EXHIBIT 10.5.1


<PAGE>



                              MODIFICATION NO. 4 TO
                              CO-TENANCY AGREEMENT
                                     BETWEEN
                      PUBLIC SERVICE COMPANY OF NEW MEXICO
                                       AND
                          TUCSON ELECTRIC POWER COMPANY

         This  Modification  No. 4 to the  Co-Tenancy  Agreement  Between PUBLIC
SERVICE  COMPANY OF NEW MEXICO ("New Mexico") and TUCSON  ELECTRIC POWER COMPANY
("Tucson"),   hereinafter   sometimes   referred   to  as   the   "Parties"   or
"Participants", is hereby entered into an executed this 25 day of October, 1984.

         WITNESSETH:

         WHEREAS,  the  Parties  entered  into  an  agreement  described  as the
Co-Tenancy  Agreement  Between New Mexico and Tucson  effective July 1, 1969, as
modified by Modification  No. 1 on May 16, 1979,  Modification No. 2 on December
31, 1983,  and  Modification  No. 3 on July 17, 1984  ("Co-Tenancy  Agreement"),
which establishes  certain terms and conditions  relating to their ownership and
operation of the San Juan Project Agreements; and

         WHEREAS,  the  Parties  desire  to  clarify  their  rights,  title  and
interests  in the San Juan Project as a result of the  contemplated  October 31,
1984  conveyance  of  Tucson's  San Juan Unit 3  ownership  interest  to Alamito
Company  ("Alamito")  pursuant  to the  purchase  agreement  between  Tucson and
Alamito dated October 1, 1984 ("San
Juan Unit No. 3 Purchase Agreement").

         NOW THEREOF, the Parties agree as follows:

                                      - 2 -

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         1.0 Effective  Date.  This  Modification  No. 4 shall become  effective
immediately  upon  Tucson's  conveyance  of its San Juan  Unit  No. 3  ownership
interest to Alamito.

         2.0  Compliance  With  Section  6.7.  Section  6.7  of  the  Co-Tenancy
Agreement  requires  that in the event either  Participant  transfers any of its
rights,  title or  interest  in the San Juan  Project,  the  Participants  shall
jointly execute a Supplement to this Co-Tenancy  Agreement,  in recordable form,
which describes the rights,  titles and interests of each Participant  following
such  transfer  or  assignment.  On  November  17,  1981,  New  Mexico  sold and
transferred an 8.475 percent undivided  ownership interest in San Juan Unit 4 to
the City of Farmington,  New Mexico.  On December 31, 1981, Tucson and the M-S-R
Public Power Agency ("M-S-R") entered into the Tucson/M-S-R Agreement--Option to
Acquire Ownership  Interest in San Juan Unit 4, wherein Tucson agreed to sell to
M-S-R and M-S-R  agreed  to  purchase  from  Tucson,  pursuant  to the terms and
conditions of such agreement,  on or before November 30, 1982, the Tucson Option
(also  referred to as the "Option to  Repurchase"  in the May 16, 1979, San Juan
Unit 4 Purchase Agreement between New Mexico and Tucson).  On November 29, 1982,
New Mexico and M-S-R  executed  the San Juan Unit 4 Purchase  and  Participation
Agreement, and on September 26, 1983, New Mexico and M-S-R executed the San Juan
Unit 4 Early Purchase and  Participation  Agreement  under which New Mexico sold
and transferred a 28.8 percent undivided  ownership  interest in San Juan Unit 4
to M-S-R effective  December 31, 1983. As of October 1, 1984, Tucson and Alamito


                                      - 3 -

<PAGE>

entered  into the San Juan Unit No. 3 Purchase  Agreement  which  provides  that
Tucson  will sell and  transfer to Alamito  its 50 percent  undivided  ownership
interest in Unit 3 on October 31, 1984. In accordance  with the  requirements of
Section 6.7,  the  following  sections of the  Co-Tenancy  Agreement  are hereby
amended to read as follows:

         Amended Section 6.3:

         6.3  Subsequent to execution of the Co-Tenancy  Agreement,  conveyances
and  assignments or agreements,  as described in paragraphs  2.3, 2.5, 5.2, 5.19
and 5.20, and subject to the  requirements  of such sections,  have been made or
will be  made  dated  as of a date  prior  to the  Transfer  Date  so that  each
Participant will have title to an equal undivided one-half (1/2) interest in the
San Juan  Site,  water  rights,  FC Line,  rights-of-way,  leases,  River  Water
Diversion and Pumping  Station,  and all San Juan Project  improvements  on such
sites. The generating units of the San Juan Project, Capital Additions,  Capital
Betterments and Capital  Replacements  placed into service prior to the Transfer
Date shall be owned in undivided  one-half (1/2)  interest by each  Participant.
The generating  units of the San Juan Project,  Capital  Additions,  and Capital
Betterments thereto, and Capital  Replacements  thereof,  placed into service on
the  Transfer  Date  and  thereafter  shall  be  owned  and  title  held  by the
Participants and Unit Participants in the following percentages:


                                      - 4 -

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         Amended Section 3.1.1:

         6.3.1 For San Juan Units 1 and 2 and for all equipment  and  facilities
directly  related  to the  Units  1 and 2,  in  accordance  with  the  following
percentages:

          A.      Participants
                   1.      New Mexico - 50 percent
                   2.      Tucson - 50 percent

          B.      Unit Participants
                   1.      M-S-R - 0 percent
                   2.      City of Farmington - 0 percent
                   3.      Alamito - 0 percent

         New Section 6.3.1.1:

         A new Section 6.3.1.1 shall be added to Section 6, after Section 6.3.1,
to read in its entirety as follows:

         6.3.1.1  For  San  Juan  Unit 3 and for all  equipment  and  facilities
directly related to Unit 3 only, in accordance with the following percentages:

          A.      Participants
                   1.      New Mexico - 50 percent
                   2.      Tucson - 0 percent

          B.      Unit Participants
                   1.      M-S-R - 0 percent
                   2.      City of Farmington - 0 percent
                   3.      Alamito - 50 percent

         Amended Section 6.3.2:

         6.3.2  For San Juan Unit 4 and for all equipment and

                                      - 5 -

<PAGE>

facilities  directly  related to Unit 4 only, in  accordance  with the following
percentages:

          A.      Participants
                   1.      New Mexico - 62.725 percent
                   2.      Tucson - 0 percent

          B.      Unit Participants
                   1.      M-S-R - 28.8 percent
                   2.      City of Farmington - 8.475 percent
                   3.      Alamito - 0 percent

         Amended Section 6.3.3:

         6.3.3 For  equipment  and  facilities  common only to Units 1 and 2, in
accordance with the following percentages:

          A.      Participants
                   1.      New Mexico - 50 percent
                   2.      City of Farmington 0 percent

          B.      Unit Participants
                   1.      M-S-R - 0 percent
                   2.      Tucson - 50 percent
                   3.      Alamito - 0 percent

         Amended Section 6.3.4:

         6.3.4 For  equipment  and  facilities  common only to Units 3 and 4, in
accordance with the following percentages:

          A.      Participants
                   1.      New Mexico - 56.351 percent
                   2.      Tucson - 0 percent

