Document:

<PAGE>
                                                                    EXHIBIT 4.01

                             PUBLIC SERVICE COMPANY
                                   OF COLORADO

                                       TO

                      U.S. BANK TRUST NATIONAL ASSOCIATION,

                                                AS TRUSTEE

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

                          SUPPLEMENTAL INDENTURE NO. 9

                          Dated as of September 1, 2002

                          Supplemental to the Indenture
                           dated as of October 1, 1993

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

                  Establishing the Securities of Series No. 8,
              designated First Collateral Trust Bonds, Series No. 8

<PAGE>
         SUPPLEMENTAL INDENTURE NO. 9, dated as of September 1, 2002, 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. 9. 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. 8", such series of
Securities to be hereinafter sometimes called "Series No. 8".

         The Company has duly authorized the execution and delivery of this
Supplemental Indenture No. 9 to establish the Securities of Series No. 8 and has
duly authorized the issuance of such Securities; and all acts necessary to make
this Supplemental Indenture No. 9 a valid agreement of the Company, and to make
the Securities of Series No. 8 valid obligations of the Company, have been
performed.

                                GRANTING CLAUSES

         NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE NO. 9 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. 9, 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, 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; (b) all plants,
         generators, turbines, engines, boilers, fuel handling and
         transportation

<PAGE>

         facilities, air and water pollution control and sewage and solid waste
         disposal facilities and other machinery and facilities for the
         generation of electric energy; (c) all switchyards, lines, towers,
         substations, transformers and other machinery and facilities for the
         transmission of electric energy; (d) all lines, poles, conduits,
         conductors, meters, regulators and other machinery and facilities for
         the distribution of electric energy; (e) all buildings, offices,
         warehouses and other structures used or to be used in or in connection
         with the Electric Utility Business; (f) 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; (g) any or
         all of the foregoing properties in the process of construction; and (h)
         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. 9 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. 9;

                             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;

                                       2
<PAGE>

         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;

         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. 8

         There are hereby established the Securities of Series No. 8, 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. 8"; 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. 8 shall be initially authenticated and
         delivered in the aggregate principal amount of $600,000,000;

         (c) interest on the Securities of Series No. 8 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. 8 shall be payable on
         October 1, 2012, the Stated Maturity.

         (e) the Securities of Series No. 8 shall bear interest at a rate of
         7.875% per annum; interest shall accrue on the Securities of Series No.
         8 from September 26, 2002, 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 1 and October 1 in each year, commencing
         April 1, 2003, and the Regular Record Dates with respect to the
         Interest Payment Dates for such Securities shall be March 15 and
         September 15 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.
         8 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. 8 shall be redeemable at the option of
         the Company at any time prior to maturity, in whole or in part, at a
         redemption price equal to the greater of (i) 100% of the principal
         amount thereof to be redeemed, or (ii) the sum of the present values of
         the remaining scheduled payments of principal and interest on such
         Securities to be redeemed, discounted to the Redemption Date on a
         semi-annual basis (assuming a 360-day year consisting of twelve 30-day
         months) at the Treasury Yield plus 50 basis points, plus in each case,
         accrued and unpaid interest to the Redemption Date. For purposes
         hereof, the following defined terms shall have the meaning ascribed to
         them:

                  "Treasury Yield" means, for any Redemption Date, the rate per
         annum equal to the semi-annual equivalent yield to maturity of the
         Comparable Treasury Issue, assuming a price for the Comparable Treasury
         Issue (expressed as a percentage of its principal amount) equal to the
         Comparable Treasury Price for the Redemption Date.

                  "Comparable Treasury Issue" means the United States Treasury
         security selected by an Independent Investment Banker as having a
         maturity comparable to the remaining term of the Securities of Series
         No. 8 that would be utilized, at the time of selection and in
         accordance with customary financial practice, in pricing new issues of
         corporate debt securities of comparable maturity to the remaining term
         of the Securities of Series No. 8.

                  "Comparable Treasury Price" means, for any Redemption Date,
         (i) the average of the bid and asked prices for the Comparable Treasury
         Issue (expressed in each case as a percentage of its principal amount)
         on the third Business Day preceding the Redemption Date, as set forth
         in the daily statistical release (or any successor release) published
         by the Federal Reserve Bank of New York and designated "Composite 3:30
         p.m. Quotations for U.S. Government Securities" or (ii) if that release
         (or any successor release) is not published or does not contain those
         prices on that Business Day, (A) the average of the Reference Treasury
         Dealer Quotations for the Redemption Date, after excluding the highest
         and lowest Reference Treasury Dealer Quotations for the Redemption
         Date, or (B) if the Trustee obtains fewer than four Reference Treasury
         Dealer Quotations, the average of all of the Quotations.

                  "Independent Investment Banker" means Banc of America
         Securities LLC or its successor or, if such firm or its successor is
         unwilling or unable to select the Comparable Treasury Issue, one of the
         remaining Reference Treasury Dealers appointed by the Trustee after
         consultation with the Company.

                  "Reference Treasury Dealer" means (i) each of Banc of America
         Securities LLC and Salomon Smith Barney Inc. and any other Primary
         Treasury Dealer designated by, and not

                                       4
<PAGE>

         affiliated with, Banc of America Securities LLC, Salomon Smith Barney
         Inc. and their respective successors, provided, however, that if either
         of the foregoing or any of its designees ceases to be a Primary
         Treasury Dealer, the Company will appoint another Primary Treasury
         Dealer as a substitute and (ii) any other Primary Treasury Dealer
         selected by the Company.

                  "Primary Treasury Dealer" means any primary U.S. Government
         securities dealer in New York City.

