10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

(Mark One)

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

For the quarterly period ended June 30, 2012

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 GP

(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

NO CHANGE

(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  x    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  x    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	x  (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  x

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 GP

FORM 10-Q

INDEX

	Page
PART I. FINANCIAL INFORMATION:
Item 1. Financial Statements -
Statement of Comprehensive Income — Three and Six Months Ended June 30, 2012 and 2011		1
Balance Sheet — June 30, 2012 and December 31, 2011		2
Statement of Cash Flows — Six Months Ended June 30, 2012 and 2011		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		11
Item 1. Legal Proceedings		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,” “forecasts,” “intends,” “might,” “goals,” “objectives,” “targets,” “planned,” “potential,” “projects,” “scheduled,” “will,” “guidance,” “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;

• Expansion and growth of our business and operations;

i

• Financial condition and liquidity;

• Business strategy;

• Cash flow from operations or results of operations;

• Rate case filings; and

• Natural gas prices and demand.

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, volatility of prices, and the availability and cost of capital;

• 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;

• Development of alternative energy sources;

• The impact of operational and development hazards;

• Costs of, changes in, or the results of laws, government regulations (including safety and climate change regulation and changes in natural gas production from exploration and production areas that we serve), 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 credit;

• Risks associated with future weather 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.

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.

ii

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, 2011.

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,
	2012			2011			2012			2011
OPERATING REVENUES	$	106,311		$	106,576		$	217,683		$	216,495
OPERATING EXPENSES:
General and administrative		17,305			13,694			33,888			28,503
Operation and maintenance		18,561			19,096			35,416			34,983
Depreciation		23,225			22,543			46,535			45,101
Regulatory credits		(115	)		(267	)		(404	)		(534	)
Taxes, other than income taxes		4,524			4,914			9,778			10,614
Total operating expenses		63,500			59,980			125,213			118,667
Operating Income		42,811			46,596			92,470			97,828
OTHER INCOME - net:
Interest income -
Affiliated		2			2			3			5
Other		1			1			6			1
Allowance for equity funds used during construction		506			287			719			407
Miscellaneous other (expense) income, net		(83	)		(27	)		(158	)		(133	)
Total other income - net		426			263			570			280
INTEREST CHARGES:
Interest on long-term debt		11,109			11,109			22,219			22,219
Other interest		478			504			961			1,014
Allowance for borrowed funds used during construction		(236	)		(133	)		(334	)		(187	)
Total interest charges		11,351			11,480			22,846			23,046
NET INCOME		31,886			35,379			70,194			75,062
CASH FLOW HEDGES:
Amortization of cash flow hedges		(15	)		(16	)		(31	)		(31	)
COMPREHENSIVE INCOME	$	31,871		$	35,363		$	70,163		$	75,031

See accompanying notes.

1

NORTHWEST PIPELINE GP

BALANCE SHEET

(Thousands of Dollars)

(Unaudited)

	June 30,		December 31,
	2012		2011
ASSETS
CURRENT ASSETS:
Cash	$	240	$	37
Receivables:
Trade		36,147		38,245
Affiliated companies		—		2,250
Advances to affiliate		61,462		52,024
Materials and supplies, less reserves of $59 at June 30, 2012 and $816 at December 31, 2011		10,049		10,488
Exchange gas due from others		1,145		3,441
Prepayments and other		4,447		3,469
Total current assets		113,490		109,954
PROPERTY, PLANT AND EQUIPMENT, at cost		3,120,625		3,068,915
Less-Accumulated depreciation		1,128,771		1,076,943
Total property, plant and equipment, net		1,991,854		1,991,972
OTHER ASSETS:
Deferred charges		8,742		10,250
Regulatory assets		59,394		59,605
Total other assets		68,136		69,855
Total assets	$	2,173,480	$	2,171,781

See accompanying notes.

