**Exhibit
        10.89**
 
 **AMENDMENT
        FOUR TO UNDERGROUND COAL SALES AGREEMENT**
 
 **THIS
        AMENDMENT FOUR TO UNDERGROUND COAL SALES AGREEMENT** (“Amendment Four”), by and between SAN JUAN COAL COMPANY, a Delaware corporation
        (referred to herein as “SJCC”) and PUBLIC SERVICE COMPANY OF NEW MEXICO, a New
        Mexico corporation, and TUCSON ELECTRIC POWER COMPANY, an Arizona corporation
        (collectively referred to herein as the “Utilities”) (with SJCC and Utilities
        herein sometimes collectively referred to as “Parties”), amends that certain
        Underground Coal Sales Agreement dated August 31, 2001 as amended (the “UG-CSA”)
        between SJCC and the Utilities.
 
 **RECITALS**
 
 **WHEREAS** , SJCC and
        the Utilities wish to add the April 24, 2006 modification to Federal Coal
        Lease
        NM 28093 as defined herein to the Coal Leases ;
  **NOW
        THEREFORE** ,
        in
        consideration of the terms, covenants and agreements contained in this Amendment
        Four and for other good and valuable consideration, the Utilities jointly
        and
        severally agree with SJCC as follows:
 
 **AGREEMENT**
 
 1.
            The
                April 24, 2006 modification to Federal Coal Lease NM 28093 is hereby
                added
                to the Coal Leases. Specifically, the UG-CSA is amended by adding
                the
                following coal lease description to Exhibit “A” “Coal
                Leases”:  **NM
        28093 Mod 1 - April 2006 modification to Federal Coal Lease NM 28093, the
        Deep
        Lease, approx. 160.6 acres.**
 Township
        29 North, Range 15 West, NMPM, approx. 160.6 acres
 Section
        1: Lots 3-4, S/2NW/4
 The
        attached map will replace the current map in Exhibit A.
  2.
            The
                UG-CSA is amended by deleting the following language at the end of
                the
                paragraph in Section A of Exhibit “F” Operating
                Costs.  and
        the
        lease acquisition costs for NM HC-0004. Recovery of the NM HC-0004 lease
        acquisition costs and other costs incurred in acquiring, developing, assessing,
        or otherwise preparing for delivery of coal from NM HC-0004 shall be pursuant
        to
        the UG-CSA and contingent on delivery of coal to Utilities from NM
        HC-0004.
  And
        replacing it with:
  and
        the
        lease acquisition costs for NM HC-0004 and NM 28093 Mod 1. Recovery of the
        NM
        28093 Mod 1 lease acquisition costs and other costs incurred in acquiring,
        developing, assessing, or otherwise preparing for delivery of coal from NM
        28093
        Mod 1 shall be pursuant to the UG-CSA and contingent on delivery of coal
        to
        Utilities from NM 28093 Mod 1.
   
  3.
            All
                other provisions of the UG-CSA not specifically amended by this Amendment
                Four remain in full force and effect. Except as otherwise stated,
                the
                terms of this Agreement shall be effective upon execution by all
                Parties.  **IN
        WITNESS WHEREOF** ,
        the
        Parties hereto have caused this Agreement to be executed on their behalf
        by
        their respective officers, thereunto duly authorized.
 
 Public
        Service Company of New Mexico
  
 By:  /s/
        Hugh W. Smith
 Name:  Hugh
        W. Smith
 Title: Senior
        Vice President, Energy Resources   Date:  3/7/07
 
 
 Tucson
        Electric Power Company
 
  By:  /s/
        Michael J. DeConcini
 Name:  Michael
        J. DeConcini
 Title:  Senior
        VP       Date:  9/21/06
 
 
 San
        Juan
        Coal Company
  
 By:  /s/
        Evan Y. Jones
 Name:  Evan
        Y. Jones
 Title:  VP
        SJCC       Date:  9/13/06
   
 
 CONSENT
        OF GUARANTOR
 
 BHP
        Minerals International Inc., a Delaware corporation, (formerly BHP-Utah
        International Inc.), the guarantor of the obligations of San Juan Coal Company
        under the Underground Coal Sales Agreement pursuant to the Guarantee dated
        September 25, 2001 (the Guarantee”), hereby consents to the foregoing Amendment
        Four to the Underground Coal Sales Agreement and agrees that all references
        in
        the Guarantee to the Underground Coal Sales Agreement shall be deemed to
        be
        references to the Underground Coal Sales Agreement as amended by this Amendment
        Four.
  
 BHP
        Minerals International, Inc.
  
 By:  /s/
        Earl K. Moore
 Name:  Earl
        K. Moore
 Title:  President      Date:  December
        7, 2006
 
  
 By:  /s/
        M.
        Ruth Rhodes
 Name:  M.
        Ruth Rhodes
 Secretary      Date:  December
        7, 2006
 
 
 
 (Corporate
        Seal)