Exhibit 4(a)




                            SUPPLEMENTAL INDENTURE


                          (Dated as of April 1, 1998)





                      PUBLIC SERVICE COMPANY OF COLORADO


                                      TO


                    U.S. BANK TRUST NATIONAL ASSOCIATION,

                                                                    As Trustee



                                    --------

                  Creating an Issue of First Mortgage Bonds,
                              Collateral Series F

                                    --------

     (Supplemental to Indenture dated as of December 1, 1939, as amended)


<PAGE>

            SUPPLEMENTAL  INDENTURE,  dated as of April 1, 1998,  between PUBLIC
SERVICE COMPANY OF COLORADO, a corporation organized and existing under the laws
of the State of Colorado (the "Company"), party of the first part, and U.S. BANK
TRUST  NATIONAL  ASSOCIATION   (formerly  First  Trust  of  New  York,  National
Association),   a  national  banking  association,  as  successor  trustee  (the
"Trustee") to Morgan Guaranty Trust Company of New York (formerly Guaranty Trust
Company of New York), party of the second part.

            WHEREAS,  the  Company  heretofore  executed  and  delivered  to the
Trustee its Indenture, dated as of December 1, 1939 (the "Principal Indenture"),
to secure its First Mortgage Bonds from time to time issued thereunder; and

            WHEREAS,  the Company has  heretofore  executed and delivered to the
Trustee the Supplemental Indentures referred to in Schedule A hereto for certain
purposes,  including the creation of series of bonds, the subjection to the lien
of the Principal Indenture of property acquired after the execution and delivery
thereof,  the amendment of certain provisions of the Principal Indenture and the
appointment of the successor Trustee; and

            WHEREAS,  the Principal Indenture as supplemented and amended by all
Supplemental  Indentures  heretofore  executed by the Company and the Trustee is
hereinafter  referred to as the  "Indenture",  and, unless the context  requires
otherwise,  references herein to Articles and Sections of the Indenture shall be
to Articles and Sections of the Principal Indenture as so amended; and

            WHEREAS,  the  Company  proposes  to  create a new  series  of First
Mortgage Bonds to be designated as First  Mortgage  Bonds,  Collateral  Series F
(the  "Collateral  Series F Bonds"),  to be issued and  delivered to the trustee
under  the  1993  Mortgage  (as  hereinafter  defined)  as  the  basis  for  the
authentication  and delivery  under the 1993 Mortgage of a series of securities,
all as hereinafter  provided,  and to vary in certain respects the covenants and
provisions  contained  in Article V of the  Indenture,  to the extent  that such
covenants and provisions apply to the Collateral Series F Bonds; and

            WHEREAS,  the Company,  pursuant to the provisions of the Indenture,
has, by appropriate  corporate  action,  duly resolved and determined to execute
this Supplemental Indenture for the purpose of providing for the creation of the
Collateral Series F Bonds and of specifying the form, provisions and particulars
thereof,  as in  the  Indenture  provided  or  permitted  and of  giving  to the
Collateral Series F Bonds the protection and security of the Indenture; and

            WHEREAS,   the  Company  has   acquired  the   additional   property
hereinafter described,  and the Company desires that such additional property so
acquired be specifically subjected to the lien of the Indenture; and

            WHEREAS,  the  Company  represents  that all  acts  and  proceedings
required by law and by the charter and  by-laws of the  Company,  including  all
action  requisite  on the  part of its  shareholders,  directors  and  officers,
necessary to make the Collateral  Series F Bonds,  when executed by the Company,
authenticated and delivered by the Trustee and duly issued,  the valid,  binding
and legal obligations of the Company,  and to constitute the Principal Indenture
and all indentures supplemental thereto,  including this Supplemental Indenture,
valid,  binding  and  legal  instruments  for the  security  of the bonds of all
series, including the Collateral Series F Bonds, in accordance with the terms of
such bonds and such instruments,  have been done,  performed and fulfilled,  and
the execution and delivery hereof have been in all respects duly authorized;


<PAGE>


            NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:

            That Public  Service  Company of Colorado,  the Company named in the
Indenture, in consideration of the premises and of One Dollar to it duly paid by
the  Trustee at or before the  ensealing  and  delivery of these  presents,  the
receipt  whereof is hereby  acknowledged,  and in pursuance of the direction and
authority of the Board of Directors  of the Company  given at a meeting  thereof
duly called and held, and in order to create the  Collateral  Series F Bonds and
to specify the form,  terms and  provisions  thereof,  and to make  definite and
certain the lien of the Indenture upon the premises hereinafter described and to
subject said premises  directly to the lien of the Indenture,  and to secure the
payment of the principal of and premium,  if any, and  interest,  if any, on all
bonds  from  time  to  time  outstanding  under  the  Indenture,  including  the
Collateral  Series F Bonds,  according to the terms of said bonds, and to secure
the performance and observance of all of the covenants and conditions  contained
in the Indenture, has executed and delivered this Supplemental Indenture and has
granted,  bargained,  sold, warranted,  aliened,  remised,  released,  conveyed,
assigned, transferred,  mortgaged, pledged, set over and confirmed, and by these
presents does grant, bargain,  sell, warrant,  alien, remise,  release,  convey,
assign,  transfer,  mortgage,  pledge, set over and confirm unto U.S. Bank Trust
National  Association,  as Trustee, and its successor or successors in the trust
and its and their assigns forever,  the property  described in Schedule B hereto
(which is  described  in such manner as to fall within and under the headings or
parts or  classifications  set forth in the  Granting  Clauses of the  Principal
Indenture);

            TO HAVE AND TO HOLD the same and all and  singular  the  properties,
rights,  privileges and franchises  described in the Principal  Indenture and in
the  several  Supplemental  Indentures  hereinabove  referred  to  and  in  this
Supplemental Indenture and owned by the Company on the date of the execution and
delivery hereof (other than property of a character  expressly excepted from the
lien of the  Indenture as therein set forth) unto the Trustee and its  successor
or successors and assigns forever;

            SUBJECT,  HOWEVER,  to  permitted  encumbrances  as defined in the
Indenture;

            IN TRUST,  NEVERTHELESS,  upon the terms and trusts set forth in the
Indenture,  for the equal and proportionate  benefit and security of all present
and future  holders of the bonds and coupons  issued and to be issued  under the
Indenture, including the Collateral Series F Bonds, without preference, priority
or distinction as to lien (except as any sinking,  amortization,  improvement or
other fund established in accordance with the provisions of the Indenture or any
indenture  supplemental  thereto may afford additional security for the bonds of
any particular series) of any of said bonds over any others thereof by reason of
series,  priority in the time of the issue or negotiation  thereof, or otherwise
howsoever, except as provided in Section 2 of Article IV of the Indenture.


                                  ARTICLE ONE

           CREATION AND DESCRIPTION OF THE COLLATERAL SERIES F BONDS

            SECTION 1. A new series of bonds to be issued  under and  secured by
the Indenture is hereby  created,  the bonds of such new series to be designated
First Mortgage Bonds,  Collateral  Series F. The Collateral Series F Bonds shall
be limited to an aggregate principal amount of Two hundred fifty million dollars
($250,000,000),   excluding  any   Collateral   Series  F  Bonds  which  may  be
authenticated  and  exchanged  for or in  lieu of or in  substitution  for or on
transfer of other  Collateral  Series F Bonds


                                      -2-

<PAGE>

pursuant to any provisions of the Indenture. The Collateral Series F Bonds shall
mature on April 15, 2003. The Collateral Series F Bonds shall not bear interest.

      The  principal  of each  Collateral  Series F Bond shall be payable,  upon
presentation  thereof,  at the  office or agency of the  Company  in the city in
which the  principal  corporate  trust office of the 1993  Mortgage  Trustee (as
hereinafter defined) is located, in any coin or currency of the United States of
America  which at the time of payment  shall be legal  tender for the payment of
public and private debts.

            The  Collateral  Series F Bonds shall be issued and delivered by the
Company to U.S. Bank Trust National Association,  as successor trustee under the
Indenture,  dated as of October 1, 1993, as supplemented  (the "1993 Mortgage"),
of the Company to such successor trustee (the "1993 Mortgage  Trustee"),  as the
basis for the authentication and delivery under the 1993 Mortgage of a series of
securities. As provided in the 1993 Mortgage, the Collateral Series F Bonds will
be registered  in the name of the 1993 Mortgage  Trustee or its nominee and will
be owned and held by the 1993 Mortgage Trustee, subject to the provisions of the
1993  Mortgage,  for the benefit of the holders of all  securities  from time to
time outstanding under the 1993 Mortgage, and the Company shall have no interest
therein.

            Any payment by the Company  under the 1993 Mortgage of the principal
of the securities  which shall have been  authenticated  and delivered under the
1993  Mortgage on the basis of the issuance  and  delivery to the 1993  Mortgage
Trustee of  Collateral  Series F Bonds  (other  than by the  application  of the
proceeds of a payment in respect of such  Collateral  Series F Bonds) shall,  to
the extent  thereof,  be deemed to satisfy and discharge  the  obligation of the
Company,  if any, to make a payment of  principal  of such  Collateral  Series F
Bonds which is then due.

            The Trustee may  conclusively  presume  that the  obligation  of the
Company to pay the principal of the Collateral  Series F Bonds as the same shall
become due and payable shall have been fully satisfied and discharged unless and
until it shall have received a written  notice from the 1993  Mortgage  Trustee,
signed by an authorized officer thereof, stating that the principal of specified
Collateral  Series F Bonds has  become  due and  payable  and has not been fully
paid, and specifying the amount of funds required to make such payment.

            Each  Collateral  Series F Bond shall be dated as of the date of its
authentication.

            The  Collateral  Series F Bonds shall be issued as fully  registered
bonds only, in denominations of $1,000 and multiples thereof.