2

NORTHWEST PIPELINE GP

BALANCE SHEET

(Thousands of Dollars)

(Unaudited)

	June 30,		December 31,
	2012		2011
LIABILITIES AND OWNER’S EQUITY
CURRENT LIABILITIES:
Payables:
Trade	$	16,848	$	13,634
Affiliated companies		13,441		8,812
Accrued liabilities:
Taxes, other than income taxes		11,622		10,252
Interest		4,045		4,045
Exchange gas due to others		2,126		10,472
Exchange gas offset		2,049		2,241
Other		3,940		5,006
Total current liabilities		54,071		54,462
LONG-TERM DEBT		693,929		693,831
DEFERRED CREDITS AND OTHER NONCURRENT LIABILITIES		105,540		103,041
CONTINGENT LIABILITIES AND COMMITMENTS (Note 3)
OWNER’S EQUITY:
Owner’s capital		1,054,292		1,051,962
Retained earnings		265,403		268,209
Accumulated other comprehensive income		245		276
Total owner’s equity		1,319,940		1,320,447
Total liabilities and owner’s equity	$	2,173,480	$	2,171,781

See accompanying notes.

3

NORTHWEST PIPELINE GP

STATEMENT OF CASH FLOWS

(Thousands of Dollars)

(Unaudited)

	Six months ended June 30,
	2012			2011
OPERATING ACTIVITIES:
Net income	$	70,194		$	75,062
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation		46,535			45,101
Regulatory credits		(404	)		(534	)
Amortization of deferred charges and credits		795			859
Allowance for equity funds used during construction		(719	)		(407	)
Changes in current assets and liabilities:
Trade accounts receivable		2,098			4,541
Affiliated receivables		2,250			84
Exchange gas due from others		2,296			7,780
Materials and supplies		439			499
Other current assets		(978	)		(1,320	)
Trade accounts payable		(2,465	)		(2,620	)
Affiliated payables		4,695			3,650
Exchange gas due to others		(2,295	)		(7,781	)
Other accrued liabilities		303			2,821
Changes in noncurrent assets and liabilities:
Deferred charges		(954	)		(1,130	)
Other deferred credits		2,639			2,748
Net cash provided by operating activities		124,429			129,353
FINANCING ACTIVITIES:
Capital contributions from parent		2,330			3,500
Distributions paid		(73,000	)		(64,000	)
Other		(1,719	)		(1,424	)
Net cash used in financing activities		(72,389	)		(61,924	)
INVESTING ACTIVITIES:
Property, plant and equipment:
Capital expenditures*		(47,147	)		(36,245	)
Proceeds from sales		4,748			1,150
Advances to affiliates		(9,438	)		(32,332	)
Net cash used in investing activities		(51,837	)		(67,427	)
NET INCREASE IN CASH		203			2
CASH AT BEGINNING OF PERIOD		37			5
CASH AT END OF PERIOD	$	240		$	7
*       Increases to property, plant and equipment	$	(54,479	)	$	(36,850	)
Changes in related accounts payable and accrued liabilities		7,332			605
Capital expenditures	$	(47,147	)	$	(36,245	)

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.”

Northwest is indirectly owned by Williams Partners L.P. (WPZ), a publicly traded Delaware limited partnership, which is consolidated by The Williams Companies, Inc. (Williams). As of June 30, 2012, 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.

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 2011 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 reclassifications from Administrative and general to Operations and maintenance, related to certain employee related expenses of $0.9 million and $1.5 million for the three and six months ended June 30, 2011, respectively, have been made to conform to the presentation utilized in the 2012 Statement of Comprehensive Income.

2. RATE AND REGULATORY MATTERS

Rate Case Settlement Filing

On April 26, 2012, the Federal Energy Regulatory Commission (FERC) unconditionally approved Northwest’s Stipulation and Settlement Agreement (Settlement) filed on March 15, 2012. The supporting or non-opposing customers named in the Settlement represent approximately 99.5 percent of our long-term firm transportation and storage capacity. The Settlement specified an annual cost of service of $466.5 million and established a new general system firm transportation rate of $0.44 per dekatherm, a 7.4 percent increase over the current rate. New rates will become effective January 1, 2013, and will remain in effect for a minimum of 3 years and a maximum of 5 years.

3. CONTINGENT LIABILITIES AND COMMITMENTS

Legal Proceedings

We are a party to legal, administrative, and regulatory proceedings arising in the ordinary course of business.