                  "Reference Treasury Dealer Quotations" means, for each
         Reference Treasury Dealer and any Redemption Date, the average, as
         determined by the Independent Investment Banker, of the bid and asked
         prices for the Comparable Treasury Issue (expressed in each case as a
         percentage of its principal amount) quoted in writing to the
         Independent Investment Banker by the Reference Treasury Dealer at 5:00
         p.m. on the third Business Day preceding the Redemption Date.

         (h) not applicable;

         (i) not applicable;

         (j) not applicable;

         (k) not applicable;

         (l) not applicable;

         (m) not applicable;

         (n) not applicable;

         (o) any Securities of Series No. 8 which are presented to the Company
         and/or the Trustee for exchange pursuant to a Registered Exchange Offer
         in accordance with the terms thereof shall be exchanged for New
         Securities of equal principal amount upon surrender to the Company
         and/or the Trustee of the Securities of Series No. 8 to be exchanged;
         provided, however, that the Securities of Series No. 8 so surrendered
         for exchange shall be duly endorsed and accompanied by a letter of
         transmittal or written instrument of transfer in form satisfactory to
         the Company, duly executed by the registered holder thereof or its
         attorney who shall be duly authorized in writing to execute such
         document. Whenever any Securities of Series No. 8 are so surrendered
         for exchange, the Company shall execute, and the Trustee shall
         authenticate and deliver to and in the name of each registered holder
         that has properly tendered its Securities of Series No. 8 for exchange,
         the same aggregate principal amount of New Securities as the Securities
         of Series No. 8 that have been so surrendered. For purposes hereof, the
         following defined terms shall have the meaning ascribed to them:

                  "Registered Exchange Offer" means the proposed offer of the
         Company to issue and deliver to the Holders of the Securities of Series
         No. 8 that are not prohibited by any law or policy of the Commission
         from participating in such offer, in exchange for the Securities of
         Series No. 8, a like aggregate principal amount of the New Securities.

                  "New Securities" means debt securities of the Company
         identical in all material respects to the Securities of Series No. 8
         presented for exchange pursuant to the Registered Exchange Offer

                                       5
<PAGE>

         (except that the transfer restrictions shall be modified or eliminated,
         as appropriate) and to be issued under the Indenture.

         (p) not applicable;

         (q)      (i) (A) the Securities of Series No. 8, if issued to persons
                  that are institutional "accredited investors" meeting the
                  requirements of Rule 501(a)(1), (2), (3) or (7) (each, an
                  "Institutional Accredited Investor") under the Securities Act
                  of 1933, as amended (the "Securities Act") that are not QIBs
                  (as defined below), shall be issued in definitive form,
                  registered in the name of the Holder thereof and (B) the
                  Securities of Series No. 8 (1) if issued to "qualified
                  institutional buyers," as defined in Rule 144A of the
                  Securities Act (each, a "QIB") in reliance on Rule 144A under
                  the Securities Act shall be issued in the form of one or more
                  global bonds that are not Regulation S global bonds, or (2) if
                  issued in offshore transactions to non-U.S. persons in
                  reliance on Regulation S shall be issued in the form of one or
                  more Regulation S global bonds, and, in the case of either (1)
                  or (2) above, shall be deposited on behalf of the Holders of
                  the Securities of Series No. 8 represented thereby with the
                  Trustee, as custodian for the securities depositary, shall be
                  registered in the name of the securities depositary or its
                  nominee and the aggregate principal amount of Securities of
                  Series No. 8 so issued may from time to time be increased or
                  decreased by adjustments made on the records of the Trustee
                  and the securities depositary or its nominee. For purposes
                  hereof, "Regulation S global bonds" means one or more global
                  bonds deposited with a custodian for, and registered in the
                  name of a nominee of, a securities depositary, interest in
                  which will be held for the benefit of purchasers of the bonds
                  in offshore transactions under Regulation S;

                  (ii) except as provided in subparagraphs (q)(i) and (v)
                  hereof, the Securities of Series No. 8 are to be initially
                  registered in the name of Cede & Co., as nominee for The
                  Depository Trust Company (the "Depositary"). Subject to
                  subparagraphs (o) and (q)(iii), (iv) and (v) hereof, such
                  Securities shall not be transferable or exchangeable, nor
                  shall any purported transfer be registered, except as follows:

                           (A) 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

                           (B) such Securities may be exchanged for definitive
                           Securities registered in the respective names of the
                           beneficial holders thereof, and, subject to
                           subparagraph (iii), (iv) and (v) below, thereafter
                           shall be transferable without restriction, if:

                                    (1) 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 or the Depositary has ceased to
                                    be a clearing agency registered under the
                                    Securities Exchange Act of 1934, as amended,
                                    and the Trustee shall not

                                       6
<PAGE>

                                    have been notified by the Company within
                                    ninety (90) days of the identity of a
                                    successor securities depositary with respect
                                    to such Securities;

                                    (2) 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;

                                    (3) (a) an Event of Default shall have
                                    occurred and be continuing, (b) the Trustee
                                    shall have given notice of such Event of
                                    Default pursuant to Section 1102 of the
                                    Original Indenture and (c) 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; or

                                    (4) the Securities or a portion thereof
                                    shall have been transferred to one or more
                                    Institutional Accredited Investors, as
                                    contemplated below.

                  (iii) all Securities of Series No. 8, whether definitive
                  Securities or global bonds, and all beneficial interest in one
                  or more Securities of Series No. 8, and all Securities issued
                  upon registration of, transfer of, or in exchange for, any
                  such Securities (other than New Securities or Securities sold
                  pursuant to an effective registration statement under the
                  Securities Act or Securities issued, directly or indirectly,
                  upon registration of transfer of, or in exchange for, any such
                  Securities), shall be restricted securities within the meaning
                  of Rule 144 under the Securities Act (collectively,
                  "Restricted Securities") and shall be subject to the
                  restrictions on transfer provided in the legends set forth on
                  the Restricted Securities. The registered Holder of each
                  Restricted Security, by such registered Holder's acceptance
                  thereof, agrees to be bound by such restrictions on transfer.
                  All Restricted Securities shall bear on their faces the
                  applicable legends limiting transferability set forth on the
                  form of the Securities of Series No.8.