            The Collateral Series F Bonds shall be registerable and exchangeable
at the  office  or  agency of the  Company  in the city in which  the  principal
corporate  trust office of the 1993 Mortgage  Trustee is located,  in the manner
and upon the terms  set  forth in  Section  5 of  Article  II of the  Indenture;
provided, however, that the Collateral Series F Bonds shall not be transferrable
except to a successor  trustee under the 1993 Mortgage.  No service charge shall
be made for any exchange or transfer of any Collateral Series F Bond.

            SECTION  2.  The  text of the  Collateral  Series  F Bonds  shall be
substantially in the form attached hereto as Exhibit A.

            SECTION  3. The  Collateral  Series F Bonds may be  executed  by the
Company and delivered to the Trustee and, upon  compliance  with all  applicable
provisions  and  requirements  of the


                                      -3-
<PAGE>

Indenture  in  respect  thereof,  shall  be  authenticated  by the  Trustee  and
delivered  (without  awaiting  the  filing  or  recording  of this  Supplemental
Indenture) in accordance with the written order or orders of the Company.


                                  ARTICLE TWO

                  REDEMPTION OF THE COLLATERAL SERIES F BONDS

            SECTION 1. Each Collateral  Series F Bond shall be redeemable at the
option of the Company in whole at any time, or in part from time to time,  prior
to maturity, at a redemption price equal to 100% of the principal amount thereof
to be redeemed.

            SECTION 2. The  provisions of Sections 3, 4, 5, 6 and 7 of Article V
of the Indenture  shall be applicable to the Collateral  Series F Bonds,  except
that (a) no publication of notice of redemption of the Collateral Series F Bonds
shall be required and (b) if less than all the Collateral  Series F Bonds are to
be redeemed,  the Collateral  Series F Bonds to be redeemed shall be selected in
the principal  amounts  designated to the Trustee by the Company,  and except as
such  provisions  may  otherwise be  inconsistent  with the  provisions  of this
Article Two.

            SECTION  3. The  holder of each and every  Collateral  Series F Bond
hereby  agrees to accept  payment  thereof  prior to  maturity  on the terms and
conditions provided for in this Article Two.


                                 ARTICLE THREE

                        ACKNOWLEDGMENT OF RIGHT TO VOTE
                          OR CONSENT WITH RESPECT TO
                       CERTAIN AMENDMENTS TO INDENTURE

            The  Company  hereby  acknowledges  the right of the  holders of the
Collateral  Series F Bonds to vote or consent  with respect to any or all of the
modifications to the Indenture  referred to in Article Three of the Supplemental
Indenture, dated as of March 1, 1980, irrespective of the fact that the Bonds of
the Second 1987 Series are no longer outstanding;  provided,  however, that such
acknowledgment  shall  not  impair  (a) the  right of the  Company  to make such
modifications without the consent or other action of the holders of the Bonds of
the 2020 Series or the bonds of any other series subsequently  created under the
Indenture with respect to which the Company has expressly reserved such right or
(b) the right of the  Company  to reserve  the right to make such  modifications
without the consent or other  action of the holders of bonds of one or more,  or
any or all, series created subsequent to the creation of the Collateral Series F
Bonds.


                                 ARTICLE FOUR

                                  THE TRUSTEE

            The  Trustee  accepts  the  trusts  created  by  this   Supplemental
Indenture  upon the terms and  conditions  set forth in the  Indenture  and this
Supplemental Indenture.  The recitals in this Supplemental


                                      -4-

<PAGE>

Indenture  are made by the Company only and not by the  Trustee.  Each and every
term and condition contained in Article XII of the Indenture shall apply to this
Supplemental Indenture with the same force and effect as if the same were herein
set forth in full, with such omissions,  variations and modifications thereof as
may be appropriate to make the same conform to this Supplemental Indenture.


                                 ARTICLE FIVE

                           MISCELLANEOUS PROVISIONS

            SECTION 1.  Subject to the  variations  contained  in Article Two of
this  Supplemental  Indenture,  the  Indenture is in all  respects  ratified and
confirmed and the Principal Indenture, this Supplemental Indenture and all other
indentures  supplemental  to the Principal  Indenture  shall be read,  taken and
construed  as one  and  the  same  instrument.  Neither  the  execution  of this
Supplemental  Indenture  nor  anything  herein  contained  shall be construed to
impair the lien of the Indenture on any of the properties  subject thereto,  and
such lien shall  remain in full force and effect as  security  for all bonds now
outstanding or hereafter issued under the Indenture.

            All covenants and provisions of the Indenture shall continue in full
force  and  effect  and  this  Supplemental  Indenture  shall  form  part of the
Indenture.

            SECTION 2. If the date for  making any  payment or the last date for
performance  of any act or the  exercising  of any right,  as  provided  in this
Supplemental  Indenture,  shall not be a  Business  Day (as  defined in the 1993
Mortgage),  such payment may be made or act performed or right  exercised on the
next  succeeding  Business  Day with the same force and effect as if done on the
nominal date provided in this Supplemental Indenture.

            SECTION  3.  The  terms  defined  in the  Indenture  shall,  for all
purposes  of this  Supplemental  Indenture,  have the meaning  specified  in the
Indenture  except as set forth in  Section 4 of this  Article or  otherwise  set
forth in this  Supplemental  Indenture or unless the context  clearly  indicates
some other meaning to be intended.

            SECTION 4. Any term  defined in Section  303 of the Trust  Indenture
Act of 1939, as amended,  and not otherwise defined in the Indenture shall, with
respect to this  Supplemental  Indenture and the Collateral Series F Bonds, have
the meaning  assigned to such term in Section 303 as in force on the date of the
execution of this Supplemental Indenture.

            SECTION 5. This Supplemental Indenture may be executed in any number
of counterparts, and all of said counterparts executed and delivered, each as an
original, shall constitute but one and the same instrument.


                                      -5-
<PAGE>


            IN WITNESS WHEREOF, Public Service Company of Colorado, party hereto
of the first part,  has caused its corporate  name to be hereunto  affixed,  and
this instrument to be signed by its President,  an Executive Vice  President,  a
Senior Vice President or a Vice President, and its corporate seal to be hereunto
affixed and attested by its  Secretary or an Assistant  Secretary for and in its
behalf; and U.S. Bank Trust National Association, the party hereto of the second
part, in evidence of its acceptance of the trust hereby created,  has caused its
corporate name to be hereunto affixed,  and this instrument to be signed and its
corporate  seal to be affixed by one of its Vice  Presidents and attested by one
of its Assistant Secretaries,  for and in its behalf, all as of the day and year
first above written.

                                          PUBLIC SERVICE COMPANY OF
                                           COLORADO



                                          By:/s/ Brian P. Jackson
                                             Name:  Brian P. Jackson
Title:    Senior Vice President


ATTEST:/s/ Teresa S. Madden
         Name:  Teresa S. Madden
         Title:    Secretary


                                              U.S. BANK TRUST
                                               NATIONAL ASSOCIATION,
                                                   as Trustee


                                          By:/s/ Catherine F. Donohue
                                             Name:  Catherine F. Donohue
                                             Title:    Vice President


ATTEST:/s/ Teresita Glasgow
         Name:  Teresita Glasgow
         Title:    Assistant Secretary


                                      -6-
<PAGE>


STATE OF COLORADO            )
                             )  ss.:
CITY AND COUNTY OF DENVER    )


        On this 20th day of April,  1998,  before me,  Jo Lynn R. Rife,  a duly
authorized Notary Public in and for said City and County in the State aforesaid,
personally  appeared  Brian P.  Jackson and Teresa S. Madden to me known to be a
Senior Vice President and the Secretary, respectively, of PUBLIC SERVICE COMPANY
OF COLORADO, a corporation organized and existing under the laws of the State of
Colorado,  one of the  corporations  that  executed  the  within  and  foregoing
instrument;   and  the  said  Senior  Vice  President  and  Secretary  severally
acknowledged  the said  instrument  to be the free and voluntary act and deed of
said  corporation,  for the uses and  purposes  therein  mentioned,  and on oath
stated that they were  authorized to execute said  instrument  and that the seal
affixed thereto is the corporate seal of said corporation.

        IN WITNESS WHEREOF,  I have hereunto set my hand and affixed my official
seal the day and year first above written.





                                        Name: /s/ Jo Lynn R. Rife
                                        Notary Public, State of Colorado

                                        Commission Expires April 28, 1998



                                      -7-
<PAGE>


STATE OF NEW YORK                )
                                 )ss.:
CITY AND COUNTY OF NEW YORK      )


        On this 17th day of April, 1998,  before  me,  Janet P.  O'Hara,  a duly
authorized Notary Public in and for said City and County in the State aforesaid,
personally  appeared Catherine F. Donahue and Teresita Glasgow to me known to be
a Vice President and an Assistant  Secretary,  respectively,  of U.S. BANK TRUST
NATIONAL  ASSOCIATION,  a national banking association,  one of the corporations
that executed the within and foregoing  instrument;  and the said Vice President
and Assistant  Secretary  severally  acknowledged  the said instrument to be the
free and voluntary act and deed of said  corporation,  for the uses and purposes
therein mentioned,  and on oath stated that they were authorized to execute said
instrument  and that the seal  affixed  thereto  is the  corporate  seal of said
corporation.

        IN WITNESS WHEREOF,  I have hereunto set my hand and affixed my official
seal the day and year first above written.





                                        Name:  /s/Janet P. O'Hara
                                        Notary Public, State of New York
                                        No. 010H5087549
                                        Qualified In Queens County

                                        Commission Expires November 3, 1999



                                      -8-
<PAGE>

                                                                     EXHIBIT A



                       FORM OF COLLATERAL SERIES F BOND

        This bond is not  transferable  except to a successor  trustee under the
Indenture, dated as of October 1, 1993, as supplemented,  between Public Service
Company of Colorado and U.S. Bank Trust  National  Association  (formerly  First
Trust of New York, National Association), as successor
trustee thereunder.