5

NORTHWEST PIPELINE GP

NOTES TO FINANCIAL STATEMENTS

(Unaudited)

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 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, 2012, we had accrued liabilities totaling approximately $6.3 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 is 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 this 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 $3 million to $4 million through 2013, the compliance date.

In February 2010, the EPA promulgated a final rule establishing a new one-hour nitrogen dioxide (NO₂) NAAQS. In February 2012, the EPA designated all areas of the country as “unclassifiable/attainment,” meaning that information available at that time did not indicate that air quality in these areas exceeded the NAAQS. Also, at that time, the EPA noted its plan to deploy an expanded NO₂ monitoring network beginning in 2013. 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.

6

NORTHWEST PIPELINE GP

NOTES TO FINANCIAL STATEMENTS

(Unaudited)

Safety Matters

Pipeline Integrity Regulations We have developed an Integrity Management Program that we believe meets the United States Department of Transportation Pipeline and Hazardous Materials Safety Administration final rule that was issued pursuant to the requirements of the Pipeline Safety Improvement Act of 2002. The rule requires gas pipeline operators to develop an integrity management program for transmission pipelines that could affect high consequence areas in the event of pipeline failure. The Integrity Management Program includes a baseline assessment plan to be completed in 2012 along with periodic reassessments to be completed within required timeframes. In meeting the integrity regulations, we have identified high consequence areas and developed our baseline assessment plan. We are on schedule to complete the required assessments within the required timeframes.

We estimate the cost to complete the required initial assessments and associated remediation through 2012 will be primarily capital in nature and range between $30 million and $35 million for the full year of 2012. Ongoing periodic reassessments and initial assessments of any new high consequence areas will be completed within the timeframes required by the rule. Management considers the costs associated with compliance with the rule to be prudent costs incurred in the ordinary course of business and, therefore, recoverable through our rates.

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.

4. DEBT AND FINANCING ARRANGEMENT

Credit Facility

Total letter of credit capacity available to WPZ under the $2.0 billion credit facility is $1.3 billion. At June 30, 2012, WPZ had a total of $345 million outstanding under the credit facility and no letters of credit have been issued. At June 30, 2012, the full $400 million under the credit facility was available to us.

5. 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 of these items approximates their fair value.

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 $693.9 million and $826.7 million, respectively, at June 30, 2012, and $693.8 million and $826.3 million, respectively, at December 31, 2011.

7

NORTHWEST PIPELINE GP

NOTES TO FINANCIAL STATEMENTS

(Unaudited)

6. TRANSACTIONS WITH AFFILIATES

We are a participant in WPZ’s cash management program, and we make advances to and receive advances from WPZ. At June 30, 2012 and December 31, 2011, the advances due to us by WPZ totaled approximately $61.5 million and $52.0 million, respectively. These advances are represented by demand notes. 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, 2012. The interest income from these advances was minimal during the six months ended June 30, 2012 and June 30, 2011. Such interest income is included in “Other Income – net: Interest income – Affiliated” on the accompanying Statement of Comprehensive Income.

The Williams Companies, Inc. (Williams) charges its subsidiary companies for management services provided by it and other affiliated companies. Such corporate expenses charged by Williams, WPZ, and other affiliated companies, for the six months ended June 30, 2012 and 2011, were $21.3 million and $18.0 million, respectively. These expenses are included in “General and administrative expense” on the accompanying Statement of Comprehensive Income. Management considers the cost of these services to be reasonable.

We have no employees. Services are provided to us by an affiliate, Northwest Pipeline Services LLC (NPS). Pursuant to an administrative services agreement, NPS provides personnel, facilities, goods, and equipment not otherwise provided by us that are necessary to operate our business. In return, we reimburse NPS for all direct and indirect expenses it incurs or payments it makes (including salary, bonus, incentive compensation, pension and other benefits) in connection with these services. For the six months ended June 30, 2012 and 2011, we were billed $33.7 million and $30.9 million, respectively. Such expenses are primarily included in “General and administrative” and “Operation and maintenance” expenses on the accompanying Statement of Comprehensive Income.