          B.      Unit Participants

                                      - 6 -

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                   1.      M-S-R - 14.4 percent
                   2.      City  of  Farmington  -  4.249   percent   (ownership
                           interest is with respect to common  facilities not in
                           service on November 17, 1981;  the City of Farmington
                           was granted an Easement and License for use of common
                           facilities  which  were in service  on  November  17,
                           1981).
                   3.      Alamito - 25 percent

         Amended Section 6.3.5:

         6.3.5  For  equipment  and  facilities  common  to all of the  units in
accordance with the following percentages:

          A.      Participants
                   1.      New Mexico - 53.741 percent
                   2.      Tucson - 19.8 percent

          B.      Unit Participants
                   1.      M-S-R - 8.7 percent
                   2.      City  of  Farmington  -  2.559   percent   (ownership
                           interest is with respect to common  facilities not in
                           service on November 17, 1981;  the City of Farmington
                           was granted an Easement and License for use of common
                           facilities  which  were in service  on  November  17,
                           1981).
                   3.      Alamito - 15.2 percent


                                      - 7 -

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         Amended Section 6.3.6:

         6.3.6 For the  Switchyard  Facilities  except as otherwise  provided in
Section 15 hereof, in accordance with the following percentages:

          A.      Participants
                   1.      New Mexico - 50 percent
                   2.      Tucson - 50 percent

          B.      Unit Participants
                   1.      M-S-R - 0 percent
                   2.      City of Farmington - 0 percent
                   3.      Alamito - 0 percent

         Sections 6.3.7, 6.3.8 and 6.3.9:  Unchanged

         3.0  Amended Section 8.1.  Section 8.1 shall be amended to
read in its entirety as follows:

                  8.1  Subject to the  provisions  of  paragraphs  10.1 and 10.2
         hereof,  the Participants  shall be entitled to share the Net Effective
         Generating  Capacity  of the  San  Juan  Project  in  equal,  undivided
         one-half  (1/2)  interests  for Units 1 and 2. New Mexico  and  Alamito
         shall be entitled to share the Net Effective Generating Capacity of the
         San Juan Project in equal  undivided  one-half (1/2) interests for Unit
         3. New Mexico and Unit  Participants to which New Mexico conveys or has
         conveyed  ownership  interests and generation  entitlements in San Juan
         Unit 4 shall have a 100 percent  (100%)  interest in the Net  Effective
         Generating Capacity of Unit 4.


                                      - 8 -

<PAGE>

         4.0 New Section 9.5.2. A new Section 9.5.2 shall be added to Section 9,
after Section 9.5.1 to read in its entirety as follows:

                  9.5.2 With respect to matters involving and not solely related
         to San Juan Unit 3, Tucson,  as a Participant  holding voting rights on
         the  Coordination  Committee,  shall  retain  such  voting  rights  for
         Alamito,  with the  obligation  to consult  with Alamito on all matters
         involving  the San Juan  Project  which  affect San Juan Unit 3, as set
         forth in the San Juan Unit No. 3 Purchase Agreement.

         5.0  Amended Section 9.7.  Section 9.7 shall be amended to
read in its entirety as follows:

                  9.7 In the event  the  Coordination  Committee  fails to reach
         agreement on a matter that has earlier been determined to relate solely
         to a  specific  San Juan  generating  unit,  which  such  committee  is
         authorized  to  determine,  approve,  or  otherwise  act  upon  after a
         reasonable  opportunity to do so, then the Project Manager or Operating
         Agent (as said terms are  respectively  defined in the San Juan Project
         Construction  Agreement and San Juan Project Operating Agreement) shall
         be authorized and obligated to take such action as in its discretion it
         deems  to be  necessary  to the  successful  and  proper  construction,
         operation and  maintenance  of such unit,  pending the  resolution,  by
         arbitration  or otherwise,  of any such  inability or failure to agree.

         6.0 Amended  Exhibit V. Exhibit V (a-g) shall be amended to read in its
entirety as shown on the attached.

                                      - 9 -

<PAGE>

         7.0  Amended Section 25.8.  Section 25.8 shall be amended to
read in its entirety as follows:

                  25.8  Except  as  modified  by the  provisions  set  forth  in
         Modification  No. 4, all of the terms and conditions of this Co-Tenancy
         Agreement,  effective as of July 1, 1969,  as modified by  Modification
         No. 1 as of May 16,  1979,  Modification  No. 2 as of December 31, 1983
         and  Modification No. 3 as of July 17, 1984, shall remain in full force
         and effect.

         IN WITNESS WHEREOF, the Parties hereto have caused this
Modification No. 4 to be executed as of this _____ day _________,
1984.


                                     - 10 -

<PAGE>

                                        PUBLIC SERVICE COMPANY OF NEW MEXICO


Attest:                                 By:  /S/ J. L. Wilkins
                                             -------------------------------  
/S/ D. E. Peckham                       Its:     Senior Vice President
-------------------------
Secretary


                                        TUCSON ELECTRIC POWER COMPANY


Attest:                                 By:      /S/
                                             ------------------------------
/S/ Jean E. Kettlewell                  Its:     Executive Vice President
-------------------------

STATE OF NEW MEXICO )
                    ) ss.
COUNTY OF BERNALILLO)

         The foregoing  instrument was  acknowledged  before me this 25th day of
October, 1984, by J. L. Wilkins, Senior Vice President of Public Service Company
of New Mexico, a New Mexico corporation, on behalf of said corporation.

                                                     /S/ Sherry Leeson
                                                     ----------------------
                                                     Notary Public
My Commission Expires:

   July 1, 1988



STATE OF ARIZONA     )
                     ) ss.
COUNTY OF PIMA       )

         The foregoing  instrument was  acknowledged  before me this 22nd day of
October,  1984, by Einar Greve,  of Tucson  Electric Power  Company,  an Arizona
corporation, on behalf of said corporation.

                                                 -------------------------------
                                                 Notary Public

My Commission Expires:
     4/14/87

                                     - 11 -

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                                  Exhibit V(a)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 1

                                    Ownership

                         New Mexico - 50%; Tucson - 50%


 1.      Turbine Generator

 2.      Condenser

 3.      Condensate and Feedwater System

          a.      Condensate Pumps
          b.      Feedwater Heaters
          c.      Boiler Feed Pumps
          d.      Storage Tanks

 4.      Boiler, including:  Air Heaters, Pulverizers, Bunkers, and
         Feeders

 5.      Forced Draft Fans and Primary Air Fans

 6.      Precipitator

 7.      Stack and Stack Monitoring System

 8.      Cooling Tower

 9.      Circulating Water Pumps

10.      Main, Start-up, Unit Auxiliary, and SO2 Scrubber Transformers

11.      Bottom Ash Systems (up to but not including Dewatering Tank or
         Ash Water Pump Building and Equipment)

12.      Fly Ash System

13.      Building HVAC System

14.      SO2 Absorbers, Scrubbers, Transfer Pumps, Booster Fans and
         Flue Gas Reheat System

15.      Emergency Diesel Generator

16.      Electrical and Control Systems

17.      SSR Protection System

18.      Unit Specific Piping for all Air Systems, Chemical Feed
         Systems and Hydrogen


                                     - 12 -

<PAGE>

                                  Exhibit V(b)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 2

                                    Ownership

                         New Mexico - 50%; Tucson - 50%


 1.      Turbine Generator

 2.      Condenser

 3.      Condensate and Feedwater System

          a.      Condensate Pumps
          b.      Feedwater Heaters
          c.      Boiler Feed Pumps
          d.      Storage Tanks

