Exhibit 10.7

                              FOUR CORNERS PROJECT

                              CO-TENANCY AGREEMENT
                                 AMENDMENT NO. 6
                                      AMONG

                         ARIZONA PUBLIC SERVICE COMPANY
                            EL PASO ELECTRIC COMPANY
                      PUBLIC SERVICE COMPANY OF NEW MEXICO
                   SALT RIVER PROJECT AGRICULTURAL IMPROVEMENT
                               AND POWER DISTRICT
                       SOUTHERN CALIFORNIA EDISON COMPANY
                          TUCSON ELECTRIC POWER COMPANY



                                EXECUTED ORIGINAL
                                February 3, 2000

                              FOUR CORNERS PROJECT

                              CO-TENANCY AGREEMENT
                                 AMENDMENT NO. 6

1    PARTIES:

     The parties to this Amendment No. 6 to the Four Corners Project  Co-Tenancy
     Agreement  are:  ARIZONA  PUBLIC SERVICE  COMPANY,  an Arizona  corporation
     (hereinafter  referred to as "Arizona");  EL PASO ELECTRIC COMPANY, a Texas
     corporation  (hereinafter referred to as "El Paso"); PUBLIC SERVICE COMPANY
     OF NEW MEXICO, a New Mexico  corporation  (hereinafter  referred to as "New
     Mexico");  SALT RIVER PROJECT AGRICULTURAL  IMPROVEMENT AND POWER DISTRICT,
     an agricultural improvement district, organized and existing under the laws
     of the State of Arizona (hereinafter  referred to as "Salt River Project");
     SOUTHERN CALIFORNIA EDISON COMPANY, a California  corporation  (hereinafter
     referred to as "Edison");  and TUCSON  ELECTRIC POWER  COMPANY,  an Arizona
     corporation,  formerly known as Tucson Gas & Electric Company  (hereinafter
     referred  to as  "Tucson"),  (collectively  hereinafter  referred to as the
     "Participants").

2    RECITALS:

     This Amendment No. 6 is made with reference to the following  facts,  among
     others:

     2.1  As of July 19, 1966,  the  Participants  entered into the Four Corners
          Project  Co-Tenancy  Agreement,   which  has  since  been  amended  by
          Amendment Nos. 1 through 5 (as so amended  hereinafter  referred to as
          the "Co-Tenancy Agreement").

     2.2  The  Participants  wish to further amend the  Co-Tenancy  Agreement in
          order to:

         2.2.1 Revise  Section  6.11 to  require a selling  Participant  to give
               written  notice of any  changes in  ownership  and to require the
               Operating Agent to prepare for signature an amendment  reflecting
               such changes in ownership;

         2.2.2 Revise  Sections  5.27 and 9.5 to clarify that  Participants  may
               only vote on actions or determinations relating to those portions
               of the Four  Corners  Project  in which  they  have an  ownership
               interest;

         2.2.3 Permit  a  Participant  to  transfer  in  whole  or in  part  its
               undivided  interests in the Four Corners Project to the parent of
               such  Participant or to a wholly owned  subsidiary of such parent
               without triggering Section 13; and

         2.2.4 Shorten the notice  periods  specified  in Section 13 and clarify
               that a Participant's right of first refusal extends only to those
               portions  of the  Four  Corners  Project  in which  they  have an
               ownership interest.

3    AGREEMENT:

     In  consideration  of the mutual benefits to be derived from this Amendment
     No. 6, the Participants agree as follows:

4    EFFECTIVE DATE:

     This  Amendment No. 6 shall be effective upon the date when executed by all
     of the Participants.

5    DEFINITIONS

     Section 5.27 of the Co-Tenancy Agreement is amended to read as follows: /

                                      -2-


     5.27 Participant(s)

          One or more entities,  including  Arizona,  El Paso, New Mexico,  Salt
          River Project,  Edison and Tucson,  with an ownership  interest in the
          Four Corners  Project.  Except with  respect to any rights,  benefits,
          duties,  or  obligations   expressly   provided  for  in  any  Project
          Agreement, a Participant's rights,  benefits,  duties, and obligations
          under this Agreement are expressly limited to those rights,  benefits,
          duties,  and  obligations  involving  that portion of the Four Corners
          Project in which the Participant has an ownership interest.

