MARKWEST HYDROCARBON, INC. 1996 STOCK INCENTIVE PLAN

(i)      “Eligible Person” shall mean any employee or officer of the Company or any Affiliate of any Director who the committee determines to be an Eligible Person.  A Director of the Company who is not also an employee of the Company or an affiliate may be an Eligible Person.

(j)      “Fair Market Value” shall mean, with respect to any property (including, without limitation, any Shares or other securities), the fair market value of such property determined by such methods or procedures as shall be established from time to time by the Committee.

(k)     “Incentive Stock Option” shall mean an option granted under Section 6(a) of the Plan that is intended to meet the requirements of Section 422 of the Code or any successor provision.

(l)      “Non-Qualified Stock Option” shall mean an option granted under Section 6(a) of the Plan that is not intended to be an Incentive Stock Option.

(m)    “Option” shall mean an Incentive Stock Option or a Non-Qualified Stock Option.

(n)     “Other Stock-Based Award” shall mean any right granted under Section 6(f) of the Plan.

(o)     “Participant” shall mean an Eligible Person designated to be granted an Award under the Plan.

(p)     “Partnership” shall mean MarkWest Hydrocarbon Partners, Ltd., a Colorado limited partnership.

(q)     “Performance Award” shall mean any right granted under Section 6(d) of the Plan.

(r)      “Person” shall mean any individual, corporation, partnership, association or trust.

(s)     “Plan” shall mean this 1996 Stock Incentive Plan, as amended from time to time.

(t)      “Reorganization Transactions” shall mean those transactions contemplated by the Reorganization Agreement to be entered into among the Company, the Partnership and the other parties thereto.

(u)     “Restricted Stock” shall mean any Share granted under Section 6(c) of the Plan.

(v)     “Restricted Stock Unit” shall mean any unit granted under Section 6(c) of the Plan evidencing the right to receive a Share (or a cash payment equal to the Fair Market Value of a Share) at some future date.

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(w)    “Rule 16b-3” shall mean Rule 16b-3 promulgated by the Securities and Exchange Commission under the Securities Exchange Act of 1934, as amended, or any successor rule or regulation.

(x)      “Shares” shall mean shares of Common Stock, $.01 par value, of the Company or such other securities or property as may become subject to Awards pursuant to an adjustment made under Section 4(c) of the Plan.

(y)     “Stock Appreciation Right” shall mean any right granted under Section 6(b) of the Plan.

(z)      “Director” shall mean a member of the Board of Directors of the Company.

Section 3. Administration .

(a)     Power and Authority of the Committee . The Plan shall be administered by the Committee. Subject to the express provisions of the Plan and to applicable law, the Committee shall have full power and authority to: (i) designate Participants; (ii) determine the type or types of Awards to be granted to each Participant under the Plan; (iii) determine the number of Shares to be covered by (or with respect to which payments, rights or other matters are to be calculated in connection with) each Award; (iv) determine the terms and conditions of any Award or Award Agreement; (v) amend the terms and conditions of any Award or Award Agreement and accelerate the exercisability of Options or the lapse of restrictions relating to Restricted Stock, Restricted Stock Units or other Awards; (vi) determine whether, to what extent and under what circumstances Awards may be exercised in cash, Shares, other securities, other Awards or other property, or canceled, forfeited or suspended; (vii) determine whether, to what extent and under what circumstances cash, Shares, other securities, other Awards, other property and other amounts payable with respect to an Award under the Plan shall be deferred either automatically or at the election of the holder thereof or the Committee; (viii) interpret and administer the Plan and any instrument or agreement relating to, or Award made under, the Plan; (ix) establish, amend, suspend or waive such rules and regulations and appoint such agents as it shall deem appropriate for the proper administration of the Plan; and (x) make any other determination and take any other action that the Committee deems necessary or desirable for the administration of the Plan. Unless otherwise expressly provided in the Plan, all designations, determinations, interpretations and other decisions under or with respect to the Plan or any Award shall be within the sole discretion of the Committee, may be made at any time and shall be final, conclusive and binding upon any Participant, any holder or beneficiary of any Award and any employee of the Company or any Affiliate. In exercising its authority pursuant to the Plan, the Committee shall adhere to all provisions of the Code as are applicable to the grant, issuance and exercise of any Award.

