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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.
 
 
 
 

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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   
 

 
 

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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)