During the periods presented, our revenues include transportation transactions and rental of communication facilities with subsidiaries of Williams. Combined revenues for these activities, for the six months ended June 30, 2012 were minimal. Combined revenues for the six months ended 2011 were $12.1 million. The reduction in revenues from 2011 is a result of Williams’ spin-off of its former exploration and production business, which was completed on December 31, 2011. These revenues, associated with transportation transactions, are now reflected with the revenues from outside parties.

During the six months ended June 30, 2012 and 2011, we declared and paid equity distributions to our parent of $73.0 million and $64.0 million, respectively. During July 2012, we declared and paid equity distributions of $34.5 million to our parent.

During the six months ended June 30, 2012 and 2011, we received contributions of $2.3 million and $3.5 million, respectively, from our parent to fund a portion of our expansion related expenditures for additions to property, plant, and equipment. In July 2012, our parent authorized an additional $1.2 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 2011 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, 2012 and 2011. 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 $1.2 million, or 1 percent. This increase is primarily attributed to higher reservation charges and the timing effect of leap year in 2012.

Transportation service and gas storage service accounted for 97 percent and 3 percent, respectively, of our operating revenues for both periods.

Operating expenses increased $6.5 million, or 6 percent, due primarily to i) higher allocated overhead from affiliates of $3.4 million; ii) higher depreciation of $1.4 million, attributed to property additions; iii) higher employee incentive compensation expense of $0.9 million; iv) higher pension costs of $0.8 million; and (v) higher labor costs of $0.8 million; partially offset by lower ad valorem taxes of $0.8 million, resulting primarily from favorable valuation settlements.

CAPITAL EXPENDITURES

Our capital expenditures were $47.1 million and $36.2 million for the six months ended June 30, 2012 and 2011, respectively. Our capital expenditures estimate for 2012 is discussed in our 2011 Annual Report on Form 10-K. That estimate includes the following new capital projects proposed by us:

North and South Seattle Lateral Delivery Expansions

We have executed agreements with Puget Sound Energy to expand the North and South Seattle laterals and provide additional lateral capacity of approximately 84 MDth per day and 74 MDth per day, respectively. We estimate the expansion of the two laterals to cost between $28 million and $30 million. North Seattle is scheduled for a fall 2012 in-service date and South Seattle is scheduled for a fall 2013 in-service date.

9

Item 4. Controls and Procedures

Our management, including our Senior Vice President and our Vice President and Treasurer, 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 and our Vice President and Treasurer. Based upon that evaluation, our Senior Vice President and our Vice President and Treasurer concluded that these Disclosure Controls are effective at a reasonable assurance level.

Second-Quarter 2012 Changes in Internal Controls

There have been no changes during the second quarter of 2012 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 3. 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.

11

ITEM 6. EXHIBITS

The following instruments are included as exhibits to this report.

Exhibit	Description
3(a)	Statement of Partnership Existence of Northwest Pipeline GP (Exhibit 3.1 to our report on Form 8-K, filed October 2, 2007) and incorporated herein by reference.
3(b)	Amended and Restated General Partnership Agreement of Northwest Pipeline GP (Exhibit 3.1 to our report on Form 8-K, filed January 30, 2008) 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** 101.SCH** 101.CAL** 101.DEF** 101.LAB** 101.PRE**	XBRL Instance Document. XBRL Taxonomy Extension Schema. XBRL Taxonomy Extension Calculation Linkbase. XBRL Taxonomy Definition Linkbase. XBRL Taxonomy Extension Label Linkbase. XBRL Taxonomy Extension Presentation Linkbase.

* Filed herewith.

** Furnished herewith.

12

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 GP
Registrant
By:	/s/ R. Rand Clark
	R. Rand Clark
	Controller
	(Duly Authorized Officer and
	Chief Accounting Officer)

Date: August 2, 2012

EXHIBIT INDEX

Exhibit	Description
3(a)	Statement of Partnership Existence of Northwest Pipeline GP (Exhibit 3.1 to our report on Form 8-K, filed October 2, 2007) and incorporated herein by reference.
3(b)	Amended and Restated General Partnership Agreement of Northwest Pipeline GP (Exhibit 3.1 to our report on Form 8-K, filed January 30, 2008) 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, Randall L. Barnard, certify that:

