Exhibit 10.2

SPECIFIC TERMS IN THIS EXHIBIT HAVE BEEN REDACTED BECAUSE CONFIDENTIAL TREATMENT FOR THOSE TERMS HAS BEEN REQUESTED. THE REDACTED MATERIAL HAS BEEN SEPERATELY FILED WITH THE SECURITIES AND EXCHANGE COMMISSION, AND THE TERMS HAVE BEEN MARKED AT THE APPROPRIATE PLACE WITH TWO ASTERISKS (**).

Execution Version

CONTRIBUTION AGREEMENT

BY AND AMONG

MARKWEST LIBERTY GAS GATHERING, L.L.C.,

M&R MWE LIBERTY, LLC,

AND

MARKWEST LIBERTY MIDSTREAM & RESOURCES, L.L.C.

TABLE OF CONTENTS

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CONTRIBUTION AGREEMENT

THIS CONTRIBUTION AGREEMENT, dated as of January 22, 2009, is entered into by and among MarkWest Liberty Gas Gathering, L.L.C., a Delaware limited liability company (“MWE Liberty”), M&R MWE Liberty, LLC, a Delaware limited liability company (“NGPMR”), and MarkWest Liberty Midstream & Resources, L.L.C., a Delaware limited liability company (the “Company”).  The parties to this Agreement are collectively referred to herein as the “Parties.”

RECITALS

WHEREAS, MWE Liberty has formed the Company, pursuant to the Act, for the purpose of engaging in the natural gas midstream business, including, but not limited to, natural gas gathering and processing, and the natural gas liquids processing, fractionation, transportation, storage and marketing business within the Area of Mutual Interest and certain other purposes (the “Business”);

WHEREAS, at the Closing MWE Liberty and NGPMR (the “Members”) shall execute and agree to that certain Amended and Restated Limited Liability Company Agreement of the Company (the “Company Operating Agreement”) in the form attached hereto as Exhibit C, which Company Operating Agreement shall become effective at the Closing;

WHEREAS, at the Closing MWE Liberty, MarkWest Hydrocarbon, Inc. and the Company shall execute and agree to that certain Services Agreement (the “Services Agreement”) in the form attached hereto as Exhibit D, which Services Agreement shall become effective at the Closing;

WHEREAS, subject to the terms and conditions of this Agreement, NGPMR desires to contribute to the Company, and the Company desires to accept from NGPMR, certain cash consideration in exchange for all of the Class A Interests; and

WHEREAS, subject to the terms and conditions of this Agreement, MWE Liberty desires to contribute, convey, assign and transfer to the Company, and the Company desires to accept from MWE Liberty, all of MWE Liberty’s right, title and interest in and to the Assets in exchange for all of the Class B Interests and the assumption of certain liabilities by the Company.

AGREEMENTS

NOW, THEREFORE, in consideration of their mutual undertakings and agreements hereunder, the Parties undertake and agree as follows:

ARTICLE 1

DEFINITIONS; INTERPRETATION

Section 1.1             Definitions.  Capitalized terms used in this Agreement but not defined in the body hereof shall have the meanings ascribed to them in Exhibit A.

Section 1.2             Headings; References; Interpretation.  In this Agreement, unless a clear contrary intention appears:  (a) the singular includes the plural and vice versa; (b) reference to a person includes such Person’s successors and assigns but, in the case of a Party, only if such successors and assigns are permitted by this Agreement, and reference to a Person in a particular capacity excludes such Person in any other capacity; (c) reference to any gender includes each other gender; (d) reference to any agreement (including this Agreement), document or instrument means such agreement, document, or instrument as amended or modified and in effect from time to time in accordance with the terms thereof and, if applicable, the terms of this Agreement; (e) reference to any Section or Article means such Section or Article of this Agreement, and references in any Section or Article or definition to any clause means such clause of such Section, Article or definition; (f) “hereunder,” “hereof,” “hereto” and words of similar import are references to this Agreement as a whole and not to any particular provision hereof; and (g) the word “or” is not exclusive, and the word “including” (in its various forms) means including without limitation.  Section titles and headings in this Agreement are inserted for convenience of reference only and are not intended to be a part of, or to affect the meaning or interpretation of, this Agreement.

ARTICLE 2

CONTRIBUTIONS, ASSUMED LIABILITIES AND CLOSING

Section 2.1             Contributions and Payments.  Subject to the terms and conditions of this Agreement, at the Closing, the following contributions, equity issuances and payments shall be made:

(a)           NGPMR shall contribute $50,000,000.00 to the Company in immediately available funds in exchange for all of the Class A Interests.  In its capacity as a holder of such interests, NGPMR shall have the obligations set forth in the Company Operating Agreement with respect to a Class A Member to contribute additional capital to the Company, but shall have no other obligation to contribute any additional capital to the Company.

(b)           MWE Liberty shall grant, contribute, bargain, convey, assign, transfer, set over and deliver to the Company, its successors and assigns, and for its and their own use forever, all of MWE Liberty’s right, title and interest in and to the Assets in exchange for all of the Class B Interests.  In its capacity as a holder of such interests, MWE Liberty shall have the obligations set forth in the Company Operating Agreement with respect to a Class B Member to contribute additional capital to the Company, but shall have no other obligation to contribute any additional capital to the Company.  The term “Assets” shall mean (i) all of the assets owned by MWE Liberty, including the natural gas gathering systems described in Exhibit B attached hereto, together with all natural gas gathering and processing and natural gas liquids processing, fractionation, transportation, storage and marketing plants and facilities constituting a part thereof or related thereto, and all easements, rights of way, privileges, franchises, tracts of land,

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surface leases, other interests in land, pipelines, equipment, permits, licenses, contract rights and personal property constituting a part thereof or necessary for the ownership and operation thereof including the easements, rights of way, permits and other instruments referenced in Exhibit B and (ii) all of the assets owned by Affiliates of MWE Liberty that are related exclusively to the Business within the Area of Mutual Interest, but in any event, excluding any and all amounts payable by Range Resources-Appalachia, LLC pursuant to Section 4.3(d) of that certain Interim Gas Processing Agreement dated March 5, 2008, between MarkWest Energy Appalachia, L.L.C. and Range Resources-Appalachia, LLC, for procuring, constructing and installing the interim plant prior to January 1, 2008 and representing 115% of all Installation Costs (as defined therein) incurred in the procurement, construction and installation of the interim plant (the “Excluded Assets”).  The Excluded Assets shall be retained by MWE Liberty and its Affiliates and shall not be considered Assets hereunder.

(c)           The Company shall pay to MWE Liberty in immediately available funds the amount of any **; provided that any such ** by MWE Liberty after the date hereof shall be consistent with Section 6.8.

Section 2.2             Assumption of Liabilities.  As part of the consideration for the contribution of the Assets by MWE Liberty to the Company, effective as of the Closing, the Company will assume and agree to duly and timely pay, perform and discharge, pursuant to the Assignment and Assumption, all of the liabilities and obligations of any kind whatsoever of MWE Liberty arising from or relating to the Assets, whether known or unknown, liquidated or contingent, and regardless of whether the same are deemed to have arisen, accrued or are attributable to periods prior to, on or after the Closing Date, including, but not limited to, obligations and liabilities of MWE Liberty: (a) concerning the use, ownership, management or operation of the Assets, (b) under or relating to any contracts, agreements, Permits and instruments existing as of the Closing Date by which the Assets are bound or subject or that relate to or are otherwise applicable to the Assets (other than obligations of MWE Liberty under the Transaction Documents) and (c) which are Disclosed Liabilities, (all of the liabilities and obligations described in this Section 2.2 are collectively referred to as the “Assumed Liabilities”); provided, however, that the Company does not assume (and Assumed Liabilities shall not include) any costs or expenses included within the amount of MWE Liberty’s initial capital contribution to the Company.

Section 2.3             Closing.  Subject to the terms and conditions of this Agreement, the closing of the transactions contemplated by this Agreement (the “Closing”) shall take place at the offices of Vinson & Elkins LLP, First City Tower, 1001 Fannin Street, Suite 2500, Houston, Texas 77002 on the second Business Day after all of the conditions precedent set forth in Article 7 have been satisfied, or if permissible, waived, or at such other place, time and date as is agreed to in writing by the Parties (the “Closing Date”).  The Closing will be deemed effective as of 11:59 p.m., Houston, Texas time on the Closing Date.

Section 2.4             Closing Deliveries.

(a)           NGPMR Deliveries.  At the Closing, NGPMR will execute and deliver, or cause to be executed and delivered, to the other Parties, as applicable, each of the following

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documents, where the execution or delivery of documents is contemplated, and will take or cause to be taken the following actions, where the taking of action is contemplated:

(i)            a certificate of the Secretary of State of the State of Delaware, dated not more than five days prior to the Closing Date, as to the existence and good standing of NGPMR;

(ii)           a certificate of an officer of NGPMR providing the following documents and certifying that each is a true and correct copy:  (A) the Organizational Documents of NGPMR and (B) resolutions of NGPMR’s governing body authorizing the transactions contemplated hereby (including designation of the Persons authorized to execute this Agreement on behalf of NGPMR and the Transaction Documents to which it is a party);

(iii)          a duly executed counterpart of the Company Operating Agreement; and

(iv)          a certificate of an officer of NGPMR, dated as of the Closing Date, certifying that all of the conditions set forth in Sections 7.1(a) and 7.3(a) have been satisfied.

(b)           MWE Liberty Deliveries.  At the Closing, MWE Liberty will execute and deliver, or cause to be executed and delivered, to the other Parties, as applicable, each of the following documents, where the execution or delivery of documents is contemplated, and will take or cause to be taken the following actions, where the taking of action is contemplated:

(i)            a certificate of the Secretary of State of the State of Delaware, dated not more than five days prior to the Closing Date, as to the existence and good standing of MWE Liberty;

(ii)           a certificate of an officer of MWE Liberty providing the following documents and certifying that each is a true and correct copy:  (A) the Organizational Documents of MWE Liberty and (B) resolutions of MWE Liberty’s governing body authorizing the transactions contemplated hereby (including designation of the Persons authorized to execute this Agreement on behalf of MWE Liberty and the Transaction Documents to which it is a party);

(iii)          a duly executed counterpart of the Company Operating Agreement;

(iv)          a duly executed counterpart of the Services Agreement;

(v)           counterparts of the Bill of Sale, Assignment and Assumption Agreement, in substantially the form attached as Exhibit E hereto (the “Assignment and Assumption”); and

(vi)          a certificate of an officer of MWE Liberty, dated as of the Closing Date, certifying that all of the conditions specified in Section 7.1(e) and Section 7.2(a) have been satisfied.

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(c)           Company Deliveries.  At the Closing, MWE Liberty will cause the Company to execute and deliver:

(i)            a certificate of the Secretary of State of the State of Delaware, dated not more than five days prior to the Closing Date, as to the existence and good standing of the Company;

(ii)           a copy of the Certificate of Formation of the Company certified by the Secretary of State of the State of Delaware;

(iii)          a duly executed counterpart of the Assignment and Assumption; and

(iv)          a duly executed counterpart of the Services Agreement;

The transactions described above, together with the issuance and sale of the Class A Interests and the Class B Interests pursuant to this Agreement and the entry into the Company Operating Agreement, are referred to herein as the “Transactions.”  The “Transaction Documents” shall mean this Agreement, the Company Operating Agreement, and the Services Agreement.

ARTICLE 3

REPRESENTATIONS AND WARRANTIES OF MWE LIBERTY

MWE Liberty hereby makes the following representations and warranties to the Company and NGPMR:

Section 3.1             Organization; Qualification.  Each of MWE Liberty and the Company is a limited liability company duly formed, validly existing and in good standing under the laws of the State of Delaware and has all requisite limited liability company power and authority to own, lease and operate its properties and to carry on its business, and is duly qualified, registered or licensed to do business as a foreign limited liability company and is in good standing in each jurisdiction in which the property owned, leased or operated by it or the nature of the business conducted by it makes such qualification necessary, except where the failure to be so duly qualified, registered or licensed and in good standing would not have or be reasonably expected to have, individually or in the aggregate, a Material Adverse Effect.

Section 3.2             Authority; Enforceability.

(a)           Each of MWE Liberty and the Company has the requisite limited liability company power and authority to execute and deliver the Transaction Documents to which it is a party, and to consummate the Transactions.  The execution and delivery by MWE Liberty and the Company of the Transaction Documents to which either of them is a party, and the consummation by MWE Liberty and the Company of the Transactions, have been duly and validly authorized by MWE Liberty and/or the Company, as applicable, and no other limited liability company proceedings on the part of MWE Liberty or the Company are necessary to authorize the Transaction Documents or to consummate the Transactions.

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(b)           Each of the Transaction Documents to which MWE Liberty or the Company is a party has been (or will be, in the case of Transaction Documents to be delivered at the Closing) duly executed and delivered by MWE Liberty and/or the Company, as applicable, and, assuming the due authorization, execution and delivery by the other parties thereto, each Transaction Document constitutes (or will constitute, in the case of Transaction Documents to be delivered at the Closing) the valid and binding agreement of MWE Liberty and the Company, and is enforceable against MWE Liberty and/or the Company, as applicable, in accordance with its terms, except as such enforceability may be limited by applicable bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws relating to or affecting creditors’ rights generally and by general principles of equity (regardless of whether such enforceability is considered in a proceeding in equity or at law).

Section 3.3             No Violation; Consents and Approvals.  Except as set forth on Schedule 3.3:

(a)           The execution, delivery and performance of the Transaction Documents by MWE Liberty and the Company and the consummation by MWE Liberty and the Company of the Transactions do not and will not:  (i) result in any breach of any provision of the organizational, governing or charter documents, as amended, of MWE Liberty or the Company; (ii) constitute a default (or an event that with notice or lapse of time or both would give rise to a default) under, or give rise to any right of termination, cancellation, amendment or acceleration (with or without notice, lapse of time or both) under any of the terms, conditions or provisions of any contract, note, bond, mortgage, indenture, license, agreement or other instrument or obligation to which MWE Liberty or the Company is a party or by which any of the Assets is bound or affected, except to the extent that such default, termination, amendment, acceleration or cancellation right (A) would not have or be reasonably expected to have, individually or in the aggregate, a Material Adverse Effect or (B) results from obtaining the Miscellaneous Consents after the Closing pursuant to Section 6.5; (iii) result in a violation of any law, statute, rule, regulation, order, judgment, injunction, decree or other restriction of any Governmental Authority to which MWE Liberty or the Company is subject (including federal and state securities laws and regulations) or by which any of the Assets is bound or affected except as may result from obtaining the Miscellaneous Consents after the Closing pursuant to Section 6.5; or (iv) result in the creation or imposition of any lien, charge or encumbrance upon any of the Assets, except for Permitted Liens or as may result from obtaining the Miscellaneous Consents and contractual consents listed on Schedule 3.3 after the Closing pursuant to Section 6.5.

(b)           No declaration, filing or registration with, or notice to, or authorization, consent or approval of, any Governmental Authority or other third party is necessary for the consummation by MWE Liberty or the Company of the Transactions contemplated by the Transaction Documents, other than such declarations, filings, registrations, notices, authorization, consents or approvals that have been or will be obtained or made prior to the Closing and other than the Miscellaneous Consents that may be obtained after the Closing pursuant to Section 6.5.

(c)           No consents are required under the Indentures to permit the consummation of the Transactions.

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Section 3.4             Capitalization.

(a)           Except for the Company, MWE Liberty does not (i) own, directly or indirectly, any capital stock, equity interests or other securities of any Person, or (ii) have any Subsidiaries.

(b)           Except as set forth on Schedule 3.4(b), prior to the Closing, the Company has not conducted any business operations, has no assets or liabilities and is not a party to any contract or agreement of any kind or nature (other than the Organizational Documents of the Company).

(c)           Upon Closing, the Class A Interests and the Class B Interests issued and sold pursuant to this Agreement (i) will constitute all of the issued and outstanding membership interests of the Company and (ii) will be duly authorized, validly issued and fully paid (to the extent required under the Company Operating Agreement).  Except as set forth in the Company’s Organizational Documents, there are no existing subscriptions, rights, warrants, calls, options, convertible or exchangeable securities, “phantom” equity rights, equity appreciation rights, equity-based performance units, commitments, contracts, agreements or undertakings of any character to which the Company is bound:  (i) obligating the Company to issue, deliver or sell, or cause to be issued, delivered or sold, additional equity interests in, or any security convertible or exercisable for, or exchangeable into, any equity interest in the Company, or (ii) obligating the Company to issue, grant, extend or enter into any such option, warrant, call, right, security, commitment, contract, arrangement or undertaking.  There are no outstanding contractual obligations of the Company to repurchase, redeem or otherwise acquire any equity interests of the Company.  There are no outstanding securities or other instruments convertible into or exchangeable for equity interests of the Company and no commitments to issue such securities or instruments.  Except as set forth in the Company’s Organizational Documents, there are no voting trusts, proxies or other agreements or understandings to which the Company is bound with respect to the voting of any equity interests or other securities of the Company.

Section 3.5             Compliance with Law.  (a) MWE Liberty is (and to MWE Liberty’s Knowledge has been) in compliance in all material respects with all Laws of any Governmental Authority applicable to the use, ownership and operation of the Assets; (b) MWE Liberty has not received written notice of any material violation of any such Law relating to the use, ownership and operation of the Assets; and (c) MWE Liberty is not in material default or violation of any order, writ, judgment, award, injunction or decree of any Governmental Authority applicable to the use, ownership or operation of the Assets.

Section 3.6             No Default.  MWE Liberty is not in violation of its organizational, governing or charter documents. Except as set forth on Schedule 3.6, MWE Liberty is not in default, and no event has occurred which, with notice or lapse of time or both, would give rise to a default, under, or give to others any rights of termination, amendment, acceleration or cancellation of or under, any agreement, credit facility, debt or other instrument (evidencing a debt or other obligation of MWE Liberty) to which MWE Liberty is a party, by which any of the Assets are bound or affected, except to the extent that such default, termination, amendment, acceleration or cancellation right (i) would not have or be reasonably expected to have,

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individually or in the aggregate, a Material Adverse Effect or (ii) results from obtaining the Miscellaneous Consents after the Closing pursuant to Section 6.5.

Section 3.7             Title to Properties and Assets.  Except as set forth on Schedule 3.7(a), MWE Liberty and its Affiliates have good, valid and defensible title to all real property (other than real property and buildings held under lease by MWE Liberty) and personal property to be transferred pursuant to this Agreement and the constituent documents contemplated hereby, free and clear of all liens, encumbrances, security interests, equities, charges or claims or other restrictions whatsoever, except for Permitted Liens.  With respect to any real property and buildings held under lease by MWE Liberty or its Affiliates, such real property and buildings are held under valid and subsisting and enforceable leases with such exceptions as do not materially interfere with the present or intended use of such properties by MWE Liberty and its Affiliates taken as a whole.  Except as set forth on Schedule 3.7(b), pursuant to the Assignment and Assumption, MWE Liberty and its Affiliates are validly transferring at Closing all of their ownership interests in the Assets to the Company, and the Assets so transferred (together with the Services (as defined in the Services Agreement) to be provided pursuant to the Services Agreement) constitute all rights and properties necessary in all material respects to operate the Business in a manner consistent with MWE Liberty’s operation of the Business immediately prior to the Closing, other than the Miscellaneous Consents and contractual consents listed on Schedule 3.3 that may be obtained after the Closing pursuant to Section 6.5.

Section 3.8             Rights-of-Way.  Except as set forth on Schedule 3.8, the Company, as of Closing, will have such easements or rights-of-way from each person (collectively, “Rights-of-Way”) as are necessary in all material respects to use, own and operate the Assets in the manner the Assets were used, owned and operated by MWE Liberty immediately prior to the Closing.  Except as set forth on Schedule 3.8, MWE Liberty has fulfilled and performed all of its material obligations with respect to such Rights-of-Way and no event has occurred that allows, or after notice or lapse of time would allow, revocation or termination thereof or would result in any impairment of the rights of the holder of any such Rights-of-Way, except for such revocations, terminations and impairments that would not have a Material Adverse Effect and the Miscellaneous Consents that may be obtained after the Closing pursuant to Section 6.5.

Section 3.9             Financial Statements.  Schedule 3.9 is an accurate copy of the trial balance (the “Trial Balance”) of MWE Liberty as of December 31, 2008 (the “Trial Balance Date”) which accurately reflects the assets and material liabilities of MWE Liberty as of such date subject to normal year-end adjustments.  Except as set forth on Schedule 3.9, since the Trial Balance Date, there has not been any change in financial condition, properties, assets, liabilities, business or results of operations of the Business, which, individually or in the aggregate, has had or is reasonably likely to have a Material Adverse Effect.  Since the Trial Balance Date, the Company has not incurred any obligation or liability (whether accrued, absolute, contingent or otherwise) of the type required to be reflected on a consolidated balance sheet of the Company prepared in accordance with GAAP applied on a basis consistent with the Trial Balance except liabilities and obligations incurred in the ordinary course of business and consistent with the Initial Budget or Section 6.8 hereof.