 4.      Boiler, including:  Air Heaters, Pulverizers, Bunkers, and
         Feeders

 5.      Forced Draft Fans and Primary Air Fans

 6.      Precipitator

 7.      Stack and Stack Monitoring System

 8.      Cooling Tower

 9.      Circulating Water Pumps

10.      Main, Start-up, Unit Auxiliary, and SO2 Scrubber Transformers

11.      Bottom Ash System (up to but not including Dewatering Tank or
         Ash Water Pump Building and Equipment)

12.      Fly Ash System

13.      Building HVAC System

14.      SO2  Absorbers, Scrubbers, Transfer Pumps, Booster Fans and
         Flue Gas Reheat System

15.      Emergency Diesel Generator

16.      Electrical and Control Systems

17.      Unit Specific Piping for all Air Systems, Chemical Feed
         Systems, and Hydrogen



                                     - 13 -

<PAGE>

                                  Exhibit V(c)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 3

                                    Ownership

                         New Mexico - 50%; Alamito - 50%


 1.      Turbine Generator

 2.      Condenser

 3.      Condensate and Feedwater System

          a.      Condensate Pumps
          b.      Feedwater Heaters
          c.      Boiler Feed Pumps
          d.      Storage Tanks

 4.      Boiler, including:  Air Heaters, Pulverizers, Bunkers, and
         Feeders

 5.      Forced Draft Fans and Primary Air Fans

 6.      Precipitator

 7.      Stack and Stack Monitoring System

 8.      Cooling Tower

 9.      Circulating Water Pumps

10.      Main, Unit Auxiliary 3A and 3B Transformers

11.      Bottom Ash System including:  Hopper, Dewatering Tank,
         Settling Tank, Surge Tank, Storage Tank, and Pump House

12.      Fly Ash System

13.      Building HVAC System

14.      SO2  Absorbers, Scrubbers, Transfer Pumps, Booster Fans, and
         Flue Gas Reheat System

15.      Emergency Diesel Generator

16.      Electrical and Control Systems

17.      Fuel Oil Ignitor Heaters and Unit Specific Piping

18.      Unit Specific Piping for all Air Systems, Chemical Feed
         Systems, and Hydrogen


                                     - 14 -

<PAGE>
                                  Exhibit V(c)
                                   (Continued)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 3

                                    Ownership

                         New Mexico - 50%; Alamito - 50%


19.      Coal Reclaim Hoppers, Feeders, Feeder Belts, Belt Scales, Fire
         Protection System, and 3C Conveyor to the Secondary Crusher
         Building

20.      SSR Protection System


                                     - 15 -

<PAGE>

                                  Exhibit V(d)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 4

                                    Ownership

                    New Mexico - 62.725; Tucson - 0%; M-S-R -
                28.8%; City of Farmington - 8.475%; Alamito - 0%


 1.      Turbine Generator

 2.      Condenser

 3.      Condensate and Feedwater System

          a.      Condensate Pumps
          b.      Feedwater Heaters
          c.      Boiler Feed Pumps
          d.      Storage Tanks

 4.      Boiler Including Air Heaters and Pulverizers, Bunkers and
         Feeders

 5.      Forced Draft Fans and Primary Air Fans

 6.      Precipitator

 7.      Stack and Stack Monitoring System

 8.      Cooling Tower

 9.      Circulating Water Pumps

10.      Main, Unit Auxiliary 4A and 4B Transformers

11.      Bottom Ash System including:  Hopper, Dewatering Tank,
         Settling Tank, Surge Tank, Storage Tank, and Pump House

12.      Fly Ash System

13.      Building HVAC System

14.      SO2  Absorbers, Scrubbers, Transfer Pumps, Booster Fans, and
         Flue Gas Reheat System

15.      Emergency Diesel Generator

16.      Electrical and Control Systems



                                     - 16 -

<PAGE>

                                  Exhibit V(d)
                                   (Continued)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 4

                                    Ownership

                    New Mexico - 62.725; Tucson - 0%; M-S-R -
                28.8%; City of Farmington - 8.475%; Alamito - 0%
                                     


17.      Fuel Oil Ignitor Heaters and Unit Specific Piping

18.      Unit Specific Piping for all Air Systems, Chemical Feed
         Systems, and Hydrogen

19.      Coal Reclaim Hoppers, Feeders, Feeder Belts, Belt Scales, Fire
         Protection System, and 3D Conveyor to the Secondary Crusher
         Building


                                     - 17 -

<PAGE>

                                  Exhibit V(e)

                            FACILITIES AND EQUIPMENT
                        COMMON TO SAN JUAN UNITS 1 AND 2

                                    Ownership

                         New Mexico - 50%; Tucson - 50%


 1.      Bearing Cooling Water System

 2.      Bottom Ash Dewatering Facility, Including Dewatering Tank,
         Settling Tank, Surge Tank, Storage Tank, and Pump House

 3.      Demineralizer System, including:  Clarifier, Storage Tanks,
         and Sump Pump

 4.      Fuel Oil System (No. 2 Oil for Ignition and Flame
         Stabilization)

 5.      Premix Tank Facility (formerly Wastewater Neutralizer
         Facility, now Operated as part of the Water Management System)

 6.      Instrument Air System, except Unit Piping

 7.      Chemical Feed System, except Unit Piping

          a.      Condensate and Feedwater System
          b.      Boiler
          c.      Bearing Cooling Water System
          d.      Cooling Tower Systems
          e.      Chlorination System

 8.      Plant Air System, except Unit Piping

 9.      Sootblowing Air System, except Unit Piping

10.      Hydrogen Storage System, except Unit Piping

11.      Coal Handling Reclaim Systems A and B including:  Hoppers,
         Feeders, Reclaim Conveyors, Belt Scales and Sprinkler System

12.      Coal Tripper System South of Column, Line 12, including Dust
         Collection System

13.      Turbine Lube Oil Storage and Transfer System

14.      Control Room, Equipment Rooms, and Associated HVAC System

15.      Building South of Column Line 12

16.      Turbine Crane South of Column Line 12

17.      Fuel Oil, Ash, and Water Pipe Racks

                                     - 18 -

<PAGE>

                                  Exhibit V(e)
                                   (Continued)

                            FACILITIES AND EQUIPMENT
                        COMMON TO SAN JUAN UNITS 1 AND 2

                                    Ownership

                         New Mexico - 50%; Tucson - 50%


18.      Boiler Fill System for Units 1 and 2

19.      SO2 Backup Scrubber - Absorber Transformer

20.      SAR Multiplexer Control System



                                     - 19 -

<PAGE>

                                  Exhibit V(f)

                            FACILITIES AND EQUIPMENT
                        COMMON TO SAN JUAN UNITS 3 AND 4

                                    Ownership

                    NewMexico - 56.351%; Tucson - 0%; M-S-R -
                  14.4%; City of Farmington - 4.249%*; Alamito - 25%


 1.      Bearing Cooling Water System

 2.      Demineralizer System including:  Sump Pumps, Filter Beds, and
         Storage Tanks

 3.      Fuel Oil System (No. 6 Oil for Ignition and Flame
         Stabilization, except Igniter Heaters and Unit Specific
         Piping)

 4.      Wastewater Neutralizer Facility (formerly operated as part of
         Water Management System)

 5.      Instrument Air System, except Unit Piping

 6.      Chemical Feed Systems, except Unit Piping

          a.      Condensate & Feedwater System
          b.      Boiler
          c.      Bearing Cooling Water System
          d.      Cooling Tower System
          e.      Chlorination System