6    OWNERSHIP AND TITLES:

     Section 6.11 of the Co-Tenancy Agreement is amended to read as follows:

     6.11 In the event that any  Participant  transfers  or  assigns  any of its
          right, title or interest (collectively, "interest") in and to the Four
          Corners  Project in accordance  with the terms and  conditions of this
          Co-Tenancy  Agreement,  the Participant assigning or transferring such
          interest  shall,  upon  completion  of such  transfer  or  assignment,
          provide  written  notice to the other  Participants  and the Operating
          Agent,  as defined in the Operating  Agreement,  of any changes in the
          interests  of that  Participant  in the  Four  Corners  Project.  Upon
          receipt  of  such  notice,  the  Operating  Agent  shall  prepare  for
          signature by the Participants an amendment to the Co-Tenancy Agreement
          reflecting such changes.

7    COORDINATION COMMITTEE:

     Section 9.5 of the Co-Tenancy Agreement is amended to read as follows:

                                      -3-

          9.5   Any action or determination of the Coordination Committee shall
                require the affirmative vote of all Participants, acting through
                their respective representatives, that have an ownership
                interest in that portion of the Four Corners Project that is the
                subject matter of the action to be taken or the determination to
                be made. Only those Participants with an ownership interest in
                the portion of the Four Corners Project that is the subject
                matter of an action or determination may participate in
                discussions relating to such actions or determinations;
                provided, however, that this restriction shall apply only when
                required by a regulatory authority with jurisdiction over the
                Participant(s), an applicable code of conduct, or a
                Participant's reasonable competitive concerns.

8    MORTGAGE AND TRANSFER OF PARTICIPANTS' INTEREST:

     8.1  Section  12.3 of the  Co-Tenancy  Agreement  is  amended by adding new
          Sections 12.3.6 and 12.3.7 to read as follows:

          12.3 Each  Participant  shall have the right to transfer or assign all
               or any portion of its  respective  rights,  undivided  titles and
               interests  in the Four  Corners  Project,  in,  to and  under the
               Project  Agreements and/or in the Granted Lands and Leased Lands,
               without  the  need  for  prior  written   consent  of  any  other
               Participant, at any time to any of the following:

             12.3.1 To  any   corporation  or  other  entity  acquiring   all or
                    substantially all of the property of such Participant; or

             12.3.2 To  any corporation or entity into which  or with which such
                    Participant may be merged or consolidated; or

                                      -4-

             12.3.3 To  any  corporation  or entity the  stock or  ownership  of
                    which is wholly owned by a Participant; or

             12.3.4 To   any  third  party   transferee  in  connection  with  a
                    financing by such Participant  involving or relating to such
                    Participant's  rights,  titles  and  interests  in the  Four
                    Corners  Project,  in, to and under the  Project  Agreements
                    and/or in the Granted Lands and Leased  Lands,  without such
                    third party transferee assuming or becoming obligated in any
                    respect  to  perform   any  of  the   obligations   of  such
                    Participant pursuant to this Co-Tenancy Agreement,  provided
                    that  any  and  all  such  rights,   titles  and   interests
                    transferred to such third party  transferee are  immediately
                    re-purchased by such  Participant and are thereupon  subject
                    to all of  the  provisions  of  this  Co-Tenancy  Agreement,
                    including,  but not limited to, the "right of first refusal"
                    provisions of Section 13 hereof; or

             12.3.5 To  the Salt  River  Valley  Water  Users'  Association,  an
                    Arizona corporation, in the case of a transfer by Salt River
                    Project; or

             12.3.6 To  any  corporation  which  owns  all  of  the  outstanding
                    common  stock  of  a  Participant,  or  in  the  case  of  a
                    Participant  which has no common  stock,  to an entity which
                    owns all of the ownership  interest of the Participant  (the
                    corporation  or entity  shall be  referred  to herein as the
                    "Parent"); or

                                      -5-

             12.3.7 To any  corporation  or entity  the  common  stock or  other
                    ownership interest of which is wholly owned by the Parent of
                    such Participant.

     8.2 A new Section 12.7 is added to read as follows:

          12.7 Without  implying  that any  provision  other than  Article 6 and
               Article  7  herein  allows  a  Participant  to own  an  undivided
               ownership  interest in any component of the Four Corners  Project
               which is not the same as the  undivided  ownership  interest such
               Participant owns in every other component, each Participant shall
               own the same undivided  percentage  interest in Unit 4 as in Unit
               5.