Section 3.10           Environmental Matters.  Except as set forth in Schedule 3.10:

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(a)           MWE Liberty and the Assets and operations thereof, are and, during the relevant time periods specified in all applicable statutes of limitations, have been in compliance in all material respects with Environmental Laws;

(b)           MWE Liberty possesses, and is in compliance in all material respects with, all Environmental Permits for MWE Liberty’s operation of the Assets as presently conducted and such Permits are in full force and effect subject to obtaining the Miscellaneous Consents after the Closing pursuant to Section 6.5;

(c)           MWE Liberty is not subject to any pending or, to MWE Liberty’s Knowledge, threatened, Proceeding with respect to its operation of the Assets, nor has MWE Liberty received any written notice of violation, noncompliance, or enforcement with respect to its operation of the Assets that remains pending or any written notice that it is or is suspected of being a potentially responsible party under CERCLA or any similar law with respect to its operation of the Assets that remains pending, or any written notice of investigation, remediation or request for information pursuant to Environmental Law from any Governmental Authority with respect to operation of the Assets that would reasonably be expected to result in a material liability to MWE Liberty pursuant to Environmental Laws, which notice of investigation, remediation or request for information remains pending;

(d)           Except for such matters that would not reasonably be expected to give rise to any material liability, costs or remedial or corrective action obligations under Environmental Laws, (i) there has been no Release or, to MWE Liberty’s Knowledge, threatened Release of Hazardous Substances by MWE Liberty or, to MWE Liberty’s Knowledge, any third party; and (ii) no Hazardous Substances are present in, on, at, under or from any of the Assets, or otherwise in connection with the operation of the Assets by MWE Liberty;

(e)           In connection with the operation of the Assets, MWE Liberty has not assumed or retained by written contract, or to MWE Liberty’s Knowledge, by operation of law, any material liabilities (including STRICT LIABILITY) under any Environmental Laws for any Hazardous Substances; and

(f)            MWE Liberty has made available to NGPMR and the Company complete and correct copies of all environmental assessment and audit reports and studies in its possession addressing potentially material environmental liabilities or obligations relating to MWE Liberty or its operation of the Assets.

Notwithstanding any other provisions of this Agreement to the contrary, this Section 3.10 contains the sole and exclusive representations and warranties of MWE Liberty on environmental matters, including Environmental Laws, Environmental Claims, Environmental Responses, Environmental Permits and Hazardous Substances.

Section 3.11           Material Contracts.  Each Material Contract is valid, binding and enforceable in accordance with its terms, and is in full force and effect.  MWE Liberty has provided to NGPMR a true and complete copy of each Material Contract. MWE Liberty has not received any written notice of default under any Material Contract in the 12-month period prior to the date of this Agreement. Except as set forth on Schedule 3.11, there are no (a) uncured

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defaults of MWE Liberty under any Material Contract that would give the counterparty thereto the right to terminate such Material Contract and (b) to MWE Liberty’s Knowledge, defaults by any of the counterparties to such Material Contracts.

Section 3.12           Legal Proceedings.  There are no Proceedings pending or, to the MWE Liberty’s Knowledge, threatened, against MWE Liberty, the Company or the Assets.  To MWE Liberty’s Knowledge, there are no events or circumstances that have occurred which would reasonably be expected to result in Proceedings against MWE Liberty, the Company or the Assets.

Section 3.13           Permits.  MWE Liberty has, and upon Closing, MWE Liberty will transfer to the Company and the Company will have (or have the benefit of pursuant to Section 6.5), all permits, approvals, consents, licenses, franchises, exemptions and other governmental authorizations, consents and approvals (collectively, “Permits”) necessary to use, own and operate the Assets as presently used, owned and operated, except for any such Permits the failure to have (or have the benefit of) would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect.  MWE Liberty has not received any written notification that it is in violation of any material Permits.  MWE Liberty is in material compliance with all Permits.

Section 3.14           Taxes.  All Tax Returns required to be filed with respect to MWE Liberty and the Assets have been filed and all such Tax Returns are complete and correct in all material respects; all Taxes due relating to MWE Liberty and the Assets have been paid in full (whether or not shown to be due on such Tax Returns).  MWE Liberty has not received any written notice of deficiency or assessment from any taxing authority with respect to liabilities for Taxes of MWE Liberty or associated with the ownership or operation of the Assets, which have not been fully paid or finally settled, unless being contested in good faith through appropriate proceedings and for which adequate reserves have been established in the Trial Balance.  All Taxes required to be withheld, collected or deposited by or with respect to MWE Liberty or associated with the ownership or operation of the Assets have been timely withheld, collected or deposited as the case may be, and to the extent required, have been paid to the relevant taxing authority.  There are no outstanding agreements or waivers extending the applicable statutory periods of limitation for Taxes of MWE Liberty or that are associated with the ownership or operation of the Assets for any period.  MWE Liberty, which was formed on March 26, 2008, is treated as a partnership or a disregarded entity for U.S. federal income Tax purposes and no election has been made to treat MWE Liberty as an association taxable as a corporation.

Section 3.15           Employees.

(a)           Except as set forth on Schedule 3.15(a), (i) neither MWE Liberty nor the Company has or previously had any employees and (ii) no Affiliate of MWE Liberty or the Company is a party to a collective bargaining agreement with its employees.

(b)           Except as set forth on Schedule 3.15(b), neither MWE Liberty nor the Company sponsors, maintains, has liability under or has an obligation to contribute to any “employee benefit plans” (within the meaning of Section 3(3) of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”), including, without limitation,

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multiemployer plans within the meaning of Section 3(37) of ERISA), or any stock purchase, stock option, severance, employment, change-in-control, fringe benefit, collective bargaining, bonus, incentive, deferred compensation, employee loan or any other employee benefit plans, agreements, programs, policies or other arrangements, whether or not subject to ERISA (all such plans, agreements, programs, policies and arrangements, collectively, the “Benefit Plans”).  Neither MWE Liberty nor the Company, nor any of their ERISA Affiliates, have any liability under Section 412 of the Code or Title IV of ERISA.

Section 3.16           Brokers’ Fee.  Except for the fee payable to Morgan Stanley, which shall be paid by MWE, no broker, finder or similar intermediary has acted for or on behalf of, or is entitled to any broker, finder or similar fee or other commission from MWE Liberty, the Company or any of their Affiliates in connection with this Agreement or the transactions contemplated hereby.

Section 3.17           Insurance.  MWE Liberty has provided or made available to NGPMR and the Company a true and complete list of all liability, property, workers’ compensation and other insurance policies currently in effect that insure or relate to the Assets.

Section 3.18           Intellectual Property.  Except as set forth on Schedule 3.18, (a) MWE Liberty owns or has the right to use, and upon Closing and subject to the Miscellaneous Consents to be obtained after the Closing pursuant to Section 6.5, the Company will own or have the right to use pursuant to license, sublicense, agreement (including the Services Agreement) or otherwise all items of Intellectual Property used in the operation of the Business as presently conducted, except for such Intellectual Property the failure of which to own or have the right to use, would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect, (b) no third party has asserted in writing delivered to MWE Liberty a claim that MWE Liberty is infringing on the Intellectual Property of such third party and (c) to MWE Liberty’s Knowledge, no third party is infringing on the Intellectual Property owned by MWE Liberty.

Section 3.19           Affiliate Transactions.  Except as set forth on Schedule 3.19, there are no existing agreements or transactions relating to the provision of material services (or otherwise providing for the payment of material amounts) between MWE Liberty, on the one hand, and any of its officers, managers, directors, employees, or any of their respective Affiliates, on the other hand.  Except for any ownership interest in MWE, no officer, director, manager or employee of MWE Liberty has any direct or indirect material ownership interest in any Person with which MWE Liberty has any material business relationship.

ARTICLE 4

REPRESENTATIONS AND WARRANTIES OF NGPMR

NGPMR hereby makes the following representations and warranties to the Company:

Section 4.1             Organization.  NGPMR is a limited liability company duly formed, validly existing and in good standing under the laws of the State of Delaware and has all requisite limited liability company power and authority to own, lease and operate its properties and to carry on its business.

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Section 4.2             Authority; Enforceability.

(a)           NGPMR has the requisite limited liability company power and authority to execute and deliver the Transaction Documents to which it is a party, and to consummate the Transactions.  The execution and delivery by NGPMR of the Transaction Documents to which it is a party, and the consummation by NGPMR of the Transactions, have been duly and validly authorized by NGPMR and no other limited liability company proceedings on the part of NGPMR is necessary to authorize the Transaction Documents or to consummate the Transactions.

(b)           Each of the Transaction Documents to which NGPMR is a party has been (or will be, in the case of Transaction Documents to be delivered at Closing) duly executed and delivered by NGPMR and, assuming the due authorization, execution and delivery by the other parties thereto, each Transaction Document to which NGPMR is a party constitutes (or will constitute, in the case of Transaction Documents to be delivered at Closing) the valid and binding agreement of NGPMR, and is enforceable against NGPMR in accordance with its terms, except as such enforceability may be limited by applicable bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws relating to or affecting creditors’ rights generally and by general principles of equity (regardless of whether such enforceability is considered in a proceeding in equity or at law).

Section 4.3             No Violation; Consents and Approvals.

(a)           The execution, delivery and performance of the Transaction Documents by NGPMR and the consummation by NGPMR of the Transactions do not and will not:  (i) result in any breach of any provision of the Organizational Documents, as amended, of NGPMR; (ii) constitute a default (or an event that with notice or lapse of time or both would give rise to a default) under, or give rise to any right of termination, cancellation, amendment or acceleration (with or without notice, lapse of time or both) under any of the terms, conditions or provisions of any contract, note, bond, mortgage, indenture, license, agreement or other instrument or obligation to which NGPMR is a party or by which any of its assets is bound, except to the extent that such default, termination, amendment, acceleration or cancellation right would not have or be reasonably expected to have, individually or in the aggregate, a Material Adverse Effect; or (iii) result in a violation of any law, statute, rule, regulation, order, judgment, injunction, decree or other restriction of any Governmental Authority to which NGPMR is subject (including federal and state securities laws and regulations) or by which any of its assets is bound.

(b)           Other than the filings with respect to the HSR Act set forth in Section 6.1, no declaration, filing or registration with, or notice to, or authorization, consent or approval of, any Governmental Authority is necessary for the consummation by NGPMR of the Transactions contemplated by the Transaction Documents, other than such declarations, filings, registrations, notices, authorization, consents or approvals that have been obtained or made prior to the Closing.

Section 4.4             Brokers’ Fee.  No broker, finder or similar intermediary has acted for or on behalf of, or is entitled to any broker, finder or similar fee or other commission from NGPMR

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or any of its Affiliates, in connection with this Agreement or the transactions contemplated hereby.

ARTICLE 5

INDEMNIFICATION

Section 5.1             Survival.

(a)           The representations and warranties of MWE Liberty contained in Article 3 shall survive the Closing until the date that is ** after the date of the Closing, with the exception that the representations and warranties in (i) ** shall survive the Closing until ** after the ** and (ii) ** shall survive **.  The representations and warranties of NGPMR contained in ** shall survive **, with the exception that the representations and warranties in ** shall survive the Closing until the date that is ** after the date of the Closing.

(b)           All covenants and agreements contained herein that by their terms are to be performed in whole or in part subsequent to the Closing, shall survive the Closing in accordance with their terms; provided that the agreement by MWE Liberty to indemnify the NGPMR Covered Persons pursuant to ** shall survive the Closing until the date that is ** after the Closing Date; provided further that the covenants contained in Section 6.3 shall survive **.

(c)           The period of time a representation or warranty or covenant or agreement survives the Closing pursuant to this Section 5.1 shall be the “Survival Period” with respect to such representation or warranty or covenant or agreement.  In the event notice of any claim for indemnification under this Article 5 shall have been asserted in writing within the applicable Survival Period and such claim has not been finally resolved by the expiration of such Survival Period, the representations or warranties or covenants or agreements that are the subject of such claim shall survive, but only to the extent of the  underlying facts of the claim (so long as the facts or circumstances alleged to give rise to such claim have been specified in reasonable detail and are not based on speculative facts, circumstances or other events) as made prior to the expiration of the Survival Period, until such claim is finally resolved.

Section 5.2             Indemnification by the Company.

(a)           Subject to the terms of this Article 5, from and after the Closing, the Company shall indemnify, defend and hold harmless MWE Liberty and its Affiliates and their respective directors, members, managers, stockholders, officers, partners, employees, agents, consultants, attorneys, representatives, successors, transferees and assignees (collectively, the “MWE Liberty Covered Persons”) from and against any losses, claims, damages, liabilities (including STRICT LIABILITY), costs and expenses (including reasonable attorneys’ fees and expenses), interest, penalties, judgments and settlements of any and every kind and character, known or unknown, fixed or contingent (collectively, “Losses”), incurred, arising out of, or relating to, the Assumed Liabilities except to the extent such Losses arise from the same facts

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and circumstances as a good faith indemnification claim by the Company or NGPMR pursuant to Section 5.3.

(b)           Subject to the terms of this Article 5, from and after the Closing, the Company shall indemnify, defend and hold harmless the NGPMR Covered Persons to the fullest extent permitted by law, from and against any Losses incurred, arising out of or related to those items set forth in Section 5.3 (for which MWE Liberty has an obligation to indemnify the NGPMR Covered Persons) to the extent that MWE Liberty fails to remedy such Losses pursuant to Section 5.7(b).

Section 5.3             Indemnification by MWE Liberty.  Subject to the terms of this Article 5, from and after the Closing, MWE Liberty shall indemnify, defend and hold harmless the Company, NGPMR and its Affiliates and their respective directors, members, managers, stockholders, officers, partners, employees, agents, consultants, attorneys, representatives, successors, transferees and assignees (collectively, the “NGPMR Covered Persons”) to the fullest extent permitted by law, from and against any Losses, incurred, arising out of or relating to (a) any breach of any of the representations or warranties (in each case, when made) of MWE Liberty contained in Article 3, (b) any breach of any of the covenants of MWE Liberty contained in this Agreement, (c) the ownership, management or operation of the Assets prior to the Closing Date, other than the Specified Liabilities, (d) those items listed on Schedule 5.3(d) or (e) those items listed on Schedule 5.3(e).  It is acknowledged and agreed by the Parties that the indemnity obligations of MWE Liberty under Section 5.3(d) and Section 5.3(e) shall **by ** in the **.

Section 5.4             Indemnification by NGPMR.  Subject to the terms of this Article 5, from and after the Closing, NGPMR shall indemnify and hold harmless the MWE Liberty Covered Persons, to the fullest extent permitted by law, from and against Losses incurred, arising out of or relating to (i) any breach of any of the representations or warranties (in each case, when made) of NGPMR contained in Article 4 or (ii) any breach of any of the covenants of NGPMR in this Agreement.

Section 5.5             No Effect on Services Agreement and Company Operating Agreement.  Notwithstanding anything to the contrary contained in this Agreement, no provision of Section 5.2 or Section 5.3 shall be construed to have any effect upon, or to otherwise limit, any indemnification obligation contained in the Services Agreement or the Company Operating Agreement.

Section 5.6             Third Party Claims Procedures.

(a)           In the event that any action, suit, claim or proceeding is commenced by a third party involving a claim for which a party required to provide indemnification hereunder (an “Indemnifying Party”) may be liable to a party entitled to indemnification (an “Indemnified Party”) hereunder (a “Third Party Claim”), the Indemnified Party shall promptly notify the Indemnifying Party in writing of such Third Party Claim indicating the nature of such claim and the basis therefore (the “Claim Notice”) and the Indemnifying Party shall assume the defense thereof, including the employment of counsel reasonably satisfactory to the Indemnified Party and the payment of all fees and expenses incurred in connection with defense thereof; provided

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that if the Indemnifying Party does not promptly take reasonable action to assume such defense, the Indemnified Party may lead the defense of such potentially indemnified claim and the Indemnifying Party shall be liable for all additional costs and expenses incurred by the Indemnified Party in connection therewith, provided further, that no failure of any Indemnified Party to give such Claim Notice and no delay on the part of the Indemnified Party in giving any such Claim Notice shall relieve the Indemnifying Party of any indemnification obligation hereunder except (and only) to the extent that it shall be finally determined by a court of competent jurisdiction (which determination is not subject to appeal or further review) that such failure shall have proximately and materially adversely prejudiced the Indemnifying Party.

(b)           An Indemnified Party shall have the right to employ separate counsel in any such Proceeding and to participate in the defense thereof, but the fees and expenses of such counsel shall be at the expense of such Indemnified Party or Parties unless:  (i) the Indemnifying Party has agreed in writing to pay such fees and expenses; (ii) the Indemnifying Party shall have failed promptly to assume the defense of such Proceeding and to employ counsel reasonably satisfactory to such Indemnified Party in any such Proceeding; or (iii) the named parties to any such Proceeding (including any impleaded parties) include both such Indemnified Party and the Indemnifying Party, and such Indemnified Party shall have been advised by counsel that a conflict of interest is likely to exist if the same counsel were to represent such Indemnified Party and the Indemnifying Party (in which case, if such Indemnified Party notifies the Indemnifying Party in writing that it elects to employ separate counsel at the expense of the Indemnifying Party, such counsel shall be at the expense of the Indemnifying Party).  It being understood, however, that the Indemnifying Party shall not, in connection with any one such Proceeding, be liable for the fees and expenses of more than one separate firm of attorneys at any time for all Indemnified Parties, which firm shall be appointed by a majority of the Indemnified Parties; provided, however, that in the case a single firm of attorneys would be inappropriate due to actual or potential differing interests or conflicts between such Indemnified Parties and any other party represented by such counsel in such Proceeding or otherwise, then the Indemnifying Party shall be liable for the fees and expenses of one additional firm of attorneys with respect to such Indemnified Parties.  The Indemnifying Party shall not be liable for any settlement of any such Proceeding effected without its written consent, which consent shall not be unreasonably withheld.  No Indemnifying Party shall, without the prior written consent of the Indemnified Party (which in the event that the Indemnified Party is the Company shall include the written consent of NGPMR, not to be unreasonably withheld), effect any settlement of any pending Proceeding in respect of which any Indemnified Party is a party, unless (A) such settlement includes a full and unconditional release of such Indemnified Party from all liability on claims that are the subject matter of such Proceeding, (B) does not contain any admission of wrongdoing or illegal conduct and (C) the Indemnifying Party has agreed in writing that it is liable to the Indemnified Party for an indemnification payment in respect of the full amount of the settlement.

Section 5.7             Satisfaction of Claims for Indemnification.

(a)           The Parties agree that in the event any Losses are determined to have been incurred as a result of an indemnification claim pursuant to Section 5.3, MWE Liberty shall have the right to first satisfy and discharge any such Losses by either (i) ** for such Losses and/or (ii) ** such Losses;

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provided that, (i) if and to the extent any such ** for any ** for which it is entitled to indemnity hereunder, MWE Liberty shall indemnify NGPMR ** for any such Losses pursuant to Section 5.7(b) and (ii) in no event shall ** a claim for indemnification made pursuant to this Article 5 has been satisfied **, or that ** any obligation hereunder, **.

(b)           In the event that MWE Liberty fails to satisfy in full any Losses in accordance with Section 5.7(a) ** such Losses being finally determined, MWE Liberty shall satisfy any such claim for indemnification by either (i) ** for any Losses incurred by NGPMR ** or (ii) having ** (as such term is defined in the Company Operating Agreement) ** the amount of any such Company Loss that has not been satisfied in full pursuant to Section 5.7(a); provided that ** set forth above by providing ** within 30 days of such Losses being finally determined.  In the event that unremedied Losses are to be indemnified pursuant to clause (ii) of this Section 5.7(b), MWE Liberty and NGPMR shall ** the Company Operating Agreement ** an amount equal to such unremedied Loss.

Section 5.8             Limits on Indemnification.

(a)           In calculating amounts payable to an Indemnified Party, the amount of any indemnified Losses shall be determined without duplication of any other Loss for which an indemnification claim has been made or could be made under any other representation, warranty, covenant, or agreement and shall be computed net of (i) payments actually recovered by the Indemnified Party under any insurance policy with respect to such Losses and (ii) any prior or subsequent actual recovery by the Indemnified Party from any Person with respect to such Losses and (iii) any Tax Benefit accruing to any Indemnified Party on account of such Losses.

(b)           Notwithstanding any other provision of this Agreement, in no event shall any Party be liable for punitive, special, incidental, indirect, consequential or lost profits damages of any kind or nature, regardless of the form of action through which such damages are sought, except for any such damages recovered by any third party against any Party in respect of which such Party would otherwise be entitled to indemnification pursuant to the terms hereof.