(b)     Replacement of Partnership Options . In addition to the power and authority granted to the Committee under Section 3(a) hereof, the Committee shall have full power and authority to make grants of Options to employees of the Partnership who shall become employees of the Company pursuant to the Reorganization Transactions, which grants shall be effective only on and after the Effective Date, and which Options shall serve to replace options held by such

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employees for equity in the Partnership by substantially equivalent rights to purchase Shares in the Company. The Committee shall determine, in its sole discretion, the terms and conditions of Award Agreements related to such Options.

(c)     Delegation . The Committee may delegate its powers and duties under the Plan to one or more officers of the Company or any Affiliate or a committee of such officers, subject to such terms, conditions and limitations as the Committee may establish in its sole discretion; provided , however , that the Committee shall not delegate its powers and duties under the Plan with regard to officers or directors of the Company or any Affiliate who are subject to Section 16 of the Securities Exchange Act of 1934, as amended.

Section 4. Shares Available for Awards .

(a)     Shares Available . Subject to adjustment as provided in Section 4(c), the number of Shares available for granting Awards under the Plan shall be 925,000. Shares to be issued under the Plan may be either Shares reacquired and held in the treasury or authorized but unissued Shares. If any Shares covered by an Award or to which an Award relates are not purchased or are forfeited, or if an Award otherwise terminates without delivery of any Shares, then the number of Shares counted against the aggregate number of Shares available under the Plan with respect to such Award, to the extent of any such forfeiture or termination, shall again be available for granting Awards under the Plan. The Company shall at all times keep available the number of Shares to satisfy Awards granted under the Plan.

(b)     Accounting for Awards . For purposes of this Section 4, if an Award entitles the holder thereof to receive or purchase Shares, the number of Shares covered by such Award or to which such Award relates shall be counted the date of grant of such Award against the aggregate number of Shares available for granting Awards under the Plan.

(c)     Adjustments . In the event that the Committee shall determine that any dividend or other distribution (whether in the form of cash, Shares, other securities or other property), recapitalization, stock split, reverse stock split, reorganization, merger, consolidation, split-up, spin-off, combination, repurchase or exchange of Shares or other securities of the Company, issuance of warrants or other rights to purchase Shares or other securities of the Company or other similar corporate transaction or event affects the Shares such that an adjustment is determined by the Committee to be appropriate in order to prevent dilution or enlargement of the benefits or potential benefits intended to be made available under the Plan, then the Committee shall, in such manner as it may deem equitable, adjust any or all of (i) the number and type of Shares (or other securities or other property) which thereafter may be made the subject of Awards, (ii) the number and type of Shares (or other securities or other property) subject to outstanding Awards and (iii) the purchase or exercise price with respect to any Award; provided , however , that the number of Shares covered by any Award or to which such Award relates shall always be a whole number.

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Section 5. Eligibility .

(a)     Designation of Participants . Any Eligible Person, including any Eligible Person who is an officer or director of the Company or any Affiliate, shall be eligible to be designated a Participant. In determining which Eligible Persons shall receive an Award and the terms of any Award, the Committee may take into account the nature of the services rendered by the respective Eligible Persons, their present and potential contributions to the success of the Company or such other factors as the Committee, in its discretion, shall deem relevant. Notwithstanding the foregoing, an Incentive Stock Option may only be granted to full or part-time employees (which term as used herein includes, without limitation, officers and directors who are also employees) and an Incentive Stock Option shall not be granted to an employee of an Affiliate unless such Affiliate is also a “subsidiary corporation” of the Company within the meaning of Section 424(f) of the Code or any successor provision.

(b)     Award Limitations Under the Plan . No Eligible Person, who is an employee of the Company at the time of grant, may be granted any Award or Awards, the value of which Awards are based solely on an increase in the value of the Shares after the date of grant of such Awards, for more than 20,000 Shares, in the aggregate, in any one calendar year, beginning with the period commencing on the Effective Date and ending on December 31, 2006. The foregoing annual limitation specifically includes the grant of any Awards representing “qualified performance-based compensation” within the meaning of Section 162(m) of the Code.

Section 6. Awards .

(a)     Options . The Committee is hereby authorized to grant Options to Participants with the following terms and conditions and with such additional terms and conditions not inconsistent with the provisions of the Plan as the Committee shall determine:

(i)        Exercise Price . The purchase price per Share purchasable under an Optio