                           Institutional Accredited Investors that are not QIBs
                  may hold interests in the Securities of Series No. 8 only in
                  definitive form. Any beneficial interest in a global bond that
                  is a Restricted Security and is transferred to an
                  Institutional Accredited Investor which is not a QIB will be
                  delivered in the form of a definitive Security and will cease
                  to be an interest in such global bond.

                           Each registered Holder of a definitive Security or a
                  beneficial interest in a global bond that is a Restricted
                  Security will be deemed to have represented and agreed to
                  offer, sell, pledge or otherwise transfer such Securities of
                  Series No. 8 or beneficial interest only in accordance with
                  the legend set forth on the face of the Restricted Securities.

                           Upon the transfer, exchange or replacement of
                  definitive Securities bearing the legend, or upon request for
                  removal of the legend on a definitive Security, the Trustee
                  will deliver Securities that do not bear such legend if the
                  Trustee has been provided evidence satisfactory to the Company
                  and to the Trustee (which may include an opinion of counsel)
                  that neither the legend nor the restrictions on transfer set
                  forth therein are required to ensure compliance with the
                  Securities Act.

                                       7
<PAGE>

                           Subject to the restrictions on transfer and exchange
                  set forth herein and in the Indenture, the holder of any
                  Securities issued hereunder may transfer or exchange such
                  Securities in whole or in part by surrendering them at the
                  Corporate Trust Office of the Trustee or its agent, together
                  with (A), an executed instrument of assignment and transfer
                  (in the case of a transfer) or a written request for exchange
                  (in the case of exchange), and, in the case of Securities of
                  Series No. 8 that are Restricted Securities, a certificate
                  substantially in the form of Exhibit B hereto, and (B)
                  additional certifications and evidence that such transfer or
                  exchange is in compliance with the Securities Act and the
                  restrictions on transfer set forth in such bonds as may be
                  required pursuant to the terms of this Supplemental Indenture
                  No. 9.

                  (iv) the following provisions shall apply with respect to any
                  proposed transfer of a Rule 144A global bond or a beneficial
                  interest therein or of a definitive Security held of record by
                  an Institutional Accredited Investor prior to (x) the date
                  which is two years (or such shorter period of time as
                  permitted by Rule 144(k) of the Securities Act) after the
                  later of the original issue date of the Securities and the
                  last date on which the Company or any "affiliate" (as defined
                  in Rule 144 under the Securities Act) of the Company was the
                  owner of the Security (or any predecessor of the Security) or
                  (y) such later date, if any, as may be required by applicable
                  law:

                           (A) a transfer of a Rule 144A global bond or a
                           beneficial interest therein or a definitive Security
                           held of record by an Institutional Accredited
                           Investor to a QIB shall be made upon the
                           representation of the transferee that it is
                           purchasing the Security for its own account or an
                           account with respect to which it exercises sole
                           investment discretion and that it and any such
                           account is a QIB and is aware that the sale to it is
                           being made in reliance on Rule 144A and acknowledges
                           that it has received such information regarding the
                           Company as it has requested pursuant to Rule 144A or
                           has determined not to request such information and
                           that it is aware that the Ftransferor is relying upon
                           its foregoing representations in order to claim the
                           exemption from registration provided by Rule 144A;

                           (B) a transfer of a Rule 144A global bond or a
                           beneficial interest therein or a definitive Security
                           held of record by an Institutional Accredited
                           Investor to an Institutional Accredited Investor
                           shall be made upon receipt by the Trustee or its
                           agent of a certificate substantially in the form set
                           forth in Exhibit C annexed hereto from the proposed
                           transferee and, if requested by the Company or the
                           Trustee, the delivery of an opinion of counsel,
                           certifications and/or other information satisfactory
                           to each of them; and

                           (C) a transfer of a Rule 144A global bond or a
                           beneficial interest therein or a definitive Security
                           held of record by an Institutional Accredited
                           Investor to a non-U.S. person shall be made upon
                           receipt by the Trustee or its agent of a certificate
                           substantially in the form set forth in Exhibit D
                           annexed hereto from the proposed transferor and, if
                           requested by the Company or the Trustee, the delivery
                           of an opinion of counsel, certifications and/or other
                           information satisfactory to each of them.

                                       8
<PAGE>

                  (v) the following provisions shall apply with respect to any
                  proposed transfer of a Regulation S global bond or a
                  beneficial interest therein prior to (x) the date which is two
                  years (or such shorter period of time as permitted by Rule
                  144(k) of the Securities Act) after the later of the original
                  issue date of the Securities and the last date on which the
                  Company or any "affiliate" (as defined in Rule 144 under the
                  Securities Act) of the Company was the owner of the Security
                  (or any predecessor of the Security) or (y) such later date,
                  if any, as may be required by applicable law:

                           (A) a transfer of a Regulation S global bond or a
                           beneficial interest therein to a QIB shall be made
                           upon the representation of the transferee that it is
                           purchasing the bond for its own account or an account
                           with respect to which it exercises sole investment
                           discretion and that it and any such account is a QIB
                           and is aware that the sale to it is being made in
                           reliance on Rule 144A and acknowledges that it has
                           received such information regarding the Company as it
                           has requested pursuant to Rule 144A or has determined
                           not to request such information and that it is aware
                           that the transferor is relying upon its foregoing
                           representations in order to claim the exemption from
                           registration provided by Rule 144A;