(c)           In addition to being entitled to exercise all rights provided herein, including recovery of damages, the Parties will be entitled to specific performance under this Agreement.  The Parties agree that monetary damages may not be adequate compensation for any loss incurred by reason of any breach of obligations described in the foregoing sentence and hereby agree to waive in any action for specific performance of any such obligation the defense that a remedy at law would be adequate.

(d)           If the Closing occurs, neither the Company nor NGPMR will be entitled to indemnity under ** of this Agreement for Losses with respect to any claim under ** until the aggregate amount of all such claims

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**, and thereafter, the Company and/or NGPMR shall ** Losses **; provided however, that all Losses resulting from or arising out of any ** shall be indemnified against ** to the **.  Except for a claim of actual fraud involving a knowing and intentional misrepresentation or omission of a material fact or willful or intentional breach, in no event will the aggregate liability of (i) ** under ** and (ii) ** under ** in respect of ** claims of ** under ** exceed **; provided, however, that the aggregate liability of ** under ** with respect to ** shall not exceed **; provided, further that the aggregate liability of ** under ** in respect of ** claims of ** under ** with respect to ** shall not exceed **.  Notwithstanding anything to the contrary in this Agreement, in no event shall the aggregate liability of (i) ** arising under this Agreement and from the transactions contemplated hereby exceed ** and (ii) ** arising under this Agreement and from the transactions contemplated hereby exceed **.  The reimbursement and indemnification obligations set forth in ** shall not be subject to any of the limitations set forth in this Section 5.8.

(e)           In no event shall the ** recovery of any Losses pursuant to this Article 5 be duplicative.

(f)            The remedies provided in this Article 5 shall be the sole and exclusive legal remedies of the Parties, from and after the Closing, with respect to this Agreement and the transactions contemplated hereby; provided that nothing in this Section 5.8(f) shall prevent either Party from (i) seeking specific performance, injunctive and/or equitable relief for claims of breach or failure to perform covenants performable under this Agreement at any time after the Closing or (ii) pursuing, and recovering in respect of, any claim based on actual fraud involving a knowing and intentional misrepresentation or omission of a material fact or willful or intentional breach.

Section 5.9             Extent of Indemnification.  WITHOUT LIMITING THE SCOPE OF THE INDEMNIFICATION, DISCLAIMER, RELEASE AND ASSUMPTION OBLIGATIONS SET FORTH IN THIS AGREEMENT, TO THE FULLEST EXTENT PERMITTED BY LAW, AN INDEMNIFIED PERSON SHALL BE ENTITLED TO INDEMNIFICATION HEREUNDER IN ACCORDANCE WITH THE TERMS HEREOF, REGARDLESS OF WHETHER THE INDEMNIFIABLE LOSS GIVING RISE TO ANY SUCH INDEMNITY OBLIGATION IS THE RESULT OF THE SOLE, ACTIVE, PASSIVE, CONCURRENT OR COMPARATIVE NEGLIGENCE, STRICT LIABILITY OR OTHER LEGAL FAULT OR VIOLATION OF ANY LAW OF OR BY ANY SUCH INDEMNIFIED PERSON.

Section 5.10           No Reliance.  THE REPRESENTATIONS AND WARRANTIES OF MWE LIBERTY CONTAINED IN ARTICLE 3 CONSTITUTE THE SOLE AND EXCLUSIVE REPRESENTATIONS AND WARRANTIES OF MWE LIBERTY TO THE COMPANY IN CONNECTION WITH THE TRANSACTIONS CONTEMPLATED HEREBY. 

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THE REPRESENTATIONS AND WARRANTIES OF NGPMR CONTAINED IN ARTICLE 4 CONSTITUTE THE SOLE AND EXCLUSIVE REPRESENTATIONS AND WARRANTIES OF NGPMR TO THE COMPANY IN CONNECTION WITH THE TRANSACTIONS CONTEMPLATED HEREBY.  EXCEPT FOR SUCH REPRESENTATIONS AND WARRANTIES (IN EACH CASE, AS MODIFIED BY THE SCHEDULES HERETO), NONE OF MWE LIBERTY, THE COMPANY, NGPMR OR ANY OTHER PERSON MAKES ANY OTHER EXPRESS OR IMPLIED REPRESENTATION OR WARRANTY WITH RESPECT TO SUCH PARTIES, THE ASSETS OR THE TRANSACTIONS CONTEMPLATED BY THIS AGREEMENT, AND EACH PARTY DISCLAIMS ANY OTHER REPRESENTATIONS OR WARRANTIES, WHETHER MADE BY SUCH PARTIES OR ANY OF THEIR AFFILIATES, OFFICERS, DIRECTORS, EMPLOYEES, AGENTS OR REPRESENTATIVES (INCLUDING WITH RESPECT TO THE DISTRIBUTION TO, OR ANY SUCH PERSON’S RELIANCE ON, ANY INFORMATION, DOCUMENTS OR OTHER MATERIAL MADE AVAILABLE TO SUCH PERSON IN ANY DATA ROOM, MANAGEMENT PRESENTATION OR IN ANY OTHER FORM IN EXPECTATION OF, OR IN CONNECTION WITH, THE TRANSACTIONS CONTEMPLATED HEREBY).  EXCEPT FOR SUCH REPRESENTATIONS AND WARRANTIES (IN EACH CASE, AS MODIFIED BY THE SCHEDULES HERETO), EACH PARTY HEREBY DISCLAIMS ALL LIABILITY AND  RESPONSIBILITY FOR ANY REPRESENTATION, WARRANTY, PROJECTION, FORECAST, STATEMENT, OR INFORMATION MADE, COMMUNICATED, OR FURNISHED (ORALLY OR IN WRITING) TO ANY OTHER PARTY OR ITS AFFILIATES, OFFICERS, DIRECTORS, EMPLOYEES, AGENTS OR REPRESENTATIVES (INCLUDING OPINION, INFORMATION, PROJECTION, OR ADVICE THAT MAY HAVE BEEN OR MAY BE PROVIDED TO ANY PARTY OR ANY DIRECTOR, OFFICER, EMPLOYEE, AGENT, CONSULTANT, OR REPRESENTATIVE OF SUCH PARTY OR ANY OF ITS AFFILIATES).

ARTICLE 6

COVENANTS

Section 6.1             HSR Filing.

(a)           As promptly as reasonably possible following the execution of this Agreement, but in no event later than 10 Business Days following such date, NGPMR shall make such filings as may be required under the Hart-Scott-Rodino Anti-Trust Improvements Act of 1976 (“HSR Act”) with respect to the transactions contemplated by this Agreement and, in making such filings, NGPMR shall request early termination of the waiting period specified in the HSR Act.  Thereafter, NGPMR shall file as promptly as possible all reports or other documents required or requested by the U.S. Federal Trade Commission (“FTC”) or the U.S. Department of Justice (“DOJ”) pursuant to the HSR Act or otherwise including requests for additional information concerning such transactions.  Without limiting the foregoing, NGPMR and MWE Liberty shall use commercially reasonable efforts to cooperate and oppose any preliminary injunction sought by any Governmental Authority under the HSR Act preventing the consummation of the transactions contemplated by this Agreement.  NGPMR and MWE Liberty shall cause their respective counsel to furnish the other party such necessary information and reasonable assistance as the other may reasonably request in connection with NGPMR’s preparation of necessary filings or submissions under the provisions of the HSR Act.  NGPMR

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shall cause its counsel to supply to MWE Liberty copies of the date stamped receipt copy of the cover letters delivering the filings or submissions required under the HSR Act to the FTC or DOJ, as applicable.  Notwithstanding anything in this Section 6.1 to the contrary, neither NGPMR nor MWE, nor any of their Affiliates, shall be required by this Section 6.1 to take any action that would require or result in holding separate or divesting assets or operations of NGPMR, MWE Liberty or any of their Affiliates in order to have satisfied their obligation to use their commercially reasonable efforts under this Section 6.1.

(b)           The cost all filing or application fees associated with filings under the HSR Act shall be **.  Within two Business Days of filing under the HSR Act, **.

Section 6.2             Tax Effect.

(a)           None of the Parties (nor such Parties’ counsel or accountants) has made or is making any representations to any other Party (nor such Party’s counsel or accountant) concerning any of the Tax effects of the transactions provided for in this Agreement.  Each Party hereto represents that it has obtained, or may obtain, independent Tax advice with respect thereto and upon which it, if so obtained, has solely relied.

Section 6.3             Tax Matters.

(a)           Each of the Parties agrees to cooperate fully with each other Party to enable each Party to more accurately determine its own tax liability and to minimize such liability to the extent legally permissible.  Each Party shall provide and make available to each other Party such records as a Party may reasonably request for the defense of any audit, examination, administrative appeal or litigation of any Tax Return or other similar governmental report or form.

(b)           MWE Liberty shall be liable for, and shall indemnify, defend and hold harmless the Company for, any and all liability for Taxes with respect to the Assets for any taxable period ending on or before the Closing Date (“Pre-Closing Tax Period”) and with respect to any taxable period that begins on or before and ends after the Closing Date (“Straddle Period”), for the portion thereof ending on the Closing Date.  In the case of any Straddle Period, the amount of Taxes with respect to the Assets allocable to the portion of the Straddle Period ending on the Closing Date shall be deemed to be the amount of such Taxes for the entire period (or, in the case of such Taxes determined on an arrears basis, the amount of such Taxes for the immediately preceding period) multiplied by a fraction, the numerator of which is the number of calendar days in the applicable period ending on and including the Closing Date and the denominator of which is the number of calendar days in the entire relevant period.

(c)           Ad valorem property Taxes imposed on or with respect to the Assets for the taxable period (for purposes of this section, “taxable period” means the period beginning on the assessment date for ad valorem property Taxes through the day before the next assessment date for such Taxes) that contains the Closing Date shall be prorated between MWE Liberty and Company based on the relative number of days prior to the Closing Date and on and after the Closing Date during the taxable period, with MWE Liberty being responsible for such prorated ad valorem property Taxes for the period prior to the Closing Date and Company being

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responsible for such prorated ad valorem property Taxes for the period beginning on the Closing Date.  Upon receipt of the ad valorem property Tax bills for the taxable period that contains the Closing Date, MWE Liberty shall calculate the prorated ad valorem property Taxes and shall bill Company for such amount, with Company making such payment within 20 days of receipt of such bill.  Company shall promptly forward to MWE Liberty any ad valorem property Tax bills for the taxable period that contains the Closing Date that are received by Company.  MWE Liberty shall be responsible as between MWE Liberty and Company for the payment of the total amount of ad valorem property Taxes imposed on or with respect to the Assets for the taxable period that contains the Closing Date.

Section 6.4             Further Assurances.  From time to time after the Closing Date, and without any further consideration, the Parties agree to, and MWE Liberty agrees to cause its Affiliates to, as applicable, execute, acknowledge and deliver all such additional deeds, assignments, bills of sale, conveyances, instruments, notices, releases, acquittances and other documents, and will do all such other acts and things, all in accordance with applicable Laws, as may be reasonably necessary to give effect to the transactions consummated by this Agreement and to collect and reduce to the possession of the Company the Assets and to effect the assumption by the Company of the Assumed Liabilities.

Section 6.5             Consents.  Except for those consents listed on Schedule 7.2(c), which are required to be obtained prior to the Closing, MWE Liberty shall use commercially reasonable efforts to obtain and, to the extent that any Assets are held in the name of an Affiliate of MWE Liberty, cause its Affiliates to use commercially reasonable efforts to obtain, any other consents of third parties, including Governmental Authorities, which are required to be obtained for the assignment of the Assets to the Company (the “Consents”) prior to the Closing.  Prior to obtaining the Consents, any Asset that is not otherwise assignable or transferable (each a “Non-Assigned Asset”) shall be deemed to be held by MWE Liberty or such Affiliate, as applicable, at all times during the Holding Period in accordance with this Section.  During the Holding Period, MWE Liberty shall and shall cause its Affiliates to, to the extent MWE Liberty or its Affiliates may lawfully and validly do so, grant to the Company a non-exclusive right and license to use each such Non-Assigned Asset and provide the Company with the economic benefits and risks of ownership of the Non-Assigned Assets, the intent of the parties being to provide the Company, to the extent the same can be reasonably done, with the same access and ability to utilize such Non-Assigned Assets as if such Non-Assigned Assets had been included within the Assets.  Upon receipt of the Consent related to a Non-Assigned Asset, such Non-Assigned Asset shall automatically be deemed to be an Asset without the need for any further action on the part of the parties or any other Person and without the payment of any additional consideration, but subject to the provisions of Section 6.4.  The Company shall cooperate in good faith with MWE Liberty and its Affiliates in connection with the pursuit of the Consents.

Section 6.6             Expenses.  Except to the extent otherwise specifically provided herein, all costs and expenses incurred by NGPMR in connection with the Transaction Documents and the Transactions shall be paid by **, including all fees of its legal counsel, financial and business advisers and accountants; provided that the ** to be **.  MWE Liberty shall bear its own expenses incurred in connection with the Transaction Documents and the Transactions whether or not the Transactions are consummated, including all fees of its legal counsel, financial and

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business advisers and accountants (which for clarity purposes shall include the fees of Morgan Stanley).

Section 6.7             Public Statements.  The Parties shall consult with each other prior to issuing any public announcement, statement or other disclosure with respect to this Agreement, the other Transaction Documents or the transactions contemplated hereby or thereby and neither MWE Liberty on one hand nor NGPMR on the other shall issue any such public announcement, statement or other disclosure without having first received the written consent of the other Party, except as may be required by law.

Section 6.8             Conduct of Business.  From the date of this Agreement through the Closing, MWE Liberty shall operate the Business in the ordinary course and, without limiting the generality or effect of the foregoing, MWE Liberty shall use reasonable efforts to maintain the Assets, comply with all applicable Laws, and preserve intact the Business and its relationships with customers, suppliers and others having business relationships with it, in each case in all material respects.  Without limiting the generality or effect of the foregoing, except as set forth on Schedule 3.4(b) or as contemplated in Section 7.2(e), prior to the Closing, without the prior written consent of NGPMR, which consent shall not be unreasonably withheld, neither MWE Liberty nor the Company shall (a) enter into any commercial contracts with an expected annual revenue in excess of ** (b) enter into any commercial, capital or construction contracts reasonably expected to cause the Company to incur obligations in excess of ** or (c) make any capital expenditures in excess of ** in the aggregate.

ARTICLE 7
CONDITIONS PRECEDENT

Section 7.1             Conditions to Each Party’s Obligations.  The respective obligation of each Party to effect the transactions contemplated hereby is subject to the satisfaction at or prior to the date hereof of the following conditions:

(a)           NGPMR shall have made all filings required under the HSR Act and the applicable waiting periods shall have expired or been terminated without any conditions that would require or result in either NGPMR or MWE Liberty holding separate or divesting assets or operations.

(b)           No temporary restraining order, preliminary or permanent injunction or other order (whether temporary, preliminary or permanent) issued by any court or other Governmental Authority of competent jurisdiction or other legal restraint or prohibition shall be in effect which prevents the consummation of the transactions contemplated by this Agreement.

(c)           No legal proceeding shall be pending that involves any challenge to or seeking damages or other relief in connection with the transactions contemplated by this Agreement or that may have the effect of preventing, delaying, making illegal, imposing limitations or conditions on or otherwise interfering with the transactions contemplated by this Agreement.

(d)           The Credit Agreement shall be amended concurrent with the Closing to (i) exclude the Company as a Subsidiary and as a Loan Party (as such terms are defined in the

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Credit Agreement), (ii) release the Assets to be contributed to the Company at Closing from any Liens (as such term is defined in the Credit Agreement) under the Credit Agreement and (iii) permit MWE Liberty’s initial contribution to, and future investments in, the Company.

(e)           (i) The Company shall ** (as such term is defined in the **) under the ** and (ii) MWE Liberty shall provide a certificate to NGPMR, dated as of the Closing Date, certifying that the condition specified in this Section 7.1(e) have been satisfied, together with supporting documentation that **.

Section 7.2             Conditions to NGPMR’s Obligations.  The obligation of NGPMR to consummate the transactions contemplated by this Agreement is subject to the satisfaction of the following conditions, any one or more of which may be waived in writing by NGPMR:

(a)           Representations, Warranties and Covenants of MWE Liberty.  (i) Each of the representations and warranties of MWE Liberty made in this Agreement will be true and correct as of the date of this Agreement (except to the extent such representations and warranties speak to an earlier date, in which case as of such earlier date) and as of the Closing (as if made anew at and as of the Closing, except to the extent such representations speak to an earlier date, in which case as of such earlier date) except to the extent the failure of such representations and warranties to be true and correct as of the Closing Date has not had, and is not reasonably expected to have, individually or in the aggregate, a Material Adverse Effect (provided that for purposes of determining whether the condition set forth in this sentence has been satisfied, all “Material Adverse Effect” and other materiality qualifiers contained in the MWE Liberty’s representations and warranties shall be disregarded), and (ii) MWE Liberty shall have performed or complied in all material respects with all of the covenants and agreements required by this Agreement to be performed or complied with by MWE Liberty on or before the Closing;

(b)           No Material Adverse Effect.  Since the date of the Agreement, there shall not have been any Material Adverse Effect with respect to MWE Liberty or the Assets;

(c)           Third Party Consents; Governmental Approvals.  The consents, authorizations, approvals, exemptions and/or waivers listed on Schedule 7.2(c) shall have been received or obtained by MWE Liberty;

(d)           Purchase and Sale Agreement.  The closing contemplated by that certain Purchase and Sale Agreement, dated as of **, between ** and MWE Liberty and/or the Company, shall have occurred;

(e)           ** Agreements.  The agreements between MWE Liberty and ** to (i) include ** from the **, (ii) provide for an ** to result in an ** and (iii) increase ** to **; and

(f)            Closing Documents.  MWE Liberty shall have delivered or caused to be delivered all of the closing deliveries set forth in Section 2.4(b).

Section 7.3             Conditions to MWE Liberty’s Obligations.  The obligation of MWE Liberty to consummate the transactions contemplated by this Agreement is subject to the satisfaction of the following conditions, any one or more of which may be waived in writing by MWE Liberty:

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(a)           Representations, Warranties and Covenants of NGPMR.  (i) Each of the representations and warranties of NGPMR made in this Agreement will be true and correct as of the date of this Agreement (except to the extent such representations and warranties speak to an earlier date, in which case as of such earlier date) and as of the Closing (as if made anew at and as of the Closing, except to the extent such representations and warranties speak to an earlier date, in which case as of such earlier date) except to the extent the failure of such representations and warranties to be true and correct as of the Closing Date has not had, and is not reasonably expected to have, individually or in the aggregate, a Material Adverse Effect (provided that for purposes of determining whether the condition set forth in this sentence has been satisfied, all “Material Adverse Effect” and other materiality qualifiers contained in the NGPMR’s representations and warranties shall be disregarded), and (ii) NGPMR shall have performed or complied in all material respects with all of the covenants and agreements required by this Agreement to be performed or complied with by NGPMR on or before the Closing; and

(b)           Closing Documents.  MWE shall have delivered or caused to be delivered all of the closing deliveries set forth in Section 2.4(a).

ARTICLE 8
TERMINATION

Section 8.1             Termination.  At any time prior to the Closing, this Agreement may be terminated and the transactions contemplated hereby abandoned:

(a)           by the mutual consent of NGPMR and MWE Liberty as evidenced in writing signed by each of NGPMR and MWE Liberty;

(b)           by NGPMR, if there has been a breach by MWE Liberty of any representation, warranty or covenant contained in this Agreement that has prevented the satisfaction of any condition to the obligations of NGPMR at the Closing and, if such breach is of a character that it is capable of being cured, such breach has not been cured by MWE Liberty within thirty (30) days after written notice thereof from NGPMR; provided that NGPMR is not then in material breach of the condition set forth in Section 8.1(c);

(c)           by MWE Liberty, if there has been a breach by NGPMR of any representation, warranty or covenant contained in this Agreement that has prevented the satisfaction of any condition to the obligations of MWE Liberty at the Closing and, if such breach is of a character that it is capable of being cured, such breach has not been cured by NGPMR within thirty (30) days after written notice thereof from MWE Liberty provided that MWE Liberty is not then in material breach of the condition set forth in Section 8.1(b);

(d)           by either NGPMR or MWE Liberty if any Governmental Authority having competent jurisdiction has issued a final, non-appealable order, decree, ruling or injunction (other than a temporary restraining order) or taken any other action permanently restraining, enjoining or otherwise prohibiting the transactions contemplated by this Agreement; or

(e)           by either NGPMR or MWE Liberty, if the transactions contemplated hereby have not been consummated by March 13, 2009, provided that neither NGPMR nor MWE Liberty will be entitled to terminate this Agreement pursuant to this Section 8.1(e) if such

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Person’s breach of this Agreement has prevented the consummation of the transactions contemplated by this Agreement.