 7.      Plant Air System, except Unit Piping

 8.      Sootblowing Air System, except Unit Piping

 9.      Start-Up Transformers and Iso-Phase Bus to Units 3 and 4
         Switchgear

10.      Hydrogen Storage System, except Unit Piping

11.      Coal Tripper System serving Units 3 and 4 including Dust
         Collection Systems


                                     - 20 -

<PAGE>

                                  Exhibit V(f)
                                   (continued)

                            FACILITIES AND EQUIPMENT
                        COMMON TO SAN JUAN UNITS 3 AND 4

                                    Ownership

                    NewMexico - 56.351%; Tucson - 0%; M-S-R -
                  14.4%; City of Farmington - 4.249%*; Alamito - 25%



12.      Turbine Lube Oil Storage and Transfer System

13.      Control Room, Equipment Rooms, and Associated HVAC System

14.      Boiler Fill System for Units 3 and 4

15.      Auxiliary Cooling Systems including Auxiliary Cooling Tower
         No. 1 and Pumps, but excepting No. 4 Tower and Pumps and
         Piping which is Unit Specific

16.      CO2 Storage System

17.      Start-up Boiler Feed Pump

18.      Turbine Bay Crane North of Column Line 12

19.      Fuel Oil, Ash, and Water Pipe Racks

20.      Fire Water Booster and Jockey Pumps

21.      Halon Fire Protection System

22.      Cooling Tower Multiplex Control System

23.      All spare parts common to either Unit

*City of Farmington's  ownership  interest is with respect to Common  Facilities
not in service on  November  17,  1981;  the City of  Farmington  was granted an
Easement  and  License  for use of Common  Facilities  which  were in service on
November 17, 1981.



                                     - 21 -

<PAGE>

                                  Exhibit V(g)

                            FACILITIES AND EQUIPMENT
                        COMMON TO ALL FOUR SAN JUAN UNITS

                                    Ownership

                  New Mexico - 53.741%; Tucson - 19.8% M-S-R -
                  8.7% City of Farmington - 2.559%*; Alamito - 15.2%


 1.      River and Raw Water System including:

          a.      Diversion and intake structures, including all equipment
                  and pump building

          b.      Raw water line to reservoir

          c.      Reservoir, pump building, and all equipment

          d.      Raw water lines to plant yard

          e.      All underground and above ground fire protection system
                  to each vendor supplied or unit specific fire
                  distribution system

 2.      Auxiliary boiler

 3.      SO2 System Chemical Plant, except Absorbers

          a.      double effect evaporator train systems

          b.      fly ash filter system

          c.      absorber product and feed tanks

          d.      condensate collection, storage, and transfer systems

          e.      soda ash storage, mixing, and distribution systems

          f.      sulfur plant

          g.      sulfate purge system including:  crystallizers,
                  centrifuges, evaporators, and salt cake system

          h.      sulfuric acid plant system including:  storage tanks and
                  load out system

          i.      auxiliary No. 2 cooling tower, pumps, and systems

 4.      Spare Main Transformer 345/24 kV, for all Units

 5.      Part of the Maintenance, Office, and Warehousing Facilities


                                     - 22 -

<PAGE>

                                  Exhibit V(g)
                                   (Continued)

                            FACILITIES AND EQUIPMENT
                        COMMON TO ALL FOUR SAN JUAN UNITS

                                    Ownership

                  New Mexico - 53.741%; Tucson - 19.8% M-S-R -
                  8.7% City of Farmington - 2.559%*; Alamito - 15.2%


 6.      Chemical Laboratory

 7.      Coal and Ash Handling control facilities

 8.      Roads and grounds such as fencing, yard lighting, guard
         facilities, drainage, and dikes

 9.      Potable Water System

10.      Environmental Monitoring including:  Air, Water, and Ground

11.      Transportation such as trucks, cars, and dozers

12.      Water Management System

          a.      Wastewater Recovery System - Northside

                  (1)      Reverse osmosis system including lime/soda
                           softening clarifier system

                  (2)      Brine concentrator Nos. 4 and 5

                  (3)      Centrifuge dewatering system

                  (4)      Effluent Pond No. 3 and pumping system

                  (5)      North Evaporation Ponds 1, 2, and 3

          b.      SO2 Waste Treatment System - Southside

                  (1)      Effluent Ponds 1A, 1B, 2 and pumping system
                  (2)      Clarifier system
                  (3)      Oxidation Towers
                  (4)      Brine concentrator Nos. 1, 2, and 3
                  (5)      Centrifuge dewatering system
                  (6)      South evaporation pond Nos. 1, 2, 3, 4, and 5

          c.      Data Acquisition System

          d.      Plant Sludge Pit

                                     - 23 -

<PAGE>
                                  Exhibit V(g)
                                   (Continued)

                            FACILITIES AND EQUIPMENT
                        COMMON TO ALL FOUR SAN JUAN UNITS

                                    Ownership

                  New Mexico - 53.741%; Tucson - 19.8% M-S-R -
                  8.7% City of Farmington - 2.559%*; Alamito - 15.2%

13.      Coal transfer facilities from the reclaim conveyors to the
         head-end of plant belts 4A and 4B and dust suppression systems

14.      Maintenance Bay Facilities including:  Bay Bridge Crane, all
         Offices, and Support Facilities

15.      Sewage Treatment Facilities

*City of Farmington's  ownership  interest is with respect to Common  Facilities
not in service on  November  17,  1981;  the City of  Farmington  was granted an
Easement  and  License  for use of Common  Facilities  which  were in service on
November 17, 1981.



                                     - 24 -

<PAGE>
                                 EXHIBIT 10.5.2


<PAGE>

                               MODIFICATION NO. 5
                                       TO
                              CO-TENANCY AGREEMENT
                                     BETWEEN
                      PUBLIC SERVICE COMPANY OF NEW MEXICO
                                       AND
                          TUCSON ELECTRIC POWER COMPANY

         This  Modification  No. 5 to the  Co-Tenancy  Agreement  Between PUBLIC
SERVICE  COMPANY OF NEW MEXICO ("New Mexico") and TUCSON  ELECTRIC POWER COMPANY
("Tucson"),  hereinafter  sometimes referred to collectively as the "Parties" or
"Participants",  is hereby  entered into and executed as of the 1st day of July,
1985.

         WITNESSETH:

         WHEREAS,  the  Parties  entered  into  an  agreement  described  as the
Co-Tenancy  Agreement  Between New Mexico and Tucson  effective July 1, 1969, as
modified by Modification  No. 1 on May 16, 1979,  Modification No. 2 on December
31, 1983, Modification No. 3 on July 17, 1984, and Modification No. 4 on October
25,  1984  ("Co-Tenancy   Agreement"),   which  establishes  certain  terms  and
conditions relating to their ownership and operation of the San Juan Project and
Project Agreements; and

         WHEREAS,  on December 28, 1984, New Mexico and the Incorporated  County
of Los Alamos, New Mexico ("Los Alamos County") entered into the Amended and

                                      - 2 -

<PAGE>

Restated San Juan Unit 4 Purchase and  Participation  Agreement  ("County PPA"),
whereby  Los Alamos  County  agreed to purchase  from New Mexico a 7.20  percent
undivided ownership interest in Unit 4; and

         WHEREAS,  the County PPA provides,  among other things, that Los Alamos
County,  upon closing of the  transaction  provided for in the County PPA,  will
have the voting rights and obligations of a Unit Participant on San Juan Project
Committees  as  said  rights  and  obligations  are  set  forth  in the  Project
Agreements; and

         WHEREAS,  New  Mexico  and  Tucson  desire to  clarify  the  rights and
responsibilities  of Participants and Unit  Participants in the San Juan Project
as a result of Los Alamos County's purchase of a 7.20 percent undivided interest
in Unit 4 pursuant to the County PPA.

