GAS GATHERING AGREEMENT Between MOUNTAIN FUEL SUPPLY COMPANY AND QUESTAR PIPELINE COMPANY EFFECTIVE SEPTEMBER 1, 1993 GAS GATHERING AGREEMENT Table of Contents

Exhibit 10.6

GAS GATHERING AGREEMENT

Between

MOUNTAIN FUEL SUPPLY COMPANY

AND

QUESTAR PIPELINE COMPANY

EFFECTIVE SEPTEMBER 1, 1993

GAS GATHERING AGREEMENT

Table of Contents

GAS GATHERING AGREEMENT

This Agreement is entered into on this 11th day of October 1993, between Mountain Fuel, Supply Company (Mountain Fuel), 180 East First South Street, Salt Lake City, Utah 84111, and QUESTAR PIPELINE COMPANY (QUESTAR), 79 South State Street, Salt Lake City, Utah 84111. Mountain Fuel and Questar are collectively referred to as “the Parties.”

The Parties represent that:

1. On October 14, 1982, Mountain Fuel, Wexpro Company, the Utah Division of Public Utilities, the Utah Committee of Consumer Services and the Staff of the Public Service Commission of Wyoming entered into an agreement (the Wexpro Agreement) that provides for the operation and development of certain oil-and-gas properties previously owned by Mountain Fuel and Wexpro Company.

2. Pursuant to the provisions of the Wexpro Agreement, Mountain Fuel owns or has the right to purchase certain supplies of natural gas that are produced by Wexpro Company.

3. Mountain Fuel requires that certain of this Wexpro Agreement production be gathered and transported from points at which it is made available or produced to Mountain Fuel’s retail distribution facilities.

4. Questar currently provides gas-gathering services for Mountain Fuel for certain Wexpro Agreement gas in part pursuant to a Gas Gathering Agreement, dated July 1, 1984.

5. Up through August 31, 1993, Mountain Fuel purchased gas from Questar under Questar’s FERC firm sales Rate Schedule CD-1. This service incorporated, among other things, the field gathering of certain gas supplies by Questar that were necessary to support firm sales service to Mountain Fuel. In partial support of its contractual obligation to provide CD-1 sales service, Questar has built or acquired, and maintains and operates, a gathering system that is contiguous to its interstate transmission system.

6. Pursuant to Questar’s FERC gas tariff, firm sales service was provided to Mountain Fuel under two Rate Schedule CD-1 service agreements executed by Mountain Fuel and Questar on March 1, 1991, and amended as of December 1, 1992, with a primary term that was to expire on June 30, 1999.

7. Pursuant to Federal Energy Regulatory Commission (FERC) Order No 636 and related FERC orders, Questar submitted a comprehensive restructuring of its transportation, storage and gathering operations in FERC Docket No. RS92-9. Under the restructuring, approved by the FERC in Docket No RS92-9, Questar has (a) restructured its various services, and (b) terminated its sales function by assigning to Mountain Fuel all the gas purchase agreements that supported Rate Schedule CD-1 sales service. 64 FERC ¶61,157 (Aug. 2, 1993).

8. As a result of Questar’s restructuring, described above, Mountain Fuel requires gathering services to transport gas purchased by Mountain Fuel from its purchase points to points on Questar’s transmission system.

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9. Pursuant to the Docket No. RS92-9 restructuring, Questar transports Mountain Fuel’s gas on its transmission system under its FERC Gas Tariff.

10. Questar and Mountain Fuel wish to enter into a new agreement, under which Questar will gather designated Wexpro Agreement gas and Mountain Fuel-purchased gas, including certain gas that formerly supported the Rate Schedule CD-1 sales service. This Agreement is intended to replace the July 1, 1984, Gas Gathering Agreement and the gathering services formerly provided under Rate Schedule CD-1.