                      PUBLIC SERVICE COMPANY OF COLORADO

                             FIRST MORTGAGE BOND,

                              CoLLATERAL SERIES F

                                   DUE 2003

REGISTERED                                                          REGISTERED

No..................                                       $..................


        FOR VALUE RECEIVED,  PUBLIC SERVICE  COMPANY OF COLORADO,  a corporation
organized  and  existing  under the laws of the State of  Colorado  (hereinafter
sometimes  called the  "Company"),  promises to pay to U.S. Bank Trust  National
Association  (formerly known as First Trust of New York, National  Association),
as successor trustee (the "1993 Mortgage Trustee") under the Indenture, dated as
of October 1, 1993 (the "1993 Mortgage"), of the Company, or registered assigns,


                                                                         Dollars
on April 15,  2003,  at the office or agency of the Company in the city in which
the principal  corporate  trust office of the 1993 Mortgage  Trustee is located.
This bond shall not bear  interest.  The principal of this bond shall be payable
in any coin or  currency  of the United  States of America  which at the time of
payment shall be legal tender for the payment of public and private debts.

        Any payment by the Company  under the 1993  Mortgage of the principal of
securities  which shall have been  authenticated  and  delivered  under the 1993
Mortgage on the basis of the issuance and delivery to the 1993 Mortgage  Trustee
of this bond (the "1993 Mortgage  Securities") (other than by the application of
the proceeds of a payment in respect of this bond) shall, to the extent thereof,
be deemed to satisfy and  discharge the  obligation  of the Company,  if any, to
make a payment of principal of this bond which is then due.

        This bond is one of an issue of bonds of the  Company,  issued and to be
issued in one or more series  under and equally and ratably  secured  (except as
any sinking, amortization,  improvement or other fund, established in accordance
with  the  provisions  of  the  indenture  hereinafter  mentioned,   may  afford
additional  security  for the  bonds  of any  particular  series)  by a  certain
indenture,  dated as of December 1, 1939, made by the Company to U.S. BANK TRUST
NATIONAL ASSOCIATION  (formerly First 


<PAGE>


Trust of New York,  National  Association),  as successor  trustee  (hereinafter
called the  "Trustee") to Morgan  Guaranty  Trust Company of New York  (formerly
Guaranty  Trust  Company of New York),  as amended and  supplemented  by several
indentures  supplemental thereto,  including the Supplemental Indenture dated as
of April 1, 1998 (said Indenture as amended and  supplemented by said indentures
supplemental  thereto  being  hereinafter  called  the  "Indenture"),  to  which
Indenture  reference is hereby made for a description of the property mortgaged,
the nature and extent of the security,  the rights and  limitations of rights of
the Company,  the Trustee,  and the holders of said bonds,  under the Indenture,
and the terms and  conditions  upon which said bonds are secured,  to all of the
provisions of which  Indenture  and of all  indentures  supplemental  thereto in
respect of such security,  including the provisions of the Indenture  permitting
the issue of bonds of any series for property which,  under the restrictions and
limitations therein specified,  may be subject to liens prior to the lien of the
Indenture,  the holder, by accepting this bond, assents. To the extent permitted
by and as provided in the Indenture,  the rights and  obligations of the Company
and of the holders of said bonds  (including  those pertaining to any sinking or
other fund) may be changed and modified, with the consent of the Company, by the
holders  of at  least  75% in  aggregate  principal  amount  of the  bonds  then
outstanding (excluding bonds disqualified from voting by reason of the Company's
interest therein as provided in the Indenture);  provided, however, that without
the consent of the holder hereof no such  modification  or  alteration  shall be
made which will  extend  the time of  payment of the  principal  of this bond or
reduce the principal amount hereof or effect any other modification of the terms
of payment of such principal or will reduce the percentage of bonds required for
the aforesaid actions under the Indenture. The Company has reserved the right to
amend the Indenture without any consent or other action by holders of any series
of bonds created after October 31, 1975  (including this series) so as to change
75% in the foregoing sentence to 60% and to change certain  procedures  relating
to bondholders'  meetings.  This bond is one of a series of bonds  designated as
the First Mortgage Bonds, Collateral Series F, of the Company.

        This bond shall be  redeemable  at the option of the Company in whole at
any time, or in part from time to time, prior to maturity, at a redemption price
equal to 100% of the principal amount thereof to be redeemed.

        The  principal of this bond may be declared or may become due before the
maturity hereof, on the conditions,  in the manner and at the times set forth in
the Indenture, upon the happening of an event of default as therein provided.

        This bond is not  transferable  except to a successor  trustee under the
1993  Mortgage,  any such  transfer  to be made at the  office  or agency of the
Company in the city in which the  principal  corporate  trust office of the 1993
Mortgage  Trustee is located,  upon surrender and cancellation of this bond, and
thereupon a new bond of this series of a like principal amount will be issued to
the transferee in exchange therefor, as provided in the Indenture.  The Company,
the Trustee, any paying agent and any registrar may deem and treat the person in
whose name this bond is registered as the absolute  owner hereof for the purpose
of receiving payment and for all other purposes.  This bond, alone or with other
bonds of this  series,  may in like manner be exchanged at such office or agency
for one or more new bonds of this series of the same aggregate principal amount,
all as provided in the Indenture.  No service charge shall be made to any holder
of any bond of this series for any exchange or transfer of bonds.

        No recourse  under or upon any covenant or obligation of the  Indenture,
or of any bonds thereby secured, or for any claim based thereon, or otherwise in
any manner in respect thereof, shall be had against any incorporator, subscriber
to the capital stock, shareholder, officer or director, as such, of the Company,
whether former,  present or future,  either directly,  or indirectly through the
Company or the 

                                      A-2
<PAGE>

Trustee, by the enforcement of any subscription to capital stock,  assessment or
otherwise,  or by any legal or equitable  proceeding by virtue of any statute or
otherwise  (including,  without  limiting the generality of the  foregoing,  any
proceeding to enforce any claimed liability of shareholders of the Company based
upon any theory of disregarding  the corporate entity of the Company or upon any
theory  that the  Company  was  acting  as the agent or  instrumentality  of the
shareholders),  any and  all  such  liability  of  incorporators,  shareholders,
subscribers,  officers  and  directors,  as such,  being  released by the holder
hereof,  by the acceptance of this bond, and being likewise  waived and released
by the terms of the Indenture under which this bond is issued.

        This bond shall not be valid or become  obligatory for any purpose until
the certificate of authentication endorsed hereon shall have been signed by U.S.
Bank  Trust  National  Association,  or its  successor,  as  Trustee  under  the
Indenture.

        IN WITNESS  WHEREOF,  Public Service Company of Colorado has caused this
bond to be signed in its name by a [_________  Vice President] and its corporate
seal  to be  affixed  hereto  and  attested  by its  Secretary  or an  Assistant
Secretary.

Dated:                                  PUBLIC SERVICE COMPANY OF
                                        COLORADO



                                        By:________________________________
                                            [__________ Vice President]

ATTEST:________________________
        [Secretary]


                         CERTIFICATE OF AUTHENTICATION


        This is one of the securities of the series designated  therein referred
to in the within-mentioned Supplemental Indenture.

Dated:                                     U.S. BANK TRUST
                                           NATIONAL ASSOCIATION,
                                              AS TRUSTEE

                                        By:____________________________________
                                                      Authorized Officer


                                      A-3
<PAGE>

                                                                    SCHEDULE A


                            SUPPLEMENTAL INDENTURES


     Date of                                                     Principal
  Supplemental                                   Principal        Amount
    Indenture           Series of Bonds        Amount Issued    Outstanding
    ---------           ---------------        -------------    -----------

March 14, 1941               None                   --              --

May 14, 1941                 None                   --              --

April 28, 1942               None                   --              --

April 14, 1943               None                   --              --

April 27, 1944               None                   --              --

April 18, 1945               None                   --              --

April 23, 1946               None                   --              --

April 9, 1947                None                   --              --

June 1, 1947*       2-7/8% Series due 1977     $ 40,000,000        None

April 1, 1948                None                   --              --

May 20, 1948                 None                   --              --

October 1, 1948     3-1/8% Series due 1978        10,000,000       None

April 20, 1949               None                   --              --

April 24, 1950               None                   --              --

April 18, 1951               None                   --              --

October 1, 1951     3-1/4% Series due 1981        15,000,000       None

April 21, 1952               None                   --              --

December 1, 1952             None                   --              --

April 15, 1953               None                   --              --

April 19, 1954               None                   --              --

October 1, 1954*    3-1/8% Series due 1984        20,000,000       None

April 18, 1955               None                   --              --

April 24, 1956               None                   --              --

May 1, 1957*        4-3/8% Series due 1987        30,000,000       None

April 10, 1958               None                   --              --

May 1, 1959         4-5/8% Series due 1989        20,000,000       None

April 18, 1960               None                   --              --


                                      I-1
<PAGE>

     Date of                                                     Principal
  Supplemental                                   Principal        Amount
    Indenture           Series of Bonds        Amount Issued    Outstanding
    ---------           ---------------        -------------    -----------