         NOW,  THEREFORE,  the Parties  agree that the  Co-Tenancy  Agreement is
hereby amended as follows:

         1.0 Effective  Date.  This  Modification  No. 5 shall become  effective
immediately upon the closing of Los Alamos County's purchase of the 7.20 percent
undivided interest in Unit 4 pursuant to the County PPA,  currently  anticipated
to be July 1, 1985.

         2.0  Compliance  With  Section  6.7.  Section  6.7  of  the  Co-Tenancy
Agreement  requires  that in the event either  Participant  transfers any of its
rights,  title or  interest  in the San Juan  Project,  the  Participants  shall
jointly execute a Supplement to the Co-Tenancy  Agreement,  in recordable  form,
which describes the rights,  titles, and interests of each Participant following
such  transfer  or  assignment.  On  November  17,  1981,  New  Mexico  sold and
transferred an 8.475 percent undivided  ownership interest in Unit 4 to the City
of Farmington,  New Mexico ("City of Farmington").  On December 31, 1981, Tucson
and the M-S-R  Public  Power  Agency  ("M-S-R")  entered  into the  Tucson/M-S-R
Agreement--Option  to Acquire  Ownership  Interest  in San Juan Unit 4,  wherein
Tucson  agreed to sell to M-S-R  and  M-S-R  agreed  to  purchase  from  Tucson,
pursuant to the terms and conditions of such  agreement,  on or before  November
30, 1982,  the Tucson Option (also  referred to as the "Option to Repurchase" in
the May 16,  1979,  San Juan Unit 4 Purchase  Agreement  between  New Mexico and
Tucson). On November 29, 1982, New Mexico and M-S-R executed the San Juan Unit 4
Purchase and Participation  Agreement, and on September 26, 1983, New Mexico and
M-S-R  executed the San Juan Unit 4 Early Purchase and  Participation  Agreement
under which New Mexico sold and transferred a 28.8 percent  undivided  ownership
interest in Unit 4 to M-S-R  effective  December 31, 1983.  On October 31, 1984,
Tucson transferred its 50 percent undivided  ownership interest in Unit 3 to the
Alamito  Company  ("Alamito").  On December 28, 1984,  New Mexico and Los Alamos
County  entered into the County PPA which provides that New Mexico will sell and
transfer to Los Alamos County a 7.20 percent

                                      - 3 -

<PAGE>

undivided ownership interest in Unit 4 which transfer is expected to occur as of
July 1, 1985. In accordance with the  requirements of Section 6.7, the following
sections of the Co-Tenancy Agreement are hereby amended to read as follows:

         Amended Section 6.3.1:

         6.3.1 For Units 1 and 2 and for all equipment and  facilities  directly
related to Units 1 and 2, in accordance with the following percentages:

          A.      Participants

                   1.      New Mexico - 50 percent
                   2.      Tucson - 50 percent

          B.      Unit Participants

                   1.      M-S-R - 0 percent
                   2.      City of Farmington - 0 percent
                   3.      Alamito - 0 percent
                   4.      Los Alamos County - 0 percent

         6.3.1.1  For  Unit 3 and  for all  equipment  and  facilities  directly
related to Unit 3 only, in accordance with the following percentages:


                                      - 4 -

<PAGE>

          A.      Participants

                   1.      New Mexico - 50 percent
                   2.      Tucson - 0 percent

          B.      Unit Participants

                   1.      M-S-R - percent
                   2.      City of Farmington - 0 percent
                   3.      Alamito - 50 percent
                   4.      Los Alamos County - 0 percent

         Amended Section 6.3.2:

         6.3.2 For Unit 4 and for all equipment and facilities  directly related
to Unit 4 only, in accordance with the following percentages:

          A.      Participants

                   1.      New Mexico - 55.525 percent
                   2.      Tucson - 0 percent

          B.      Unit Participants

                   1.      M-S-R - 28.8 percent
                   2.      City of Farmington - 8.475 percent

                                      - 5 -

<PAGE>

                   3.      Alamito - 0 percent
                   4.      Los Alamos County - 7.20 percent

         Amended Section 6.3.3:

         6.3.3 For  equipment  and  facilities  common only to Units 1 and 2, in
accordance with the following percentages:

          A.      Participants

                   1.      New Mexico - 50 percent
                   2.      Tucson - 50 percent

          B.      Unit Participants

                   1.      M-S-R - 0 percent
                   2.      City of Farmington - 0 percent
                   3.      Alamito - 0 percent
                   4.      Los Alamos County - 0 percent

         Amended Section 6.3.4:

         6.3.4 For  equipment  and  facilities  common only to Units 3 and 4, in
accordance with the following percentages:

          A.      Participants


                                      - 6 -

<PAGE>

                   1.      New Mexico - 52.739 percent
                   2.      Tucson - 0 percent

          B.      Unit Participants

                   1.      M-S-R - 14.4 percent

                   2.      City  of  Farmington  -  4.249   percent   (ownership
                           interest is with respect to common  facilities not in
                           service on November 17, 1981;  the City of Farmington
                           was granted an Easement and License for use of common
                           facilities  which  were in service  on  November  17,
                           1981).
                   3.      Alamito - 25 percent
                   4.      Los Alamos County - 3.612 percent

         Amended Section 6.3.5:

         6.3.5  For  equipment  and  facilities  common  to all of the  units in
accordance with the following percentages:

          A.      Participants

                   1.      New Mexico - 51.566 percent
                   2.      Tucson - 19.8 percent

          B.      Unit Participants

                                      - 7 -

<PAGE>

                   1.      M-S-R - 8.7 percent

                   2.      City  of  Farmington  -  2.559   percent   (ownership
                           interest is with respect to common  facilities not in
                           service on November 17, 1981;  the City of Farmington
                           was granted an Easement and License for use of common
                           facilities  which  were in service  on  November  17,
                           1981).

                   3.      Alamito - 15.2 percent

                   4.      Los Alamos County - 2.175 percent Amended 
                           Section 6.3.6:

         6.3.6 For the  Switchyard  Facilities  except as otherwise  provided in
Section 15 hereof, in accordance with the following percentages:

          A.      Participants

                   1.      New Mexico - 50 percent
                   2.      Tucson - 50 percent

          B.      Unit Participants

                   1.      M-S-R - 0 percent
                   2.      City of Farmington - 0 percent

                                      - 8 -

<PAGE>

                   3.      Alamito - 0 percent
                   4.      Los Alamos County - 0 percent

         3.0  Amended Section 8.1:  Section 8.1 shall be amended to
read in its entirety as follows:

                  8.1  Subject to the  provisions  of  paragraphs  10.1 and 10.2
         hereof,  the Participants  shall be entitled to share the Net Effective
         Generating Capacity of Units 1 and 2 in equal, undivided one-half (1/2)
         interests.  New Mexico and  Alamito  shall be entitled to share the Net
         Effective  Generating  Capacity of Unit 3 in equal  undivided  one-half
         (1/2) interests.  New Mexico and Unit  Participants to which New Mexico
         conveys or has conveyed ownership interests and generation entitlements
         in Unit 4 shall have a 100 percent (100%) interest in the Net Effective
         Generating Capacity of Unit 4.