Section 8.2             Effect of Termination.  If this Agreement is terminated under Section 8.1, all further obligations of the Parties under this Agreement will terminate without further liability or obligation of either Party to the other Parties hereunder; provided, however, nothing herein shall prejudice the ability of the non-breaching party from seeking damages from any other Party for any actual fraud involving a knowing and intentional misrepresentation or omission of a material fact or willful or intentional breach of this Agreement, including attorneys’ fees and the right to pursue any remedy at law or in equity; provided further that if NGPMR terminates this Agreement as a result of a failure of a condition set forth in Section 8.1(b) due to a material misrepresentation or inaccuracy of a representation or warranty by MWE Liberty made as of the date hereof, then MWE Liberty shall ** as set forth in **.  The Confidentiality Agreement shall not be affected by a termination of this Agreement.  Nothing in this Section 8.2 will relieve any Party of their obligation to ** as set forth in **.

ARTICLE 9
GENERAL PROVISIONS

Section 9.1             Effective Time.  If the transactions contemplated hereby are consummated in accordance with the terms and conditions of this Agreement, the ownership of the Assets and the Assumed Liabilities shall be deemed transferred as of 11:59 p.m., Houston, Texas time, on the Closing Date.

Section 9.2             Costs; Taxes.  The Company shall be responsible for recording and filing documents associated with the transfer of the Assets to it and for all costs and fees associated therewith, including (i) filing the assignments with appropriate federal, state and local Governmental Authorities as required by applicable Law and (ii) the payment of any and all stamp, documentary, real property transfer, sales, gross receipts, use or similar Taxes or assessments (if any) arising out of the conveyance of the Assets and the assumption of the Assumed Liabilities as contemplated by this Agreement (collectively, the “Transfer Taxes”).  Each Party shall cooperate with the other in timely making all filings, returns, reports and forms as may be required in connection with the payment of the expenses, fees and costs contemplated by the previous sentence, including delivering all instruments and certificates as are reasonably necessary to minimize such expenses, fees and costs and to enable the other Party to timely comply with the filing of any tax return that relates to such expenses, fees and costs.

Section 9.3             Notices.  Any notice, demand or communication required or permitted under this Agreement shall be in writing and delivered personally or by reputable overnight delivery service or other courier, and shall be deemed to have been duly given as of the date and time reflected on the delivery receipt, addressed as follows:

If to the Company:

MarkWest Liberty Midstream & Resources, L.L.C.

1515 Arapahoe Street

Tower 2, Suite 700

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Denver, Colorado 80202-2126

Attention:  Senior Vice President and Chief Operations Officer

and

MarkWest Liberty Midstream & Resources, L.L.C.

1515 Arapahoe Street

Tower 2, Suite 700

Denver, Colorado 80202-2126

Attention: General Counsel

If to MWE Liberty:

MarkWest Liberty Gas Gathering, L.L.C.

1515 Arapahoe Street

Tower 2, Suite 700

Denver, Colorado 80202-2126

Attention:  Senior Vice President and Chief Operations Officer

and

MarkWest Liberty Gas Gathering, L.L.C.

1515 Arapahoe Street

Tower 2, Suite 700

Denver, Colorado 80202-2126

Attention: General Counsel

If to NGPMR:

M&R MWE Liberty, LLC

1401 McKinney, Suite 1025

Houston, Texas 77010

Attention: Jeffrey C. Rawls

with a copy to:

Locke Lord Bissell & Liddell, LLP

600 Travis Street, Suite 3400

Houston, Texas 77002

Fax  (713) 229-2518

Attention: H. William Swanstrom

A Party may change its address for the purposes of notices hereunder by giving notice to the other Party specifying such changed address in the manner specified in this Section 9.3.

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Section 9.4             Binding Effect.  This Agreement will be binding upon, and will inure to the benefit of, the Parties and their respective successors, permitted assigns and legal representatives.

Section 9.5             No Third Party Rights.  The provisions of this Agreement are intended to bind the Parties as to each other and are not intended to and do not create rights in any other Person or confer upon any other Person (other than the express beneficiaries of the indemnity provisions contained in Sections 5.2, 5.3 and 5.4) any benefits, rights or remedies and no Person is or is intended to be a third party beneficiary of any of the provisions of this Agreement.

Section 9.6             No Waiver.  No waiver or consent, express or implied, by any Party to or of any breach or default by any Person in the performance by such Person of its obligations hereunder shall be deemed or construed to be a consent or waiver to or of any other breach or default in the performance by such Person of the same or any other obligations of such Person hereunder. Failure on the part of a Party to complain of any act of any Person or to declare any Person in default, irrespective of how long such failure continues, shall not constitute a waiver by such Party of its rights hereunder until the applicable statute of limitations period has run.

Section 9.7             Applicable Law.  THIS AGREEMENT AND THE RIGHTS OF THE PARTIES HEREUNDER SHALL BE INTERPRETED IN ACCORDANCE WITH THE LAWS OF THE STATE OF DELAWARE AND ALL RIGHTS AND REMEDIES SHALL BE GOVERNED BY SUCH LAWS WITHOUT REGARD TO PRINCIPLES OF CONFLICT OF LAWS; PROVIDED, HOWEVER, THAT MATTERS CONCERNING TITLE TO THE TRANSFERRED ASSETS SHALL BE GOVERNED AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE JURISDICTION WHERE SUCH TRANSFERRED ASSETS ARE LOCATED.  THE PARTIES FURTHER AGREE THAT ANY LEGAL ACTION OR PROCEEDING WITH RESPECT TO THIS AGREEMENT OR ANY DOCUMENT RELATING HERETO MAY BE BROUGHT ONLY IN A FEDERAL OR STATE COURT OF COMPETENT JURISDICTION IN HOUSTON, TEXAS.  EACH PARTY HEREBY IRREVOCABLY WAIVES ANY OBJECTION, INCLUDING, BUT NOT LIMITED TO, ANY OBJECTION TO THE LAYING OF VENUE OR BASED ON THE GROUNDS OF FORUM NON-CONVENIENCE, WHICH IT MAY NOW OR HEREAFTER HAVE TO THE BRINGING OF SUCH ACTION OR PROCEEDING IN ANY SUCH RESPECTIVE JURISDICTION.

Section 9.8             Severability.  If any of the provisions of this Agreement are held by any court of competent jurisdiction to contravene, or to be invalid under, the laws of any political body having jurisdiction over the subject matter hereof, such contravention or invalidity shall not invalidate the entire Agreement. Instead, this Agreement shall be construed as if it did not contain the particular provision or provisions held to be invalid and an equitable adjustment shall be made and necessary provision added so as to give effect to the intention of the Parties as expressed in this Agreement at the time of execution of this Agreement.

Section 9.9             Amendment or Modification.  This Agreement may be amended, modified or supplemented from time to time only by a written agreement executed by all the Parties.

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Section 9.10           Assignment; Deed; Bill of Sale.  No Party shall have the right to assign its right or obligations under this Agreement without the prior written consent of the other Parties.  To the extent required and permitted by applicable Law, this Agreement shall also constitute a “deed,” “bill of sale” or “assignment” of the assets and interests referenced herein.

Section 9.11           Conspicuousness of Provisions.  THE PARTIES ACKNOWLEDGE AND AGREE THAT THE PROVISIONS CONTAINED IN THIS AGREEMENT THAT ARE IN CAPITALIZED LETTERS SATISFY THE REQUIREMENT OF THE “EXPRESS NEGLIGENCE RULE” AND ANY OTHER REQUIREMENT AT LAW OR IN EQUITY THAT PROVISIONS CONTAINED IN A CONTRACT BE CONSPICUOUSLY MARKED OR HIGHLIGHTED.

Section 9.12           Counterparts.  This Agreement may be executed in any number of counterparts with the same effect as if all Parties had signed the same document.  All counterparts shall be construed together and shall constitute one and the same instrument.  Execution and delivery of this Agreement by exchange of facsimile or other electronically transmitted counterparts bearing the signature of a Party shall be equally as effective as delivery of a manually executed counterpart by such Party.

Section 9.13           No Recourse Against Officers or Directors.  For the avoidance of doubt, the provisions of this Agreement shall not give rise to any right of recourse against any officer, director or manager of any Party.

Section 9.14           Entire Agreement; Supersedure.  This Agreement and the instruments referenced herein supersede all previous understandings or agreements among the Parties, whether oral or written, with respect to their subject matter. This Agreement and such instruments contain the entire understanding of the Parties with respect to the subject matter hereof and thereof. No understanding, representation, promise or agreement, whether oral or written, is intended to be or shall be included in or form part of this Agreement unless it is contained in a written amendment hereto executed by the Parties hereto after the date of this Agreement.

[Signature Page Follows]

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IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the date first written above.

Signature Page to Contribution Agreement

EXHIBIT A

DEFINED TERMS

“Act” means the Delaware Limited Liability Company Act, 6 Del.C. §§ 18-101 et seq., as it may be amended from time to time, and any successor thereto.

“Affiliate” means with respect to a Person, any other Person that, directly or indirectly, Controls, is Controlled by, or is under Common Control with, the specified Person.

“Agreement” means this Contribution Agreement, as it may be amended, supplemented or modified from time to time.

“Area of Mutual Interest” has the meaning ascribed to such term in the Company Operating Agreement.

“Assets” shall have the meaning set forth in Section 2.1(b).

“Assignment and Assumption” shall have the meaning set forth in Section 2.4(b)(v).

“Assumed Liabilities” shall have the meaning set forth in Section 2.2.

“Base Cap” means **.

“Basket Amount” means **.

“Benefit Plans” shall have the meaning set forth in Section 3.15(b).

“Business” shall have the meaning set forth in the recitals.

“Business Day” means any day that is not a Saturday, Sunday or other day on which commercial banks are required or authorized by law to be closed in the State of Texas or the State of Colorado.

“CERCLA” means the Comprehensive Environmental Response, Compensation and Liability Act, 42 U.S.C. §9601 et seq., as amended.

“Class A Interests” has the meaning ascribed to such term in the Company Operating Agreement.

“Class A Member” has the meaning ascribed to such term in the Company Operating Agreement.

“Class A Percentage Interests” has the meaning ascribed to such term in the Company Operating Agreement.

“Class B Interests” has the meaning ascribed to such term in the Company Operating Agreement.

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“Class B Member” has the meaning ascribed to such term in the Company Operating Agreement.

“Claim Notice” shall have the meaning set forth in Section 5.6(a).

“Closing” shall have the meaning set forth in Section 2.3.

“Closing Date” shall have the meaning set forth in Section 2.3.

“Code” means the Internal Revenue Code of 1986, as amended.

“Company” shall have the meaning set forth in the preamble.

** means an amount equal to the lesser of (a) ** or (b) the ** at the time of an indemnification claim pursuant to **, in each case, less any amount paid by ** in respect of indemnification claims under this Agreement.

“Company Operating Agreement” shall have the meaning set forth in the recitals.

“Confidentiality Agreement” shall mean that certain Amended and Restated Confidentiality Agreement, dated as of **, by and between MarkWest Energy Partners, L.P. and NGP Midstream & Resources, L.P.

“Consents” shall have the meaning set forth in Section 6.5.

“Control,” including the correlative terms “Controlling,” “Controlled by” and “under Common Control with” means possession, directly or indirectly (through one or more intermediaries), of the power to direct or cause the direction of the management or policies (whether through ownership of securities or any partnership or other ownership interest, by contract or otherwise) of a Person.  For the purposes of this definition, ownership of more than 50% of the voting interests of any entity shall be conclusive evidence that Control exists.

“Credit Agreement” means that certain Credit Agreement, dated as of February 20, 2008, among MWE, certain subsidiary guarantors, Royal Bank of Canada, as Administrative Agent and Collateral Agent, and the other lenders party thereto.

“Disclosed Liabilities” means any and all liabilities of MWE Liberty and/or the Company (i) arising from or relating to matters set forth on the disclosure schedules of MWE Liberty or (ii) set forth on the Trial Balance or arising after the date of the Trial Balance in the ordinary course of business.

“DOJ” shall have the meaning set forth in Section 6.1(a).

“Effective Date” means 12:01 a.m. on January 1, 2009.

“Environmental Claim” means any Proceeding or Loss resulting from or arising out of: (i) violation of or liability (including STRICT LIABILITY) under any Environmental Law or

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Environmental Permit; (ii) the performance of an Environmental Response; (iii) unlawful exposure to Hazardous Substances; or (iv) the Release of any Hazardous Substances.

“Environmental Laws” means any and all applicable laws (including common law), rules, ordinances, codes, decrees, judgments, directives, judicial or administrative orders or regulations of any Governmental Authority having jurisdiction over MWE Liberty or its Assets pertaining to prevention of pollution, protection of the environment, remediation of contamination, or workplace health and safety, including CERCLA; the Resource Conservation and Recovery Act, 42 U.S.C. § 6901 et seq.; the Federal Water Pollution Control Act, 33 U.S.C. § 1251 et seq.; the Clean Air Act, 42 U.S.C. § 7401 et seq.; the Hazardous Materials Transportation Act, 49 U.S.C. § 5101 et seq.; the Toxic Substances Control Act, 15 U.S.C. §§ 2601 through 2629; the Oil Pollution Act, 33 U.S.C. § 2701 et seq.; the Emergency Planning and Community Right-to-Know Act, 42 U.S.C. § 11001 et seq.; the Safe Drinking Water Act, 42 U.S.C. §§ 300f through 300j; the Occupational Safety and Health Act, 29 U.S.C. § 651 et seq.; each as amended, and all similar laws, rules and regulations of any Governmental Authority having jurisdiction over MWE Liberty or its Assets.

“Environmental Permits” means Permits required under Environmental Law.

“Environmental Response” means any action required under Environmental Law: (i) to prevent, respond to, remove, remediate, abate, investigate or monitor the release or threatened release of Hazardous Substances at, on, in, about, under, within or near the air, soil, surface water, groundwater, or other environmental media; or (ii) to correct a violation under Environmental Law.

“ERISA” shall have the meaning set forth in Section 3.15(b).

“ERISA Affiliate” means any entity (whether or not incorporated) which is a member of a controlled group including MWE Liberty or the Company or which is under Common Control with MWE Liberty or the Company within the meaning of Sections 414(b), (c), (m) or (o) of the Code.

“Excluded Assets” shall have the meaning set forth in Section 2.1(b)(ii).

“FTC” shall have the meaning set forth in Section 6.1(a).

“GAAP” means generally accepted accounting principles in the United States.

“Governmental Authority” means any governmental, quasi-governmental, state, county, city or other political subdivision of the United States or any other country, or any agency, court or instrumentality, foreign or domestic, or statutory or regulatory body thereof.

“Hazardous Substances” means and includes each substance, waste or material regulated, defined, designated or classified as a hazardous waste, hazardous substance, hazardous material, pollutant, contaminant or toxic (or words of similar import) substance under any Environmental Law and any petroleum or petroleum products that have been Released into the environment, radioactive materials, asbestos, urea formaldehyde foam insulation, polychlorinated biphenyls and naturally occurring radioactive material.

A-3

“Holding Period” means, for any particular Non-Assigned Asset, the period beginning on the Closing Date and ending on the earlier of (i) the date upon which the contract or agreement for which the Consent was not obtained expires, or (ii) the date upon which such Consent or an alternative arrangement is obtained on terms that are substantially similar in operational and economic effects as would have been achieved if the Non-Assigned Asset had been included within the Assets.

“HSR Act” shall have the meaning set forth in Section 6.1(a).

“Indebtedness” of any Person means any obligations of such Person: (a) for borrowed money, (b) evidenced by notes, bonds, indentures or similar instruments, (c) for the deferred purchase price of goods and services (other than trade payables incurred in the ordinary course of business), (d) under capital leases or (e) in the nature of guarantees of the obligations described in clauses (a) through (d) above of any other Person.

“Indemnified Party” shall have the meaning set forth in Section 5.6(a).

“Indemnifying Party” shall have the meaning set forth in Section 5.6(a).

“Indentures” means (a) that certain Indenture, dated as of April 15, 2008, by and among MWE, MarkWest Energy Finance Corporation, a Delaware corporation, the Subsidiary Guarantors (as defined therein), and Wells Fargo Bank, National Association, a national banking association, as trustee, (b) that certain Indenture, dated as of July 6, 2006, by and among MWE, MarkWest Energy Finance Corporation, a Delaware corporation, the Subsidiary Guarantors (as defined therein), and Wells Fargo Bank, National Association, a national banking association, as trustee, as amended and supplemented, and (c) that certain Indenture, dated as of October 25, 2004, by and among MWE, MarkWest Energy Finance Corporation, a Delaware corporation, the Subsidiary Guarantors (as defined therein), and Wells Fargo Bank, National Association, a national banking association, as trustee, as amended and supplemented.

“Initial Budget” shall have the meaning ascribed to such term in the Company Operating Agreement.

“Intellectual Property” means intellectual property rights, statutory or common Law, worldwide, including (a) trademarks, service marks, trade dress, slogans, logos and all goodwill associated therewith, and any applications or registrations for any of the foregoing; (b) copyrights and any applications or registrations for any of the foregoing; and (c) patents, all confidential know-how, trade secrets and similar proprietary rights in confidential inventions, discoveries, improvements, processes, techniques, devices, methods, patterns, formulae, specifications, and lists of suppliers, vendors, customers, and distributors.

“Investment Balance” shall have the meaning ascribed to such term in the Company Operating Agreement.

“Knowledge” means the actual knowledge of the Persons listed on Schedule 1.1.

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“Law” means any law, statute, code, ordinance, order, rule, rules of common law, regulation, judgment, decree, injunction, franchise, permit, certificate, license, authorization, or other directional requirement of any Governmental Authority.

“Losses” shall have the meaning set forth in Section 5.2.

“Material Adverse Effect” means any effect, event, development or change, (a) which individually or in the aggregate with all effects, events, developments or changes is or is reasonably likely to become materially adverse to the business, assets, liabilities, properties, results of operations or financial condition of the Person, taken as a whole, or (b) prevents or has an adverse effect on the ability of the Person to execute and perform their obligations under this Agreement or the other Transaction Documents or to consummate the transactions contemplated hereby and thereby in accordance with the terms hereof and thereof, excluding any such result or consequence resulting from or related to (i) changes in general economic, political or business conditions which affect the Person, except any such changes that affect the Person in a disproportionate manner compared to similarly situated participants in the industries in which the Person operates; (ii) conditions affecting the oil and gas industry or oil and gas services industry generally except any such changes that affect the Person in a disproportionate manner compared to similarly situated participants in the industries in which the Person operates; (iii) any change in law or in accounting rules except any such change that affects the Person in a disproportionate manner compared to similarly situated participants in the industries in which the Person operates; or (iv) conditions or effects that have been demonstrated by the Person as resulting from the announcement of the existence of this Agreement.

“Material Contracts” shall mean all contracts, agreements, personal property leases, commitments, understandings or instruments of MWE Liberty or by which MWE Liberty is bound that (a) is reasonably expected to (i) result in expenditures or liabilities in excess of ** or (ii) generate annual revenues in excess of **, (b) contains any provision or covenant, which after the Closing will apply to the Business, or the Company, prohibiting or materially restricting MWE Liberty from engaging in any lawful business activity or competing with any person or entity within the Area of Mutual Interest (as such term is defined in the Company Operating Agreement), (c) relates to Indebtedness of MWE Liberty or (d) is in respect of any partnership, joint venture or other similar agreement or arrangement or otherwise relates to the joint ownership or operation of the assets owned by MWE Liberty.

“Members” shall have the meaning set forth in the recitals.

“Miscellaneous Consents” means (a) all Consents that are not set forth on Schedule 7.2(c) and which relate to interests in real property, including, without limitation, leases, rights-of-way, easements and other property use agreements and (b) Permits or Environmental Permits issued by Governmental Authorities which are required in connection with the ownership or operation of the Assets **, and which Consents shall include any requirements of the applicable Governmental Authorities requiring the reissuance of any such Permits or Environmental Permits in connection with the Closing and by the Transaction Documents.

“MWE” means MarkWest Energy Partners, L.P., a Delaware limited partnership.

A-5

“MWE **” means an amount equal to MWE Liberty’s ** as of the Closing Date after giving effect to ** the Company contemplated hereby (prior to the **).

“MWE Liberty” shall have the meaning set forth in the preamble.

“MWE Liberty Covered Person” shall have the meaning set forth in Section 5.2.

“NGPMR” shall have the meaning set forth in the preamble.

“NGPMR Covered Persons” shall have the meaning set forth in Section 5.3.

“Non-Assigned Asset” is defined in Section 6.5.

“Organizational Documents” means the articles of incorporation, certificate of incorporation, certificate of formation, certificate of limited partnership, bylaws, operating agreement, partnership agreement, stockholders’ agreement and all other similar documents, instruments or certificates executed, adopted or filed in connection with the creation, formation or organization of a Person, including any amendments thereto.