April 19, 1961               None                   --              --

October 1, 1961     4-1/2% Series due 1991        30,000,000       None

March 1, 1962       4-5/8% Series due 1992         8,800,000       None

June 1, 1964        4-1/2% Series due 1994        35,000,000        None

May 1, 1966         5-3/8% Series due 1996        35,000,000        None

July 1, 1967*       5-7/8% Series due 1997        35,000,000        None

July 1, 1968*       6-3/4% Series due 1998        25,000,000     25,000,000

April 25, 1969               None                   --              --

April 21, 1970               None                   --              --

September 1, 1970   8-3/4% Series due 2000        35,000,000        None

February 1, 1971    7-1/4% Series due 2001        40,000,000         None

August 1, 1972      7-1/2% Series due 2002        50,000,000         None

June 1, 1973        7-5/8% Series due 2003        50,000,000         None

March 1, 1974     Pollution Control Series A      24,000,000     21,500,000

December 1, 1974  Pollution Control Series B      50,000,000       None

October 1, 1975     9-3/8% Series due 2005        50,000,000       None

April 28, 1976               None                   --              --

April 28, 1977               None                   --              --

November 1, 1977*   8-1/4% Series due 2007        50,000,000         None

April 28, 1978               None                   --              --

October 1, 1978     9-1/4% Series due 2008        50,000,000        None

October 1, 1979*  Pollution Control Series C      50,000,000       None

March 1, 1980*        15% Series due 1987         50,000,000       None

April 28, 1981               None                   --              --

November 1, 1981* Pollution Control Series D      27,380,000       None

December 1, 1981*   16-1/4% Series due 2011       50,000,000       None

April 29, 1982               None                   --              --

May 1, 1983*      Pollution Control Series E      42,000,000       None

April 30, 1984               None                   --              --

March 1, 1985*        13% Series due 2015         50,000,000       None


                                      I-2
<PAGE>

     Date of                                                     Principal
  Supplemental                                   Principal        Amount
    Indenture           Series of Bonds        Amount Issued    Outstanding
    ---------           ---------------        -------------    -----------

November 1, 1986*  Pollution Control Series F     27,250,000     27,250,000

May 1, 1987*         8.95% Series due 1992        75,000,000        None

July 1, 1990*       9-7/8% Series due 2020        75,000,000     75,000,000

December 1, 1990*  Secured Medium-Term Notes,    191,500,000**   68,500,000
                           Series A

March 1, 1992*    8-1/8% Series due 2004 and     100,000,000    100,000,000
                    8-3/4% Series due 2022       150,000,000    150,000,000

April 1, 1993*    Pollution Control Series G      79,500,000     79,500,000

June 1, 1993*     Pollution Control Series H      50,000,000     50,000,000

November 1, 1993*     Collateral Series A        134,500,000    134,500,000

January 1, 1994*    Collateral Series B due 
                           2001 and              102,667,000    102,667,000
                    Collateral Series B due
                             2024                110,000,000    110,000,000

September 2, 1994            None                   --              --
(Appointment of
Successor Trustee)

May 1, 1996           Collateral Series C       125,000,000     125,000,000

November 1, 1996      Collateral Series D       250,000,000     250,000,000

February 1, 1997      Collateral Series E       150,000,000      50,000,000


--------------------
* Contains amendatory provisions
** $200,000,000 authorized


                                      I-3
<PAGE>


                                                                    SCHEDULE B


                             PROPERTY DESCRIPTION



                                 PART SECOND.

                                 (Substations)

        The following electric  substations and substation sites of the Company,
including all buildings,  structures,  towers,  poles, lines, and all equipment,
appliances and devices for  transforming,  converting and distributing  electric
energy,  and all the right, title and interest of the Company in and to the land
on which  the same are  situated,  and all of the  Company's  lands,  easements,
rights-of-way, rights, franchises, privileges, machinery, equipment, appliances,
devices, appurtenances and supplies forming a part of said substations or any of
them, or used or enjoyed, or capable of being used or enjoyed, in conjunction or
connection  with any  thereof,  all  situated in the State of  Colorado  and the
counties thereof, more particularly described as follows:

                                 ADAMS COUNTY

1.  WASHINGTON ELECTRIC SUBSTATION

    Lot 1, Block 1, Washington  Electric  Substation,  Filing No. 1, County of
    Adams, State of Colorado

                                DOUGLAS COUNTY

2.  NEW MARCY SUBSTATION SITE

    A parcel of land more particularly described as follows:

    THAT  PORTION OF SECTION  14,  TOWNSHIP 6 SOUTH,  RANGE 68 WEST OF THE SIXTH
    PRINCIPAL MERIDIAN, IN THE COUNTY OF DOUGLAS, STATE OF COLORADO, AS SHOWN ON
    THE LAND SURVEY PLAT  RECORDED AT RECEPTION  NUMBER  254255 IN THE OFFICE OF
    THE CLERK AND  COUNTY  RECORDER  OF SAID  COUNTY OF  DOUGLAS,  DESCRIBED  AS
    FOLLOWS:

    COMMENCING AT THE SOUTHWEST  CORNER OF SAID SECTION 14, WHENCE THE SOUTHEAST
    CORNER OF SAID SECTION 14 BEARS NORTH  89(Degree)58'33"  EAST 5297.28  FEET;
    THENCE  NORTH  68(Degree)07'34"  EAST  2841.07  FEET TO THE  TRUE  POINT  OF
    BEGINNING;  THENCE NORTH  00(Degree)00'00"  EAST 300.00  FEET;  THENCE NORTH
    90(Degree)00'00" EAST 300.00 FEET; THENCE SOUTH 00(Degree)00'00" EAST 300.00
    FEET;  THENCE  NORTH  90(Degree)00'00"  WEST  300.00  TO THE  TRUE  POINT OF
    BEGINNING, EXCEPT WATER RIGHTS AND GROUND WATER, MINERALS AND MINERAL RIGHTS
    CONTAINING 2.066 ACRES, MORE OR LESS.

                                  WELD COUNTY

                                      II-1
<PAGE>

3. GREELEY SUBSTATION: ADDITIONAL LAND

        A tract of land lying in the Northeast  Quarter of the Northeast Quarter
    (NE 1/4 NE 1/4) of Section Twelve  (12),  Township  Five  (5)  North,  Range
    Sixty-six (66) West of the Sixth (6th) Principal  Meridian,  situate,  lying
    and being in the County of Weld, State of Colorado, more particularly
    described as follows:

        Beginning  at a point on the  north  line and 287 feet  easterly  of the
    northwest corner of a tract of land conveyed by warranty deed dated June 10,
    1930 and  recorded in Book 896,  Page 476,  of the  records of Weld  County,
    Colorado,  wherein Simon Peterson is the grantor and Public Service  Company
    of Colorado is the grantee, thence westerly along said north line a distance
    of 287 feet to a point;  thence  southerly  along  west line of said tract a
    distance of 230 feet to a point;  thence easterly and parallel to said north
    line of said tract a distance of 302 feet to a point;  thence  northerly and
    parallel  to west  line of said  tract a  distance  of 215  feet to a point;
    thence  northwesterly  a distance  of 21.2 feet more or less to the point of
    beginning.

                                  PART THIRD.

                           (Miscellaneous Property)

        The following residences,  garages, warehouses,  buildings,  structures,
works and sites and the Company's lands on which the same are situated,  and all
easements,  rights, rights of way, permits,  franchises,  consents,  privileges,
licenses,  machinery,  equipment,  furniture  and  fixtures,  appurtenances  and
supplies  forming a part of said  residences,  garages,  warehouses,  buildings,
structures,  works and sites,  or any of them,  or used or enjoyed or capable of
being used or enjoyed in connection or  conjunction  therewith,  situated in the
State of Colorado  and the  Counties  thereof,  more  particularly  described as
follows:

                                 DENVER COUNTY

4.  LIPAN SERVICE CENTER: ADDITIONAL LAND
    (KEYS/GRIMES TRACT)

    A parcel of land more particularly described as follows:

    PART OF THE  SOUTHEAST  1/4 OF THE  NORTHEAST  1/4 OF SECTION 9,  TOWNSHIP 4
    SOUTH, RANGE 68 WEST OF THE 6TH PRINCIPAL MERIDIAN,  BEGINNING AT A POINT ON
    THE NORTH LINE OF WEST 3RD AVENUE  WHICH IS 186.82 FEET EAST AND 378.31 FEET
    SOUTH OF THE NORTHWEST  CORNER OF SAID SOUTHEAST 1/4 OF THE NORTHEAST 1/4 OF
    SAID SECTION 9; THENCE NORTH 143.00 FEET TO THE SOUTHWEST  RIGHT OF WAY LINE
    OF DENVER AND RIO GRANDE RAILROAD;  THENCE SOUTHERLY ALONG SAID RIGHT OF WAY
    LINE TO THE NORTH LINE OF WEST 3RD AVENUE;  THENCE WEST ALONG THE NORTH LINE
    OF WEST 3RD AVENUE 71.38 FEET TO THE POINT OF BEGINNING,  CITY AND COUNTY OF
    DENVER, STATE OF COLORADO.

                                      II-2
<PAGE>


                                                                    Exhibit 4(b)




                             PUBLIC SERVICE COMPANY
                                   OF COLORADO


                                       TO


                      U.S. BANK TRUST NATIONAL ASSOCIATION,



                                                                      as Trustee


                             ---------------------



                          Supplemental Indenture No. 7

                            Dated as of April 1, 1998


                          Supplemental to the Indenture
                           dated as of October 1, 1993


                             ---------------------


                 Establishing the Securities of Series No.  6,
            designated First Collateral Trust Bonds, Series No.  6





<PAGE>


      SUPPLEMENTAL  INDENTURE NO. 7, dated as of April 1, 1998,  between  PUBLIC
SERVICE COMPANY OF COLORADO, a corporation duly organized and existing under the
laws of the State of Colorado (hereinafter sometimes called the "Company"),  and
U.S. BANK TRUST NATIONAL ASSOCIATION (formerly First Trust of New York, National
Association),  a national banking association, as successor trustee (hereinafter
sometimes  called the  "Trustee") to Morgan  Guaranty  Trust Company of New York
under the  Indenture,  dated as of  October  1,  1993  (hereinafter  called  the
"Original Indenture"), as previously supplemented and as further supplemented by
this  Supplemental  Indenture  No.  7. The  Original  Indenture  and any and all
indentures  and all  other  instruments  supplemental  thereto  are  hereinafter
sometimes collectively called the "Indenture".

