gas Pipe Line Company, LLC (Transco). At June 30,2013,the full $400 million under the credit facility was available to us.

       On July 31, 2013, WPZ amended the $2.4 billion credit facility to increase the aggregate commitments to $2.5 billion and extend the maturity date to July 31, 2018. The amended credit facility may also, under certain conditions, be increased by up to an additional $500 million. We may borrow up to $500 million under the amended credit facility to the extent not otherwise utilized by WPZ and Transco.

       WPZ participates in a commercial paper program, and WPZ management considers amounts outstanding under this program to be a reduction of available capacity under thecredit facility. At June 30, 2013, WPZ had $710 million in outstanding commercial paper.

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Balance Sheet (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
CURRENT ASSETS:
Cash	$ 100	$ 117
Receivables:
Trade	37,964	39,836
Affiliated companies	2,253	1,683
Advances to affiliate	112,195	29,322
Other	7,977	6,700
Materials and supplies, less reserves of $28 at June 30, 2013 and $81 at December 31, 2012	10,320	10,137
Exchange gas due from others	3,456	3,426
Exchange gas offset	1,069	1,277
Prepayments and other	4,343	3,353
Total current assets	179,677	95,851
PROPERTY, PLANT AND EQUIPMENT, at cost	3,173,360	3,163,489
Less-Accumulated depreciation	1,190,852	1,159,944
Total property, plant and equipment, net	1,982,508	2,003,545
OTHER ASSETS:
Deferred charges	7,474	7,918
Regulatory assets	58,645	60,298
Total other assets	66,119	68,216
Total assets	2,228,304	2,167,612
Payables:
Trade	19,076	18,383
Affiliated companies	10,163	10,912
Accrued liabilities:
Taxes, other than income taxes	12,354	10,961
Interest	4,045	4,045
Exchange gas due to others	2,925	6,572
Other	5,044	4,467
Total current liabilities	53,607	55,340
LONG-TERM DEBT	694,125	694,027
OTHER NONCURRENT LIABILITIES:
Asset retirement obligations	69,502	67,557
Other	24,200	22,450
Total other noncurrent liabilities	93,702	90,007
CONTINGENT LIABILITIES AND COMMITMENTS (Note 2)
OWNER'S EQUITY:
Owner's capital	1,060,592	1,060,592
Retained earnings	326,095	267,432
Accumulated other comprehensive income	183	214
Total owner's equity	1,386,870	1,328,238
Total liabilities and owner's equity	$ 2,228,304	$ 2,167,612

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Debt and Financing Arrangements (Details Textual) (USD $)	Jun. 30, 2013 Williams Partners L.P. [Member]	Jun. 30, 2013 $2.4 billion credit facility [Member]	Jun. 30, 2013 $2.4 billion credit facility [Member] Williams Partners L.P. [Member]	Jun. 30, 2013 $2.4 billion credit facility [Member] Williams Partners L.P. [Member] LetterOfCreditMember	Jul. 31, 2013 $2.5 billion credit facility [Member]	Jul. 31, 2013 $2.5 billion credit facility [Member] Williams Partners L.P. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 400,000,000	$ 2,400,000,000	$ 1,300,000,000	$ 500,000,000	$ 2,500,000,000
Letters of Credit Outstanding, Amount				0
Line of Credit Facility, Amount Outstanding			0
Additional Amount By Which Credit Facility Can Be Increased						500,000,000
Commercial Paper	$ 710,000,000

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Statement of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
OPERATING ACTIVITIES:
Net income	$ 85,663	$ 70,194
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation	47,740	46,535
Regulatory debits (credits)	350	(404)
Amortization of deferred charges and credits	830	795
Allowance for equity funds used during construction	(436)	(719)
Changes in current assets and liabilities:
Trade and other accounts receivable	595	2,098
Affiliated receivables	(570)	2,250
Exchange gas due from others	3,647	2,296
Materials and supplies	(183)	439
Other current assets	(990)	(978)
Trade accounts payable	(2,686)	(2,465)
Affiliated payables	(749)	4,695
Exchange gas due to others	(3,647)	(2,295)
Other accrued liabilities	1,974	303
Changes in noncurrent assets and liabilities:
Deferred charges	(3,434)	(954)
Noncurrent liabilities	4,193	2,639
Net cash provided by operating activities	132,297	124,429
FINANCING ACTIVITIES:
Capital contributions from parent	0	2,330
Distributions paid	(27,000)	(73,000)
Other	(2,194)	(1,719)
Net cash used in financing activities	(29,194)	(72,389)
Property, plant and equipment:
Capital expenditures	(21,898)	(47,147)
Proceeds from sales	1,651	4,748
Advances to affiliates	(82,873)	(9,438)
Net cash used in investing activities	(103,120)	(51,837)
NET (DECREASE) INCREASE IN CASH	(17)	203
CASH AT BEGINNING OF PERIOD	117	37
CASH AT END OF PERIOD	$ 100	$ 240