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

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: August 2, 2012

By:	/s/ Randall L. Barnard
	Randall L. Barnard
	Senior Vice President
	(Principal Executive Officer)

EX-31.B

Exhibit 31(b)

SECTION 302 CERTIFICATION

I, Richard D. Rodekohr, certify that:

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

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: August 2, 2012

By:	/s/ Richard D. Rodekohr
	Richard D. Rodekohr
	Vice President and Treasurer
	(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 GP (the “Company”) on Form 10-Q for the period ending June 30, 2012 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/ Randall L. Barnard

Randall L. Barnard

Senior Vice President

August 2, 2012

/s/ Richard D. Rodekohr

Richard D. Rodekohr

Vice President and Treasurer

August 2, 2012

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.

XML

Contingent Liabilities and Commitments

6 Months Ended

Jun. 30, 2012

Contingent Liabilities and Commitments [Abstract]

CONTINGENT LIABILITIES AND COMMITMENTS

3. CONTINGENT LIABILITIES AND COMMITMENTS

Legal Proceedings

We are a party to legal, administrative, and regulatory proceedings arising in the ordinary course of business.

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 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, 2012, we had accrued liabilities totaling approximately $6.3 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 is 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 this 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 $3 million to $4 million through 2013, the compliance date.

In February 2010, the EPA promulgated a final rule establishing a new one-hour nitrogen dioxide (NO2) NAAQS. In February 2012, the EPA designated all areas of the country as “unclassifiable/attainment,” meaning that information available at that time did not indicate that air quality in these areas exceeded the NAAQS. Also, at that time, the EPA noted its plan to deploy an expanded NO2 monitoring network beginning in 2013. 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.

Safety Matters

Pipeline Integrity Regulations We have developed an Integrity Management Program that we believe meets the United States Department of Transportation Pipeline and Hazardous Materials Safety Administration final rule that was issued pursuant to the requirements of the Pipeline Safety Improvement Act of 2002. The rule requires gas pipeline operators to develop an integrity management program for transmission pipelines that could affect high consequence areas in the event of pipeline failure. The Integrity Management Program includes a baseline assessment plan to be completed in 2012 along with periodic reassessments to be completed within required timeframes. In meeting the integrity regulations, we have identified high consequence areas and developed our baseline assessment plan. We are on schedule to complete the required assessments within the required timeframes.

We estimate the cost to complete the required initial assessments and associated remediation through 2012 will be primarily capital in nature and range between $30 million and $35 million for the full year of 2012. Ongoing periodic reassessments and initial assessments of any new high consequence areas will be completed within the timeframes required by the rule. Management considers the costs associated with compliance with the rule to be prudent costs incurred in the ordinary course of business and, therefore, recoverable through our rates.

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.

XML

Rate and Regulatory Matters

6 Months Ended

Jun. 30, 2012

Rate and Regulatory Matters [Abstract]

RATE AND REGULATORY MATTERS

2. RATE AND REGULATORY MATTERS

Rate Case Settlement Filing

On April 26, 2012, the Federal Energy Regulatory Commission (FERC) unconditionally approved Northwest's Stipulation and Settlement Agreement (Settlement) filed on March 15, 2012. The supporting or non-opposing customers named in the Settlement represent approximately 99.5 percent of our long-term firm transportation and storage capacity. The Settlement specified an annual cost of service of $466.5 million and established a new general system firm transportation rate of $0.44 per dekatherm, a 7.4 percent increase over the current rate. New rates will become effective January 1, 2013, and will remain in effect for a minimum of 3 years and a maximum of 5 years.