                             Recitals of the Company

      The Original  Indenture  was  authorized,  executed  and  delivered by the
Company to provide for the issuance  from time to time of its  Securities  (such
term and all other capitalized  terms used herein without  definition having the
meanings  assigned to them in the  Original  Indenture),  to be issued in one or
more series as contemplated  therein, and to provide security for the payment of
the principal of and premium, if any, and interest, if any, on the Securities.

      The Company  has  heretofore  executed  and  delivered  to the Trustee the
Supplemental  Indentures  referred  to in  Schedule A hereto for the  purpose of
establishing a series of bonds and appointing the successor Trustee.

      The Company  desires to establish a series of  Securities to be designated
"First  Collateral  Trust Bonds,  Series No. 6", such series of Securities to be
hereinafter sometimes called "Series No. 6".

      The Company  has duly  authorized  the  execution  and  delivery of this
Supplemental  Indenture No. 7 to establish the  Securities of Series No. 6 and
has duly  authorized the issuance of such  Securities;  and all acts necessary
to make this  Supplemental  Indenture No. 7 a valid  agreement of the Company,
and to make the  Securities of Series No. 6 valid  obligations of the Company,
have been performed.

                                Granting Clauses

      NOW,  THEREFORE,  THIS SUPPLEMENTAL  INDENTURE NO. 7 WITNESSETH,  that, in
consideration  of the  premises  and of the  purchase of the  Securities  by the
Holders  thereof,  and in order to secure the  payment of the  principal  of and
premium,  if any,  and  interest,  if any, on all  Securities  from time to time
Outstanding  and the performance of the covenants  contained  therein and in the
Indenture and to declare the terms and  conditions on which such  Securities are
secured, the Company hereby grants, bargains, sells, releases, conveys, assigns,
transfers, mortgages, pledges, sets over and confirms to the Trustee, and grants
to the Trustee a security interest in, the following:

                              Granting Clause First

            All right, title and interest of the Company,  as of the date of the
      execution  and delivery of this  Supplemental  Indenture  No. 7, in and to
      property  (other than  Excepted  Property),  real,  personal and mixed and
      wherever situated, in any case used or to be used in or in connection with
      the Electric Utility Business  (whether or not such use is the sole use of
      such property),  including without  limitation (a) all lands and interests
      in land  described  or  referred  to in  Schedule B hereto;  (b) all other
      lands, easements,  servitudes,  licenses, permits, rights of way and other
      rights and interests in or relating to real property used or to be used in
      or in  connection  with the Electric  Utility  Business or relating to the
      occupancy or use of such real property, subject however, to the exceptions
      and  exclusions  set forth in clause (a) of Granting  Clause  First of the
      Original  Indenture;  (c)  all  plants,  generators,   turbines,  engines,


<PAGE>


      boilers,  fuel  handling  and  transportation  facilities,  air and  water
      pollution control and sewage and solid waste disposal facilities and other
      machinery and facilities for the  generation of electric  energy;  (d) all
      switchyards, lines, towers, substations,  transformers and other machinery
      and facilities for the  transmission  of electric  energy;  (e) all lines,
      poles, conduits,  conductors,  meters,  regulators and other machinery and
      facilities for the  distribution  of electric  energy;  (f) all buildings,
      offices,  warehouses  and  other  structures  used  or to be used in or in
      connection  with the Electric  Utility  Business;  (g) all pipes,  cables,
      insulators,  ducts,  tools,  computers  and other data  processing  and/or
      storage equipment and other equipment, apparatus and facilities used or to
      be used in or in connection with the Electric Utility Business; (h) any or
      all of the foregoing  properties in the process of  construction;  and (i)
      all other property, of whatever kind and nature, ancillary to or otherwise
      used or to be used in  conjunction  with  any or all of the  foregoing  or
      otherwise,  directly or indirectly, in furtherance of the Electric Utility
      Business;

                             Granting Clause Second

            Subject to the applicable  exceptions  permitted by Section  810(c),
      Section  1303 and Section  1305 of the  Original  Indenture,  all property
      (other  than  Excepted  Property)  of the kind  and  nature  described  in
      Granting Clause First which may be hereafter  acquired by the Company,  it
      being the intention of the Company that all such property  acquired by the
      Company after the date of the execution and delivery of this  Supplemental
      Indenture  No. 7 shall be as fully  embraced  within and  subjected to the
      Lien hereof as if such  property  were owned by the Company as of the date
      of the execution and delivery of this Supplemental Indenture No. 7;

                             Granting Clause Fourth

            All other property of whatever kind and nature subjected or required
      to be  subjected  to the Lien of the  Indenture  by any of the  provisions
      thereof;

                                Excepted Property

            Expressly  excepting  and  excluding,  however,  from  the  Lien and
      operation of the Indenture all Excepted  Property of the Company,  whether
      now owned or hereafter acquired;

      TO HAVE AND TO HOLD all such property,  real, personal and mixed, unto the
Trustee, its successors in trust and their assigns forever;

      SUBJECT,  HOWEVER,  to (a) Liens existing at the date of the execution and
delivery of the Original Indenture  (including,  but not limited to, the Lien of
the PSCO 1939  Mortgage),  (b) as to property  acquired by the Company after the
date of the execution and delivery of the Original Indenture,  Liens existing or
placed  thereon  at the  time of the  acquisition  thereof  (including,  but not
limited to, the Lien of any Class A Mortgage  and  purchase  money  Liens),  (c)
Retained  Interests and (d) any other Permitted Liens, it being understood that,
with respect to any property  which was at the date of execution and delivery of
the Original  Indenture or thereafter became or hereafter becomes subject to the
Lien of any Class A Mortgage,  the Lien of the  Indenture  shall at all times be
junior, subject and subordinate to the Lien of such Class A Mortgage;

      IN  TRUST,  NEVERTHELESS,  for the  equal and  proportionate  benefit  and
security of the Holders from time to time of all Outstanding  Securities without
any priority of any such Security over any other such Security;


                                      -2-

<PAGE>

      PROVIDED,  HOWEVER,  that the right,  title and interest of the Trustee in
and to the  Mortgaged  Property  shall  cease,  terminate  and  become  void  in
accordance with, and subject to the conditions set forth in, Article Nine of the
Original  Indenture,  and if, thereafter,  the principal of and premium, if any,
and  interest,  if any,  on the  Securities  shall have been paid to the Holders
thereof,  or shall have been paid to the Company  pursuant to Section 603 of the
Original Indenture, then and in that case the Indenture shall terminate, and the
Trustee shall execute and deliver to the Company such instruments as the Company
shall require to evidence such  termination;  otherwise the  Indenture,  and the
estate and rights thereby  granted shall be and remain in full force and effect;
and

      THE PARTIES HEREBY FURTHER COVENANT AND AGREE as follows:

                                   ARTICLE ONE

                           Securities of Series No. 6

      There are hereby  established  the Securities of Series No. 6, which shall
have the terms and  characteristics  set forth below (the lettered  subdivisions
set forth below corresponding to the lettered subdivisions of Section 301 of the
Original Indenture):

      (a) the title of the Securities of such series shall be "First  Collateral
      Trust Bonds, Series No. 6"; provided, however, that, at any time after the
      PSCO 1939 Mortgage shall have been satisfied and  discharged,  the Company
      shall have the right,  without any consent or other  action by the Holders
      of such Securities, to change such title in such manner as shall be deemed
      by  the  Company  to be  appropriate  to  reflect  such  satisfaction  and
      discharge, such change to be evidenced in an Officer's Certificate;

      (b)   the   Securities   of  Series  No.  6  shall  be   initially
      authenticated  and delivered in the aggregate  principal amount of
      $250,000,000;

      (c)  interest  on the  Securities  of Series No. 6 shall be payable to the
      Persons in whose  names such  Securities  are  registered  at the close of
      business on the Regular Record Date for such interest, except as otherwise
      expressly  provided in the form of such  Securities  attached as Exhibit A
      hereto;

      (d) the  principal of the  Securities  of Series No. 6 shall be payable on
      April 15, 2003, the Stated Maturity.

      (e) the Securities of Series No. 6 shall bear interest at a rate of 6% per
      annum;  interest shall accrue on the Securities of Series No. 6 from April
      20, 1998, or the most recent date to which  interest has been paid or duly
      provided  for; the Interest  Payment  Dates for such  Securities  shall be
      April 15 and October 15 in each year, commencing October 15, 1998, and the
      Regular  Record Dates with respect to the Interest  Payment Dates for such
      Securities  shall  be April 1 and  October  1 in each  year,  respectively
      (whether or not a Business Day);


                                      -3-
<PAGE>


      (f) the Corporate Trust Office of U.S. Bank Trust National  Association in
      New  York,  New York  shall be the place at which  (i) the  principal  of,
      premium,  if any, and interest,  if any, on the Securities of Series No. 6
      shall be payable,  (ii) registration of transfer of such Securities may be
      effected,  (iii)  exchanges  of such  Securities  may be effected and (iv)
      notices and  demands to or upon the Company in respect of such  Securities
      and the Indenture may be served; and U.S. Bank Trust National  Association
      shall be the Security  Registrar for such Securities;  provided,  however,
      that the Company  reserves the right to change,  by one or more  Officer's
      Certificates,  any such place or the  Security  Registrar;  and  provided,
      further, that the Company reserves the right to designate,  by one or more
      Officer's  Certificates,  its principal office in Denver,  Colorado as any
      such place or itself as the Security Registrar;

      (g) the  Securities  of  Series  No. 6 shall  not be  redeemable  prior to
      maturity;