Therefore, the Parties agree as follows:

Article I – Dedication

(a) Except as limited in §§ I(b) and I(d), the following categories of gas are dedicated under this Agreement, up to a combined maximum daily quantity (MDQ) of 322,812 Dth: (1) gas purchased by or produced for Mountain Fuel pursuant to the Wexpro Agreement, and (2) gas purchased by Mountain Fuel at the wellhead or any other point on or near Questar’s gathering system that is upstream from the interstate transmission system into which the gas will be delivered for Mountain Fuel’s account.

(b) The Parties acknowledge that Questar does not provide exclusive service to Mountain Fuel in certain fields. Excluded from dedication under this Agreement, at Mountain Fuel’s discretion, is gas from (i) wells, producing at the initial effective date [defined in § IV(a)] and gathered exclusively through facilities not owned by Questar, or (ii) wells completed in the future that would require reimbursement when evaluated under the criteria described in § III(c) of this Agreement.

(c) Subject to the physical and contractual limitations of Questar’s system, Mountain Fuel may adjust its MDQ to reflect its anticipated 12-month service requirement upon at least 180 days’ advanced written notice to Questar to be effective the next September 1. Any reduction under this provision will be effective no sooner than September 1, 1997.

(d) After August 31, 1997, gas produced for or purchased by Mountain Fuel under the Wexpro Agreement will remain subject to the terms of this Agreement In addition, any gas being purchased by Mountain Fuel from a third party and dedicated to this Agreement under §I(a)(2) on August 31, 1997, may, at Mountain Fuel’s option, continue to be dedicated under this Agreement from year to year (September 1 through August 31) until Mountain Fuel’s underlying gas-purchase agreement expires or until Mountain Fuel, on 180 days’ prior written notice, terminates dedication on the next August 31. The MDQ for use under this Agreement shall be accordingly modified to reflect the demonstrated deliverability of Wexpro Agreement gas and such third-party purchases.

Article II – Gathering Service, Receipts and Deliveries

(a) Questar shall gather up to the MDQ of 322,812 Dth/day of gas dedicated under this Agreement on a firm basis for delivery for Mountain Fuel’s account into Questar’s transmission system or the pipelines of others connected to Questar’s gathering facilities.

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(b) The gathering service shall include essential wellhead gas conditioning, collection and measurement through Questar’s gathering laterals, and field compression to enable delivery into connected pipelines.

(c) At the request of Mountain Fuel, Questar shall install all necessary facilities to connect any new well to Questar’s then-existing gathering system. If requested, Questar shall provide an estimate of the costs to connect any new well under this Agreement. Reimbursement of Questar’s costs, if any, shall be determined under § III(c). A “new well” is one that was not identified on Appendix A on the initial effective date. Except when prevented by a force majeure event, Questar shall connect each new well from which gas is to be gathered under this Agreement within 30 days of the later of:

(1) Authorization from Mountain Fuel to connect the well, or

(2) Receipt of all rights of way, permits and necessary authorizations.

(d) Mountain Fuel shall be permitted to change or add new receipt and delivery points, within its MDQ, upon 10 days’ advance written notification to Questar, subject to available capacity at the desired points.

(e) Questar shall receive gas from Mountain Fuel at the receipt points listed on Appendix A.

(f) So long as Mountain Fuel does not exceed the MDQ under § II(a), Mountain Fuel may use any gathering receipt or delivery point on an interruptible basis at any time.

(g) Mountain Fuel shall tender gas at pressures sufficient for delivery into Questar’s facilities against the existing pressures, but not exceeding the maximum allowable operating pressures (MAOPs) of Questar’s facilities.

(h) Questar shall deliver equivalent quantities of gas for Mountain Fuel’s account, less fuel and lost-and-unaccounted-for gas under § 6 of the General Terms and Conditions of this Agreement Delivery for Mountain Fuel’s account by Questar shall take place at the delivery points listed on Appendix A. Questar shall deliver these volumes of gas at the existing pressures, but not exceeding the MAOP in Questar’s facilities at the delivery points.

Article III – Gathering Charges, Reimbursements and Credits

(a) Gathering Rates.

