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                                                               EXHIBIT 10.22 (f)

                                 AMENDMENT NO. 5
                                       TO
                          MERGER AND PURCHASE AGREEMENT

THIS AMENDMENT NO. 5 TO MERGER AND PURCHASE AGREEMENT (the "Fifth Amendment") is
made as of the 21st day of May, 1999, among Union Pacific Resources Company, a
Delaware corporation, Duke Energy Fuels, LP, now a wholly owned entity of Buyer,
and Duke Energy Field Services, Inc., a Colorado corporation.

         WHEREAS, the parties heretofore entered into a Merger and Purchase
Agreement dated November 20, 1998, which was amended by the Amendment No. 1
dated as of February 1, 1999, Amendment No. 2 dated as of March 5, 1999,
Amendment No. 3 dated as of March 30, 1999, and Amendment No. 4 dated as of
March 30, 1999 (collectively, the "Amended Agreement") (capitalized terms not
otherwise defined herein have the same meanings ascribed to such terms in the
Amended Agreement);

         WHEREAS, the parties hereto desire to amend the Amended Agreement as
described below by entering into this Fifth Amendment;

         NOW, THEREFORE, in consideration of the premises and the mutual
agreements, representations, warranties, provisions and covenants herein
contained, the parties hereto hereby agree as follows:

         1. Schedule 7.08(a) and 7.08(d) are hereby amended and restated in
their entirety as attached hereto.

         2. This Fifth Amendment is executed, and shall be considered, as an
amendment to the Amended Agreement and shall form a part thereof, and the
provisions of the Amended Agreement, as amended by this Fifth Amendment, are
hereby ratified and confirmed in all respects.

         3. This Fifth Amendment may be executed in any number of counterparts,
each of which shall be deemed an original, and all of which taken together shall
constitute but one and the same instrument. This Agreement shall become binding
only when each party hereto has executed and delivered to the other parties one
or more counterparts.

         IN WITNESS WHEREOF, the parties hereto have duly executed this Fifth
Amendment or have caused this Fifth Amendment to be duly executed by their
respective authorized officers as of the day and year first written above.



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                              UNION PACIFIC RESOURCES COMPANY


                              By:      /s/ Joseph A. LaSala
                                 -------------------------------------------
                              Name:    Joseph A. LaSala
                              Title:   Vice President, General Counsel
                                       And Corporate Secretary


                              DUKE ENERGY FUELS, LP
                              By:  Fuels Holding Company Operating LLC
                              Its: General Partner



                              By: /s/ J.W. Mogg
                                 -------------------------------------------
                              Name:    J. W. Mogg
                              Title:   President and CEO



                              DUKE ENERGY FIELD SERVICES, INC.


                              By: /s/ J.W. Mogg
                                 -------------------------------------------
                              Name:    J. W. Mogg
                              Title:   President



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