      (h)   not applicable;

      (i)   not applicable;

      (j)   not applicable;

      (k)   not applicable;

      (l)   not applicable;

      (m)   not applicable;

      (n)   not applicable;

      (o)   not applicable;

      (p)   not applicable;

      (q) the  Securities of Series No. 6 are to be initially  registered in the
      name of Cede & Co.,  as nominee  for The  Depository  Trust  Company  (the
      "Depositary").  Such Securities shall not be transferable or exchangeable,
      nor shall any purported transfer be registered, except as follows:

            (i) such  Securities may be transferred  in whole,  and  appropriate
            registration  of  transfer  effected,  if such  transfer  is by such
            nominee to the  Depositary,  or by the Depositary to another nominee
            thereof,  or by any nominee of the  Depositary  to any other nominee
            thereof,  or by  the  Depositary  or  any  nominee  thereof  to  any
            successor securities depositary or any nominee thereof; and

            (ii) such  Securities  may be exchanged  for  definitive  Securities
            registered  in  the  respective  names  of  the  beneficial  holders
            thereof,  and thereafter shall be transferable  without restriction,
            if:

                  (A) The Depositary,  or any successor  securities  depositary,
                  shall have  notified  the Company  and the Trustee  that it is
                  unwilling   or  unable  to  continue  to  act  as   securities
                  depositary  with  respect to such  Securities  and the Trustee
                  shall not have been notified by the Company within ninety (90)
                  days

                                      -4-
<PAGE>

                  of the identity of a successor  securities  depositary  with
                  respect to such Securities;

                  (B) The Company shall have  delivered to the Trustee a Company
                  Order  to  the  effect  that  such  Securities   shall  be  so
                  exchangeable on and after a date specified therein; or

                  (C)  (1) an  Event  of  Default  shall  have  occurred  and be
                  continuing,  (2) the Trustee  shall have given  notice of such
                  Event of  Default  pursuant  to Section  1102 of the  Original
                  Indenture  and (3)  there  shall  have been  delivered  to the
                  Company  and the  Trustee  an Opinion of Counsel to the effect
                  that the interests of the beneficial owners of such Securities
                  in respect  thereof will be  materially  impaired  unless such
                  owners become Holders of definitive Securities.

      (r)   not applicable;

      (s) no service  charge shall be made for the  registration  of transfer or
      exchange of the  Securities of Series No. 6; provided,  however,  that the
      Company may require  payment of a sum sufficient to cover any tax or other
      governmental charge payable in connection with the exchange or transfer;

      (t)   not applicable;

      (u)   (i)   If  the  Company   shall  have  caused  the  Company's
            indebtedness  in respect of any  Securities  of Series No. 6 to have
            been satisfied and discharged  prior to the Maturity of such 
            Securities, as provided in  Section  901 of the Original Indenture,
            the Company shall,  promptly after the date of such satisfaction and
            discharge, give a notice to each Person who was a Holder of any of
            such  Securities on such date stating (A)(1) the aggregate principal
            amount of such Securities and (2) the aggregate amount of any money
           (other than amounts, if any, deposited in respect of accrued interest
            on such Securities) and the aggregate principal amount of, the rate
            or rates of interest on, and the aggregate fair market value of, any
            Eligible Obligations deposited pursuant to Section 901 of the
            Original Indenture with respect to such Securities and (B) that the
            Company will provide (and the Company shall promptly so provide) to
            such Person, or any beneficial owner of such Securities holding
            through such Person (upon written request to the Company sent to an
            address specified in such notice), such other information as such
            Person or beneficial owner, as the case may be, reasonably may
            request in order to enable it to determine the federal income tax
            consequences to it resulting from the satisfaction and discharge of
           the Company's indebtedness in respect of such Securities. Thereafter,
            the Company shall, within forty-five (45) days after the end of each
            calendar year, give to  each  Person  who at any  time  during  such
            calendar year was a Holder of such Securities a notice containing(X)
            such information as may be necessary to enable such Person to report
           its income, gain or loss for federal income tax purposes with respect
            to such Securities or the assets held on deposit in respect thereof
            during such calendar year or the portion  thereof during which such
            Person was a Holder of such  Securities,  as the case may be (such
            information to be set forth for such calendar year as a whole and
            for each month during such year) and (Y) a statement to the effect
            that the Company  will provide (and the Company shall promptly so 
            provide)

                                      -5-
<PAGE>

          to such Person,  or any beneficial  owner of such  Securities  holding
          through  such Person (upon  written  request to the Company sent to an
          address  specified in such  notice),  such other  information  as such
          Person or beneficial owner, as the case may be, reasonably may request
          in  order to  enable  it to  determine  its  income,  gain or loss for
          federal  income tax purposes  with respect to such  Securities or such
          assets  for such  year or  portion  thereof,  as the case may be.  The
          obligation  of  the  Company  to  provide  or  cause  to  be  provided
          information  for  purposes  of income tax  reporting  by any Person as
          described in the first two sentences of this paragraph shall be deemed
          to have been  satisfied to the extent that the Company has provided or
          caused to be provided substantially comparable information pursuant to
          any requirements of the Internal Revenue Code of 1986, as amended from
          time to time (the  "Code")  and  United  States  Treasury  regulations
          thereunder.

            (ii)  Notwithstanding  the provisions of subparagraph (i) above, the
            Company  shall not be required to give any notice  specified in such
            subparagraph  or  to  otherwise   furnish  any  of  the  information
            contemplated  therein if the  Company  shall have  delivered  to the
            Trustee an Opinion of Counsel to the effect that the Holders of such
            Securities  will not  recognize  income,  gain or loss  for  federal
            income tax purposes as a result of the satisfaction and discharge of
            the Company's  indebtedness  in respect of such  Securities and such
            Holders  will be  subject  to federal  income  taxation  on the same
            amounts  and in the same  manner  and at the  same  times as if such
            satisfaction and discharge had not occurred.

            (iii)  Anything in this clause (u) to the contrary  notwithstanding,
            the Company  shall not be required to give any notice  specified  in
            subparagraph   (i)  or  to   otherwise   furnish   the   information
            contemplated   therein  or  to  deliver   any   Opinion  of  Counsel
            contemplated by  subparagraph  (ii) if the Company shall have caused
            Securities  of  Series  No. 6 to be  deemed  to have  been  paid for
            purposes  of  the  Indenture,  as  provided  in  Section  901 of the
            Original Indenture, but shall not have effected the satisfaction and
            discharge of its indebtedness in respect of such Securities pursuant
            to such Section.

      (v) The  Securities  of Series  No. 6 shall be  substantially  in the form
      attached  hereto as Exhibit A and shall have such further terms as are set
      forth in such form.

                                   ARTICLE TWO

                            Miscellaneous Provisions

      This  Supplemental  Indenture  No.  7 is a  supplement  to the  Original
Indenture.  As  previously  supplemented  and  further  supplemented  by  this
Supplemental  Indenture  No.  7, the  Original  Indenture  is in all  respects
ratified,  approved and confirmed,  and the Original  Indenture,  all previous
supplements  thereto  and this  Supplemental  Indenture  No. 7 shall  together
constitute one and the same instrument.



                                      -6-
<PAGE>


            IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture No. 7 to be duly executed as of the day and year first above written.

                                    PUBLIC SERVICE COMPANY OF COLORADO



                                    By:s/ Brian P. Jackson
                                         Name:  Brian P. Jackson
                                         Title: Senior Vice President




                                    U.S. BANK TRUST NATIONAL ASSOCIATION,
                                                                 Trustee



                                    By:s/ Catherine F. Donohue
                                       Name:  Catherine F. Donohue
                                       Title: Vice President



                                      -7-
<PAGE>


STATE OF COLORADO             )
                              ) ss.:
CITY AND COUNTY OF DENVER     )


            On the 20th day of April, 1998,  before me personally came Brian P.
Jackson to me known,  who, being by me duly sworn, did depose and say that he is
a Senior  Vice  President  of Public  Service  Company of  Colorado,  one of the
corporations described in and which executed the foregoing instrument;  and that
he signed  his name  thereto  by  authority  of the Board of  Directors  of said
corporation.


                                    s/ Martha L. Palomar
                                    Name: Martha L. Palomar
                                    Notary Public, State of Colorado

                                    Commission Expires February  29, 2000



                                      -8-
<PAGE>


STATE OF NEW YORK                     )
                                      ) ss.:
CITY AND COUNTY OF NEW YORK           )


            On the 17th day of April,  1998, before me personally came Catherine
F. Donohue,  to me known,  who, being by me duly sworn,  did depose and say that
she is a Vice  President of U.S. Bank Trust  National  Association,  the banking
association described in and which executed the foregoing  instrument;  and that
she  signed her name  thereto by  authority  of the Board of  Directors  of said
banking association.


                                    s/ Janet O'Hara
                                    Name:  Janet O'Hara
                                    Notary Public, State of New York
                                    No. 010H5087549
                                    Qualified in Queens County

                                    Commission Expires November 3, 1999



                                      -9-
<PAGE>



                                                                      EXHIBIT A
                                FORM OF SECURITY


                  (See legend at the end of this Security for
                 restrictions on transfer and change of form)


                       PUBLIC SERVICE COMPANY OF COLORADO
                    First Collateral Trust Bond, Series No. 6


     Original Interest Accrual Date:       April 20, 1998
                      Interest Rate:       6%
                    Stated Maturity:       April 15, 2003
             Interest Payment Dates:       April 15 and October 15
               Regular Record Dates:       April 1 and October 1



                   This Security is not a Discount  Security  within the meaning
             of the within-mentioned Indenture.