         4.0 New Section  9.5.3. A new Section 9.5.3 shall be added to Section 9
to read in its entirety as follows:

                  9.5.3 With respect to matters involving and not solely related
         to Unit 4, New Mexico will in good faith  solicit the views of the City
         of Farmington  and Los Alamos County on matters  involving the San Juan
         Project which affect Unit 4.



                                      - 9 -

<PAGE>

         5.0 Amended  Exhibit V. Exhibit V (a-h) shall be amended to read in its
entirety as shown on the attached.

         6.0 Amended Section 25.8.  Section 25.8 shall be amended to read in its
entirety as follows:

                  25.8  Except  as  modified  by the  provisions  set  forth  in
         Modification  No. 5, all of the terms and conditions of the Co- Tenancy
         Agreement,  effective as of July 1, 1969,  as modified by  Modification
         No.  1 on May 16,  1979,  Modification  No.  2 on  December  31,  1983,
         Modification  No. 3 on July 17, 1984, and Modification No. 4 on October
         25, 1984, shall remain in full force and effect.

         6.0 Amended Section 26. Section 26 shall be amended to read as follows:

         26.0  RECOGNITION  OF M-S-R,  THE CITY OF  FARMINGTON,  ALAMITO AND LOS
ALAMOS COUNTY ACKNOWLEDGEMENT.

         26.1 The Parties recognize that M-S-R, the City of Farmington, Alamito,
and Los  Alamos  County,  each has  acknowledged  that it is  familiar  with the
Project  Agreements as amended between New Mexico and Tucson and such agreements
govern the activities of the San Juan Project. Where a specific provision of the
EPPA, the Farmington  PAPA, or the County PPA, is in conflict with the provision
in one or more of the Project Agreements, then (a) as

                                     - 10 -

<PAGE>

between New Mexico and M-S-R,  the  provisions of the EPPA shall govern,  all as
provided in Section 5.2 of such EPPA, and (b) as between New Mexico and the City
of  Farmington,  the  provisions of the  Farmington  PAPA shall  govern,  all as
provided in Section 8.2 of the  Farmington  PAPA,  and (c) as between New Mexico
and Los Alamos  County,  the  provisions of the County PPA shall govern,  all as
provided in Section 5.2 of the County PPA. "EPPA" shall mean the San Juan Unit 4
Early Purchase and Participation  Agreement entered into by New Mexico and M-S-R
on September 26, 1983. "Farmington PAPA" shall mean the San Juan Unit 4 Purchase
Agreement and Participation  Agreement entered into by New Mexico and Farmington
on November 17, 1981.  "County PPA" shall mean the Amended and Restated San Juan
Unit 4 Purchase and  Participation  Agreement entered into by New Mexico and Los
Alamos County on December 28, 1984.


                                     - 11 -

<PAGE>

         IN WITNESS  WHEREOF,  the Parties hereto have caused this  Modification
No. 5 to the  Co-Tenancy  Agreement  to be  executed  as of the 1st day of July,
1985.



                                       PUBLIC SERVICE COMPANY OF NEW MEXICO


Attest:                                By:      /S/ J. L. Wilkins
                                            -------------------------------
/S/ M. Mason-Plunkett                       Its:     Senior Vice President,
--------------------------                           Power Supply
Assistant Secretary                                  



                                       TUCSON ELECTRIC POWER COMPANY


Attest:                                By:      /S/
                                            ------------------------------
/S/                                         Its:     President
--------------------------
Assistant Secretary



                                     - 12 -

<PAGE>

STATE OF NEW MEXICO   )
                      ) ss.
COUNTY OF BERNALILLO  )


         The foregoing instrument was acknowledged before this 24th day of June,
1985, by J. L. Wilkins, a Senior Vice President of Public Service Company of New
Mexico, a New Mexico corporation on behalf of said corporation.


My Commission Expires:


    July 1, 1988                       /S/ Sherry Leeson
                                       -----------------------
                                       Notary Public



STATE OF ARIZONA   )
                   )  ss.
COUNTY OF PIMA     )

         The foregoing  instrument was  acknowledged  before me this 14th day of
June,  1985, by Einar Greve,  President of Tucson  Electric  Power  Company,  an
Arizona corporation, on behalf of said corporation.


My Commission Expires:


   January 9, 1987                      /S/


                                     - 13 -

<PAGE>

                                  Exhibit V(a)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 1

                                    Ownership

                          New Mexico - 50% Tucson - 50%
                       M-S-R - 0% City of Farmington - 0%
                       Alamito - 0% Los Alamos County - 0%


 1.      Turbine Generator

 2.      Condenser

 3.      Condensate and Feedwater System

          a.      Condensate Pumps
          b.      Feedwater Heaters
          c.      Boiler Feed Pumps
          d.      Storage Tanks

 4.      Boiler including:  Air Heaters, Pulverizers, Bunkers, and
         Feeders

 5.      Forced Draft Fans and Primary Air Fans

 6.      Precipitator

 7.      Stack and Stack Monitoring System

 8.      Cooling Tower

 9.      Circulating Water Pumps

10.      Main, Start-up, Unit Auxiliary, and SO2 Scrubber Transformers

11.      Bottom Ash System (Up to but not including Dewatering Tank or
         Ash Water Pump building and equipment.)

12.      Fly Ash System

13.      Building HVAC System

14.      SO2 Absorbers, Scrubbers, Transfer Pumps, Booster Fans, and
         Flue Gas Reheat System including the 650-pound Reheat Steam
         Line and Desuperheater from the Plant Main Steam Line but not
         including the 165-pound Control Valve and Branch Line to the
         Chemical Plant

15.      Emergency Diesel Generator


                                      - 1 -

<PAGE>
                                  Exhibit V(a)
                                   (continued)


16.      Electrical and Control Systems

17.      SSR Protection System

18.      Unit Specific Piping for all Air Systems, Chemical Feed
         Systems, and Hydrogen



                                      - 2 -

<PAGE>

                                  Exhibit V(b)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 2

                                    Ownership

                          New Mexico - 50% Tucson - 50%
                       M-S-R - 0% City of Farmington - 0%
                       Alamito - 0% Los Alamos County - 0%


 1.      Turbine Generator

 2.      Condenser

 3.      Condensate and Feedwater System

          a.      Condensate Pumps
          b.      Feedwater Heaters
          c.      Boiler Feed Pumps
          d.      Storage Tanks

 4.      Boiler including:  Air Heaters, Pulverizers, Bunkers, and
         Feeders

 5.      Forced Draft Fans and Primary Air Fans

 6.      Precipitator

 7.      Stack and Stack Monitoring System

 8.      Cooling Tower

 9.      Circulating Water Pumps

10.      Main, Start-up, Unit Auxiliary, and SO2 Scrubber
         Transformers

11.      Bottom Ash System (Up to but not including Dewatering Tank
         or Ash Water Pump building and equipment.)

12.      Fly Ash System

13.      Building HVAC System

14.      SO2 Absorbers, Scrubbers, Transfer Pumps, Booster Fans, and
         Flue Gas Reheat System including the 650-pound Reheat Steam
         Line and Desuperheater from the Plant Main Steam Line but
         not including the 165-pound Control Valve and Branch Line to
         the Chemical Plant