XML

Statement of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
STATEMENT OF COMPREHENSIVE INCOME
Operating Revenues	$ 106,311	$ 106,576	$ 217,683	$ 216,495
OPERATING EXPENSES:
General and administrative	17,305	13,694	33,888	28,503
Operation and maintenance	18,561	19,096	35,416	34,983
Depreciation	23,225	22,543	46,535	45,101
Regulatory credits	(115)	(267)	(404)	(534)
Taxes, other than income taxes	4,524	4,914	9,778	10,614
Total operating expenses	63,500	59,980	125,213	118,667
Operating Income	42,811	46,596	92,470	97,828
Interest income -
Affiliated	2	2	3	5
Other	1	1	6	1
Allowance for equity funds used during construction	506	287	719	407
Miscellaneous other (expense) income, net	(83)	(27)	(158)	(133)
Total other income - net	426	263	570	280
INTEREST CHARGES:
Interest on long-term debt	11,109	11,109	22,219	22,219
Other interest	478	504	961	1,014
Allowance for borrowed funds used during construction	(236)	(133)	(334)	(187)
Total interest charges	11,351	11,480	22,846	23,046
NET INCOME	31,886	35,379	70,194	75,062
CASH FLOW HEDGES:
Amortization of cash flow hedges	(15)	(16)	(31)	(31)
COMPREHENSIVE INCOME	$ 31,871	$ 35,363	$ 70,163	$ 75,031

XML

Statement of Cash Flows (Unaudited) (Parenthetical) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Statement of Cash Flows [Abstract]
Increases to property, plant and equipment	$ (54,479)	$ (36,850)
Changes in related accounts payable and accrued liabilities	7,332	605
Capital expenditures	$ (47,147)	$ (36,245)

XML

Basis of Presentation

6 Months Ended

Jun. 30, 2012

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.”

Northwest is indirectly owned by Williams Partners L.P. (WPZ), a publicly traded Delaware limited partnership, which is consolidated by The Williams Companies, Inc. (Williams). As of June 30, 2012, 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.

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 2011 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 reclassifications from Administrative and general to Operations and maintenance, related to certain employee related expenses of $0.9 million and $1.5 million for the three and six months ended June 30, 2011, respectively, have been made to conform to the presentation utilized in the 2012 Statement of Comprehensive Income.

XML

Balance Sheet (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
CURRENT ASSETS:
Cash	$ 240	$ 37
Receivables:
Trade	36,147	38,245
Affiliated companies	0	2,250
Advances to affiliate	61,462	52,024
Materials and supplies, less reserves of $59 at June 30, 2012 and $816 at December 31, 2011	10,049	10,488
Exchange gas due from others	1,145	3,441
Prepayments and other	4,447	3,469
Total current assets	113,490	109,954
PROPERTY, PLANT AND EQUIPMENT, at cost	3,120,625	3,068,915
Less-Accumulated depreciation	1,128,771	1,076,943
Total property, plant and equipment, net	1,991,854	1,991,972
OTHER ASSETS:
Deferred charges	8,742	10,250
Regulatory assets	59,394	59,605
Total other assets	68,136	69,855
Total assets	2,173,480	2,171,781
Payables:
Trade	16,848	13,634
Affiliated companies	13,441	8,812
Accrued liabilities:
Taxes, other than income taxes	11,622	10,252
Interest	4,045	4,045
Exchange gas due to others	2,126	10,472
Exchange gas offset	2,049	2,241
Other	3,940	5,006
Total current liabilities	54,071	54,462
LONG-TERM DEBT	693,929	693,831
DEFERRED CREDITS AND OTHER NONCURRENT LIABILITIES	105,540	103,041
CONTINGENT LIABILITIES AND COMMITMENTS (Note 3)
OWNER'S EQUITY:
Owner's capital	1,054,292	1,051,962
Retained earnings	265,403	268,209
Accumulated other comprehensive income	245	276
Total owner's equity	1,319,940	1,320,447
Total liabilities and owner's equity	$ 2,173,480	$ 2,171,781

XML

Financial Instruments (Details Textual) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	$ 826.7
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	693.9	693.8
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	$ 826.7	$ 826.3

XML

Document and Entity Information	6 Months Ended
	Jun. 30, 2012
Document and Entity Information [Abstract]
Entity Registrant Name	Northwest Pipeline GP
Entity Central Index Key	0000110019
Document Type	10-Q
Document Period End Date	Jun. 30, 2012
Amendment Flag	false
Document Fiscal Year Focus	2012
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