                   -----------------------------------------



Principal Amount                                      Registered No.
$                                                     CUSIP


      PUBLIC  SERVICE  COMPANY OF COLORADO,  a  corporation  duly  organized and
existing  under the laws of the State of Colorado  (herein called the "Company,"
which term includes any successor  corporation  under the Indenture  referred to
below), for value received, hereby promises to pay to

                                   , or registered assigns, the principal sum of

Dollars on the Stated Maturity specified above, and to pay interest thereon from
the  Original  Interest  Accrual  Date  specified  above or from the most recent
Interest  Payment  Date to which  interest has been paid or duly  provided  for,
semi-annually  in arrears on the Interest  Payment Dates specified above in each
year,  commencing  with the Interest  Payment Date next  succeeding the Original
Interest Accrual Date specified above, and at Maturity, at the Interest Rate per
annum specified above,  until the principal hereof is paid or duly provided for.
The interest so payable,  and paid or duly provided for, on any Interest Payment
Date shall, as provided in such  Indenture,  be paid to the Person in whose name
this Security (or one or more Predecessor Securities) is registered at the close
of  business  on the  Regular  Record  Date  specified  above  (whether or not a
Business Day) next preceding  such Interest  Payment Date.  Notwithstanding  the
foregoing,  interest  payable  at  Maturity  shall be paid to the Person to whom
principal shall be paid.  Except as otherwise  provided in said  Indenture,  any
such  interest  not so paid or duly  provided  for shall  forthwith  cease to be
payable to the Holder on such Regular  Record Date and may either be paid to the
Person in whose name this Security (or one or


                                      A-1
<PAGE>

more Predecessor Securities) is registered at the close of business on a Special
Record  Date  for the  payment  of such  Defaulted  Interest  to be fixed by the
Trustee,  notice of which shall be given to Holders of Securities of this series
not less than 15 days  prior to such  Special  Record  Date,  or be paid in such
other manner as permitted by the Indenture.

      Payment of the principal of this Security and interest  hereon at Maturity
shall be made upon  presentation  of this Security at the Corporate Trust Office
of U.S. Bank Trust National Association,  in New York, New York or at such other
office or agency as may be designated  for such purpose by the Company from time
to time.  Payment of interest on this Security (other than interest at Maturity)
shall be made by check mailed to the address of the Person  entitled  thereto as
such address shall appear in the Security  Register,  except that if such Person
shall be a securities  depositary,  such payment may be made by such other means
in lieu of check as shall be agreed  upon by the  Company,  the Trustee and such
Person. Payment of the principal of and interest on this Security, as aforesaid,
shall be made in such coin or currency of the United States of America as at the
time of  payment  shall be legal  tender for the  payment of public and  private
debts.

      This  Security  is one of a duly  authorized  issue of  securities  of the
Company  (herein  called the  "Securities"),  issued and issuable in one or more
series under and equally  secured by an  Indenture,  dated as of October 1, 1993
(such  Indenture as originally  executed and delivered  and as  supplemented  or
amended from time to time thereafter,  together with any constituent instruments
establishing  the  terms of  particular  Securities,  being  herein  called  the
"Indenture"),  between  the  Company and U.S.  Bank Trust  National  Association
(formerly First Trust of New York,  National  Association) as successor  trustee
(herein  called the "Trustee,"  which term includes any successor  trustee under
the  Indenture),  to which  Indenture and all  indentures  supplemental  thereto
reference is hereby made for a description  of the property  mortgaged,  pledged
and held in trust,  the  nature and extent of the  security  and the  respective
rights, limitations of rights, duties and immunities of the Company, the Trustee
and the Holders of the  Securities  thereunder  and of the terms and  conditions
upon which the Securities  are, and are to be,  authenticated  and delivered and
secured.  The  acceptance  of this Security  shall be deemed to  constitute  the
consent and agreement by the Holder hereof to all of the terms and provisions of
the Indenture. This Security is one of the series designated above.

      If any  Interest  Payment  Date  or the  Stated  Maturity  shall  not be a
Business  Day (as  hereinafter  defined),  payment  of the  amounts  due on this
Security on such date may be made on the next  succeeding  Business Day; and, if
such  payment is made or duly  provided  for on such  Business  Day, no interest
shall accrue on such amounts for the period from and after such Interest Payment
Date or Stated Maturity, as the case may be, to such Business Day.


                                      A-2
<PAGE>


      This  Security is not subject to redemption  prior to the Stated  Maturity
hereof.

      If an Event of Default  shall occur and be  continuing,  the  principal of
this  Security may be declared due and payable in the manner and with the effect
provided in the Indenture.

      The Indenture permits,  with certain  exceptions as therein provided,  the
Trustee to enter into one or more  supplemental  indentures  for the  purpose of
adding any provisions  to, or changing in any manner or  eliminating  any of the
provisions  of, the Indenture with the consent of the Holders of not less than a
majority in  aggregate  principal  amount of the  Securities  of all series then
Outstanding  under the Indenture,  considered as one class;  provided,  however,
that if there shall be Securities of more than one series  Outstanding under the
Indenture and if a proposed  supplemental  indenture  shall directly  affect the
rights of the Holders of Securities  of one or more,  but less than all, of such
series,  then  the  consent  only of the  Holders  of a  majority  in  aggregate
principal  amount  of the  Outstanding  Securities  of all  series  so  directly
affected,  considered as one class,  shall be required;  and provided,  further,
that if the  Securities  of any series  shall have been  issued in more than one
Tranche and if the proposed  supplemental  indenture  shall directly  affect the
rights of the Holders of Securities  of one or more,  but less than all, of such
Tranches,  then the  consent  only of the  Holders  of a majority  in  aggregate
principal  amount of the  Outstanding  Securities  of all  Tranches  so directly
affected,  considered as one class,  shall be required;  and provided,  further,
that the  Indenture  permits the Trustee to enter into one or more  supplemental
indentures  for  limited   purposes  without  the  consent  of  any  Holders  of
Securities.  The Indenture also contains provisions  permitting the Holders of a
majority in principal  amount of the Securities then  Outstanding,  on behalf of
the Holders of all Securities,  to waive  compliance by the Company with certain
provisions of the  Indenture  and certain past defaults  under the Indenture and
their  consequences.  Any such consent or waiver by the Holder of this  Security
shall be conclusive  and binding upon such Holder and upon all future Holders of
this  Security  and of any  Security  issued upon the  registration  of transfer
hereof or in exchange  therefor or in lieu  hereof,  whether or not  notation of
such consent or waiver is made upon this Security.

      As provided in the  Indenture and subject to certain  limitations  therein
set forth,  this Security or any portion of the principal  amount hereof will be
deemed to have been paid for all purposes of the  Indenture  and to be no longer
Outstanding  thereunder,  and, at the  election of the  Company,  the  Company's
entire  indebtedness  in respect  thereof will be satisfied and  discharged,  if
there has been irrevocably deposited with the Trustee or any Paying Agent (other
than the Company),  in trust, money in an amount which will be sufficient and/or
Eligible  Obligations,  the principal of and interest on which when due, without
regard to any  reinvestment  thereof,  will provide moneys which,  together with
moneys so deposited,  will be  sufficient,  to pay when due the principal of and
interest on this Security when due.

      As provided in the  Indenture and subject to certain  limitations  therein
set  forth,  the  transfer  of this  Security  is  registrable  in the  Security
Register,  upon surrender of this Security for  registration  of transfer at the
office of U.S. Bank Trust  National  Association,  in New York, New York or such
other  office or agency as may be  designated  by the Company from time to time,
duly  endorsed by, or  accompanied  by a written  instrument of transfer in form
satisfactory  to the Company and the Security  Registrar  duly  executed by, the
Holder hereof or his attorney duly  authorized in writing,  and thereupon one or
more new Securities of this series of authorized denominations and of like tenor
and aggregate principal amount,  will be issued to the designated  transferee or
transferees.

      The Securities of this series are issuable only as registered  Securities,
without coupons,  and in denominations of $1,000 and integral multiples thereof.
As provided in the  Indenture  and  subject to certain  limitations  therein set
forth, Securities of this series are exchangeable for a like aggregate principal
amount of Securities of the same series,  of any  authorized  denominations,  as
requested by the Holder  surrendering the same, and of like tenor upon surrender
of the Security or  Securities  to be exchanged at the office of U.S. Bank


                                      A-3
<PAGE>

Trust National Association, in New York, New York or such other office or agency
as may be designated by the Company from time to time.

      No service charge shall be made for any such  registration  of transfer or
exchange,  but the Company may require  payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

      Prior to due  presentment of this Security for  registration  of transfer,
the  Company,  the Trustee and any agent of the Company or the Trustee may treat
the Person in whose name this  Security  is  registered  as the  absolute  owner
hereof for all purposes,  whether or not this  Security be overdue,  and neither
the  Company,  the Trustee nor any such agent shall be affected by notice to the
contrary.

      The  Indenture  and the  Securities  shall be governed by and construed in
accordance with the laws of the State of New York.

      As used  herein  "Business  Day" means any day,  other than a Saturday  or
Sunday,  which is not a day on which banking  institutions or trust companies in
The City of New York,  New York or other city in which is located  any office or
agency maintained for the payment of principal or interest on this Security, are
authorized or required by law,  regulation or executive  order to remain closed.
All other terms used in this Security  which are defined in the Indenture  shall
have the meanings assigned to them in the Indenture.

      As provided in the Indenture,  no recourse shall be had for the payment of
the principal of or interest on any Securities,  or any part thereof, or for any
claim based  thereon or otherwise  in respect  thereof,  or of the  indebtedness
represented  thereby,  or upon any  obligation,  covenant or agreement under the
Indenture,  against, and no personal liability whatsoever shall attach to, or be
incurred by, any incorporator,  shareholder, officer or director, as such, past,
present or future of the Company or of any predecessor or successor  corporation
(either   directly  or  through  the  Company  or  a  predecessor  or  successor
corporation), whether by virtue of any constitutional provision, statute or rule
of law, or by the  enforcement  of any  assessment or penalty or  otherwise;  it
being expressly  agreed and understood that the Indenture and all the Securities
are solely corporate  obligations and that any such personal liability is hereby
expressly   waived  and  released  as  a  condition  of,  and  as  part  of  the
consideration  for,  the  execution  of the  Indenture  and the  issuance of the
Securities.