15.      Emergency Diesel Generator


                                      - 3 -

<PAGE>
                                  Exhibit V(b)
                                   (continued)


16.      Electrical and Control Systems

17.      Unit Specific Piping for all Air Systems, Chemical Feed
         Systems, and Hydrogen


                                      - 4 -

<PAGE>

                                  Exhibit V(c)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 3

                                    Ownership

                         New Mexico - 50% Alamito - 50%
                       M-S-R - 0% City of Farmington - 0%
                       Tucson - 0% Los Alamos County - 0%


 1.      Turbine Generator

 2.      Condenser

 3.      Condensate and Feedwater System

          a.      Condensate Pumps
          b.      Feedwater Heaters
          c.      Boiler Feed Pumps
          d.      Storage Tanks

 4.      Boiler including:  Air Heaters, Pulverizers, Bunkers, and
         Feeders

 5.      Forced Draft Fans and Primary Air Fans

 6.      Precipitator

 7.      Stack and Stack Monitoring System

 8.      Cooling Tower

 9.      Circulating Water Pumps

10.      Main, Unit Auxiliary 3A and 3B Transformers

11.      Bottom Ash System including:  Hopper, Dewatering Tank,
         Settling Tank, Surge Tank, and Pump House

12.      Fly Ash System

13.      Building HVAC System

14.      SO2 Absorbers, Scrubbers, Transfer Pumps, Booster Fans, and
         Flue Gas Reheat System

15.      Emergency Diesel Generator

16.      Electrical and Control Systems

                                      - 5 -

<PAGE>
                                  Exhibit V(c)
                                   (continued)


17.      Fuel Oil Ignitor Heaters and Unit Specific Piping

18.      Unit Specific Piping for all Air Systems, Chemical Feed
         Systems, and Hydrogen

19.      Coal Reclaim Hoppers, Feeders, Feeder Belts, Belt Scales, Fire
         Protection System, and 3C Conveyor to the Secondary Crusher
         Building

20.      SSR Protection System

21.      Auxiliary Steam Header Piping System:

          a.      Including the Unit Specific Branch Line to the Reheat
                  System

          b.      Not included is the Branch Line to the Chemical Plant


                                      - 6 -

<PAGE>
                                  Exhibit V(d)

                            FACILITIES AND EQUIPMENT
                         SPECIFIC TO SAN JUAN UNIT NO. 4

                                    Ownership


                        New Mexico - 55.525% Tucson - 0%
                    M-S-R - 28.8% City of Farmington - 8.475%
                     Alamito - 0% Los Alamos County - 7.20%


 1.      Turbine Generator

 2.      Condenser

 3.      Condensate and Feedwater System

          a.      Condensate Pumps
          b.      Feedwater Heaters
          c.      Boiler Feed Pumps
          d.      Storage Tanks

 4.      Boiler including:  Air Heaters, Pulverizers, Bunkers, and
         Feeders

 5.      Forced Draft Fans and Primary Air Fans

 6.      Precipitator

 7.      Stack and Stack Monitoring System

 8.      Cooling Tower

 9.      Circulating Water Pumps

10.      Main, Unit Auxiliary 4A and 4B Transformers

11.      Bottom Ash System including:  Hopper, Dewatering Tank,
         Settling Tank, Surge Tank, Storage Tank, and Pump House

12.      Fly Ash System

13.      Building HVAC System

14.      SO2 Absorbers, Scrubbers, Transfer Pumps, Booster Fans, and
         Flue Gas Reheat System

15.      Emergency Diesel Generator

16.      Electrical and Control Systems

                                      - 7 -

<PAGE>

                                  Exhibit V(d)
                                   (continued)


17.      Fuel Oil Ignitor Heaters and Unit Specific Piping

18.      Unit Specific Piping for all Air Systems, Chemical Feed
         Systems, and Hydrogen

19.      Coal Reclaim Hoppers, Feeders, Feeder Belts, Belt Scales, Fire
         Protection System, and 3D Conveyor to the Secondary Crusher
         Building

20.      Auxiliary Steam Header Piping System:

          a.      Including the Unit Specific Branch Line to the Reheat
                  System

          b.      Not included is the Branch Line to the Chemical Plant


                                      - 8 -

<PAGE>

                                  Exhibit V(e)

                            FACILITIES AND EQUIPMENT
                        COMMON TO SAN JUAN UNITS 1 AND 2

                                    Ownership



                          New Mexico - 50% Tucson - 50%
                       M-S-R - 0% City of Farmington - 0%
                       Alamito - 0% Los Alamos County - 0%


 1.      Bearing Cooling Water System

 2.      Bottom Ash Dewatering Facility including:  Dewatering Tank,
         Settling Tank, Surge Tank, Storage Tank, and Pump House

 3.      Demineralizer System including:  Clarifier, Storage Tanks, and
         Sump Pump

 4.      Fuel Oil System (No. 2 Oil for Ignition and Flame
         Stabilization)

 5.      Premix Tank Facility (This was the wastewater neutralizer
         facility and is now operated as part of the Water Management
         System.)

 6.      Instrument Air System, except Unit Piping

 7.      Chemical Feed System, except Unit Piping

          a.      Condensate and Feedwater System
          b.      Boiler
          c.      Bearing Cooling Water System
          d.      Cooling Tower Systems
          e.      Chlorination System

 8.      Plant Air System, except Unit Piping

 9.      Sootblowing Air System, except Unit Piping

10.      Hydrogen Storage System, except Unit Piping

11.      Coal Handling Reclaim Systems A and B including:  Hoppers,
         Feeders, Reclaim Conveyors, Belt Scales, and Sprinkler System

12.      Coal Tripper System south of column, Line 12 including Dust
         Collection System

13.      Turbine Lube Oil Storage and Transfer System

14.      Control Room, Equipment Rooms, and Associated HVAC System

                                      - 9 -

<PAGE>

                                  Exhibit V(e)
                                   (continued)


15.      Turbine Crane south of column, Line 12

16.      Fuel Oil, Ash, and Water Pipe Racks

17.      Boiler Fill System for Units 1 and 2

18.      All spare parts common to either unit.

19.      SO2 Backup Scrubber-Absorber Transformer

20.      SAR Multiplexer Control System


                                     - 10 -

<PAGE>

                                  Exhibit V(f)

                            FACILITIES AND EQUIPMENT
                        COMMON TO SAN JUAN UNITS 3 AND 4

                                    Ownership


                        New Mexico - 52.739% Tucson - 0%
                   M-S-R - 14.4% City of Farmington - 4.249%*
                    Alamito - 25% Los Alamos County - 3.612%


 1.      Bearing Cooling Water System

 2.      Demineralizer System:  including Sump Pumps, Filter Beds, and
         Storage Tanks

 3.      Fuel Oil System (No. 6 Oil for Ignition and Flame
         Stabilization except Ignitor Heaters and Unit Specific Piping)

 4.      Wastewater Neutralizer Facility (This facility is operated as
         part of Water Management System.)

 5.      Instrument Air System except Unit Piping

 6.      Chemical Feed System except Unit Piping

          a.      Condensate and Feedwater System
          b.      Boiler
          c.      Bearing Cooling Water System
          d.      Cooling Tower Systems
          e.      Chlorination System

