AMENDMENT No. 1
                                     To The
                      RESTATED AND AMENDED SAN JUAN UNIT 4
                      PURCHASE AND PARTICIPATION AGREEMENT
                                     Between
                      Public Service Company of New Mexico
                                       and
                     Utah Associated Municipal Power Systems

1.0      PARTIES

         This  Amendment  No. 1 to the  Restated  and  Amended  San Juan  Unit 4
Purchase and  Participation  Agreement  ("Amendment  No. 1") is made and entered
into this 27th day of October 1999, by and between PUBLIC SERVICE COMPANY OF NEW
MEXICO,  a New Mexico  corporation  ("PNM") and UTAH ASSOCIATED  MUNICIPAL POWER
SYSTEMS,  a political  subdivision of the State of Utah  ("UAMPS"),  hereinafter
sometimes  referred  to  individually  as  a  "Party"  or  collectively  as  the
"Parties."

2.0      RECITALS

         This  Amendment No. 1 is made with  reference to the  following  facts,
among others:

         2.1 The Restated and Amended San Juan Unit 4 Purchase and Participation
Agreement  (the "PPA") was entered into by the Parties as of May 27,  1993.  The
PPA  governs  the  purchase  by UAMPS  of a 7.028  percent  undivided  ownership
interest  in San Juan Unit 4 and  associated  common  facilities,  supplies  and
inventories and the operation  thereof by PNM as Operating Agent of the San Juan
Project.

         2.2 PNM and Tucson  Electric Power Company  ("TEP") only are parties to
the San Juan Project Co-Tenancy  Agreement (the "Co-Tenancy  Agreement") and the
San Juan Project Operating Agreement (the "Operating Agreement").


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         2.3 The  Co-Tenancy  Agreement  and the Operating  Agreement  have been
previously  amended by action of PNM and TEP,  through and including  Amendments
Number 10 to the Co-Tenancy Agreement and the Operating Agreement.

         2.4 The San Juan Project Construction  Agreement was terminated in 1995
by action of PNM and TEP.

         2.5 PNM, TEP, Century Power Company,  Southern  California Public Power
Authority ("SCPPA"),  the City of Farmington,  New Mexico ("Farmington"),  M-S-R
Public Power Agency ("M-S-R"), the Incorporated County of Los Alamos, New Mexico
("Los Alamos") and the City of Anaheim,  California ("Anaheim") entered into the
San Juan Project  Designated  Representative  Agreement  ("DR  Agreement") as of
April 29,  1994,  for the purpose of  complying  with the federal  Clean Air Act
Amendments  of 1990;  the DR  Agreement  was  thereafter  accepted  by UAMPS and
Tri-State  Generation and Transmission  Association,  Inc.  ("Tri-State") at the
time of  their  respective  purchases  of  ownership  interests  in the San Juan
Project.

         2.6 The owners of the San Juan Project,  including PNM and UAMPS,  have
negotiated  a  San  Juan  Project   Participation   Agreement  among  PNM,  TEP,
Farmington,  M-S-R,  Los  Alamos,  SCPPA,  Anaheim,  UAMPS  and  Tri-State  (the
"Participation  Agreement") to amend,  restate and replace in their entirety the
Co-Tenancy  Agreement  and  the  Operating  Agreement  and  to  set  out  in one
instrument all of the matters  previously  included in the Co-Tenancy  Agreement
and the Operating Agreement.

         2.7 The Participation  Agreement will, upon its effective date, provide
UAMPS with all the rights,  privileges and  obligations of a  "Participant,"  as
that  term  is  defined  in the  Participation  Agreement,  and is  intended  to
supersede  the  rights,   privileges  and   obligations  of  UAMPS  as  a  "Unit
Participant," as that term is defined in the Operating Agreement.


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         2.8 The Parties  desire to amend the PPA to harmonize  the PPA with the
Participation Agreement.