XML

Transactions with Affiliates (Details Textual) (USD $)	3 Months Ended		6 Months Ended			6 Months Ended		1 Months Ended	6 Months Ended
	Jun. 30, 2012 Employees	Jun. 30, 2011	Jun. 30, 2012 Employees	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2012 Affiliated Entity [Member]	Jun. 30, 2011 Affiliated Entity [Member]	Jul. 31, 2012 Williams Partners L.P. [Member]	Jun. 30, 2012 Williams Partners L.P. [Member]	Jun. 30, 2011 Williams Partners L.P. [Member]	Jun. 30, 2012 Northwest Pipeline Services LLC [Member]	Jun. 30, 2011 Northwest Pipeline Services LLC [Member]
Related Party Transaction [Line Items]
Advances to affiliate	$ 61,462,000		$ 61,462,000		$ 52,024,000				$ 61,500,000	$ 52,000,000
Related Party Transaction, Rate			0.01%
General and administrative	17,305,000	13,694,000	33,888,000	28,503,000		21,300,000	18,000,000
Entity Number of Employees	0		0
Labor and Related Expense											33,700,000	30,900,000
Operating Revenues	106,311,000	106,576,000	217,683,000	216,495,000			12,100,000
Distributions paid			73,000,000	64,000,000				34,500,000	73,000,000	64,000,000
Capital contributions from parent			$ 2,330,000	$ 3,500,000				$ 1,200,000	$ 2,300,000	$ 3,500,000

XML

Balance Sheet (Unaudited) (Parenthetical) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Receivables:
Reserves, materials and supplies	$ 59	$ 816

XML

Transactions with Affiliates

6 Months Ended

Jun. 30, 2012

Transactions with Affiliates [Abstract]

TRANSACTIONS WITH AFFILIATES

6. TRANSACTIONS WITH AFFILIATES

We are a participant in WPZ's cash management program, and we make advances to and receive advances from WPZ. At June 30,2012 and December 31, 2011, the advances due to us by WPZ totaled approximately $61.5 million and $52.0 million, respectively. These advances are represented by demand notes. 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 30,2012. The interest income from these advances was minimal during the six months ended June 30,2012and June 30, 2011. Such interest income is included in “Other Income – net: Interest income – Affiliated” on the accompanying Statement of Comprehensive Income.

The Williams Companies, Inc. (Williams) charges its subsidiary companies for management services provided by it and other affiliated companies. Such corporate expenses charged by Williams, WPZ, and other affiliated companies, for the six months ended June 30,2012 and 2011, were $21.3 million and $18.0 million, respectively. These expenses are included in “General and administrative expense” on the accompanying Statement of Comprehensive Income. Management considers the cost of these services to be reasonable.

We have no employees. Services are provided to us by an affiliate, Northwest Pipeline Services LLC (NPS). Pursuant to an administrative services agreement, NPS provides personnel, facilities, goods, and equipment not otherwise provided by us that are necessary to operate our business. In return, we reimburse NPS for all direct and indirect expenses it incurs or payments it makes (including salary, bonus, incentive compensation, pension and other benefits) in connection with these services. For the six months ended June 30, 2012 and 2011, we were billed $33.7 million and $30.9 million, respectively. Such expenses are primarily included in “General and administrative” and “Operation and maintenance” expenses on the accompanying Statement of Comprehensive Income.

During the periods presented, our revenues include transportation transactions and rental of communication facilities with subsidiaries of Williams. Combined revenues for these activities, for the six months ended June 30,2012were minimal. Combined revenues for the six months ended 2011were $12.1 million. The reduction in revenues from 2011 is a result of Williams' spin-off of its former exploration and production business, which was completed on December 31, 2011. These revenues, associated with transportation transactions, are now reflected with the revenues from outside parties.

During the six months ended June 30, 2012 and 2011, we declared and paid equity distributions to our parent of $73.0 million and $64.0 million, respectively. During July 2012, we declared and paid equity distributions of $34.5 million to our parent.

During the six months ended June 30, 2012 and 2011, we received contributions of $2.3 million and $3.5 million, respectively, from our parent to fund a portion of our expansion related expenditures for additions to property, plant, and equipment. In July 2012, our parent authorized anadditional $1.2 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.