(1) Through August 31, 1995. From the initial effective date of this Agreement until August 31, 1995, rates for gathering services and their derivation are set forth in Appendix B and were calculated on the basis of:

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(2) September 1, 1995—August 31, 1997. For the period from September 1, 1995, through August 31, 1997, rates will be determined by an application of the methodology shown in Appendix B and will be based on:

(3) After August 31, 1997. From September 1, 1997, until the termination of this Agreement, rates will be redetermined each year, to be effective from September 1 through the following August 31, and will be based on:

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(b) Independent Facilities. Questar may construct new gathering facilities that will be operated independently of systems in operation on the initial effective date (i.e., facilities through which gas will flow that do not require the use of any part of Questar’s gathering system as it existed on the initial effective date). To the extent these facilities are not operated to provide service for Mountain Fuel, the costs and revenues associated with or derived from these systems shall be excluded when determining Mountain Fuel’s gathering rates under this Agreement.

(c) New Well Connection Reimbursement. For any new well to be connected to Questar’s gathering system at Mountain Fuel’s request under this Agreement that was not subject to this Agreement on the initial effective date, Mountain Fuel shall reimburse Questar according to the formula set forth in Appendix C of this Agreement.

Article IV – Effective Date and Term

(a) For all purposes in this Agreement, the “initial effective date” is September 1, 1993, the date of implementation of Questar’s restructuring in FERC Docket No. RS92-9.

(b) This Agreement will become effective on the initial effective date and will remain in full force and effect so long as Mountain Fuel is producing or purchasing gas pursuant to the Wexpro Agreement.

(c) Upon termination of this Agreement, deliveries and receipts shall continue for as long as necessary to eliminate any imbalance in quantities of gas owed by either Party to the other.

Article V – 1984 Gas Gathering Agreement

Upon implementation of the terms of this Agreement on the initial effective date, the July 1, 1984, Gas Gathering Agreement shall be terminated and superseded by this Agreement

Article VI – Government Authorization

(a) The Parties shall cooperate to obtain any necessary governmental authorization to implement this Agreement. To the extent that a governmental agency with jurisdiction over the rates, facilities or services addressed by this Agreement imposes terms or conditions on this Agreement that materially alter the rights or obligations of either party, this Agreement may be terminated or rescinded, as appropriate, by either party upon 15 days’ written notice to the other party.

(b) The Parties have entered into this Agreement with the expectation that the facilities, services and rates that are the subject of this Agreement do not come within the jurisdiction of the FERC. The Parties may, however, seek FERC approval of all or part of the Agreement to expedite its implementation. Any such action by the Parties will not be construed as a concession, acquiescence or waiver by either party of any legal position concerning the regulation of gathering facilities, service or rates.

(c) If the rates for Questar’s gathering services are deemed to be subject to regulation by an administrative agency that prescribes rates other than those specified in this Agreement for any period governed by this Agreement, the rates so specified shall be substituted for the rates

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provided for in Article III, Any substitution under this provision will apply only to the extent that, and for the period during which, the administrative agency lawfully exercises rate regulation over the services. Nothing in this provision will preclude either party from exercising its termination rights under § VI(a).

Article VII – Notices

All notices required in this agreement shall be in writing and shall be considered as having been given if delivered personally, by mail or facsimile transmission to either Questar or Mountain Fuel at the designated address. Normal operating instructions can be delivered by telephone or any electronic means. Notice of events of force majeure may be made by any electronic means and confirmed in writing. Monthly statements, payments, and any communications will be considered as delivered when mailed to the addresses listed below or to such other address as either Party designates in writing:

THIS AGREMENT is entered into by the authorized representatives of the Parties, whose signatures appear below.

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GENERAL TERMS AND CONDITIONS

OF

GAS GATHERING AGREEMENT

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APPENDIX A

TO THE

GAS GATHERING AGREEMENT

DATED: OCTOBER 11, 1993

BETWEEN

MOUNTAIN FUEL SUPPLY COMPANY

AND

QUESTAR PIPELINE COMPANY

RECEIPT POINTS

The interconnection of Questar’s gathering facilities and the production facilities associated with the following wells:

Receipt points associated with Wexpro Agreement.