9    RIGHT OF FIRST REFUSAL:

     Sections 13.3, 13.4, 13.6, and 13.8 of the Co-Tenancy Agreement are amended
to read as follows:

     13.3 At least one hundred  eighty (180) days prior to its intended  date to
          Assign, and after its receipt of a bona fide written offer of the type
          described in Section 13.1 above,  the  Participant  desiring to Assign
          its Transfer  Interest  shall serve written notice of its intention to
          do so upon the  remaining  Participants  who have an  interest in that
          portion  of the  Four  Corners  Project  that  is the  subject  of the
          Transfer  Interest in  accordance  with Section 23 of this  Co-Tenancy
          Agreement. Such notice to the remaining Participants shall contain the
          approximate  proposed date to Assign, the terms and conditions of said
          bona fide written offer  received by such  Participant,  and the terms
          and  conditions of the proposed  assignment.  The terms and conditions
          contained  in such  notice  shall  be at  least  as  favorable  to the

                                      -6-

          remaining  Participants  as the terms and conditions of said bona fide
          written offer, or may be the same terms and conditions as set forth in
          said offer.

     13.4 Each remaining Participant having an ownership interest in the portion
          of Four Corners Project that is the subject of the Transfer  Interest,
          including the Outside  Party if such Outside  Party is a  Participant,
          shall signify its desire to purchase the entire Transfer Interest,  or
          any  percentage  interest  therein,  or  not  to  purchase  all or any
          percentage   interest  therein,  by  serving  written  notice  of  its
          intention  upon  the  Participant  desiring  to  Assign  and  upon the
          remaining  Participants  pursuant  to  Section  23 hereof  within  one
          hundred twenty (120) days after such service  pursuant to Section 13.3
          of the written notice of intention to Assign. Failure by a Participant
          to serve notice as provided hereunder within the time period specified
          shall be  conclusively  deemed to be notice  of its  intention  not to
          purchase any portion of the Transfer Interest.

     13.6 If the  remaining  Participants,  or any one or more of  them,  should
          signify its or their  intention  under  Section 13.4 to purchase  less
          than the entire Transfer Interest,  the Participant desiring to Assign
          shall  serve   written   notice  of  this  fact  upon  the   remaining
          Participants in accordance with Section 23 hereof within ten (10) days
          after its receipt of the last of the written notices given pursuant to
          Section 13.4 hereof, or after the expiration of the one hundred twenty
          (120) day period  referred to in Section  13.4  hereof,  whichever  is
          earlier.

                                      -7-

     13.8 When  intention  to purchase  the entire  Transfer  Interest  has been
          indicated   by  notices  duly  given   hereunder  by  the   applicable
          Participant(s)   desiring  to  purchase  the  Transfer  Interest,  the
          Participants shall thereby incur the following obligations:

          13.8.1 The Participant  desiring to  Assign  and the  Participant(s)
                 desiring to purchase the Transfer  Interest shall  be obligated
                 to proceed  in  good  faith  and with  diligence  to obtain all
                 required authorizations and approvals to Assign;

          13.8.2 The Participant desiring to Assign shall be obligated to obtain
                 the release of any liens imposed by or through it upon any part
                 of the  Transfer Interest,  and to Assign the Transfer Interest
                 at the earliest practicable date thereafter; and

          13.8.3 The  Participant(s)  desiring to purchase the Transfer Interest
                 shall be obligated to perform all terms and conditions required
                 of  it  or  them  to  complete  the  purchase of  the  Transfer
                 Interest.

          The  purchase  of the  Transfer  Interest  shall be fully  consummated
          within eighteen (18) months  following the date upon which all notices
          required  to be given  under this  Section  13 have been duly  served,
          unless the Participant(s) are then diligently pursuing applications to
          appropriate regulatory bodies (if any) for required  authorizations to
          effect such assignment or are then diligently prosecuting or defending
          appeals from orders  entered or  authorizations  issued in  connection
          with such  application,  in which case the  purchase  of the  Transfer
          Interest  shall be fully

                                      -8-

          consummated at the earliest  possible date  following  issuance of the
          requested authorization(s) or the resolution of any appeal.

10   Execution by Counterparts:

     This  Amendment  No. 6 may be executed in any number of  counterparts,  and
     upon execution by all  Participants,  the counterparts  shall have the same
     force and effect as an original  instrument and as if all  Participants had
     signed the same instrument.  Any signature page of this Amendment No. 6 may
     be detached from any counterpart of this Amendment No. 6 without  impairing
     the legal effect of any signature  thereon,  and may be attached to another
     counterpart  of this  Amendment  No. 6 identical  in form hereto but having
     attached to it one or more signature pages.

