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Exhibit 10.1    
  


PNG CORPORATION






	 	 	*	 	NATURAL GAS TRANSPORTATION, PURCHASING, SALES	 	*	 	 








	 	 	5100 WESTHEIMER, SUITE 320

HOUSTON, TEXAS 77056

TELEPHONE (713) 965-9151

FAX (713) 965-9156





April 11, 2003 


MarkWest
Hydrocarbon Inc.

155 Inverness Drive West

Suite 200

Englewood, Colorado 80112

Attention: John C. Mollenkopf 



 Assignment of Employment Agreement  




Gentlemen
and Ladies: 


        Reference
is made to the Employment Agreement, dated as of October 2002 (the "Employment Agreement"), between PNG Corporation, a Delaware corporation ("PNG"), and William G.
Janacek ("Janacek"). 


        This
letter will confirm that as of the Effective Time (as defined in the Plan of Merger, which is defined below) (i) PNG shall hereby assign to MarkWest Hydrocarbon Inc.,
a Delaware corporation ("MarkWest Hydrocarbon"), all of its rights and interests under the Employment Agreement, (ii) MarkWest Hydrocarbon shall hereby assume and agree to pay, perform and
discharge all of the debts, liabilities and obligations of PNG arising under the Employment Agreement and (iii) Janacek shall hereby consent to (a) the assignment by PNG and the
assumption by MarkWest Hydrocarbon provided for in clauses (i) and (ii) above and (b) the following provisions, notwithstanding any provisions in the Employment Agreement to the
contrary: 



        1)    Janacek
will not be President or Chief Operating Officer of MarkWest Hydrocarbon; 


        2)    Janacek
will not report to the board of directors of MarkWest Hydrocarbon; 


        3)    Janacek
will be the Vice President of an affiliate of MarkWest Energy Partners, L.P. and will report to an officer of MarkWest Energy Partners, L.P.; and 



        4)    Janacek's
primary job responsibilities will be materially similar to Janacek's job responsibilities at PNG, including, without limitation, the management of the assets
acquired by certain affiliates of MarkWest Energy Partners, L.P. pursuant to the Plan of Merger and business development related to MarkWest Energy Partners L.P. 




        This
letter will also confirm that each of MarkWest Hydrocarbon and Janacek acknowledges and agrees that, for purposes of the Employment Agreement, the Board of Directors of PNG has
approved and there has been consummated a sale of substantially all of the assets of PNG pursuant to the Plan of Merger, dated as of the date hereof, among certain subsidiaries of PNG and certain
affiliates of MarkWest Hydrocarbon (the "Plan of Merger"). 


        This
letter shall be binding upon, and shall inure to the benefit of the parties hereto and their respective successors and assigns and shall be governed by and construed in accordance
with the laws of the State of Texas, without regard to principles of conflicts of laws. 





 



        If
the foregoing is acceptable to you, please so indicate by placing your signature in the appropriate space set forth below, whereupon this letter shall become a binding obligation of
each of the undersigned. 



	 	 	Very truly yours,
	

 	
 	

PNG CORPORATION
	

 	
 	

By:	







	 	 	Name:	Ted Smith
	 	 	Title:	Senior Vice President & CFO





Agreed to, accepted,

and acknowledged as of

the date first written above: 


MARKWEST
HYDROCARBON INC. 



	By:	
	 	 





	Name:	
	 	 





	Title:	
	 	 
	

 William G. Janacek	
 	

 




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Exhibit 10.1