      Unless the certificate of  authentication  hereon has been executed by the
Trustee or an Authenticating Agent by manual signature,  this Security shall not
be entitled to any benefit under the Indenture or be valid or obligatory for any
purpose.

                                      A-4
<PAGE>


      IN WITNESS  WHEREOF,  the Company has caused  this  instrument  to be duly
executed and its corporate seal to be hereunto affixed and attested.

                                          PUBLIC SERVICE COMPANY OF COLORADO

                                          By:
                                                [Title]




Attest:
      [Title]


                          CERTIFICATE OF AUTHENTICATION

      This is one of the Securities of the series designated therein referred to
in the within-mentioned Indenture.


Dated:

       U.S. BANK TRUST                 OR               U.S. BANK TRUST
     NATIONAL ASSOCIATION,                            NATIONAL ASSOCIATION,
          as Trustee                                       as Trustee


By:                                             By:[                        ],
   Authorized Officer                                 as Authenticating Agent


                                                By:
                                                      Authorized Officer

      Unless this  certificate is presented by an authorized  representative  of
The Depository Trust Company, a New York Corporation  ("DTC"), to the Company or
its  agent  for  registration  of  transfer,   exchange,  or  payment,  and  any
certificate issued is registered in the name of Cede & Co. or in such other name
as is requested by an authorized  representative of DTC (and any payment is made
to  Cede  & Co.  or to  such  other  entity  as is  requested  by an  authorized
representative  of DTC), ANY TRANSFER,  PLEDGE, OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

      This Security may not be transferred  or exchanged,  nor may any purported
transfer be  registered,  except (i) this Security may be  transferred in whole,
and appropriate registration of transfer effected, if such transfer is by Cede &
Co., as nominee for The  Depository  Trust  Company (the  "Depositary"),  to the
Depositary,  or by the Depositary to another nominee thereof,  or by any nominee
of the  Depositary to any other  nominee  thereof,  or by the  Depositary or any
nominee thereof to any successor  securities  depositary or any nominee thereof;
and (ii) this Security may be exchanged for definitive  Securities registered in
the respective names of the beneficial  holders hereof,  and thereafter shall be
transferable  without  restrictions  if: (A) the  Depositary,  or any  successor
securities  depositary,  shall have notified the Company and the Trustee that it
is unwilling or unable to continue to act as securities  depositary with respect
to the  Securities  and the Trustee  shall not have been notified by the Company
within  ninety (90) days of the  identity of a successor  securities  depositary
with  respect to the  Securities;  (B) the Company  shall have  delivered to the
Trustee  a  Company  Order  to  the  effect  that  the  Securities  shall  be so
exchangeable  on and  after a date  specified  therein;  or  (C)(1)  an Event of
Default shall have occurred and be continuing,  (2) the Trustee shall have given
notice of such Event of Default  pursuant to Section 1102 of the


                                      A-5

<PAGE>

  Indenture  and
(3) there shall have been delivered to the Company and the Trustee an Opinion of
Counsel  to the  effect  that the  interests  of the  beneficial  owners  of the
Securities  in respect  thereof will be materially  impaired  unless such owners
become Holders of definitive Securities.


                               -------------------

                                      A-6
<PAGE>


    FOR VALUE RECEIVED the undersigned hereby sells, assigns and transfers unto


--------------------------------------------------------------------------------

     [please insert social security or other identifying number of assignee]


--------------------------------------------------------------------------------
            [please print or typewrite name and address of assignee]


--------------------------------------------------------------------------------

the within  Security  of PUBLIC  SERVICE  COMPANY OF  COLORADO  and does  hereby
irrevocably   constitute   and  appoint   __________________________________   ,
Attorney,  to  transfer  said  Security  on the  books  of the  within-mentioned
Company, with full power of substitution in the premises.



Dated:__________________________



             ------------------------------------------------------

      Notice:  The signature to this assignment must correspond with the name as
      written  upon  the  face  of the  Security  in  every  particular  without
      alteration or enlargement or any change whatsoever.




                                   A-7
<PAGE>


                                                                      SCHEDULE A

                             SUPPLEMENTAL INDENTURES


     Date of                                                     Principal
  Supplemental                                   Principal        Amount
    Indenture           Series of Bonds        Amount Issued    Outstanding
    ---------           ---------------        -------------    -----------

November 1, 1993         Series No. 1          $134,500,000    $134,500,000

January 1, 1994      Series No. 2 due 2001     $102,667,000    $102,667,000
                              and
                     Series No. 2 due 2024     $110,000,000    $110,000,000

September 2, 1994            None                  None            None
(Appointment of
Successor Trustee)

May 1, 1996              Series No. 3          $125,000,000    $125,000,000

November 1, 1996         Series No. 4          $250,000,000    $250,000,000

February 1, 1997         Series No. 5          $150,000,000    $ 50,000,000


================================================================================




                                      I-1
<PAGE>


                                                                     SCHEDULE B

                             DESCRIPTION OF PROPERTY

The following  properties are situated in the State of Colorado and the counties
thereof:

                                  ADAMS COUNTY

1.    WASHINGTON ELECTRIC SUBSTATION

      Lot 1, Block 1, Washington Electric Substation,  Filing No. 1, County of
      Adams, State of Colorado

                                  DENVER COUNTY

2.    LIPAN SERVICE CENTER: ADDITIONAL LAND (KEYS/GRIMES TRACT)

      A parcel of land more particularly described as follows:

      PART OF THE  SOUTHEAST  1/4 OF THE  NORTHEAST 1/4 OF SECTION 9, TOWNSHIP 4
      SOUTH, RANGE 68 WEST OF THE 6TH PRINCIPAL  MERIDIAN,  BEGINNING AT A POINT
      ON THE NORTH LINE OF WEST 3RD AVENUE  WHICH IS 186.82 FEET EAST AND 378.31
      FEET SOUTH OF THE NORTHWEST  CORNER OF SAID SOUTHEAST 1/4 OF THE NORTHEAST
      1/4 OF SAID SECTION 9; THENCE NORTH 143.00 FEET TO THE SOUTHWEST  RIGHT OF
      WAY LINE OF DENVER AND RIO GRANDE  RAILROAD;  THENCE  SOUTHERLY ALONG SAID
      RIGHT OF WAY LINE TO THE NORTH LINE OF WEST 3RD AVENUE;  THENCE WEST ALONG
      THE NORTH  LINE OF WEST 3RD AVENUE  71.38 FEET TO THE POINT OF  BEGINNING,
      CITY AND COUNTY OF DENVER, STATE OF COLORADO.

                                 DOUGLAS COUNTY

3.    NEW MARCY SUBSTATION SITE

      A parcel of land more particularly described as follows:

      THAT PORTION OF SECTION 14,  TOWNSHIP 6 SOUTH,  RANGE 68 WEST OF THE SIXTH
      PRINCIPAL MERIDIAN, IN THE COUNTY OF DOUGLAS,  STATE OF COLORADO, AS SHOWN
      ON THE LAND SURVEY PLAT RECORDED AT RECEPTION  NUMBER 254255 IN THE OFFICE
      OF THE CLERK AND COUNTY  RECORDER OF SAID COUNTY OF DOUGLAS,  DESCRIBED AS
      FOLLOWS:

      COMMENCING  AT THE  SOUTHWEST  CORNER  OF  SAID  SECTION  14,  WHENCE  THE
      SOUTHEAST  CORNER OF SAID  SECTION 14 BEARS  NORTH  89(Degree)58'33"  EAST
      5297.28 FEET; THENCE NORTH  68(Degree)07'34" EAST 2841.07 FEET TO THE TRUE
      POINT OF BEGINNING; THENCE NORTH 00(Degree)00'00" EAST 300.00 FEET; THENCE
      NORTH  90(Degree)00'00"  EAST 300.00 FEET;  THENCE SOUTH  00(Degree)00'00"
      EAST 300.00 FEET;  THENCE NORTH  90(Degree)00'00"  WEST 300.00 TO THE TRUE
      POINT OF  BEGINNING,  EXCEPT WATER RIGHTS AND GROUND  WATER,  MINERALS AND
      MINERAL RIGHTS CONTAINING 2.066 ACRES, MORE OR LESS.

                                      II-1



<PAGE>

                                   WELD COUNTY

4. GREELEY SUBSTATION: ADDITIONAL LAND

      A tract of land lying in the Northeast  Quarter of the  Northeast  Quarter
      (NE1/4NE1/4)  of Section  Twelve  (12),  Township  Five (5)  North,  Range
      Sixty-six (66) West of the Sixth (6th) Principal Meridian,  situate, lying
      and being in the  County of Weld,  State of  Colorado,  more  particularly
      described as follows:

      Beginning  at a point  on the  north  line and 287  feet  easterly  of the
      northwest  corner of a tract of land  conveyed by warranty deed dated June
      10,  1930 and  recorded  in Book 896,  Page 476,  of the  records  of Weld
      County, Colorado, wherein Simon Peterson is the grantor and Public Service
      Company of Colorado is the grantee,  thence westerly along said north line
      a distance  of 287 feet to a point;  thence  southerly  along west line of
      said tract a distance of 230 feet to a point; thence easterly and parallel
      to said north line of said tract a distance of 302 feet to a point; thence
      northerly  and  parallel to west line of said tract a distance of 215 feet
      to a point;  thence  northwesterly a distance of 21.2 feet more or less to
      the point of beginning.




                                      II-2