                           (B) a transfer of a Regulation S global bond or a
                           beneficial interest therein to an Institutional
                           Accredited Investor shall be made upon receipt by the
                           Trustee or its agent of a certificate substantially
                           in the form set forth in Exhibit C annexed hereto
                           from the proposed transferee and, if requested by the
                           Company or the Trustee, the delivery of an opinion of
                           counsel, certifications and/or other information
                           satisfactory to each of them; and

                           (C) a transfer of a Regulation S global bond or a
                           beneficial interest therein to a non-U.S. person
                           prior to the expiration of the 40-day "distribution
                           compliance period" within the meaning of Rule 903 of
                           Regulation S under the Securities Act (the
                           "Distribution Compliance Period") shall be made upon
                           receipt by the Trustee or its agent of a certificate
                           substantially in the form set forth in Exhibit D
                           annexed hereto from the proposed transferor and, if
                           requested by the Company or the Trustee, the delivery
                           of an opinion of counsel, certifications and/or other
                           information satisfactory to each of them.

                                    Prior to or on the expiration of the
                           Distribution Compliance Period, beneficial interests
                           in a Regulation S global bond may only be held
                           through the operator of the Euroclear System
                           ("Euroclear") or Clearstream Banking, a societe
                           anonyme ("Clearstream") (as indirect participants in
                           the Depositary) or another agent member of Euroclear
                           or Clearstream acting for and on behalf of them,
                           unless exchanged for interests in the Rule 144A
                           global bond in accordance with the certification
                           requirements hereof. During the Distribution
                           Compliance Period, interests in the Regulation S
                           global bond, if any, may be exchanged for interests
                           in the Rule 144A global bond or for definitive
                           Securities only in accordance with the certification
                           requirements described in this subparagraph (q)(v).

                                       9
<PAGE>

                                    After expiration of the Distribution
                           Compliance Period, interests in the Regulation S
                           global bond may be transferred to a non-U.S. person
                           without requiring the certification set forth in
                           Exhibit D annexed hereto or any additional
                           certification.

         (r) not applicable;

         (s) no service charge shall be made for the registration of transfer or
         exchange of the Securities of Series No. 8; 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. 8 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) 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

                                       10
<PAGE>

                  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. 8 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. 8 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. 9 is a supplement to the Original
Indenture. As previously supplemented and further supplemented by this
Supplemental Indenture No. 9, the Original Indenture is in all respects
ratified, approved and confirmed, and the Original Indenture, all previous
supplements thereto and this Supplemental Indenture No. 9 shall together
constitute one and the same instrument.

                                       11
<PAGE>

                  IN WITNESS WHEREOF, the parties hereto have caused this
Supplemental Indenture No. 9 to be duly executed as of the day and year first
above written.

                                        PUBLIC SERVICE COMPANY OF COLORADO

                                        By: /s/ Paul E. Pender
                                           -------------------------------------

                                           Name:    Paul E. Pender
                                           Title:   Vice President and Treasurer

STATE OF MINNESOTA               )
                                 ) ss.:
CITY OF MINNEAPOLIS              )

         On the 17th day of September, 2002, before me personally came Paul E.
Pender to me known, who, being by me duly sworn, did depose and say that he is a
Vice President and Treasurer 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/ Sharon M. Quellhorst
                                        ----------------------------------------
                                        Name: Sharon M. Quellhorst
                                        Notary Public, State of Minnesota

                                        Commission Expires:  January 31, 2005

                                       12
<PAGE>

                                        U.S. BANK TRUST NATIONAL ASSOCIATION,
                                                               Trustee

                                        By: /s/ Ignazio Tamburello
                                           -------------------------------------

                                           Name:    Ignazio Tamburello
                                           Title:   Assistant Vice President

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

         On the 17th day of September, 2002, before me personally came Ignazio
Tamburello, to me known, who, being by me duly sworn, did depose and say that he
is an Assistant Vice President of U.S. Bank Trust National Association, the
banking association described in and which executed the foregoing instrument;
and that he signed his name thereto by authority of the Board of Directors of
said banking association.

                                        /s/ Rouba Fakih
                                        ----------------------------------------
                                        Name:  Rouba Fakih
                                        Notary Public, State of New York

                                        Commission Expires: February 20, 2003

                                       13
<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. 8

      Original Interest Accrual Date          September 26, 2002
                      Interest Rate:          7.875%
                    Stated Maturity:          October 1, 2012
             Interest Payment Dates:          April 1 and October 1
               Regular Record Dates:          March 15 and September 15

                    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 more Predecessor Securities) is
registered at the close of business on a Special Record Date for the payment of
such Defaulted Interest to

                                  EXHIBIT A-1
<PAGE>

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.

         This Security shall be redeemable at the option of the Company at any
time prior to maturity, in whole or in part, at a redemption price equal to the
greater of (i) 100% of the principal amount hereof to be redeemed, or (ii) the
sum of the present values of the remaining scheduled payments of principal and
interest on this Security, discounted to the Redemption Date on a semi-annual
basis (assuming a 360-day year consisting of twelve 30-day months) at the
Treasury Yield plus 50 basis points, plus in each case, accrued and unpaid
interest to the Redemption Date. For purposes hereof, the following defined
terms shall have the meaning ascribed to them:

         "Treasury Yield" means, for any Redemption Date, the rate per annum
equal to the semi-annual equivalent yield to maturity of the Comparable Treasury
Issue, assuming a price for the Comparable Treasury Issue (expressed as a
percentage of its principal amount) equal to the Comparable Treasury Price for
the Redemption Date.

         "Comparable Treasury Issue" means the United States Treasury security
selected by an Independent Investment Banker as having a maturity comparable to
the remaining term of the Securities of Series No. 8 that would be utilized, at
the time of selection and in accordance with customary financial

                                  EXHIBIT A-2
<PAGE>

practice, in pricing new issues of corporate debt securities of comparable
maturity to the remaining term of the Securities of Series No. 8.