11  EFFECT OF AMENDMENTS:

     Except as  specifically  amended  herein,  this  Co-Tenancy  Agreement,  as
     previously amended, shall remain in full force and effect.


                                       -9-

12   SIGNATURE CLAUSE:

     The  signatories   hereto  represent  that  they  have  been  appropriately
     authorized to enter into this Amendment No. 6 on behalf of the  Participant
     for whom they sign.  This Amendment No. 6 is hereby executed as of this 3rd
     day of February, 2000.

                                        ARIZONA PUBLIC SERVICE COMPANY

                                        By John R. Denman
                                          --------------------------------------
                                        Its Vice President - Fossil
                                           -------------------------------------

                                        EL PASO ELECTRIC COMPANY

                                        By John C. Horne
                                          --------------------------------------
                                        Its Vice President - Generation
                                           -------------------------------------

                                        PUBLIC SERVICE COMPANY OF NEW MEXICO

                                        By Patrick Goodman
                                          --------------------------------------
                                        Its Vice President - Power Production
                                           -------------------------------------

                                        SALT RIVER PROJECT AGRICULTURAL
                                        IMPROVEMENT AND POWER DISTRICT

ATTEST AND COUNTERSIGN                  By William P. Schrader
                                          --------------------------------------
T. A. Lonon                             Its President
- --------------------------------           -------------------------------------

                                        SOUTHERN CALIFORNIA EDISON COMPANY

                                        By Harold Ray
                                          --------------------------------------
                                        Its Executive Vice President
                                           -------------------------------------

                                        TUCSON ELECTRIC POWER COMPANY

                                        By Thomas A. Delawder
                                          --------------------------------------
                                        Its Vice President
                                           -------------------------------------

                                      -10-

STATE OF ARIZONA    )
                    ) ss
County of Maricopa  )


     The foregoing instrument was acknowledged before me this 21st day of April,
2000, by John R. Denman, Vice President, Fossil, Arizona Public Service Company,
on behalf of the corporation.


                                        Christine A. LaBrash
                                        ----------------------------------------
                                        Notary Public

My Commission Expires: August 29, 2003

[SEAL]

                                      -11-

STATE OF TEXAS      )
                    ) ss
County of El Paso   )


     The  foregoing  instrument  was  acknowledged  before  me  this  9th day of
February,  2000,  by John C.  Horne,  Vice  President  -  Generation  of El Paso
Electric Company, on behalf of the corporation.


                                        Hilda Vargas
                                        ----------------------------------------
                                        Notary Public

My Commission Expires:

June 26, 2001
- ----------------------

[SEAL]

                                      -12-

STATE OF NEW MEXICO      )
                         ) ss
County of San Juan       )


     The  foregoing  instrument  was  acknowledged  before  me  this  4th day of
February,  2000, by Patrick Goodman, of Public Service Company of New Mexico, on
behalf of the corporation.


                                        Beverly A. Olim
                                        ----------------------------------------
                                        Notary Public

My Commission Expires:

1-16-2001
- ----------------------------

                                      -13-

STATE OF ARIZONA    )
                    ) ss
County of Maricopa  )


     The foregoing  instrument was acknowledged before me this 6th day of March,
2000,  by William P.  Schrader,  President  of Salt River  Project  Agricultural
Improvement and Power District, on behalf of the corporation.


                                        Margaret A. Sullivan
                                        ----------------------------------------
                                        Notary Public

My Commission Expires: September 16, 2001

[SEAL]

                                      -14-

STATE OF CALIFORNIA      )
                         ) ss
County of Los Angeles    )

     The foregoing  instrument was acknowledged  before me this 9th day of Feb.,
2000, by Harold Ray, of Southern  California  Edison  Company,  on behalf of the
corporation.


                                        Sarah C. Perez
                                        ----------------------------------------
                                        Notary Public

My Commission Expires:

Aug. 6, 2001
- -------------------------------

[SEAL]

                                      -15-

STATE OF ARIZONA    )
                    ) ss
County of Pima      )


The foregoing instrument was acknowledged before me this 7th day of February,
2000, by Thomas A. Delawder, Vice President, Energy Resources of Tucson Electric
Power Company, on behalf of the corporation.


                                        Bertha A. Kissinger
                                        ----------------------------------------
                                        Notary Public

My Commission Expires:

Jan. 21, 2003
- ---------------------------------

[SEAL]

                                      -16-