AMENDMENT TO GAS PROCESSING AGREEMENT

Exhibit 10.30

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 (**).

AMENDMENT TO GAS PROCESSING AGREEMENT

                This Amendment to Gas Processing Agreement (“Amendment”) is made and entered into this 11^th day of December, 2007, by and between Markwest Javelina Company (“Processor”) and CITGO Refining and Chemicals Company, L.P. (“Supplier”).

RECITALS

                A.            Processor and Supplier are parties to that certain Gas Processing Agreement made and entered into effective November 1, 2007 (the “Gas Processing Agreement”).

                B.            Processor and Supplier desire to enter into this Amendment to correct and clarify certain inadvertent mutual mistakes and omissions as contained in the Gas Processing Agreement executed by the parties.

                NOW, THEREFORE, in consideration of the mutual covenants and agreements contained herein, the parties agree as follows:

                1.             Section 10.1 of the Gas Processing Agreement is hereby amended to delete the date “July 1, 2007” and replace it with the date “November 1, 2007.”

                2.             The Gas Processing Agreement is hereby amended by deleting Exhibit B attached thereto and replacing it with the complete Exhibit B attached to this Amendment.

                3.             Except for the foregoing, all other terms and provisions of the Gas Processing Agreement shall remain in full force and effect.

                4.             This Amendment may be executed in counterparts, each of which shall be deemed an original but which together shall constitute one and the same instrument.

                IN WITNESS WHEREOF, this Amendment is executed effective by the parties as of the date hereof.

Supplier:

CITGO REFINING AND CHEMICALS COMPANY, L.P.

Processor:

MARKWEST JAVELINA COMPANY

EXHIBIT B

Plant Allocation Statement

Statement 1 of Exhibit B

Statement 1

Javelina Plant Allocation

Measurement and Analysis Data

Month, Year

Molecular Analysis

* All volumes and amounts are fictional and intended for this example only.

EXHIBIT B

Plant Allocation Statement

Statement 2 of Exhibit B

Statement 2

Javelina Plant Allocation

Plant Thermal Reduction "PTR"

Month, Year

* All volumes and amounts are fictional and intended for this example only.

EXHIBIT B

Plant Allocation Statement

Statement 3 of Exhibit B

Statement 3

Javelina Plant Allocation

Residue Gas Imbalance

Month, Year

* All volumes and amounts are fictional and intended for this example only.

EXHIBIT B

Plant Allocation Statement

Statement 4 of Exhibit B

Statement 4

Javelina Plant Allocation

Energy Expense Charge

Month, Year

* All volumes and amounts are fictional and intended for this example only.

EXHIBIT B

Plant Allocation Statement

Statement 5 of Exhibit B

Statement 5

Javelina Plant Allocation

Plant Net Proceeds Attributable to Supplier by Refinery and

Credit(s) due Processor on Curtailments

Month, Year

* All volumes and amounts are fictional and intended for this example only.

EXHIBIT B

Plant Allocation Statement

Statement 6 of Exhibit B

Statement 6

Javelina Plant Allocation

Supplier Proceeds Calculation

Month, Year

* All volumes and amounts are fictional and intended for this example only.