         "Comparable Treasury Price" means, for any Redemption Date, (i) the
average of the bid and asked prices for the Comparable Treasury Issue (expressed
in each case as a percentage of its principal amount) on the third Business Day
preceding the Redemption Date, as set forth in the daily statistical release (or
any successor release) published by the Federal Reserve Bank of New York and
designated "Composite 3:30 p.m. Quotations for U.S. Government Securities" or
(ii) if that release (or any successor release) is not published or does not
contain those prices on that Business Day, (A) the average of the Reference
Treasury Dealer Quotations for the Redemption Date, after excluding the highest
and lowest Reference Treasury Dealer Quotations for the Redemption Date, or (B)
if the Trustee obtains fewer than four Reference Treasury Dealer Quotations, the
average of all of the Quotations.

         "Independent Investment Banker" means Banc of America Securities LLC or
its successor or, if such firm or its successor is unwilling or unable to select
the Comparable Treasury Issue, one of the remaining Reference Treasury Dealers
appointed by the Trustee after consultation with the Company.

         "Reference Treasury Dealer" means (i) each of Banc of America
Securities LLC and Salomon Smith Barney Inc. and any other Primary Treasury
Dealer designated by, and not affiliated with, Banc of America Securities LLC,
Salomon Smith Barney Inc. and their respective successors, provided, however,
that if either of the foregoing or any of its designees ceases to be a Primary
Treasury Dealer, the Company will appoint another Primary Treasury Dealer as a
substitute and (ii) any other Primary Treasury Dealer selected by the Company.

         "Primary Treasury Dealer" means any primary U.S. Government securities
dealer in New York City.

         "Reference Treasury Dealer Quotations" means, for each Reference
Treasury Dealer and any Redemption Date, the average, as determined by the
Independent Investment Banker, of the bid and asked prices for the Comparable
Treasury Issue (expressed in each case as a percentage of its principal amount)
quoted in writing to the Independent Investment Banker by the Reference Treasury
Dealer at 5:00 p.m. on the third Business Day preceding the Redemption Date.

         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

                                  EXHIBIT A-3
<PAGE>

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 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.

         Any Securities of this series which are presented to the Company and/or
the Trustee for exchange pursuant to a Registered Exchange Offer in accordance
with the terms thereof shall be exchanged for New Securities of equal principal
amount upon surrender to the Company and/or the Trustee of the Securities to be
exchanged; provided, however, that the Securities of this series so surrendered
for exchange shall be duly endorsed and accompanied by a letter of transmittal
or written instrument of transfer in form satisfactory to the Company, duly
executed by the registered holder thereof or its attorney who shall be duly
authorized in writing to execute such document. Whenever any Securities of this
series are so surrendered for exchange, the Company shall execute, and the
Trustee shall authenticate and deliver to and in the name of each registered
holder that has properly tendered its Securities for exchange, the same
aggregate principal amount of New Securities as the Securities of this series
that have been so surrendered. For purposes hereof, the following defined terms
shall have the meaning ascribed to them:

         "Registered Exchange Offer" means the proposed offer of the Company to
issue and deliver to the Holders of the Securities of this series that are not
prohibited by any law or policy of the Commission from participating in such
offer, in exchange for the Securities of this series, a like aggregate principal
amount of the New Securities.

                                  EXHIBIT A-4
<PAGE>

         "New Securities" means debt securities of the Company identical in all
material respects to the Securities of this series presented for exchange
pursuant to the Registered Exchange Offer (except that the transfer restrictions
shall be modified or eliminated, as appropriate) and to be issued under the
Indenture.

         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.

                                  EXHIBIT A-5
<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.](1)

                                     ------

--------------
(1) To be inserted only in global bond.

                                   EXHIBIT A-6
<PAGE>

                                 RESTRICTED NOTE

         [THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
         1933, AS AMENDED (THE "SECURITIES ACT"). THE HOLDER HEREOF, BY
         PURCHASING THIS SECURITY, AGREES FOR THE BENEFIT OF THE COMPANY THAT
         THIS SECURITY MAY NOT BE RESOLD, PLEDGED OR OTHERWISE TRANSFERRED OTHER
         THAN (A)(1) TO THE COMPANY, (2) IN A TRANSACTION ENTITLED TO AN
         EXEMPTION FROM REGISTRATION PROVIDED BY RULE 144 UNDER THE SECURITIES
         ACT, (3) SO LONG AS THIS SECURITY IS ELIGIBLE FOR RESALE PURSUANT TO
         RULE 144A UNDER THE SECURITIES ACT ("RULE 144A"), TO A PERSON WHOM THE
         SELLER REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL BUYER WITHIN
         THE MEANING OF RULE 144A PURCHASING FOR ITS OWN ACCOUNT OR FOR THE
         ACCOUNT OF A QUALIFIED INSTITUTIONAL BUYER TO WHOM NOTICE IS GIVEN THAT
         THE RESALE, PLEDGE OR OTHER TRANSFER IS BEING MADE IN RELIANCE ON RULE
         144A, (4) OUTSIDE THE UNITED STATES IN A TRANSACTION MEETING THE
         REQUIREMENTS OF REGULATION S UNDER THE SECURITIES ACT, (5) IN
         ACCORDANCE WITH ANOTHER APPLICABLE EXEMPTION FROM THE REGISTRATION
         REQUIREMENTS OF THE SECURITIES ACT (AND BASED UPON AN OPINION OF
         COUNSEL ACCEPTABLE TO THE COMPANY) OR (6) PURSUANT TO A REGISTRATION
         STATEMENT WHICH HAS BEEN DECLARED EFFECTIVE UNDER THE SECURITIES ACT
         AND (B) IN EACH CASE IN ACCORDANCE WITH APPLICABLE SECURITIES LAWS OF
         EACH STATE OF THE UNITED STATES. AN INSTITUTIONAL ACCREDITED INVESTOR
         HOLDING THIS SECURITY AGREES IT WILL FURNISH TO THE COMPANY AND THE
         TRUSTEE SUCH CERTIFICATES AND OTHER INFORMATION AS THEY MAY REASONABLY
         REQUIRE TO CONFIRM THAT ANY TRANSFER BY IT OF THIS SECURITY COMPLIES
         WITH THE FOREGOING RESTRICTIONS. THE HOLDER HEREOF, BY PURCHASING THIS
         SECURITY, REPRESENTS AND AGREES FOR THE BENEFIT OF THE COMPANY THAT IT
         IS (1) A QUALIFIED INSTITUTIONAL BUYER WITHIN THE MEANING OF RULE 144A
         OR (2) AN INSTITUTION THAT IS AN "ACCREDITED INVESTOR" AS DEFINED IN
         RULE 501(A)(1), (2), (3) OR (7) UNDER THE SECURITIES ACT AND THAT IS
         HOLDING THIS SECURITY FOR INVESTMENT PURPOSES AND NOT FOR DISTRIBUTION
         OR (3) A NON-U.S. PERSON OUTSIDE THE UNITED STATES WITHIN THE MEANING
         OF REGULATION S UNDER THE SECURITIES ACT.]