 7.      Plant Air System except Unit Piping

 8.      Sootblowing Air System except Unit Piping

 9.      Start-Up Transformers and Nonseg Bus to Units 3 and 4
         Switchgear

10.      Hydrogen Storage System except Unit Piping

11.      Coal Tripper System Serving Units 3 and 4 including Dust
         Collection Systems

12.      Turbine Lube Oil Storage and Transfer System

13.      Control Room, Equipment Rooms, and Associated HVAC System

14.      Boiler Fill System for Units 3 and 4



                                     - 11 -

<PAGE>

                                  Exhibit V(f)
                                   (continued)



15.      Auxiliary Cooling Systems including Auxiliary Cooling Tower
         No. 1 and Pumps, but excepting No. 4 Tower Pumps and Piping
         which is Unit Specific

16.      CO2 Storage System

17.      Start-Up Boiler Feed Pump

18.      Turbine Bay Crane north of column, Line 12

19.      Fuel Oil, Ash, and Water Pipe Racks

20.      Fire Water Booster and Jockey Pumps

21.      Halon Fire Protection System

22.      Cooling Tower Multiplex Control System

23.      All spare parts common to either unit.

*City of Farmington's  ownership  interest is with respect to Common  Facilities
not in service on  November  17,  1981;  the City of  Farmington  was granted an
Easement  and  License  for use of Common  Facilities  which  were in service on
November 17, 1981.


                                     - 12 -

<PAGE>

                                  Exhibit V(g)

                            FACILITIES AND EQUIPMENT
                          COMMON TO ALL SAN JUAN UNITS

                                    Ownership


                       New Mexico - 51.566% Tucson - 19.8%
                    M-S-R - 8.7% City of Farmington - 2.559%*
                   Alamito - 15.2% Los Alamos County - 2.175%


 1.      River and Raw Water System including:

          a.      Diversion and intake structures including all equipment
                  and pump building.
          b.      Raw water line to reservoir.
          c.      Reservoir and pump building and all equipment
          d.      Raw water lines to plant and yard.
          e.      All underground and above ground fire protection system
                  to each vendor supplied or unit specific fire
                  distribution system.

 2.      Auxiliary Boiler

 3.      SO2 System Chemical Plant except Absorbers

          a.      Double effect evaporator train systems.
          b.      Fly ash filter system.
          c.      Absorber product and feed tanks.
          d.      Condensate collection, storage, and transfer systems.
          e.      Soda ash storage, mixing, and distribution system.
          f.      Sulfur plant.
          g.      Sulfate purge system including crystallizers,
                  centrifuges, evaporators, and salt cake system.
          h.      Sulfuric acid plant system including storage tanks and
                  load out system.
          i.      Auxiliary No. 2 cooling tower, pumps, and system.

 4.      Spare Main Transformer 345/24 kV for all units

 5.      Maintenance, Office, and Warehousing Facilities

 6.      Chemical Laboratory

 7.      Coal and Ash Handling Control Facilities

 8.      Roads and grounds such as fencing, yard lighting, guard
         facilities, drainage, and dikes.

 9.      Potable Water System


                                     - 13 -

<PAGE>

                                  Exhibit V(g)
                                   (continued)


10.      Environmental Monitoring Systems including Air, Water, and
         Ground.  Excludes Stack Monitoring Systems which are unit
         specific.

11.      Transportation such as trucks, cars, and dozers

12.      Water Management System

          a.      Wastewater Recovery System - Northside

                  1)       Reverse osmosis system including lime/soda
                           softening clarifier system.
                  2)       Brine concentrator Nos. 4 and 5.
                  3)       Centrifuge dewatering system.
                  4)       Effluent pond No. 3 and pumping system.
                  5)       North evaporation ponds 1, 2, and 3.

          b.      SO2 Waste Treatment System - Southside

                  1)       Effluent ponds 1A, 1B, 2, and pumping system.
                  2)       Clarifier system.
                  3)       Oxidation towers.
                  4)       Brine concentrator Nos. 1, 2, and 3.
                  5)       Centrifuge dewatering system.
                  6)       South evaporation pond Nos. 1, 2, 3, 4, and 5.

          c.      Data Acquisition System

          d.      Solid Waste Disposal Pit

13.      Coal Transfer Facilities from the Reclaim Conveyors to the
         Head-End of Plant Belts 4A and 4B and Dust Suppression Systems

14.      Maintenance Bay Facilities including:  Bay Bridge Crane, all
         Offices, and Support Facilities

15.      Sewage Treatment Facilities

16.      On each of Units 1 and 2, the Chemical Plant 165-pound Control
         Valve, and Branch Line from the Unit Specific 650-pound Reheat
         Steam Line

17.      On each of Units 3 and 4, the Chemical Plant Branch Steam Line
         from the Unit Specific Auxiliary Steam Header System

*City of Farmington's  ownership  interest is with respect to Common  Facilities
not in service on  November  17,  1981;  the City of  Farmington  was granted an
Easement  and  License  for use of Common  Facilities  which  were in service on
November 17, 1981.


                                     - 14 -

<PAGE>

                                  Exhibit V(h)

                                SAN JUAN PROJECT

                              SWITCHYARD FACILITIES


                               Cost Allocation (%)



                                                       Replacement/Improvements
                                      Installed Cost          Betterments
                                      --------------          -----------
                              New Mexico     Tucson     New Mexico      Tucson
                              ----------     ------     ----------      ------


345 kV Bus 1 & 3 (East Bus)       50           50           50            50
Bus 2 (West Bus)                  50           50           50            50

Circuit Breakers
----------------

06582 (345/230)                   50           50           50            50
05482                             50           50           50            50
04382 (OJO)                       50           50           50            50

12982 (McKinley)                  50           50           50            50
11882                             50           50           50            50
10782 (Unit 4)                    50           50           50            50

09882 (McKinley)                 58.33       41.67         62.5          37.5
08782                            54.16       45.84         56.25         43.75
07682 (Unit 3)                    50           50           50            50

15282 (Corers)                    50           50           50            50
14182                             50           50           50            50
13082 (Unit 2)                    50           50           50            50
18582 (West Mesa)                 50           50           50            50
17482                             50           50           50            50
16382 (Unit 1)                    50           50           50            50
20782                             50           50           50            50


                                     - 15 -

<PAGE>


                                  Exhibit V(h)
                                   (continued)



Shunt Reactors
--------------

Ojo                           100          0          100          0
McKinley 1                   5.36        94.64       5.36        94.64
McKinley 2                   16.67       83.33        25           75
WW (BA)                       100          0          100          0

Transformers
------------

Station Aux. No. 2            100          0          100          0
  400 MVA, 345/230-12.5
Station Aux. No. 1            50           50         50           50
  345/4.16-12.5
Station Aux. No. 3            50           50         50           50

Future Facilities
-----------------

345/69/12 kV                 66.67       33.33       66.67       33.33
2-345 kV Bkrs (Durango)       50           50         50           50

Lower Voltage
-------------

230 kV Control Hse           83.33       16.67       83.33       16.67
230/69 kV Trf                66.67       33.33       66.67       33.33
Shiprock 230 kV line          100          0          100          0


                                     - 16 -


<PAGE>