“Parties” shall have the meaning set forth in the preamble.

“Permits” shall have the meaning set forth in Section 3.13.

“Permitted Liens” means (a) statutory liens for current Taxes applicable to the assets of MWE Liberty or assessments not yet delinquent or the amount or validity of which is being contested in good faith and for which adequate reserves have been established in the Trial Balance; (b) mechanics’, carriers’, workers’, repairers’, landlords’, and other similar liens arising or incurred in the ordinary course of business MWE Liberty relating to obligations as to which there is no default on the part of MWE Liberty; and (c) any liens, encumbrances, security interests, equities, charges or other restrictions with respect to assets of MWE Liberty, which, together with all other liens, encumbrances, security interests, equities, charges or other restrictions, do not materially detract from the value of the Assets or materially interfere with the present use of the Assets or the conduct of the business of MWE Liberty.

“Person” means any natural person, corporation, limited partnership, general partnership, limited liability company, joint stock company, joint venture, association, company, estate, trust, bank trust company, land trust, business trust, or other organization, whether or not a legal entity, custodian, trustee-executor, administrator, nominee or entity in a representative capacity and any Governmental Authority.

**

“Pre-Closing Tax Period” shall have the meaning set forth in Section 6.3(b).

“Proceeding” means any legal action, litigation, arbitration, hearing, written claim, legal proceeding, prosecution, investigation (for which investigation a Governmental Authority has provided notice to MWE Liberty), or suit (whether civil, criminal or administrative) commenced,

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brought, conducted, or heard by or before, or otherwise involving, any Governmental Authority or any arbitrator.

“Release” means any depositing, spilling, leaking, pumping, pouring, placing, emitting, discarding, abandoning, emptying, discharging, migrating, injecting, escaping, leaching, dumping, or disposing.

“Rights-of-Way” shall have the meaning set forth in Section 3.8.

“Services Agreement” shall have the meaning set forth in the recitals.

“Specified Liabilities” means (a) the Disclosed Liabilities and (b) liabilities first arising after the Closing Date and relating to the ownership, management or operation of the Assets under any contract, agreement, Permit or other instrument existing as of the Closing Date.  “Specified Liabilities” shall not include those items listed on Schedule 5.3(d) and Schedule 5.3(e).

“Straddle Period” shall have the meaning set forth in Section 6.3(b).

“Subsidiary” of any Person (the “Subject Person”) means any Person, whether incorporated or unincorporated, of which (a) at least 50% of the securities or ownership interests having by their terms ordinary voting power to elect a majority of the board of directors or other Persons performing similar functions, (b) a general partner interest or (c) a managing member interest, is directly or indirectly owned or Controlled by the Subject Person or by one or more of its respective Subsidiaries.

“Survival Period” shall have the meaning set forth in Section 5.1(c).

“Tax” or “Taxes” means (a) any taxes, assessments, fees, unclaimed property and escheat obligations and other governmental charges imposed by any Governmental Authority, including, but not limited to, income, profits, gross receipts, net proceeds, alternative or add-on minimum, ad valorem, value added, turnover, sales, use, property, personal property (tangible and intangible), environmental, stamp, leasing, lease, user, excise, duty, franchise, capital stock, transfer, registration, license, withholding, social security (or similar), unemployment, disability, payroll, employment, social contributions, fuel, excess profits, occupational, premium, windfall profit, severance, estimated, or other charge of any kind whatsoever, including any interest, penalty, or addition thereto, whether disputed or not; (b) any liability for the payment of any amounts of the type described in clause (a) arising by reason of transferee or successor liability; and (c) any liability for the payment of any amounts of the type described in clause (a) or (b) as a result of the operation of all or any express or implied obligation to indemnify any other Person.

“Tax Benefit” means the reduction in the amount of Taxes that otherwise would have been paid by any Indemnified Party as a result of incurring any Losses.

“Tax Return” means any return, declaration, report, claim for refund, or information return or statement relating to Taxes, including any schedule or attachment thereto, and including any amendment thereof.

“Third Party Claim” shall have the meaning set forth in Section 5.6(a).

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“Transaction Documents” shall have the meaning set forth in Section 2.4.

“Transactions” shall have the meaning set forth in Section 2.4.

“Transfer Taxes” shall have the meaning set forth in Section 9.2.

“Trial Balance” shall have the meaning set forth in Section 3.9.

“Trial Balance Date” shall have the meaning set forth in Section 3.9.

** means that certain **, by and between MWE Liberty and **, as amended by Amendment No. 1 to **, by and between MWE Liberty and **.

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EXHIBIT B

ASSETS

The Assets include, without limitation, the following:

1.     The lease of the “Interim Plant” **.

2.     All natural gas gathering and processing facilities and equipment located on the property that is the subject of that certain **, which are not either (i) the Interim Plant; (ii) that certain natural gas processing plant, and all of the equipment and appurtenances relating thereto, referred to as the “Fisk Plant” in that **; or (iii) facilities and equipment otherwise owned by **.

3.     The contractual right to purchase the Fisk Plant pursuant to the Fisk Purchase Agreement.

4.     The natural gas gathering and processing systems located in Washington County, Pennsylvania and identified on the map set forth as Annex A to this exhibit.

5.     The following compressor sites:

a.     Zappi-Hoskins

b.     Shaw

c.     Johnston

d.     Godwin

e.     Stewart

f.      Fulton

g.     Dryer

h.     Black

i.      Gapen

6.     The fixed assets listed on Annex B to this exhibit.

7.     The assets related to the construction in progress listed on Annex C to this exhibit.

8.     The Air Permits listed on Annex D to this exhibit.

9.     The Road Bore Permits listed on Annex E to this exhibit.

10.   The Stream Crossing Permits listed on Annex F to this exhibit.

11.   The Easements listed on Annex G to this exhibit.

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**

[4 pages have been omitted and filed separately with the Securities and Exchange Commission pursuant to the request for confidential treatment.]

Annex D

AIR PERMITS

MARKWEST LIBERTY GAS GATHERING, L.L.C.
COMPRESSOR STATIONS AND PLANTS

**

[26 pages have been omitted and filed separately with the Securities and Exchange Commission pursuant to the request for confidential treatment.]

EXHIBIT C

COMPANY OPERATING AGREEMENT

See attached.

AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT

of

MARKWEST LIBERTY MIDSTREAM & RESOURCES, L.L.C.

Dated as of                       , 2009

TABLE OF CONTENTS

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AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT

OF

MARKWEST LIBERTY MIDSTREAM & RESOURCES, L.L.C.

THIS AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT (“Agreement”) of MarkWest Liberty Midstream & Resources, L.L.C., a Delaware limited liability company (the “Company”), is executed and agreed to as of [            ] [    ], 2009, by and among MarkWest Liberty Gas Gathering, L.L.C., a Delaware limited liability company (“MWE Liberty”), M&R MWE Liberty, LLC, a Delaware limited liability company (“NGPMR”), and such other Persons who may become Members of the Company from time to time pursuant hereto.

WHEREAS, MWE Liberty, as the then sole member of the Company, entered into that certain Limited Liability Company Agreement (the “Original Agreement”) of the Company, dated as of January 20, 2009;

WHEREAS, in order to initially capitalize the Company, at or before the Closing, the Members shall make the Initial Capital Contributions and from time to time thereafter, certain of the Members shall make additional Capital Contributions in accordance with Article 4;

WHEREAS, in order to effect the contribution of the cash consideration comprising NGPMR’s Initial Capital Contribution and the assets comprising MWE Liberty’s Initial Capital Contribution, the Company, MWE Liberty and NGPMR entered into that certain Contribution Agreement, dated January 22, 2009 (the “Contribution Agreement”), pursuant to which MWE Liberty agreed to contribute, convey, assign and transfer to the Company all of MWE Liberty’s right, title and interest in and to the assets referenced thereunder;

WHEREAS, contemporaneously with the execution of this Agreement and in order to provide for the provision of certain services to the Company, the Company, MWE Liberty and MarkWest Hydrocarbon, Inc., a Delaware corporation (“MWE Hydrocarbon”) shall enter into that certain Services Agreement in the form attached hereto as Exhibit F (the “Services Agreement”), pursuant to which MWE Hydrocarbon shall provide certain services, or cause such services to be provided, to the Company;

WHEREAS, upon the Closing, the parties to the Contribution Agreement shall consummate the transactions contemplated by the Contribution Agreement and this Agreement shall become effective; and

WHEREAS, the Company and the Members desire to amend and restate the Original Agreement in its entirety to reflect the agreement of the Company and the Members as set forth herein;

NOW THEREFORE, in consideration of the foregoing and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, effective as of the Closing the Original Agreement is hereby amended and restated in its entirety to read as follows:

ARTICLE 1
DEFINED TERMS

Section 1.1                                      Definitions.

Unless the context otherwise requires, the terms defined in this Article I shall, for the purposes of this Agreement, have the meanings herein specified.

“AAA” shall have the meaning set forth in Section 6.15(e).

“Accountants shall have the meaning set forth in Section 4.1(a)(iii).

“Act” means the Delaware Limited Liability Company Act, 6 Del. C. §§ 18-101 et seq., as it may be amended from time to time, and any successor statute thereto.

“Additional Member” shall have the meaning set forth in Section 5.3(a).

“Additional Projects” shall have the meaning set forth in Section 3.3(a).

“Adjusted Capital Account” means the Capital Account maintained for each Member (a) increased by any amounts the Member is obligated to contribute or restore to the Company pursuant to the penultimate sentences of Treasury Regulations Sections 1.704-2(g)(1) and 1.704-2(i)(5), and (b) decreased by any amounts described in Treasury Regulations Sections 1.704-1(b)(2)(ii)(d)(4), (5), or (6) with respect to such Member.

“Adjusted Capital Account Deficit” means a deficit balance in the Adjusted Capital Account of a Member.

“Affiliate” means with respect to a Person, any other Person that, directly or indirectly, Controls, is Controlled by, or is under Common Control with, the specified Person.

“Affiliate Contract” means any contract between the Company or any Subsidiary of the Company, on the one hand, and a Member or an Affiliate of a Member, on the other hand.

“Affiliated Member Group” means (a) the MWE Liberty Group, (b) the NGPMR Group and (c) any other Member and transferee of Interests directly or indirectly (in the chain of title) from such Member that is an Affiliate of such transferee Member; provided, however, that once a Person is designated as a member of any Affiliated Member Group, such Person shall, as long as it owns any Interests, at all times be a member of such Affiliated Member Group and not a member of any other Affiliated Member Group, and provided, further, that for purposes of this clause (c) of this definition, an Affiliate shall not include a member of the MWE Liberty Group or the NGPMR Group.

“Agreement” means this Amended and Restated Limited Liability Company Agreement, as amended, modified, supplemented or restated from time to time.

“Annual Financial Statements” shall have the meaning set forth in Section 10.3(a).

“Approved Budget” shall have the meaning set forth in Section 6.15(b).

“Arbitration Panel” shall have the meaning set forth in Section 6.15(e).

“Area of Mutual Interest” means the area ** identified ** as Exhibit A.

“Assumed Tax Liability” shall have the meaning set forth in Section 8.5(a).

“Available Cash” means, with respect to any period prior to the dissolution of the Company, all cash and cash equivalents of the Company on hand at the end of such period less the amount of any cash reserves established by the Operator to provide for the proper conduct of the business of the Company, including reserves for: future capital expenditures; current, future or contingent liabilities; anticipated future credit needs of the Company; and debt service and repayments; provided that such reserves shall

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not equal less than ** as authorized in the Approved Budget nor more than ** in the Approved Budget, without the approval of the Board and Requisite Member Approval.

“Base Project” shall have the meaning set forth in Section 3.3(a).

“Board” shall have the meaning set forth in Section 6.1.

“Bring Down Certificate” means a certificate, in the form attached hereto as Exhibit I, to be delivered by the Company to the Class A Members in respect of the Capital Contributions set forth in Section 4.1(b)(i) stating that the Company has spent or committed to spend all previous Capital Contributions by the Class A Members in accordance with an Approved Budget, and will spend the Capital Contribution to which the Bring Down Certificate relates in accordance with an Approved Budget.

“Budget Rejection Notice” shall have the meaning set forth in Section 6.15(b).

“Business Day” means any day that is not a Saturday, Sunday or other day on which commercial banks are required or authorized by law to be closed in the State of Texas or the State of Colorado.

“Capital Account” means, with respect to any Member, the capital account maintained for such Member in accordance with the provisions of Section 4.5.

“Capital Call” means a call or request for additional capital in writing (which may include electronic mail) by or on behalf of the Company, specifying the amount of capital requested to be contributed by each Member receiving such notice in accordance with the terms of this Agreement.

“Capital Contribution” means, with respect to any Member, the aggregate amount of cash and the initial Gross Asset Value of any property other than cash contributed to the Company pursuant to Article 4 hereof by such Member.  Any reference in this Agreement to a Capital Contribution of a Member shall include a Capital Contribution contributed by its predecessors in interest.

“Certificate” means the Certificate of Formation of the Company filed on behalf of the Company with the office of the Secretary of State of the State of Delaware pursuant to the Act on January 20, 2009, and any and all amendments thereto and restatements thereof.

“Claims” shall have the meaning set forth in Section 6.5.

“Class A Interest” means an Interest in the Company which is classified on Exhibit B as a Class A Interest and which has the rights, powers and privileges enjoyed by a Member holding a Class A Percentage Interest (under the Act, the Certificate, this Agreement or otherwise) in its capacity as a Member, and all obligations, duties and liabilities imposed on such a Member (under the Act, the Certificate, this Agreement or otherwise) in its capacity as a Member.

“Class A Manager” shall have the meaning set forth in Section 6.2.

“Class A Member” means a Member who is designated on Exhibit B as a Class A Member, in its capacity as a holder of a Class A Percentage Interest.

“Class A Percentage Interest” means, with respect to a Class A Member, the quotient (expressed as a percentage) obtained by dividing such Class A Member’s Investment Balance by the aggregate Investment Balances of all Class A Members.

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“Class B Interest” means an Interest in the Company which is classified on Exhibit B as a Class B Interest and which has the rights, powers and privileges enjoyed by a Member holding a Class B Percentage Interest (under the Act, the Certificate, this Agreement or otherwise) in its capacity as a Member, and all obligations, duties and liabilities imposed on such a Member (under the Act, the Certificate, this Agreement or otherwise) in its capacity as a Member.

“Class B Manager” shall have the meaning set forth in Section 6.2.

“Class B Member” means a Member who is designated on Exhibit B as a Class B Member, in its capacity as a holder of a Class B Percentage Interest.

“Class B Percentage Interest” means, with respect to a Class B Member, the quotient (expressed as a percentage) obtained by dividing such Class B Member’s Investment Balance by the aggregate Investment Balances of all Class B Members.

“Class B Seller” shall have the meaning set forth in Section 7.2(b).

“Closing” has the meaning ascribed to such term in the Contribution Agreement.

“Code” means the Internal Revenue Code of 1986, as amended from time to time, or any corresponding federal tax statute enacted after the date of this Agreement.

“Company” shall have the meaning set forth in the preamble.

“Company Minimum Gain” shall have the meaning assigned to the term “partnership minimum gain” in Treasury Regulations Sections 1.704-2(b)(2) and 1.704-2(d).

“Company Nonrecourse Liability” shall have the meaning assigned to the term “nonrecourse liability” in Treasury Regulations Section 1.704-2(b)(3)

** shall have the meaning set forth in Section 4.9(b).

** shall have the meaning set forth in Section 4.9(c).

“Confidential Information” shall mean all information provided or made available by or on behalf of the Company or its Representatives to a Member or its Representatives, including all information, data, reports, interpretations, contract terms and conditions, forecasts and records containing or otherwise reflecting information concerning the Company or its Affiliates, potential counterparties or customers or their Affiliates, potential projects, business plans or proposals, market or economic data, identities of actual or potential counterparties or customers, designs, concepts, trade secrets and other business, operational or technical information (irrespective of the form of communication of such information) and together with analyses, compilations, studies or other documents, whether prepared by or on behalf of a Member or its Representatives, which contain or otherwise reflect such information (irrespective of the form of communication of such information).  “Confidential Information” also includes information of third parties, including such information as may be subject to any Third Party Confidentiality Agreements.  Notwithstanding the foregoing, Confidential Information shall not include the following:  (a) information which at the time of disclosure by or on behalf of the Company is publicly available or which later becomes publicly available through no act or omission of the disclosing Member or its Representatives; (b) information which a Member can demonstrate was in its possession on a non-confidential basis prior to disclosure by or on behalf of the Company hereunder; (c) information received by a Member from a third party who is not prohibited from transmitting the information by a contractual,

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legal or fiduciary obligation; or (d) information which a Member can demonstrate was independently developed by it or for it and which was not derived or obtained, in whole or in part, from Confidential Information or from the Company or its Representatives hereunder.

“Contributing Member” shall mean a Class A Member who makes a Quarterly Budgeted Funding Election in accordance with Section 4.1(c).

“Contribution Agreement” shall have the meaning set forth in the recitals.

“Control,” including the correlative terms “Controlling,” “Controlled by” and “Under Common Control with” means possession, directly or indirectly (through one or more intermediaries), of the power to direct or cause the direction of the management or policies (whether through ownership of securities or any partnership or other ownership interest, by contract or otherwise) of a Person.  For the purposes of this definition, ownership of more than 50% of the voting interests of any entity shall be conclusive evidence that Control exists.

“Covered Person” means, in each case, whether or not a Person continues to have the applicable status referred to in the following list: a Member; a Manager; the Operator; any Affiliate of a Member or a Manager or of the Operator; any officers of the Company, whether or not such officers are employees of the Company; any officers, directors, members, managers, stockholders, partners, employees, representatives or agents of any Manager or Member or of the Operator, or of any of their respective Affiliates; any employee or agent of the Company or its Affiliates; and any Tax Matters Member of the Company.

“CP Index” means the United States Department of Labor, Bureau of Labor Statistics Consumer Price Index — All Urban Consumers, U.S. City Average, Not Seasonally Adjusted, or, if such index is discontinued, any successor or substitute index, which, in the Board’s reasonable opinion, is most nearly equivalent to such index.

“Debt” for any Person means, without duplication: (a)  indebtedness of such Person for borrowed money, including obligations under letters of credit and agreements relating to the issuance of letters of credit or acceptance financing; (b) obligations of such Person evidenced by bonds, debentures, notes, or other similar instruments; (c) obligations of such Person to pay the deferred purchase price of property or services (including, without limitation, obligations that are non-recourse to the credit of such Person but are secured by the assets of such Person, but excluding trade accounts payable); (d) obligations of such Person under capital leases; and (e) obligations of such Person under guarantees in respect of indebtedness or obligations of others of the kinds referred to in clauses (a) through (d) above; provided that “Debt” shall not include the incurrence of trade debt in the ordinary course of business.

“Default Rate” means a per annum rate of interest equal to the lower of ** and the maximum rate of interest then permitted by law.

“Defaulting Member” shall have the meaning set forth in Section 4.2.

“Depreciation” means, for each Fiscal Year or other period, an amount equal to the depreciation, amortization or other cost recovery deduction allowable for federal income tax purposes with respect to an asset for such Fiscal Year or other period and in a manner consistent with the methodologies employed by MWE or otherwise determined by the Board; provided, however, that if the Gross Asset Value of an asset differs from its adjusted basis for federal income tax purposes at the beginning of such Fiscal Year or other period, Depreciation for such Fiscal Year or other period shall equal to the amount of book basis recovered for such Fiscal Year or other period under the rules prescribed by Treasury Regulation Section 

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1.704-3(d)(2) and provided further, that if the federal income tax depreciation, amortization or other cost recovery deduction for such Fiscal Year or other period is zero, Depreciation shall be determined with reference to such beginning Gross Asset Value using any reasonable method selected by the Board.

“Designated MWE Employees” has the meaning ascribed to such term in the Services Agreement.

“Economic Risk of Loss” shall have the meaning assigned to that term in Treasury Regulation Section 1.752-2(a).

“Effective Time” means 12:01 a.m. on January 1, 2009.

“Election Period” shall have the meaning set forth in Section 5.7(b).

“Electing Member” shall have the meaning set forth in Section 5.7(b).

“Eligible Member” shall have the meaning set forth in Section 5.7(a).

“Enforcement Activities” shall have the meaning set forth in Section 6.3(a).

“Equalization Date” shall mean the first date after ** on which the quotient (expressed as a percentage) obtained by dividing the aggregate Investment Balances of all members of the MWE Liberty Group by the aggregate Investment Balances of all members of the MWE Liberty Group plus all members of the NGPMR Group is equal to or greater than 60%.

“Equalization Target Date” shall have the meaning set forth in Section 4.9(a).