         [THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
         1933, AS AMENDED (THE "SECURITIES ACT"), AND ACCORDINGLY, MAY NOT BE
         OFFERED OR SOLD WITHIN THE UNITED STATES OR TO OR FOR THE ACCOUNT OR
         BENEFIT OF, U.S. PERSONS EXCEPT AS SET FORTH IN THE PRECEDING
         PARAGRAPH. BY ITS ACQUISITION HEREOF, THE HOLDER (1) REPRESENTS THAT IT
         IS NOT A U.S. PERSON AND IS ACQUIRING THIS SECURITY IN AN OFFSHORE
         TRANSACTION, (2) BY ITS ACCEPTANCE HEREOF AGREES TO OFFER, SELL OR
         OTHERWISE TRANSFER SUCH SECURITY, PRIOR TO THE DATE (THE RESALE
         RESTRICTION TERMINATION DATE) WHICH IS TWO YEARS AFTER THE LATER OF THE
         ORIGINAL ISSUE DATE HEREOF AND THE LAST DATE ON WHICH THE COMPANY OR
         ANY AFFILIATE OF THE COMPANY WAS THE OWNER OF THIS SECURITY (OR ANY
         PREDECESSOR OF SUCH SECURITY), ONLY AS SET FORTH IN THE PRECEDING
         PARAGRAPH, SUBJECT TO THE COMPANY'S AND THE TRUSTEE'S RIGHTS PRIOR TO
         ANY SUCH OFFER, SALE OR TRANSFER TO REQUIRE THE DELIVERY OF AN OPINION
         OF COUNSEL, CERTIFICATION AND/OR OTHER INFORMATION SATISFACTORY TO EACH
         OF THEM (FORMS OF WHICH MAY BE OBTAINED FROM THE COMPANY OR THE
         TRUSTEE) COMPLETED AND DELIVERED BY THE TRANSFEROR TO THE COMPANY AND
         THE TRUSTEE.](2)

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

(2) To be inserted only in Regulation S global bond.

                                   EXHIBIT A-7
<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.

                                   EXHIBIT A-8
<PAGE>

                                                                       EXHIBIT B

                        [Form of Transferor Certificate]

                CERTIFICATE TO PUBLIC SERVICE COMPANY OF COLORADO
   AND TRUSTEE FIRST COLLATERAL TRUST BONDS, SERIES NO. 8 DUE OCTOBER 1, 2012

This is to certify that as of the date hereof with respect to U.S. $
principal amount of the above-captioned securities presented or surrendered on
the date hereof (the "Surrendered Bonds") for registration of transfer or for
exchange where the securities issuable upon such exchange are to be registered
in a name other than that of the undersigned holder (each such transaction being
a "transfer"), the undersigned holder of the Surrendered Bonds represents and
certifies for the benefit of Public Service Company of Colorado and U.S. Bank
Trust National Association, as Trustee, that the transfer of Surrendered Bonds
associated with such transfer complies with the restrictive legend set forth on
the face of the Surrendered Bonds for the reason checked below:

[ ]      The Surrendered Bonds are being transferred to a person whom we
         reasonably believe is a "qualified institutional buyer" (as defined in
         Rule 144A under the Securities Act of 1933) (a "QIB") that purchases
         for its own account or for the account of a QIB to whom notice is given
         that the resale, pledge or transfer is being made in reliance on Rule
         144A under the Securities Act; or

[ ]      The Surrendered Bonds are being transferred to an institution that is
         an "accredited investor" meeting the requirements of Rule 501(a)(1),
         (2), (3) or (7) under the Securities Act that is acquiring the
         Surrendered Bonds for investment purposes and not for distribution;1 or

[ ]      The transfer of the Surrendered Bonds complies with Rule 144 under the
         Securities Act;2 or

[ ]      The transfer of the Surrendered Bonds complies with another applicable
         exemption from the registration requirements of the Securities Act.2

                                [Name of holder]

                  Dated:                    ,
                           -----------------  -------
         [To be dated the date of presentation or surrender]

--------------
(1) These transfers require that the transferee deliver a letter substantially
in the form of Exhibit C to Supplemental Indenture No. 9 dated as of September
1, 2002.

(2) These transfers may require an opinion of counsel.