XML

Financial Instruments

6 Months Ended

Jun. 30, 2012

Financial Instruments [Abstract]

FINANCIAL INSTRUMENTS

5. 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 of these items approximates their fair value.

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 $693.9 million and $826.7 million, respectively, at June 30,2012, and $693.8 million and $826.3 million, respectively, at December 31, 2011.

XML

Contingent Liabilities and Commitments (Details Textual) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Environmental Matters [Abstract]
Accrual for Environmental Loss Contingencies	$ 6.3
Minimum [Member]
Environmental Matters [Abstract]
Estimated Capital Costs For Compliance With Hazardous Air Pollutant Regulations	3
Pipeline Integrity Regulations [Abstract]
Cost To Complete Required Initial Assessments	30
Maximum [Member]
Environmental Matters [Abstract]
Estimated Capital Costs For Compliance With Hazardous Air Pollutant Regulations	4
Pipeline Integrity Regulations [Abstract]
Cost To Complete Required Initial Assessments	$ 35

XML

Basis of Presentation (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
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 Reclassification Adjustment [Abstract]
Prior Period Reclassification Adjustment	$ 0.9		$ 1.5

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Rate and Regulatory Matters (Details Textual) (USD $) In Millions, unless otherwise specified	1 Months Ended	6 Months Ended
	Apr. 30, 2012	Jun. 30, 2012 Minimum [Member]	Jun. 30, 2012 Maximum [Member]
Settlement Agreement [Line Items]
Percentage Of Capacity Representing Non Opposing Customers	99.50%
Annual Cost Of Service	$ 466.5
General System Firm Transportation Rate Per Unit	0.44
General System Firm Transportation Rate Increase	7.40%
Duration Of Effective Period Of Rate Case Settlement		3 years	5 years

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Debt and Financing Arrangements (Details Textual) (USD $)	Jun. 30, 2012
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 400,000,000
Letters of Credit Outstanding, Amount	0
$2 billion unsecured credit facility [Member] | Williams Partners L.P. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,000,000,000
Line of Credit Facility, Amount Outstanding	345,000,000
$2 billion unsecured credit facility [Member] | Letter Of Credit Capacity [Member] | Williams Partners L.P. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,300,000,000

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Statement of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
OPERATING ACTIVITIES:
Net income	$ 70,194	$ 75,062
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation	46,535	45,101
Regulatory credits	(404)	(534)
Amortization of deferred charges and credits	795	859
Allowance for equity funds used during construction	(719)	(407)
Changes in current assets and liabilities:
Trade accounts receivable	2,098	4,541
Affiliated receivables	2,250	84
Exchange gas due from others	2,296	7,780
Materials and supplies	439	499
Other current assets	(978)	(1,320)
Trade accounts payable	(2,465)	(2,620)
Affiliated payables	4,695	3,650
Exchange gas due to others	(2,295)	(7,781)
Other accrued liabilities	303	2,821
Changes in noncurrent assets and liabilities:
Deferred charges	(954)	(1,130)
Other deferred credits	2,639	2,748
Net cash provided by operating activities	124,429	129,353
FINANCING ACTIVITIES:
Capital contributions from parent	2,330	3,500
Distributions paid	(73,000)	(64,000)
Other	(1,719)	(1,424)
Net cash used in financing activities	(72,389)	(61,924)
Property, plant and equipment -
Capital expenditures	(47,147)	(36,245)
Proceeds from sales	4,748	1,150
Advances to affiliates	(9,438)	(32,332)
Net cash used in investing activities	(51,837)	(67,427)
NET INCREASE IN CASH	203	2
CASH AT BEGINNING OF PERIOD	37	5
CASH AT END OF PERIOD	$ 240	$ 7

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Debt and Financing Arrangements

6 Months Ended

Jun. 30, 2012

Debt and Financing Arrangement [Abstract]

DEBT AND FINANCING ARRANGEMENT

4. DEBT AND FINANCING ARRANGEMENT

Credit Facility

Total letter of credit capacity available to WPZ under the$2.0 billion credit facility is $1.3 billion. At June 30,2012, WPZ had a total of $345 million outstanding under the credit facility and no letters of credit have been issued. At June 30, 2012,the full $400 million under the credit facility was available to us.