“Escrow Account” shall have the meaning set forth in Section 10.5.

“Escrow Agent” means Wells Fargo Bank, N.A.

“Escrow Agreement” means that certain Escrow Agreement to be entered into among the Company, NGPMR and the Escrow Agent in substantially the form attached hereto as Exhibit J.

“Escrow Letter” shall have the meaning set forth in Section 10.5.

“Exchange Act” means the Securities Exchange Act of 1934, and the rules and regulations promulgated thereunder, as amended and any successor statutes thereto.

“Exempted Project” shall have the meaning set forth in Section 3.3(b).

“Final Calculations” shall have the meaning set forth in Section 4.1(a)(ii).

“Final Cost” shall have the meaning set forth in Section 4.1(a)(iv).

“First Notice” shall have the meaning set forth in Section 5.7(b).

“Fiscal Year” means (i) the period commencing at the Effective Time and ending on December 31, 2010 and (ii) any subsequent 12 month period commencing on January 1 and ending on December 31.

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“Fractionation and NGL Purchase Agreement” shall have the meaning set forth in Section 3.3(b)(ii).

“G&A Services” has the meaning ascribed to such term in the Services Agreement.

“GAAP” means generally accepted accounting principles in the United States.

** means that certain ** by and between MarkWest Liberty Gas Gathering, L.L.C. and **.

“Gross Asset Value” means, with respect to any asset, such asset’s adjusted basis for federal income tax purposes, except as follows:

(a)                                  the initial Gross Asset Value of any asset contributed by a Member to the Company shall be the gross fair market value of such asset, as agreed to by the contributing Member and the Board, except that MWE Liberty’s Initial Capital Contribution shall have the gross asset value determined in accordance with Section 4.1(a);

(b)                                 the Gross Asset Value of all Company assets shall be adjusted to equal their respective gross fair market values, as determined by the Board, in connection with: (i) the acquisition of an additional interest in the Company by any new or existing Member in exchange for more than a de minimis Capital Contribution or in exchange for the performance of services to or for the benefit of the Company; (ii) the distribution by the Company to a Member of more than a de minimis amount of Company assets as consideration for an interest in the Company; and (iii) the liquidation of the Company within the meaning of Treasury Regulations Section 1.704-1(b)(2)(ii)(g) (other than pursuant to Section 708(b)(1)(B) of the Code) or any other event to the extent determined by the Board to be necessary to properly reflect the Gross Asset Values in accordance with the standards set forth in Treasury Regulations Section 1.704-1(b)(2)(iv)(q); provided, however, that adjustments pursuant to clause (i) and clause (ii) of this sentence shall be made only if the Board reasonably determines that such adjustments are necessary or appropriate to reflect the relative economic interests of the Members in the Company;

(c)                                  the Gross Asset Value of any Company asset distributed to any Member shall be the gross fair market value of such asset on the date of distribution, as determined by the Board and the distributee Member; and

(d)                                 the Gross Asset Values of Company assets shall be adjusted to reflect any adjustments to the adjusted basis of such assets pursuant to Code Section 734(b) or Code Section 743(b), but only to the extent that such adjustments are taken into account in determining Capital Accounts pursuant to Treasury Regulations Section 1.704-1(b)(2)(iv)(m).

If the Gross Asset Value of an asset has been determined or adjusted pursuant to paragraph (a) or paragraph (b) above, such Gross Asset Value shall thereafter be adjusted by the Depreciation taken into account with respect to such asset for purposes of computing Profits and Losses.

“Incentive Interest Transaction” shall have the meaning set forth in Section 5.6.

“Indentures” has the meaning ascribed to such term in the Contribution Agreement.

“Indemnitee” shall have the meaning set forth in Section 12.7.

“Indemnitor” shall have the meaning set forth in Section 12.7.

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“Initial Budget” shall have the meaning set forth in Section 5.5.

“Initial Capital Contribution” shall have the meaning set forth in Section 4.1(a)(i).

“Interest” means the interest of a Member in the Company, including both Class A Percentage Interests and Class B Percentage Interests, including rights to distributions (liquidating or otherwise), allocations, notices and information, rights to approve of or consent to certain matters (if applicable) and all other rights, benefits and privileges enjoyed by that Member (under the Act, the Certificate, this Agreement, or otherwise) in its capacity as a Member; and all obligations, duties and liabilities imposed on that Member (under the Act, the Certificate, this Agreement, or otherwise) in its capacity as a Member.

“Investment Account” shall have the meaning set forth in Section 4.8.

“Investment Balance” shall have the meaning set forth in Section 4.8.

“Investment Balance Costs” shall have the meaning set forth in Section 4.1(a)(ii).

“IPO Issuer” means (a) the Company or (b) an Affiliate of the Company which will be a successor to the Company and the issuer in a Qualified Public Offering.

“Lien” means, with respect to any asset, any mortgage, lien, pledge, charge, security interest or encumbrance of any kind in respect of such asset.

 “Liquidating Trustee” shall have the meaning set forth in Section 13.4(a).

“Manager” shall have the meaning set forth in Section 6.1.

“Member” means any Person (but not any Affiliate or entity in which such Person has an equity interest) executing this Agreement and any Person admitted as an Additional Member or a Substitute Member pursuant to the provisions of this Agreement, in such Person’s capacity as a Member of the Company, and “Members” means two or more of such Persons, in their capacities as Members of the Company.  Such terms do not include any Person or Persons who have ceased to be Members in the Company.

“Member Nonrecourse Debt” has the meaning assigned to the term “partner nonrecourse debt” in Treasury Regulation Section 1.704-2(b)(4).

“Member Nonrecourse Debt Minimum Gain” shall have the meaning assigned to the term “partner nonrecourse debt minimum gain” in Treasury Regulation Section 1.704-2(i)(2).

“Member Nonrecourse Deductions” shall have the meaning assigned to the term “partner nonrecourse deductions” in Treasury Regulation Section 1.704-2(i)(1).

“Minimum Gain” shall have the meaning assigned to that term in Treasury Regulation Section 1.704-2(d).

“Minimum Price” shall have the meaning set forth in Section 7.2(b)(ii).

“Monthly Reports” shall have the meaning set forth in Section 10.3(c).

“MWE” means MarkWest Energy Partners, L.P., a Delaware limited partnership.

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“MWE Hydrocarbon” shall have the meaning set forth in the recitals.

“MWE Liberty” shall have the meaning set forth in the preamble.

“MWE Liberty Group” means MWE Liberty and each transferee of Interests directly or indirectly (in the chain of title) from MWE Liberty that is an Affiliate of MWE Liberty; provided, however, that once a Person is designated as a member of the MWE Liberty Group such Person shall, as long as it owns any Interests, at all times be a member of the MWE Liberty Group and not a member of any other Affiliated Member Group; provided further, that for purposes of this definition, an Affiliate shall not include a member of any other Affiliated Member Group.

“New Interests” shall have the meaning set forth in Section 5.7(a).

“NGPMR” shall have the meaning set forth in the preamble.

“NGPMR Covered Persons” has the meaning ascribed to such term in the Contribution Agreement.

“NGPMR Exit Transaction” means ** involving the Company in which ** in which the ** prior to the ** of the Company ** or a ** of the Company**.  For the avoidance of doubt, any **

“NGPMR Group” means NGPMR and each transferee of Interests directly or indirectly (in chain of title) from NGPMR that is an Affiliate of NGPMR; provided, however, that once a Person is designated as a member of the NGPMR Group such Person shall, as long as it owns any Interests, at all times be a member of the NGPMR Group and not a member of any other Affiliated Member Group, and, provided further, that for purposes of this definition, an Affiliate shall not include a member of any other Affiliated Member Group.

“NGPMR Portfolio Companies” shall have the meaning set forth in Section 3.3(c).

“NGPMR Representatives” shall mean the members, managers and employees of NGPMR or any Affiliate thereof, together with all other persons serving as representatives of NGPMR, including those Persons who are serving as Managers at the request of NGPMR pursuant to this Agreement.

“Non-Contributing Member” shall mean a Class A Member who does not elect to make a Quarterly Budgeted Funding Election in accordance with Section 4.1(c).

“Nonrecourse Deductions” shall have the meaning assigned to that term in Treasury Regulation Section 1.704-2(b).

“Objection Notice” shall have the meaning set forth in Section 4.1(a)(iii).

“Operator” means the Person designated as the “Operator” of the Company in accordance with Section 6.11.

“Original Agreement” shall have the meaning set forth in the recitals.

“Out of Scope Project” means any project, activity, or business venture (a) outside the Area of Mutual Interest or (b) not within the scope of the Primary Business of the Company (whether inside or outside the Area of Mutual Interest).

“Over-Allotment Amount” shall have the meaning set forth in Section 5.7(b).

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“Overfunded Capital” means, as of any determination date, the difference (expressed as a dollar amount) between **.

“Partial NGPMR Exit Transaction” means ** after which the ** in the ** after which the **

“Percentage Interest” means:

(a)                                  at any time prior to the earlier to occur of the Equalization Date and **:

(i)                                     with respect to a Class A Member, the product (expressed as a percentage) of (1) 40% and (2) such Member’s Class A Percentage Interest; and

(ii)                                  with respect to a Class B Member, the product (expressed as a percentage) of (1) 60% and (2) such Member’s Class B Percentage Interest.

(b)                                 at any time on or after the earlier to occur of the Equalization Date and **, with respect to any Member (including any Class A Member or Class B Member), the quotient (expressed as a percentage) obtained by dividing the Investment Balance of such Member by the Investment Balances of all Members.

“Permitted Liens” means (a) statutory liens for current taxes or assessments not yet due and delinquent or the validity of which is being contested in good faith by appropriate proceedings and for which adequate reserves have been established; (b) mechanics’, carriers’, workers’, repairers’ and other similar liens arising or incurred in the ordinary course of business; and (c) all applicable zoning ordinances and land use restrictions.

“Permitted Transfers” shall have the meaning set forth in Section 7.1.

“Personnel Services” has the meaning ascribed to such term in the Services Agreement.

“Person” means any natural person, corporation, limited partnership, general partnership, limited liability company, joint stock company, joint venture, association, company, estate, trust, bank trust company, land trust, business trust, or other organization, whether or not a legal entity, custodian, trustee-executor, administrator, nominee or entity in a representative capacity and any government or agency or political subdivision thereof.

“Post-Effective Date Capital Expenditures” shall have the meaning ascribed to such term in the Contribution Agreement.

 “Preference Amount” means an amount calculated on the last day of each calendar quarter following the Effective Time and prior to the Equalization Date by determining the difference between (a) the amount of Overfunded Capital as of the last day of such quarter multiplied by the Preference Rate and (b) the amount of all distributions made during such calendar quarter pursuant to Section 8.1(b)(i)(A).  The Preference Amount for the prior calendar quarter shall be added to the Investment Balance as of the first day of the following calendar quarter.

“Preference Rate” means a quarterly rate expressed as a percentage equal to ** per annum, divided by four.

“Primary Business” shall have the meaning set forth in Section 3.1(a).

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“Profits” or “Losses” means, for each Fiscal Year, an amount equal to the Company’s taxable income or loss for such Fiscal Year, determined in accordance with Section 703(a) of the Code (but including in taxable income or loss, for this purpose, all items of income, gain, loss or deduction required to be stated separately pursuant to Section 703(a)(1) of the Code), with the following adjustments:

(a)           any income of the Company exempt from federal income tax and not otherwise taken into account in computing Profits or Losses pursuant to this definition shall be added to such taxable income or loss;

(b)           any expenditures of the Company described in Section 705(a)(2)(B) of the Code (or treated as expenditures described in Section 705(a)(2)(B) of the Code pursuant to Treasury Regulations Section 1.704-1(b)(2)(iv)(i)) and not otherwise taken into account in computing Profits or Losses pursuant to this definition shall be subtracted from such taxable income or loss;

(c)           in the event the Gross Asset Value of any Company asset is adjusted in accordance with paragraph (b) or paragraph (c) of the definition of “Gross Asset Value”, the amount of such adjustment shall be taken into account as gain (if the adjustment increases the Gross Asset Value of the Company asset) or loss (if the adjustment decreases the Gross Asset Value of the Company asset) from the disposition of such asset for purposes of computing Profits or Losses;

(d)           gain or loss resulting from any disposition of any Company asset with respect to which gain or loss is recognized for federal income tax purposes shall be computed by reference to the Gross Asset Value of the asset disposed of, notwithstanding that the adjusted tax basis of such asset differs from its Gross Asset Value;

(e)           in lieu of the depreciation, amortization and other cost recovery deductions taken into account in computing such taxable income or loss, there shall be taken into account Depreciation for such Fiscal Year or other period, computed in accordance with the definition of “Depreciation”;

(f)            to the extent an adjustment to the adjusted tax basis of any asset pursuant to Code Section 734(b) is required, pursuant to Treasury Regulation Section 1.704-1(b)(2)(iv)(m)(4), to be taken into account in determining Capital Account balances as a result of a distribution other than in liquidation of a Member’s interest in the Company, the amount of such adjustment shall be treated as an item of gain (if the adjustment increases the basis of the asset) or an item of loss (if the adjustment decreases such basis) from the disposition of such asset and shall be taken into account for purposes of computing Profits or Losses; and

(g)           notwithstanding any other provisions of this definition, any items which are specially allocated pursuant to Section 9.2 or 9.3 shall not be taken into account in computing Profits or Losses.

“Project Period” shall have the meaning set forth in Section 7.1.

“Projects” shall have the meaning set forth in Section 3.3(a).

“Property” means all of the assets and property now owned or hereafter acquired by the Company.

“Proposed Budget” shall have the meaning set forth in Section 6.15(a).

“Proposed Purchaser” shall have the meaning set forth in Section 5.7(a).

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“Prudent Industry Practices” means, at a particular time, any of the practices, methods and acts which, ** based upon the **, and the **, at such time, is ** operation and maintenance of the Company assets and shall include, without limitation, the practices, methods and acts engaged in or approved by ** at such time with respect to the assets of the same or similar types as the Company assets. Prudent Industry Practices are not intended to be limited to ** to the exclusion of all others, but rather is ** practices, methods and acts which ** at a ** as well as with the **. Prudent Industry Practices are intended to entail the **, in the **, use from time to time.

“Qualified Public Offering” means any underwritten initial public offering by the IPO Issuer of equity securities pursuant to an effective registration statement under the Securities Act and for which aggregate cash proceeds to be received by the IPO Issuer from such offering (without deducting underwriting discounts, expenses and commissions) are at least $50,000,000.

“Qualifying Third Party Offer” shall have the meaning set forth in Section 7.2(a)(ii).

“Quarterly Budgeted Funding Election” shall have the meaning set forth in Section 4.1(c).

“Quarterly Financial Statements” shall have the meaning set forth in Section 10.3(b).

“Regulatory Allocations” shall have the meaning set forth in Section 9.3.

“Remaining Members” shall have the meaning set forth in Section 7.2(a).

“Representatives” means (a) with respect to the Company, any of: (i) the Company’s Affiliates; and (ii) directors, officers, managers, employees, members, partners, agents and authorized representatives (including attorneys, accountants, consultants, bankers, lenders and financial advisors) of the Company and the Company’s Affiliates and (b) with respect to a Member, any of: (i) such Member’s Affiliates; (ii) directors, officers, managers, employees, members, stockholders, partners, agents and authorized representatives (including attorneys, accountants, consultants, bankers, lenders and financial advisors) of the Member and the Member’s Affiliates; and (iii) Persons who are (or who are prospective) beneficial owners of equity interests in such Member.

“Requisite Member Approval” means the approval of each Affiliated Member Group holding Interests with (i) an aggregate Percentage Interest equal to or exceeding ** or (ii) an **.

“Restricted Project” has the meaning set forth in Section 3.3(b).

“ROFO Interest” shall have the meaning set forth in Section 7.2(a).

“ROFO Offer” shall have the meaning set forth in Section 7.2(a).

“Rules” shall have the meaning set forth in Section 6.15(e).

“Sale Proposal” shall have the meaning set forth in Section 7.2(b)(i).

“Securities Act” means the Securities Act of 1933, and the rules and regulations promulgated thereunder, as amended and any successor statutes thereto.

“Services Agreement” shall have the meaning set forth in the recitals.

“Solicitation Notice” shall have the meaning set forth in Section 7.2(b)(ii).

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“Solicitation Period” shall have the meaning set forth in Section 7.2(a)(ii).

“Solicitation Response” shall have the meaning set forth in Section 7.2(b)(ii).

“Subsidiary” means, with respect to any Person, (a) any corporation, of which a majority of the total voting power of shares of stock entitled (without regard to the occurrence of any contingency) to vote generally in the election of directors thereof is at the time owned or controlled, directly or indirectly, by that Person or one or more of the other Subsidiaries of that Person or a combination thereof or (b) any limited liability company, partnership, association or other business entity, of which a majority of the partnership or other similar ownership interests thereof is at the time owned or controlled, directly or indirectly, by that Person or one or more Subsidiaries of that Person or a combination thereof.  For purposes of this definition, a Person or Persons will be deemed to have a majority ownership interest in a limited liability company, partnership, association or other business entity if such Person or Persons will be allocated a majority of limited liability company, partnership, association or other business entity gains or losses, or is or controls the managing member or general partner of such limited liability company, partnership, association or other business entity.

“Substitute Member” means a Person who is admitted to the Company as a Member pursuant to Article 7, and then designated as a “Member” on an amended Exhibit B to this Agreement.

“Tag-Along Members” shall have the meaning set forth in Section 7.2(b).

“Tag-Along Notice” shall have the meaning set forth in Section 7.2(b)(i).

“Tag-Along Notice Period” shall have the meaning set forth in Section 7.2(b)(i).

“Tag-Along Rights” shall have the meaning set forth in Section 7.2(b).

“Tax Distribution Date” shall have the meaning set forth in Section 8.5(a).

“Tax Matters Member” shall have the meaning set forth in Section 11.4(a).

“Third Party Confidentiality Agreements” means that certain ** among MWE Liberty, **, the **, that certain ** between ** and MWE Liberty, that certain ** between ** and MWE Liberty ** and that certain ** between ** and MWE Liberty ** or any other third party agreement entered into by or on behalf of the Company and delivered to a Member.

“Third Party Offer” shall have the meaning set forth in Section 7.2(a)(ii).

“** Payout” shall mean the dollar threshold, if any, at which the NGPMR Group has received a cumulative cash amount in respect of the NGPMR Group’s Interests (whether as distributions from the Company or as cash payment in an Incentive Interest Transaction) equal to the ** as of the date of such cash payment ** where ** is equal to the ** determined as of the date of such cash payment or distribution.

“** Payout Threshold” shall mean the receipt by the NGPMR Group of a cumulative cash amount in respect of the NGPMR Group’s Interests (whether as distributions from the Company or as cash payment in an Incentive Interest Transaction) equal to the ** where ** is equal to the ** determined as of the date of such distribution or cash payment.

“** Percentage” shall mean **.

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**

“Transaction Documents” shall have the meaning set forth in Section 5.1(b).

“Transfer” means any direct or indirect transfer, assignment, sale, conveyance, license, lease, or partition of any Interest, and includes any “involuntary transfer” such as a sale of any part of the Interest therein in connection with any bankruptcy or similar insolvency proceedings, or any other disposition of any Interest.  A Transfer shall not include any pledge, hypothecation or encumbrance of any Interest.

“Transferring Member” shall have the meaning set forth in Section 7.2(a).

“Treasury Regulations” means the income tax regulations, including temporary regulations, promulgated under the Code, as such regulations may be amended from time to time (including corresponding provisions of succeeding regulations).

“True-Up Contribution” shall have the meaning set forth in Section 4.9(a).

** means that certain ** by and between MWE Liberty and ** as amended by Amendment No. 1 to ** by and between MWE Liberty and **.

“Unrelated Information” shall have the meaning set forth in Section 10.2.

“Weighted Average Capital Contribution Factor” shall mean as of any date of calculation, a weighted average ** the amounts determined for each date on which NGPMR has made Capital Contributions (including without limitation the Capital Contributions funded on the date hereof) calculated as ** of the total ** years from the date of each Capital Contribution until the date of such calculation (with a partial year being expressed as a decimal determined by dividing the number of days which have passed since the most recent anniversary by 365).  Solely for purposes of determining Capital Contributions under this definition, (i) ** shall be treated as a Capital Contribution made by the NGPMR Group as of the date **, and (ii) any other amounts ** shall be treated as Capital Contributions made by the NGPMR Group as of the date **.

ARTICLE 2
FORMATION AND TERM

Section 2.1             Formation.

(a)           The Company was organized as a Delaware limited liability company under and pursuant to the Act by the filing of the Certificate by an authorized person and is being continued pursuant to the terms of this Agreement.