                                   EXHIBIT B-1

<PAGE>

                                                                       EXHIBIT C

                        [Form of Institutional Accredited
                     Investor Transferee Compliance Letter]

Public Service Company of Colorado
1225 17th Street
Denver, Colorado  80202
Attention:  Vice President and Treasurer

U.S. Bank Trust National Association
100 Wall Street
New York, New York   10005
[Attention:                         ]
           -------------------------

Dear Ladies and Gentlemen:

         In connection with our proposed purchase of the 7.875% First Collateral
Trust Bonds, Series No. 8 due 2012 (the "first collateral trust bonds") of
Public Service Company of Colorado, a Colorado corporation (the "Issuer"), we
confirm that:

                  1. We are purchasing the first collateral trust bonds for our
         own account, or for one or more investor accounts for which we are
         acting as a fiduciary or agent, in each case for investment, and not
         with a view to, or for offer or sale in connection with, any
         distribution in violation of the Securities Act, as amended (the
         "Securities Act"), subject to any requirement of law that the
         disposition of our property or the property of such investor account or
         accounts be at all times within our or their control and subject to our
         or their ability to resell the first collateral trust bonds pursuant to
         Rule 144A, Regulation S or any exemption from registration available
         under the Securities Act.

                  2. We are an institutional "accredited investor" within the
         meaning of Rule 501(a)(1), (2), (3) or (7) under the Securities Act who
         is purchasing first collateral trust bonds with a principal amount of
         at least $250,000 and, if the first collateral trust bonds are to be
         purchased for one or more accounts (the "investor accounts") for which
         we are acting as fiduciary or agent, each such account is an
         institutional accredited investor who is purchasing first collateral
         trust bonds with a principal amount of at least $250,000. In the normal
         course of business or our investing activities, we invest in or
         purchase securities similar to the first collateral trust bonds and we
         have such knowledge and experience in financial business matters that
         we are capable of evaluating the merits and risks of purchasing the
         first collateral trust bonds. We are aware that we (or any investor
         account) may be required to bear the economic risk of an investment in
         the first collateral trust bonds for an indefinite period of time and
         we (or such investor account) are able to bear such risk for an
         indefinite period.

                  3. We acknowledge that none of the Issuer, the initial
         purchasers or any persons representing any of them has made any
         representation to us with respect to any such entity or the offering or
         sale of any first collateral trust bonds, other than the information
         contained in the Issuer's offering memorandum dated September 18, 2002,
         related to the first collateral trust bonds, which offering memorandum
         has been delivered to us and upon which we are relying in making our
         investment decision with respect to the first collateral trust bonds.
         Accordingly, we acknowledge that no representation or warranty is made
         by the initial purchasers as to the accuracy or completeness of such
         materials. We have had access to such financial and other

                                   EXHIBIT C-1

<PAGE>

         information concerning the Issuer and the first collateral trust bonds
         as we have deemed necessary in connection with our decision to purchase
         any of the first collateral trust bonds including an opportunity to ask
         questions of, and request information from, the Issuer and the initial
         purchasers.

                  4. We understand and agree that the offer and sale of the
         first collateral trust bonds have not been registered under the
         Securities Act and that such first collateral trust bonds are being
         offered only in a transaction not involving any public offering within
         the meaning of the Securities Act, and that (A) if we decide to resell,
         pledge or otherwise transfer such first collateral trust bonds on which
         a legend setting forth these restrictions appears, such first
         collateral trust bonds may be resold, pledged or otherwise transferred
         only (1) to the Issuer, (2) in a transaction entitled to an exemption
         from registration provided by Rule 144 under the Securities Act, (3) so
         long as such first collateral trust bonds are eligible for resale
         pursuant to Rule 144A, to a person whom we reasonably believe is a
         qualified institutional buyer that purchases for its own account or for
         the account of a qualified institutional buyer to whom notice is given
         that the resale, pledge or other transfer is being made in reliance on
         Rule 144A, (4) outside the United States in a transaction meeting the
         requirements of Regulation S, (5) in accordance with another exemption
         from the registration requirements of the Securities Act (and based
         upon an opinion of counsel acceptable to the Issuer) or (6) pursuant to
         a registration statement which has been declared effective under the
         Securities Act, in each case in accordance with any applicable
         securities laws of any state of the United States and (B) we will, and
         each subsequent holder is required to, notify any purchaser of first
         collateral trust bonds from us or it of the resale restrictions
         referred to in (A) above, if then applicable. We acknowledge that the
         foregoing restrictions apply to holders of beneficial interest in the
         first collateral trust bonds, as well as to holders of the first
         collateral trust bonds.

                  5. We understand that, on any proposed resale of any first
         collateral trust bonds, we will be required to furnish to the trustee
         and the Issuer such certifications, legal opinions and other
         information as the trustee and the Issuer may reasonably require to
         confirm that the proposed sale complies with the foregoing
         restrictions. We further understand that the first collateral trust
         bonds purchased by us will bear a legend to the foregoing effect.

                  6. We acknowledge that the Issuer, the trustee, the initial
         purchasers and others will rely upon the truth and accuracy of the
         foregoing acknowledgements, representations and agreements and agree
         that if any of the foregoing acknowledgements, representations or
         agreements are no longer accurate, we shall promptly notify the Issuer,
         the trustee and the initial purchasers. If we are acquiring the first
         collateral trust bonds as a fiduciary or agent for one or more investor
         accounts, we represent that we have sole investment discretion with
         respect to each such account and we have full power to make the
         foregoing acknowledgements, representations and agreements on behalf of
         each account and that each such investor account is eligible to
         purchase the first collateral trust bonds.

                                   EXHIBIT C-2

<PAGE>

                  The Issuer, the trustee and the initial purchasers are
         entitled to rely upon this letter and are irrevocably authorized to
         produce this letter or a copy hereof to any interested party in any
         administrative or legal proceeding or official inquiry with respect to
         the matters covered hereby.