         NOW, THEREFORE, based on the foregoing recitals and in consideration of
the mutual  promises,  terms and covenants of this  Amendment No. 1, the Parties
hereby agree as follows:

3.0      TERM AND TERMINATION

         3.1 This Amendment No. 1 shall become effective as of the date on which
the Participation Agreement becomes effective.

         3.2  Sections  1.1, 1.2 and 1.3 of the PPA are amended to read in their
entirety as follows:

                1.1 This Agreement shall become  effective on the Effective Date
             and shall,  unless  terminated  earlier by the  Parties,  remain in
             effect until July 1, 2022; provided,  however,  that if the term of
             the  San  Juan  Project  Participation   Agreement,   dated  as  of
             ________________, 1999 (the "Participation Agreement") is extended,
             the term of this  Agreement  shall  be  extended,  without  further
             action of the Parties,  so that the terms of this  Agreement and of
             the Participation Agreement shall be coterminous.

         3.3      Section 1.4 is renumbered as Section 1.2.

4.0      CHANGES IN REFERENCES TO CO-TENANCY AGREEMENT
         AND OPERATING AGREEMENT

         4.1 Section 7 of the PPA is hereby  amended to read in its  entirety as
follows:

                7.1  Participation  Agreement.  Except as otherwise  provided in
             this  Agreement,  the rights and  obligations  of the Parties  with
             respect  to  the  San  Juan   Project  are  as  set  forth  in  the
             Participation  Agreement.  Any  reference in this  Agreement to any
             provision of the San Juan Project  Agreements shall be deemed to be
             a reference  to the  corresponding  or  successor  provision of the
             Participation Agreement.


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                7.2 PNM/UAMPS  Relationship.  The  relationship  between PNM and
             UAMPS with  respect to Unit 4 shall be governed  by this  Agreement
             and the Interconnection  Agreement. As between PNM and UAMPS, where
             a  specific  provision  of this  Agreement  is in  conflict  with a
             provision  in one or more of the San Juan Project  Agreements,  the
             provisions of this Agreement shall govern.

         4.2 Except as otherwise  provided herein,  the Participation  Agreement
shall be applicable to all aspects of UAMPS' ownership interest in San Juan Unit
4.

5.0      FINANCING

         5.1      Section 8.2 of the PPA is hereby deleted in its entirety.

6.0      PNM AS OPERATING AGENT

         6.1 Section 10 of the PPA is hereby  amended to read in its entirety as
follows:

                10.1 UAMPS  recognizes that PNM is the Operating  Agent, as that
             term is defined in Section 5.31 of the Participation Agreement.

                10.2  PNM's  responsibilities  as  Operating  Agent to UAMPS are
             described in Section 28 of the Participation Agreement.

7.0      APPLICABILITY OF CERTAIN PROVISIONS OF CO-TENANCY AGREEMENT

         7.1      Section 11 of the PPA is hereby deleted in its entirety.

8.0      ENTITLEMENT TO AND SCHEDULING OF POWER AND ENERGY 8.1 Section 12 of the
         PPA is hereby deleted in its entirety.

9.0      START-UP AND AUXILIARY POWER

         9.1 Section 13 of the PPA is hereby  amended to read in its entirety as
follows:

                13.1 The  provisions  of this  Section 13 shall  apply after the
             Closing Date. Each Party shall be obligated to provide its share of
             start-up  and  auxiliary  power  and  energy in  proportion  to its
             Participation Share in San Juan Unit 4 as provided in Section 17 of
             the Participation Agreement.  Any supplementary  arrangements which
             may be  required  to  facilitate  UAMPS'  supply  of  start-up  and
             auxiliary  power  and  energy  shall  be  made in  accordance  with
             procedures established by the Operating Committee,  as that term is
             defined in Section 7 of the Interconnection Agreement.