(b)           The name and mailing address of each Member and the total amount which shall be contributed to the capital of the Company through the Closing is listed on Exhibit B.  The Board shall cause Exhibit B to be updated, from time to time, as may be necessary to accurately reflect the information therein.  Any amendment or revision to Exhibit B made in accordance with this Agreement shall not be deemed an amendment to this Agreement.  Any reference in this Agreement to Exhibit B shall be deemed to be a reference to Exhibit B, as amended, revised and in effect from time to time.

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Section 2.2             Name.

The business and affairs of the Company shall be conducted under the name “MarkWest Liberty Midstream & Resources, L.L.C.” and such name shall be used at all times in connection with the Company’s business and affairs, except to the extent the Board agrees to the use by the Company of assumed names or other trade names or fictitious names.  The Company’s Managers or officers or the Operator shall execute such assumed or fictitious name certificates as may be desirable or required by law to be filed in connection with the business and affairs of the Company and shall cause such certificates to be filed in all appropriate public records.

Section 2.3             Term.

The term of the Company commenced upon the effectiveness of the Certificate and shall continue perpetually, unless the Company is dissolved in accordance with the provisions of this Agreement.

Section 2.4             Registered Agent and Office.

The registered office of the Company required by the Act to be maintained in Delaware shall be the office of the initial registered agent named in the Certificate or such other office (which need not be a place of business of the Company) as the Board may designate in the manner provided by law.  The registered agent of the Company in Delaware shall be the initial registered agent named in the Certificate or such other Person or Persons as the Board may designate in the manner provided by law.

Section 2.5             Principal Place of Business.

The principal place of business of the Company shall be 1515 Arapahoe Street, Tower 2, Suite 700, Denver, CO 80202.  At any time, the Board may change the location of the Company’s principal place of business.  The Company may have such other places of business as the Board or the Operator may designate.

Section 2.6             Qualification in Other Jurisdictions.

The Managers, the officers of the Company or the Operator shall cause the Company to be qualified, formed or registered under assumed or fictitious name statutes or similar laws in any jurisdiction in which the Company transacts business.  The Managers, the officers of the Company or the Operator shall execute, deliver and file any certificates (and any amendments and/or restatements thereof) necessary or appropriate for the Company to qualify and continue to do business in a jurisdiction in which the Company may wish to conduct business. At the request of the Board or the Operator, each Member shall execute, acknowledge, swear to and deliver all certificates and other instruments conforming with this Agreement that are necessary or appropriate to qualify, continue and terminate the Company as a foreign limited liability company in all such jurisdictions in which the Company may conduct business, provided that no Member shall be required to file any general consent to service of process or to qualify as a foreign corporation, limited liability company, partnership or other entity in any jurisdiction in which it is not already so qualified.

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ARTICLE 3
PURPOSE AND POWERS OF THE COMPANY

Section 3.1             Purpose.

(a)           The purpose of the Company is to engage in the natural gas midstream business, including but not limited to natural gas gathering and processing, and the natural gas liquids processing, fractionation, transportation, storage and marketing businesses in the Area of Mutual Interest and to fulfill the obligations of the Company pursuant to any contract entered into by the Company or under which the Company has assumed obligations of any Person (the “Primary Business”), and to engage in any other business or activity that now or in the future may be necessary, incidental, proper, advisable or convenient to accomplish the foregoing purpose and that is not forbidden by the law of the jurisdiction in which the Company engages in such business or activity.

(b)           In no event shall this Agreement be held or construed to imply the existence of a partnership (including a limited partnership) or joint venture among the Members and no Member shall be held or construed to be a partner or joint venturer of any other Member, for any purposes other than federal and state tax purposes.  No Member shall have any power or authority under this Agreement to act as the agent or representative of the Company or any other Member with regard to any matter beyond the scope of this Company.

Section 3.2             Powers of the Company.

The Company shall have all powers and privileges granted by the Act, any other law, or by this Agreement, including incidental powers thereto, to the extent that such powers and privileges are necessary, customary, convenient or incidental to the attainment of the Company’s purpose.

Section 3.3             Projects, Restricted Projects, Exempted Projects and Out of Scope Projects.

(a)           As part of the Primary Business, the Company shall use commercially reasonable efforts to pursue the acquisition, development, construction and operation of natural gas gathering and processing, and natural gas liquids fractionation, transportation, storage and marketing assets described on Exhibit C (such activities, the “Base Project”).  From time to time, the Company may also pursue the acquisition, development, construction and operation of additional midstream assets in the Area of Mutual Interest in accordance with this Agreement (such activities, the “Additional Projects” and, collectively with the Base Project, the “Projects”).

(b)           No Class B Member (either directly or indirectly through one or more Affiliates) shall, own, operate, manage, control, engage in, participate in, invest in, finance, render services for, assist others in, or otherwise carry out any Primary Business (a “Restricted Project”) other than through the Company, without Requisite Member Approval, except as follows (any Restricted Project engaged in pursuant to one of the following exceptions is an “Exempted Project”):

(i)            MWE Liberty or its Affiliates may engage in a Restricted Project outside the Company without Requisite Member Approval if the pursuit of such Restricted Project by the Company does not receive approval of the Board pursuant to Section 6.1 and Requisite Member Approval pursuant to Section 6.12, and the Company therefore is unable to pursue the Restricted Project;

(ii)           MWE Hydrocarbon may perform its obligations under that certain Fractionation and NGL Purchase Agreement, dated as of the date hereof, by and between MWE

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Hydrocarbon and the Company in the form attached hereto as Exhibit K (the “Fractionation and NGL Purchase Agreement”); and

(iii)          A Class B Member or its Affiliates may ** as part of ** Restricted Projects, provided that ** such Class B Member ** the Company ** of ** as ** the Class B Member.  In connection with ** the Company and the other Members **.  Members holding Interests with an aggregate Percentage Interest ** Class B Member ** shall have the ** this Section 3.3(b)(iii) (which, for clarity purposes, shall not **).  Such Members may, by written notice to the Company ** the Class B Member ** the Class B Member ** the Class B Member **.  For the avoidance of doubt, ** the Restricted Project shall have ** prior to **.  In the event that ** the Restricted Project, the ** the Class B Member ** the Class B Member or ** the Class B Member.  ** Class B Member ** the Company.

Each Member recognizes and affirms that in the event of breach by such Member of any of the provisions of this Section 3.3(b), money damages may be inadequate and the non-breaching Members may have no adequate remedy at law.  Accordingly, each Member agrees that the non-breaching Members shall have the right, in addition to any other rights and remedies existing in their favor, to enforce their rights and each of the Members’ obligations under this Section 3.3(b) not only by an action or actions for damages, but also by an action or actions for specific performance, injunctive and/or other equitable relief in order to enforce or prevent any violations (whether anticipatory, continuing or future) of the provisions of this Section 3.3(b).

(c)           The Company and the Members recognize that: (i) NGPMR and its Affiliates own and will own substantial equity interests in other companies (existing and future) that participate in the energy industry (“NGPMR Portfolio Companies”) and have in the past and will in the future enter into advisory service agreements with such NGPMR Portfolio Companies; (ii) the NGPMR Representatives who serve as Managers also serve as principals of other NGPMR Portfolio Companies; and (iii) at any time, other NGPMR Portfolio Companies may be in direct or indirect competition with the Company and/or its Subsidiaries.  The Company and the Members acknowledge and agree that NGPMR, its Affiliates and NGPMR Representatives: (A) shall not be prohibited or otherwise restricted by their relationship with the Company and its Subsidiaries from engaging in the business of investing in NGPMR Portfolio Companies, entering into agreements to provide services to such NGPMR Portfolio Companies or acting as directors or advisors to, or other principals of, such NGPMR Portfolio Companies, regardless of whether such activities are in direct or indirect competition with the Company or the Primary Business, (B) shall not have any obligation to offer the Company or its Subsidiaries any business opportunity resulting from NGPMR and its Affiliates’ ownership in the NGPMR Portfolio Companies, and (C) the Company and the Members hereby renounce any interest or expectancy in any such business opportunity pursued by NGPMR, its Affiliates, the NGPMR Representatives or another NGPMR Portfolio Company and waive any claim that any such business opportunity constitutes a corporate, partnership or other business opportunity of the Company or any of its Subsidiaries; provided, however, that nothing contained in this Section 3.3(c) is intended to limit the confidentiality obligations in Section 5.4 and NGPMR, its Affiliates, the NGPMR Portfolio Companies and the NGPMR Representatives are expressly prohibited from using any Confidential Information (i) to pursue any such business opportunity, (ii) in providing services to the NGPMR Portfolio Companies or (iii) in acting as directors or advisors to, or other principals of, such companies.

(d)           No Member or its Affiliates shall have any obligation to communicate or offer any Out of Scope Projects to the Company or the other Members.  The Members acknowledge and agree that each Member, and their respective Affiliates, may presently or in the future engage in and/or possess an interest in other business ventures of every nature and description, independently or with others, outside of the Area of Mutual Interest, whether or not such business ventures are within the scope of the

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Primary Business, or within the Area of Mutual Interest, so long as such ventures constitute Out of Scope Projects or Exempted Projects, and neither the Company nor any other Members shall have any right by virtue of this Agreement in and to any Out of Scope Projects or Exempted Projects, or to the income or profits derived therefrom.

ARTICLE 4
CAPITAL CONTRIBUTIONS, MEMBER INTERESTS,
CAPITAL ACCOUNTS AND FUTURE CAPITAL REQUIREMENTS

Section 4.1             Capital Contributions.

(a)           Initial Capital Contributions.

(i)            At Closing, MWE Liberty and NGPMR shall have made the respective Capital Contributions (each, an “Initial Capital Contribution”) to the Company in the amounts set forth on Exhibit B in exchange for the initial Percentage Interest and the type of Interest set forth on Exhibit B.  In connection with such contributions, the Company, MWE Liberty and NGPMR shall execute the Contribution Agreement in order to effect the contribution to the Company of the cash consideration comprising NGPMR’s Initial Capital Contribution and the assets comprising MWE Liberty’s Initial Capital Contribution.  The Members hereby acknowledge and agree that the gross fair market value of MWE Liberty’s Initial Capital Contribution shall equal the actual out-of-pocket costs incurred by MWE Liberty and its Affiliates that specifically relate to developing the assets to be contributed and the established value of other property to be contributed by MWE Liberty to the Company pursuant to the Contribution Agreement, but that such actual cost will not be finally determinable as of the date hereof and is subject to adjustment as set forth in Section 4.1(a)(ii) below.

(ii)           As soon as reasonably practicable following the Closing, and in any event within ninety (90) days thereafter, MWE Liberty shall prepare and deliver to NGPMR a schedule, prepared by MWE Liberty in good faith that describes in reasonable detail the actual out-of-pocket costs incurred by MWE Liberty that specifically relate to the assets contributed by MWE Liberty pursuant to the Contribution Agreement (the “Final Calculations”).  The Final Calculations shall separately identify (A) actual out-of-pocket costs incurred by MWE Liberty and its Affiliates through December 31, 2008 that specifically relate to developing assets contributed, plus the established value of other property contributed, by MWE Liberty to the Company pursuant to the Contribution Agreement, which collectively correspond to MWE Liberty’s initial Investment Balance after taking into account the adjustment provisions in Section 4.8 (the “Investment Balance Costs”) and (ii) the **.

(iii)          NGPMR shall have the right to review and verify the Final Calculations.  MWE Liberty shall provide NGPMR reasonable access to its records and employees and shall cooperate and cause the Company to cooperate in all reasonable respects with NGPMR in connection with its review of such work papers and other documents and information relating to the Final Calculations.  If within thirty (30) days after NGPMR’s receipt of the Final Calculations, NGPMR shall not have given written notice to MWE Liberty of objection thereto, then NGPMR shall be deemed to have accepted the Final Calculations, which shall then be final, binding and conclusive for all purposes hereunder.  In the event that NGPMR gives written notice of any objection to the Final Calculations (an “Objection Notice”) within such thirty (30) day period, then NGPMR and MWE Liberty will use all commercially reasonable efforts to resolve the disputed matter(s) within the thirty (30) day period following the delivery of such Objection Notice.  If, at the end of the thirty (30) day resolution period, the parties are unable to resolve any

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disagreement between them with respect to the preparation of the Final Calculations, then each party shall deliver simultaneously to a nationally recognized accounting firm mutually agreed on by the parties (the “Accountants”) (i) the Objection Notice and such work papers, invoices and other reports and information relating to the disputed matter(s) as the Accountants may request and (ii) such party’s proposed resolution of the disputed matter(s) and any materials it wishes to present to justify the resolution it so presents.  MWE Liberty and NGPMR shall each be afforded the opportunity to discuss the disputed matter(s) with the Accountants.  The Accountants, acting as experts and not as arbitrators, shall have thirty (30) days to carry out a review and prepare a written statement of its determination regarding the disputed matter(s) (including a statement regarding the Accountants’ determination of the prevailing party in any such disputed matter) which determination shall be final and binding upon NGPMR and MWE Liberty.  Any fees and expenses of the Accountants incurred in resolving the disputed matter(s) shall be borne equally by NGPMR, on the one hand, and by MWE Liberty, on the other hand.

(iv)          The aggregate amount of MWE Liberty’s Initial Capital Contribution finally determined pursuant to this Section 4.1(a) shall be referred to as the “Final Cost.”  Upon determination of the Final Cost, MWE Liberty’s Initial Capital Contribution and Investment Balance (pursuant to Section 4.8) shall be adjusted to reflect such Final Cost; provided that in no event shall **.

(v)           In the event that the Final Cost reflects that the Investment Balance Costs are greater or less than the Investment Balance of MWE Liberty initially specified on Exhibit B, a corresponding adjustment shall be made to MWE Liberty’s Investment Balance to reflect such amount determined as part of the Final Cost.

(vi)          In the event that the Final Cost reflects that the **, MWE Liberty shall within two Business Days pay to the Company in immediately available funds an amount equal to such difference; in the event that the Final Cost reflects that the **, the Company shall within two Business Days pay to MWE Liberty in immediately available funds an amount equal to such difference.

(b)           Additional Capital Contributions Prior to the Equalization Date.

(i)            The Class A Members hereby collectively agree to make additional cash Capital Contributions of $** to the Company on ** upon receipt by each Class A Member, at least ten Business Days prior to each of such dates, of a Bring Down Certificate from the Company and a Capital Call properly made by the Board to such Class A Members for such amount.  In the event that any of these Capital Contributions are made by the Class A Members prior to the respective dates set forth in the preceding sentence, such Capital Contributions shall be deemed to be made as of such dates.  No Class A Member shall have an obligation to make a Capital Contribution pursuant to this Section 4.1(b)(i) unless the Company has issued a Bring Down Certificate to such Class A Member and the Board has issued a Capital Call to such Class A Member.  Upon contribution of the Class A Member’s Initial Capital Contribution and each of the additional Capital Contributions pursuant to this Section 4.1(b)(i), the Class A Members shall have no obligation to contribute any additional capital to the Company other than pursuant to Section 4.1(b)(iii).

(ii)           The Class B Members hereby agree to make additional Capital Contributions to the Company, on an as needed basis, until the occurrence of the Equalization Date.  Prior to the occurrence of the Equalization Date, at each time when the Company requires additional capital, the Board shall issue a Capital Call to the Class B Members, and the Class B

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Members shall contribute to the Company the amount of capital so requested, in accordance with their respective Class B Percentage Interests, within ten days after receipt of such Capital Call.  Notwithstanding the foregoing, the Class B Members shall not make any Capital Contributions pursuant to this Section 4.1(b)(ii) and the Company shall not issue any Capital Calls for any such Capital Contributions unless and until each of the Capital Contributions by the Class A Members set forth in Section 4.1(b)(i) have been spent by the Company or committed to be spent in accordance with an Approved Budget.

(iii)          The Class B Members hereby agree that, any distributions of Available Cash payable to a Class B Member pursuant to Section 8.1(a) prior to the earlier to occur of (i) December 31, 2010 and (ii) the Equalization Date shall be distributed and automatically reinvested by each Class B Member as additional Capital Contributions, without the issuance of any Capital Call.  In accordance with Section 8.1(a), the Class A Members acknowledge and agree that they shall not receive any distributions of Available Cash prior to the earlier to occur of (i) December 31, 2010 and (ii) the Equalization Date; provided, however that the amount that each Class A Member would have received if Available Cash were distributed prior to the earlier of (i) December 31, 2010 and (ii) the Equalization Date, shall increase the Investment Balance of such Class A Member on a dollar-for-dollar basis.  Once the Equalization Date has occurred, Available Cash shall be distributed in accordance with Section 8.1(b)(ii).

(c)           Capital Contributions After the Equalization Date.  Upon contribution of the Class A Member’s Initial Capital Contribution and each of the additional Capital Contributions pursuant to Section 4.1(b)(i), no Class A Member shall be obligated to contribute additional capital to the Company except as agreed upon by such Class A Member pursuant to this Section 4.1(c).  If the Company requires additional capital to pursue any Project or in connection with the operation of the Primary Business after the Equalization Date, then, with respect to funding for Projects or operations within the then current Approved Budget, the Class A Members shall elect (such election, a “Quarterly Budgeted Funding Election”) on a quarterly basis whether to contribute additional capital that may be required to fund such Projects or operations for the upcoming calendar quarter based on their respective Percentage Interests.  Such Quarterly Budgeted Funding Election shall be irrevocable, and shall be made in writing (which may include electronic mail) to the Company no less than 30 days prior to the commencement of the upcoming calendar quarter.  If one or more Class A Members elect not to participate, or fail to make any election (which shall be deemed to be an election not to contribute), then such Non-Contributing Member(s) shall have no obligation to contribute additional capital to fund Projects or operations within the then current Approved Budget for such upcoming calendar quarter.  With respect to each Contributing Member, at least ten days prior to the beginning of such calendar quarter, the Board shall issue to such Contributing Member a Capital Call that identifies the amount of capital that the Company needs in connection with such Projects or operations for such quarter.  Each Contributing Member shall contribute such requested capital to the Company within ten days after the issuance of each such quarterly Capital Call.

After the Equalization Date, the Class B Member(s) may contribute on a quarterly basis all additional capital (less any capital to be contributed by the Contributing Members for such upcoming calendar quarter) required to fund Projects or operations within the then current Approved Budget for the upcoming calendar quarter, including any capital required to reduce any capital shortfall that may result from Non-Contributing Member elections during such calendar quarter; provided, that the Class B Member(s) shall provide written notice to the other Members on a quarterly basis regarding their decision to fund additional capital and the amount of such Capital Contribution.

For the avoidance of doubt, the Percentage Interests of the Members shall be subject to adjustment (upward and downward) pursuant to this Section 4.1(c), based upon the Members’ respective

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Investment Balances giving effect to such additional Capital Contributions. If elections to contribute capital by the Contributing Members and the Class B Member(s) are less than the total amount of capital required by the Company pursuant to this Section 4.1(c), then the Company may seek to obtain the requested capital from third parties, which may include issuing additional Interests in the Company pursuant to Sections 5.3 and subject to Section 5.7, if applicable.

Section 4.2             Capital Contribution Defaults.

If a Member fails to contribute any capital to the Company that is required to be so contributed pursuant to Section 4.1, such Member shall be considered in default (a “Defaulting Member”), but shall remain fully obligated to contribute such capital to the Company.  The Company shall be entitled to pursue all remedies available at law or in equity against the Defaulting Member, including any one or more of the following:

(a)           the Company may take all actions, including court proceedings, as the other Members may deem appropriate, to obtain payment by the Defaulting Member of the required amount of the Capital Contribution remaining unpaid, together with interest thereon at the Default Rate from the date that the required Capital Contribution was required to be contributed to the Company until the date it is so contributed, at the cost and expense of the Defaulting Member; and

(b)           the non-defaulting Members may advance the portion of the Defaulting Member’s Capital Contribution that is in default, in accordance with the non-defaulting Members’ respective Percentage Interests, and, at the option of the non-defaulting Members, the non-defaulting Members making such advance may be deemed to have made a loan to the Defaulting Member in the amount of the Capital Contribution so advanced, which loan shall bear interest at the Default Rate from the date that such advance is made until the loan is repaid in full, and until such loan is repaid in full, the non-defaulting Members making such loan to the Defaulting Member shall be entitled to receive all distributions of Available Cash that would otherwise be payable to the Defaulting Member hereunder, in accordance with the non-defaulting Members’ respective Percentage Interests.

Section 4.3             Member’s Interest.

A Member’s Interest shall for all purposes be personal property.  Title to the Company’s assets, whether real, personal or mixed and whether tangible or intangible, shall be deemed to be owned by the Company as an entity, and no Member, Manager, Operator or officer of the Company shall have any ownership interest in such Company assets.

Section 4.4             Status of Capital Contributions.

(a)           Except as otherwise provided in this Agreement, no Member, or the successor or assign of a Member, may demand a return of its Capital Contributions, in whole or in part.  An unrepaid Capital Contribution is not a liability of the Company or of any Member.