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Statement of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
STATEMENT OF COMPREHENSIVE INCOME
Operating Revenues	$ 113,853	$ 106,311	$ 232,587	$ 217,683
OPERATING EXPENSES:
General and administrative	15,773	17,417	31,983	34,231
Operation and maintenance	18,693	19,236	35,488	36,652
Depreciation	23,728	23,225	47,740	46,535
Regulatory debits (credits)	165	(115)	350	(404)
Taxes, other than income taxes	4,352	3,737	8,692	8,199
Total operating expenses	62,711	63,500	124,253	125,213
Operating Income	51,142	42,811	108,334	92,470
OTHER (INCOME) AND OTHER EXPENSES:
Interest expense	11,555	11,587	23,109	23,180
Allowance for equity and borrowed funds used during construction	(371)	(742)	(647)	(1,053)
Miscellaneous other (income) expenses, net	(67)	80	209	149
Total other (income) and other expenses	11,117	10,925	22,671	22,276
NET INCOME	40,025	31,886	85,663	70,194
CASH FLOW HEDGES:
Amortization of cash flow hedges into Other Interest	(16)	(15)	(31)	(31)
COMPREHENSIVE INCOME	$ 40,009	$ 31,871	$ 85,632	$ 70,163

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Contingent Liabilities and Commitments (Details Textual) (USD $)	6 Months Ended
	Jun. 30, 2013
Environmental Matters [Abstract]
Accrual for Environmental Loss Contingencies	$ 7,500,000
Minimum [Member]
Environmental Matters [Abstract]
Estimated Capital Costs For Compliance With Hazardous Air Pollutant Regulations	500,000
Maximum [Member]
Environmental Matters [Abstract]
Estimated Capital Costs For Compliance With Hazardous Air Pollutant Regulations	$ 1,000,000

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Transactions with Affiliates (Details Textual) (USD $)	6 Months Ended					3 Months Ended		6 Months Ended		1 Months Ended	6 Months Ended
	Jun. 30, 2013 Employees	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Williams Partners L.P. [Member]	Dec. 31, 2012 Williams Partners L.P. [Member]	Jun. 30, 2013 The Williams Companies, Inc.[Member]	Jun. 30, 2012 The Williams Companies, Inc.[Member]	Jun. 30, 2013 The Williams Companies, Inc.[Member]	Jun. 30, 2012 The Williams Companies, Inc.[Member]	Jul. 31, 2013 Williams Partners Operating LLC [Member]	Jun. 30, 2013 Williams Partners Operating LLC [Member]	Jun. 30, 2012 Williams Partners Operating LLC [Member]
Related Party Transaction [Line Items]
Advances to affiliate	$ 112,195,000		$ 29,322,000	$ 112,200,000	$ 29,300,000
Related Party Transaction, Rate	0.01%
Entity Number of Employees	0
RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty						27,900,000	28,800,000	54,300,000	55,000,000
Distributions paid	27,000,000	73,000,000								35,000,000	27,000,000	73,000,000
Capital contributions from parent	$ 0	$ 2,330,000								$ 1,900,000	$ 0	$ 2,300,000

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Basis of Presentation (Details Textual) (USD $) In Millions, unless otherwise specified	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012 Operation and maintenance [Member]	Jun. 30, 2012 Operation and maintenance [Member]	Jun. 30, 2012 General and administrative [Member]	Jun. 30, 2012 General and administrative [Member]	Jun. 30, 2012 Taxes Other Than Income [Member]	Jun. 30, 2012 Taxes Other Than Income [Member]
Basis of Presentation [Abstract]
Parent, total ownership percentage	68.00%
Parent, limited partner ownership percentage	66.00%
Parent, general partner ownership percentage	2.00%
Prior Period
Prior Period Reclassification Adjustment		$ 0.7	$ 1.2	$ 0.1	$ 0.4	$ 0.8	$ 1.6

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Basis of Presentation

6 Months Ended

Jun. 30, 2013

Basis of Presentation [Abstract]

BASIS OF PRESENTATION

1. BASIS OF PRESENTATION

In this report, Northwest Pipeline GP (Northwest) is at times referred to in the first person as “we”, “us” or “our.”

On June 30, 2013, Northwest was indirectly owned by Williams Partners L.P. (WPZ), a publicly traded Delaware limited partnership, which is consolidated by The Williams Companies, Inc. (Williams). AtJune 30, 2013, Williams holds an approximate 68 percent interest in WPZ, comprised of an approximate 66 percent limited partner interest and all of WPZ's 2 percent general partner interest.

       On July 1, 2013, Northwest converted from a Delaware general partnership to a Delaware limited liability company, Northwest Pipeline LLC (Company). Following the conversion, the sole member of the Company, Williams Partners Operating LLC, a Delaware limited liability company, executed a limited liability company operating agreement. In connection with the conversion of the Company to a limited liability company, the Amended and Restated Partnership Agreement of Northwest was terminated.

General

       The accompanying interim financial statements do not include all the notes in our annual financial statements, and therefore, should be read in conjunction with the financial statements and notes thereto in our 2012 Annual Report on Form 10-K. The accompanying unaudited financial statements include all adjustments both normal recurring and others which, in the opinion of our management, are necessary to present fairly our interim financial statements.

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.

Certain prior period amounts reported within Total operating expenses in the Statement of Comprehensive Income have been reclassified to conform to the current presentation. For the three and six months endedJune 30, 2012, the effect of the correction increased Operation and maintenance costs$0.7 million and $1.2 million, respectively;increased General and administrative expenses $0.1 million and $0.4 million, respectively; and decreased Taxes, other than income taxes$0.8 million and $1.6 million, respectively; with no net impact on Total operating expenses, Operating Income, or Net Income.

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Financial Instruments (Details Textual) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	$ 817.4	$ 840.2
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	694.1	694.0
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	$ 817.4	$ 840.2

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Document and Entity Information	6 Months Ended
	Jun. 30, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	Northwest Pipeline LLC
Entity Central Index Key	0000110019
Document Type	10-Q
Document Period End Date	Jun. 30, 2013
Amendment Flag	false
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding	0