A-1

A-2

A-3

A-4

A-5

A-6

A-7

A-8

A-9

Non-Wexpro Agreement receipt points.

A-10

A-11

A-12

A-13

A-14

A-15

A-16

A-17

A-18

A-19

A-20

DELIVERY POINTS

Delivery points associated with Wexpro Agreement.

A-21

Non-Wexpro Agreement Delivery Points.

A-22

A-23

APPENDIX B

TO THE

GAS GATHERING AGREEMENT

DATED: OCTOBER 11, 1993

BETWEEN

MOUNTAIN FUEL SUPPLY COMPANY

AND

QUESTAR PIPELINE COMPANY

GATHERING RATE DETERMINATION

The reservation and usage rates to be charged for gathering natural gas under the terms of this Agreement shall be determined according to the following provisions and guidelines.

1. The calculation of the gathering rates under § III(a) of the Agreement shall incorporate data and accounting and other information for the most recent calendar year for which complete data are available. For the initial rates, this will be the calendar year 1992, as adjusted to reflect the elements incorporated and approved in FERC Docket No. RS92-9. For subsequent rate determinations under this Agreement, such information shall be adjusted as necessary to reflect known and measurable changes¹ in Questar’s gathering operations that will be effective during the years for which rates are to be in effect. Such changes shall be consistent with the provisions of ¶¶ 2 and 3.

2. The net costs to be included in determining the gathering rates shall include: (a) operating and maintenance expenses; (b) depreciation and amortization expenses; (c) taxes other than income taxes; (d) return on rate base; (e) federal and state income taxes; and (f) other operating revenue credits.

3. For purposes of ¶ 2, the following guidelines will apply:

(a) Operation and Maintenance (O&M) Expenses. These expenses include gathering expenses recorded in FERC Account Nos. 750-754 and 756-769 and 807, including administrative and general (A&G) expenses in Account Nos. 920-932 (excluding 924.1, 928.1, 928.2 and 920.3) and 935.

(b) Depreciation and Amortization Expense. This includes gathering expenses recorded in FERC Account Nos. 403 and 404, including general and intangible amortization expense.

(c) Taxes Other Than Income Taxes. This includes gathering expenses recorded in FERC Account Nos. 408.1 and 408.9, including payroll and property tax expense associated with general plant.

B-1

(d) Federal and State Income Taxes. Questar Pipeline’s combined federal and state income tax rate shall be applied to the equity portion of the return on rate base.

(e) Rate Base. The end-of-period rate base shall be determined from accounting data for the last month for which data are being used pursuant to ¶ 1 above (adjusted as necessary pursuant to that paragraph) and shall include that portion of the following that are directly related or allocable to the gathering services performed under this Agreement:

(i) Gas plant,

(ii) Accumulated depreciation and amortization,

(iii) Working capital,

(iv) Deferred income taxes, and

(v) Questar’s general and intangible plant

(f) Rate of Return. The rate of return on rate base shall be the pre-tax rate of return specified for or derivable from the FERC’s determination of Questar’s transmission-service rates as they are effective at the end of the period. This shall incorporate:

(g) The costs of Questar’s gathering activities determined under this Appendix shall be reduced by other operating revenues that are directly related to those costs.

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APPENDIX C

TO THE

GAS GATHERING AGREEMENT

DATED: OCTOBER 11, 1993

BETWEEN

MOUNTAIN FUEL SUPPLY COMPANY

AND

QUESTAR PIPELINE COMPANY

NEW WELL CONNECTION

REIMBURSEMENT UNDER § III(c)

For any new well to be connected to Questar’s gathering system under this Agreement that was not subject to this Agreement on the initial effective date, Mountain Fuel shall reimburse Questar according to the following formula:

where

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