(b)           No Member or Affiliate of any Member shall receive any interest, return, compensation or drawing with respect to its Capital Contributions or its Capital Account, except as otherwise specifically provided in this Agreement.

(c)           Except as otherwise provided in this Agreement, no Member shall be required to lend any funds or make any additional Capital Contributions to the Company.  No Member shall have any personal liability for the repayment of any other Member’s Capital Contribution or be required to

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contribute or lend any cash or property to the Company to enable the Company to repay any Member’s Capital Contributions.

Section 4.5             Capital Accounts.

(a)           A separate Capital Account shall be established and maintained for each Member in accordance with the requirements of Treasury Regulations Section 1.704-1(b)(2)(iv).  The original Capital Account established for any Member who acquires an Interest by virtue of an assignment in accordance with the terms of this Agreement shall be in the same amount as and shall replace the Capital Account of the assignor of such Interest.  To the extent such Member acquires less than all of the Interest of the assignor of the Interest so acquired by such Member, the original Capital Account of such Member and its Capital Contributions shall be in proportion to the Interest it acquires, and the Capital Account of the assignor who retains an Interest shall be reduced in proportion to the Interest it retains.

(b)           The Capital Account of each Member shall be maintained in accordance with the following provisions:

(i)            to such Member’s Capital Account there shall be credited such Member’s Capital Contributions, such Member’s distributive share of Profits, special allocations of income and gain, and the net amount of any Company liabilities that are assumed by such Member or that are secured by any Company assets distributed to such Member;

(ii)           to such Member’s Capital Account there shall be debited the amount of cash and the Gross Asset Value of any Company assets distributed to such Member pursuant to any provision of this Agreement, such Member’s distributive share of Losses, special allocations of loss and deduction, and the net amount of any liabilities of such Member that are assumed by the Company or that are secured by any property contributed by such Member to the Company;

(iii)          in determining the amount of any liability for purposes of this Section 4.5(b), there shall be taken into account Section 752(c) of the Code and any other applicable provisions of the Code and the Treasury Regulations; and

(iv)          the Capital Accounts shall be increased or decreased upon a revaluation of Company property pursuant to clause (b) of the definition of Gross Asset Value in the manner prescribed in Treasury Regulation Section 1.704-1(b)(2)(iv)(f).

Section 4.6             Capital Accounts Generally.

(a)           Except as otherwise provided in this Agreement, whenever it is necessary to determine the Capital Account of any Member for any purpose hereunder, the Capital Account of such Member shall be determined after giving effect to all adjustments provided for in Section 4.5 for the current Fiscal Year in respect of transactions effected prior to the date such determination is to be made.

(b)           No Member shall be entitled to withdraw any part of its Capital Account, or to receive any distribution from the Company except as specifically provided in this Agreement.

Section 4.7             Preferred Return.

For the avoidance of doubt, the Class A Interests shall accrue the Preference Amount until the Equalization Date, after which time the Preference Amount shall no longer accrue.

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Section 4.8             Investment Accounts.

The Company shall maintain an investment account (an “Investment Account”) for each Member, the balance of which (the “Investment Balance”) shall represent the sum of a Member’s Initial Capital Contribution, any additional Capital Contributions made by a Member pursuant to Sections 4.1(b), 4.1(c) and 4.9, and with respect to each Class A Member, (i) the Preference Amount and (ii) the amount that is retained by the Company in accordance with Section 4.1(b)(iii) and which such Class A Member would have otherwise received if Available Cash were distributed prior to the earlier to occur of (i) December 31, 2010 and (ii) the Equalization Date.  The Investment Balance for each Class A Member shall be reduced by any actual distributions to such member of Available Cash pursuant to Section 8.1(b)(i)(A) and Sections 13.4(a)(i)(A) and (B).  The Investment Balance of the Class B Members shall be reduced by the amount of any **, subject to adjustment pursuant to Section 4.1(a).  For the avoidance of doubt, the Investment Balance of each Member immediately following the Closing, after giving effect to Capital Contributions and reimbursements, shall be as set forth on Exhibit B.  An assignee of all or any portion of an Interest shall succeed to a portion of the assignor Member’s Investment Account in proportion to the Interest acquired.

Section 4.9             Equalization Target Date.

(a)           In the event that the Equalization Date has not occurred on or before **, then all distributions of Available Cash received by the MWE Liberty Group after ** pursuant to any provision of this Agreement shall automatically be contributed to the Company as additional Capital Contributions until the Equalization Date occurs.  If the Equalization Date has not occurred on or before December 31, 2011 (the “Equalization Target Date”), then the Class A Members holding at least a majority of the Class A Percentage Interests may elect by written notice to require MWE Liberty to make an additional cash Capital Contribution (the “True-Up Contribution”) sufficient to result in the Equalization Date occurring within ** after the Equalization Target Date.  MWE Liberty shall cause such True-Up Contribution to be made and the Equalization Date to occur within ** of the requesting notice of the requisite Class A Members.  To the extent that the Company does not have commitments to spend the True-Up Contribution in accordance with the Approved Budget (and any amendments or modifications to such Approved Budget approved prior to the date of the True-up Contribution) in effect at the time MWE Liberty is required to make the True-Up Contribution, then, at the end of the first full fiscal quarter following the date of the True-Up Contribution, the Company shall distribute any amount of the True-Up Contribution not spent or committed to be spent in accordance with such Approved Budget, and any approved amendments thereto, to the Members in accordance with their Percentage Interests.  For clarification purposes, it is the intent of the Members that the True-Up Contribution be an amount such that after payment of the True-Up Contribution is made by MWE Liberty, the Percentage Interest of the MWE Liberty Group is 60% and the Percentage Interest of the NGPMR Group is 40%.

(b)           If MWE Liberty fails to make the True-Up Contribution in accordance with Section 4.9(a) above, then the Interests held by the MWE Liberty Group shall not be ** of the Company; provided, however, that the then controlling Members shall not ** to the MWE Liberty Group in any material respect ** of the MWE Liberty Group.  Additionally, NGPMR shall have the ** subject to the provisions of ** to any Person, other than an Affiliate or partner of any member of the NGPMR Group or any NGPMR Portfolio Company, **, (B) all Members ** any Person, other than an Affiliate or partner of any member of the NGPMR Group or any NGPMR Portfolio Company, of all of ** or (C) the Company to ** other than an Affiliate or partner of any member of the NGPMR Group or any NGPMR Portfolio Company, **.

(c)           Within five days after receipt of any notice of **, the Board shall notify each Member, in writing, ** shall identify the **, including the form of the ** and provide a copy of **.  Each

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Member agrees that ** it will (i) take such action as may reasonably be required, including **, (ii) cause its designated Managers to take such action required, to **, (iii) provide for the execution of such agreements and such instruments and other actions reasonably necessary to provide, to the extent necessary, ** relating to such **, in each case only to the extent that **; provided that, no Affiliated Member Group shall be obligated in respect of any ** and referred to in the immediately preceding clause in such ** for an ** to such Affiliated Member Group in **.  The Member proposing ** shall have the right in connection with ** (or in connection with the **) to require the Company to cooperate fully with ** by taking all customary and other actions reasonably requested by the Member **, including making the ** reasonably available **, establishing a ** in connection with such processes and making ** activities, in each case subject to **. The Company and each Member shall provide assistance with respect to these actions as reasonably requested by the Member **. In addition, once ** under this Section 4.9, the Board shall be entitled to take all steps reasonably necessary to carry out **, including **; provided, however, that the rights granted the Board in this sentence shall not permit the Board to **.

ARTICLE 5
MEMBERS, MEETINGS AND AMENDMENTS

Section 5.1             Powers of Members.

(a)           Except for the right to consent to or approve certain matters as expressly provided in this Agreement, the Members in their capacity as Members shall not have any other power or authority to manage the business or affairs of the Company or to bind the Company or enter into agreements on behalf of the Company.

(b)           To the fullest extent permitted by law and notwithstanding any provision of this Agreement or any other document executed in connection with this Agreement (a “Transaction Document”) to the contrary, no Member in its capacity as a Member shall have any duty, fiduciary or otherwise, to the Company or any other Member in connection with the business and affairs of the Company or any consent or approval given or withheld pursuant to this Agreement or any other Transaction Document.

(c)           Any matter requiring the consent or approval of the Members pursuant to this Agreement may be taken without a meeting, without prior notice and without a vote, by a consent in writing, setting forth such consent or approval, and signed by Members holding Interests not less than the requisite Interests necessary to consent to or approve such action; provided that at least one Class A Member shall be required to sign such consent or approval in order for such consent to be effective in the event that the Class A Members did not receive prior written notice of the action to be so taken.  Prompt notice of such consent or approval shall be given by the Company to those Members who have not joined in such consent or approval.

Section 5.2             No Resignation or Expulsion.

A Member may not take any action to resign, withdraw or retire as a Member voluntarily, and a Member may not be expelled or otherwise removed involuntarily as a Member, prior to the dissolution and winding up of the Company, other than as a result of a Permitted Transfer of all of such Member’s Interests in accordance with Article 7 and each of the transferees of such Interests being admitted as a Substitute Member.

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Section 5.3             Additional Members.

(a)           After the Board makes a Capital Call pursuant to Section 4.1(c) that was not fully funded by the Members and subject to the preemptive rights set forth in Section 5.7 to the extent applicable, the Company is authorized to issue additional Interests and to admit any Person as an additional member of the Company (each, an “Additional Member” and collectively, the “Additional Members”).  Upon receipt of requisite approval of the Board and the Members, the Company is authorized to issue additional Interests and to admit any Person as an additional member of the Company (each, an “Additional Member” and collectively, the “Additional Members”).  Each such Person receiving additional Interests shall be admitted as an Additional Member at the time such Person (i) executes a counterpart signature page agreeing to be bound hereby and such other documents or instruments as may be required in the Board’s reasonable judgment to effect the admission, and (ii) is designated as a Member (with a corresponding Percentage Interest) on an amended or supplemental Exhibit B.  The Company may issue additional Interests or additional classes of membership interests to existing Members or to new or Additional Members in exchange for such Capital Contributions, including cash, property or services or any combination thereof.

(b)           Additional Members shall not be entitled to any retroactive allocation of the Company’s income, gains, losses, deductions, credits or other items; provided that, subject to the restrictions of Section 706(d) of the Code, Additional Members shall be entitled to their respective share of the Company’s income, gains, losses, deductions, credits and other items arising under contracts entered into before the effective date of the admission of any Additional Members to the extent that such income, gains, losses, deductions, credits and other items arise after such effective date.  To the extent consistent with Section 706(d) of the Code and Treasury Regulations promulgated thereunder, the Company’s books may be closed at the time Additional Members are admitted (as though the Company’s tax year had ended) or the Company may credit to the Additional Members pro rata allocations of the Company’s income, gains, losses, deductions, credits and items for that portion of the Company’s Fiscal Year after the effective date of the admission of the Additional Members.

Section 5.4             Confidentiality Obligations of Members.

(a)           Each Member agrees that all Confidential Information shall be kept confidential by the Member, shall only be used for the purpose of reviewing and evaluating the performance of the Company and the Member’s Interest therein, and shall not be disclosed in any manner, except to such of the Member’s Representatives who have a need to know and who agree to be, or are otherwise, bound by the Member’s obligations hereunder and except as otherwise expressly permitted in this Section 5.4.  Each Member shall be responsible for any breach of this Section 5.4 by itself or any of its Representatives, and each Member covenants and agrees that it shall promptly notify the Company of any actual, potential or threatened breach of this Section 5.4 and shall, at its own expense, enforce, and assist the Company in its enforcement of, the provisions of this Section 5.4, including, to the extent reasonably necessary, seeking specific enforcement through court proceedings.  Subject to Section 5.4(b), if a Member or any of its Representatives is requested or required by applicable law, rule or regulation, regulatory authority, subpoena, civil investigation, court order, demand or similar legal process to disclose any Confidential Information, the Member shall, to the maximum extent permitted by applicable law, provide the Company with prompt written notice thereof and will use reasonable efforts to resist disclosure, until an appropriate protective order or motion to quash may be sought or a waiver of compliance with this Section may be granted.  If, in the absence of a protective order or the receipt of a waiver hereunder, such Member or any of its Representatives is, in the opinion of its legal counsel, legally required to disclose Confidential Information, then such Member or its Representatives may disclose only that portion of the Confidential Information legally required to be disclosed, without liability hereunder, provided that such Member or its Representatives uses reasonable efforts to obtain reliable assurance that

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confidential treatment will be accorded the Confidential Information.  Each Member acknowledges and agrees that the Company and the other Members may be irreparably harmed by disclosure of the Confidential Information, that money damages would not be a sufficient remedy for any breach of this Section 5.4 by such Member or its Representatives and that, in addition to any other remedies available at law or in equity, specific performance and injunctive or other equitable remedies shall be available to the Company and the Members as a remedy for any such breach or threatened breach, without the requirement of posting bond or other security.  The Company and the other Members shall be entitled to recover their costs and expenses, including attorneys’ fees, incurred in connection with any successful action brought by them to enforce the terms of this Agreement.  With respect to Confidential Information that is subject to confidentiality agreements under any Third Party Confidentiality Agreements, each Member covenants and agrees to, and shall cause its Representatives to, treat such Confidential Information confidentially in accordance with, and to comply with the terms of, the confidentiality provisions contained in those Third Party Confidentiality Agreements that have been disclosed to such Member, including, any provisions thereof that impose more stringent or additional obligations than those set forth herein (provided such has been disclosed to such Member).  The obligations of a Member pursuant to this Section 5.4 shall continue following the time such Person ceases to be a Member, but thereafter such Person shall not have the right to enforce the provisions hereof.  Notwithstanding anything set forth herein, all covenants made herein by a Member are for the sole benefit of the Company and the other Members and there shall be no third party beneficiaries of any of such covenants.

(b)           Notwithstanding anything to the contrary in this Agreement, each Member may disclose any information about the Company, including any Confidential Information, without any liability to the Company or to any other Member or to their respective Affiliates and without any notice to any Member, to the extent that such disclosing Member believes that such disclosure is necessary or appropriate to satisfy its public disclosure obligations under the Securities Act, the Exchange Act, the rules of any stock exchange, or any similar public disclosure obligations.

Section 5.5             Initial Budget.

By execution of this Agreement, the Members hereby approve and consent to the initial budget attached hereto as Exhibit D (the “Initial Budget”) and acknowledge and agree that such Initial Budget shall be deemed to be an Approved Budget for all purposes of this Agreement.

Section 5.6             Incentive Interests to MWE Liberty Upon Transfer of NGPMR’s Interest.

In the event NGPMR receives cash from any NGPMR Exit Transaction or Partial NGPMR Exit Transaction (for the purposes of this section, such transaction an “Incentive Interest Transaction”) that would result in ** Payout**, simultaneously with the consummation of any such transaction, NGPMR shall pay to MWE Liberty as a fee the following amount**, to the extent applicable:

** Following ** Payout Threshold, if any, an amount equal to the ** of (i) the cash proceeds of all Incentive Interest Transactions plus cumulative cash distributions to NGPMR in respect of its Interest, **

**

Exhibit E contains illustrative examples of the calculation and operation of amount** payable pursuant to Section 5.6** based upon hypothetical Incentive Interest Transactions.  This Section 5.6 shall be interpreted and applied in a manner consistent with the examples set forth in Exhibit E. The obligations of NGPMR to make payment** to MWE Liberty pursuant to this Section 5.6 shall survive the closing of any

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NGPMR Exit Transaction or Partial NGPMR Exit Transaction and any liquidation, dissolution or winding up of the Company until such payment to MWE Liberty has been made.

Section 5.7             Preemptive Rights.

(a)           After the Equalization Date, prior to the Company issuing any Interests or options or rights to acquire Interests (other than (i) any equity issuance associated with an acquisition previously approved by NGPMR, (ii) Interests issued in connection with any split, distribution or recapitalization of the Company, (iii) Interests issued in any initial public offering registration statement filed under the Securities Act, or (iv) in connection with any capital raising or financing efforts by the Company the purpose of which is to fund any activities of the Company which were the subject of a Capital Call made pursuant to Section 4.1(c) that was not fully funded by the Members; provided, however, that any Interests to be issued in such capital raising or financing efforts, and the pricing of such Interests, are equivalent to the terms of such Capital Call), whether through exchange, conversion or otherwise (the “New Interests”), to a proposed third party purchaser (the “Proposed Purchaser”), each Member who is not in default of this Agreement and which certifies to the Company’s reasonable satisfaction that it is an “accredited investor” within the meaning of Rule 501 under the Securities Act (an “Eligible Member”) shall have the right to purchase a portion of the New Interests in accordance with this Section 5.7.

(b)           The Company shall give each Eligible Member prior written notice (the “First Notice”) of any proposed issuance of New Interests, which shall set forth in reasonable detail the proposed terms and conditions thereof (as determined by the Board in good faith) and shall offer to each Eligible Member the opportunity to purchase its Percentage Interest (as of the date of such notice) of the New Interests, on the same terms and conditions and at the same time as the New Interests are proposed to be issued by the Company.  If any Eligible Member desires to exercise its preemptive rights under this Section 5.7, it must deliver an irrevocable written notice within 30 days after the Eligible Member’s receipt of the First Notice (the “Election Period”) setting forth the dollar amount of the New Interests the Eligible Member (the “Electing Member”) is electing to purchase, up to its Percentage Interest plus any additional amount of New Interests it desires to purchase in excess of its Percentage Interest (the “Over-Allotment Amount”) if other Eligible Members do not exercise their preemptive rights hereunder.  The right of each Electing Member to purchase New Interests in excess of its Percentage Interest shall be based on the relative Percentage Interests of the Electing Members desiring to purchase Over-Allotment Amounts.

(c)           If the Eligible Members do not subscribe for all of the New Interests, the Company shall have the right, but not the obligation, to issue and sell the unsubscribed portion of the New Interests to the Proposed Purchaser at any time during the 90 days following the end of the Election Period, at the same price and pursuant to the terms and conditions set forth in the First Notice.  The Board may, in its reasonable discretion, impose such other reasonable and customary terms and procedures such as setting a closing date and requiring customary closing deliveries in connection with any preemptive rights offering.  In the event any Electing Member refuses to purchase the New Interests for which it subscribed pursuant to this Section 5.7, then in addition to any other rights the Company may have at law or in equity, such Electing Member and any transferee thereof shall not be considered an Eligible Member for any future rights granted under this Section 5.7 unless the Board expressly designates otherwise (which the Board may, in its sole discretion, do on an offer-by-offer basis or not at all) and shall be deemed a Defaulting Member under Section 4.2.

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Section 5.8             Registration Rights.

If the Board with Requisite Member Approval determines to effect a Qualified Public Offering, each of the Members shall be granted customary registration rights, including piggyback registration rights, with respect to such Qualified Public Offering.

ARTICLE 6
MANAGEMENT

Section 6.1             Management Under Direction of the Board.

Except as otherwise expressly provided in this Agreement or required under the Act, the business and affairs of the Company shall be managed by a board of managers (the “Board” and each member of the Board, a “Manager”), and the Board shall have full and complete authority, power, and discretion to manage and control the business, affairs, and properties of the Company, to make all decisions regarding those matters and to perform any and all other acts or activities customary or incidental to the management of the Company’s business.  Without limiting the generality of the foregoing the approval of the Board shall be required for all matters not delegated by the Board to the Operator, the officers of the Company or to other authorized persons in accordance with Section 6.10, including approval of the following matters, which the Board shall not have the power to delegate to any Person, in each case except as otherwise approved in any Approved Budget:

(a)           Proposed Budgets for the Company, other than the Initial Budget;

(b)           distributions of Available Cash (including Tax Distributions);

(c)           efforts by the Company to raise additional capital, including the issuance of additional Interests or any options to acquire Interests and the issuance of additional equity interests or options to acquire equity interests in the Company’s subsidiaries;

(d)           incurrence or guarantee of Debt by the Company in excess of $**;

(e)           acquisitions or dispositions of assets by the Company in excess of $**;

(f)            commencing or resolving litigation;

(g)           election or removal of officers of the Company;

(h)           material contracts to which the Company (or a subsidiary of the Company) is a party or by which it is bound; and

(i)            the registration of any equity or debt securities of the Company or its subsidiaries under applicable United States federal or foreign securities laws or any public offering of equity or debt securities of the Company or its subsidiaries (including any Qualified Public Offering).

Section 6.2             Number, Tenure and Qualifications.

(a)           Prior to the Equalization Date, the Board shall be comprised of five Managers, designated as follows:

(i)            two Managers (each, a “Class A Manager”) designated by Class A Members with an aggregate Class A Percentage Interest of at least 50%; and

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(ii)           three Managers (each, a “Class B Manager”) designated by Class B Members with an aggregate Class B Percentage Interest of at least 50%.