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10.0     CAPITAL BETTERMENTS, ADDITIONS AND REPLACEMENTS

         10.1     Section 14 of the PPA is hereby deleted in its entirety.

11.0     DEFAULTS

         11.1  Sections  19.5,  19.6 and 19.7 of the PPA are  hereby  deleted in
their entirety.

12.0     DISPUTES; ARBITRATION

         12.1 Section 20 of the PPA is hereby amended to read in its entirety as
follows:

                20.1 In the event  that a dispute  between  the  Parties  should
             arise under this  Agreement,  such dispute shall be first submitted
             to the PNM and  UAMPS  members  on the  Engineering  and  Operating
             Committee for resolution.  In the event these members are unable to
             resolve such dispute within ninety (90) days after submission,  the
             dispute  shall be  referred in writing to the  President  or a Vice
             President  designated  by PNM  and the  Chairman  of the  Board  of
             Directors of UAMPS, or his or her designee. If such dispute has not
             been  resolved  within  thirty (30) days after the referral made by
             either  Party  (unless  such  thirty (30) day period is extended by
             mutual agreement of the Parties),  either Party may thereafter call
             for  submission  of such dispute to  arbitration  in the manner set
             forth in  Section  37 of the  Participation  Agreement,  which call
             shall be binding upon the Parties, except that the notices required
             under  Section 37.1 of the  Participation  Agreement  shall only be
             provided  to the  Parties  to this  Agreement  unless  the  dispute
             between the Parties to this  Agreement  affects  the  interests  of
             other parties to the Participation Agreement.

13.0     DESTRUCTION, DAMAGE OR CONDEMNATION OF SAN JUAN UNIT 4

         13.1     Section 22 of the PPA is hereby deleted in its entirety.

14.0     RELATIONSHIP OF THE PARTIES

         14.1     Section 24.2 of the PPA is hereby deleted in its entirety.


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15.0     ASSIGNMENT, TRANSFER, CONVEYANCE OR OTHER DISPOSITION

         15.1 Section 29.2 of the PPA is hereby  amended to read in its entirety
as follows:

                29.2 Except as otherwise  specifically  provided in this Section
             29,  should UAMPS desire to assign,  transfer,  convey or otherwise
             dispose of ("Assign") the Transfer Interest to any person, company,
             corporation, governmental agency or other entity other than PNM (an
             "Outside  Party"),  PNM  shall  have a right  of first  refusal  to
             purchase  the Transfer  Interest.  Such right shall be exercised in
             accordance with the terms and conditions and the procedures set out
             in Section 11 of the Participation Agreement.

         15.2 Sections 29.3,  29.4,  29.5,  29.6, 29.7, 29.8 and 29.9 of the PPA
are hereby deleted in their entirety.

         15.3 Section 29.10 of PPA is hereby  renumbered as Section 29.3, and is
amended to read in its entirety as follows:

                29.3 UAMPS shall have a right of first  refusal  with respect to
             any sale,  transfer or other  disposition of all or any part of any
             interest  of PNM in Unit 4 (the "PNM  Transfer  Interest")  by PNM.
             UAMPS  shall  have no right of first  refusal  with  respect to any
             sale,  transfer or other disposition by any party of any part of or
             interest in Unit 1, Unit 2 or Unit 3; or in any such sale, transfer
             or  other  disposition  of any part of or  interest  in Unit 4 by a
             party  other  than PNM;  provided  further  that the right of first
             refusal  granted herein to UAMPS shall be subordinate to any rights
             of first refusal  previously  granted to other parties with respect
             to Unit 4.  Such  right  of first  refusal  shall  commence  on the
             Closing  Date,  shall  continue for the term of this  Agreement and
             shall be exercised in accordance  with the terms and conditions and
             the  procedures  set  out  in  Section  11  of  the   Participation
             Agreement.

         15.4 Sections 29.11, 29.12, 29.13, 29.14, 29.15, 29.16 and 29.17 of the
PPA are hereby deleted in their entirety.

16.0     NOTICES

         16.1  Section  30.1.2  of the  PPA is  hereby  revised  to  read in its
entirety as follows:

                  30.1.2     Utah Associated Municipal Power Systems
                             c/o General Manager
                             2825 E. Cottonwood Parkway
                             Suite 200
                             Salt Lake City, UT 84121


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17.0     CONTINUATION IN EFFECT

         17.1 Except as herein modified, all provisions of the PPA are unchanged
and continue in full force and effect.

         IN WITNESS WHEREOF,  the Parties have caused this Amendment No. 1 to be
executed  by their  duly  authorized  representatives  as of the date set  forth
above.

                                   PUBLIC SERVICE COMPANY OF NEW MEXICO

                                   By:       /s/ Patrick J. Goodman
                                       --------------------------------------
                                             Patrick J. Goodman
                                             Vice President, Power Production



                                   UTAH ASSOCIATED MUNICIPAL POWER
                                   SYSTEMS

                                   By:
                                       --------------------------------------
                                            Chairman, Board of Directors

[SEAL]
ATTEST:


-----------------------
Secretary

73200

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