                                                     Very truly yours,

                                                     ---------------------------
                                                     (Name of Purchaser)

                                                     By:
                                                        ------------------------

         Date:
              ---------------------------

                                   EXHIBIT C-3

<PAGE>

                                                                       EXHIBIT D

                   [Form of Regulation S Transfer Certificate]

                                                                          [date]
Public Service Company of Colorado
1225 17th Street
Denver, Colorado  80202
Attention:  Vice President and Treasurer

U.S. Bank Trust National Association
100 Wall Street
New York, New York   10005
[Attention:                         ]
           -------------------------

Dear Ladies and Gentlemen:

         In connection with our proposed sale of $      aggregate principal
amount of 7.875% First Collateral Trust Bonds, Series No. 8 due October 1, 2012
(the "Bonds") of Public Service Company of Colorado, a Colorado corporation (the
"Company"), we confirm that:

                  (a)      the offer of the Bonds was not made to a person in
                           the United States;

                  (b)      either (i) at the time the buy order was originated,
                           the transferee was outside the United States or we
                           and any person acting on our behalf reasonably
                           believed that the transferee was outside the United
                           States or (ii) the transaction was executed in, on or
                           through the facilities of a designated off-shore
                           securities market and neither we nor any person
                           acting on our behalf knows that the transaction has
                           been pre-arranged with a buyer in the United States;

                  (c)      no directed selling efforts have been made in the
                           United States in contravention of the requirements of
                           Rule 903(b) or Rule 904(b) of Regulation S, as
                           applicable; and

                  (d)      the transaction is not part of a plan or scheme to
                           evade the registration requirements of the Securities
                           Act.

                           In addition, if the sale is made during a
Distribution Compliance Period and the provisions of Rule 903(a)(3) or Rule
904(b)(1) of Regulation S are applicable thereto, we confirm that such sale has
been made in accordance with the applicable provisions of Rule 903(a)(3) or Rule
904(b)(1), as the case may be.

                                   EXHIBIT D-1
<PAGE>

                           The Company and the Trustee are entitled to rely upon
this letter and are irrevocably authorized to produce this letter or a copy
hereof to any interested party in any administrative or legal proceedings or
official inquiry with respect to the matters covered hereby. Terms used in this
certificate have the meanings set forth in Regulation S.

                                                  Very truly yours,
                                                  (Name of Transferor]

                                                  By:
                                                     ---------------------------

         Date:
              --------------------------

                                   EXHIBIT D-2
<PAGE>

                                                                      SCHEDULE A

                             SUPPLEMENTAL INDENTURES

<TABLE>
<CAPTION>
         DATE OF                      SERIES OF BONDS                    PRINCIPAL               PRINCIPAL
      SUPPLEMENTAL                    ---------------                  AMOUNT ISSUED               AMOUNT
        INDENTURE                                                      -------------            OUTSTANDING
        ---------                                                                               -----------
<S>                              <C>                                 <C>                      <C>
November 1, 1993                        Series No. 1                    $134,500,000            $134,500,000
January 1, 1994                    Series No. 2 due 2001                $102,667,000                None
                                            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            $175,000,000
February 1, 1997                        Series No. 5                    $150,000,000                None
April 1, 1998                           Series No. 6                    $250,000,000            $250,000,000
August 15, 2002                         Series No. 7                    $ 48,750,000            $ 48,750,000
</TABLE>

                                  SCHEDULE A-1<PAGE>
                                                                    EXHIBIT 4.02

                             SUPPLEMENTAL INDENTURE

                         (DATED AS OF SEPTEMBER 1, 2002)

                                   ----------

                       PUBLIC SERVICE COMPANY OF COLORADO

                                       TO

                      U.S. BANK TRUST NATIONAL ASSOCIATION,
                                                          AS TRUSTEE

                                   ----------

                   CREATING AN ISSUE OF FIRST MORTGAGE BONDS,
                               COLLATERAL SERIES H

                                   ----------

      (SUPPLEMENTAL TO INDENTURE DATED AS OF DECEMBER 1, 1939, AS AMENDED)

<PAGE>

                  SUPPLEMENTAL INDENTURE, dated as of September 1, 2002, 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 H
(the "Collateral Series H 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 H 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 H Bonds and of specifying the form, provisions
and particulars thereof, as in the Indenture provided or permitted and of giving
to the Collateral Series H Bonds the protection and security 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 H 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 H 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;

                                       1

<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 H
Bonds and to specify the form, terms and provisions thereof, 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 H 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 unto U.S. Bank
Trust National Association, as Trustee, and its successor or successors in the
trust and its and their assigns forever;

                  TO HAVE AND TO HOLD all and singular the properties, rights,
privileges and franchises described in the Principal Indenture and in the
several Supplemental Indentures hereinabove referred to 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 H 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 H 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 H. The Collateral Series H
Bonds shall be limited to an aggregate principal amount of Six Hundred Million
dollars ($600,000,000), excluding any Collateral Series H Bonds which may be
authenticated and exchanged for or in lieu of or in substitution for or on
transfer of other Collateral Series H Bonds pursuant to any provisions of the
Indenture. The Collateral Series H Bonds shall mature on October 1, 2012. The
Collateral Series H Bonds shall not bear interest.

                                       2

<PAGE>

                  The principal of each Collateral Series H 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 H 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 H 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 H Bonds (other than by the application of
the proceeds of a payment in respect of such Collateral Series H 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 H
Bonds which is then due.

                  The Trustee may conclusively presume that the obligation of
the Company to pay the principal of the Collateral Series H 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 H 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 H Bond shall be dated as of the date of
its authentication.

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

                  The Collateral Series H 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 H 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 H Bond.

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

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

                                       3

<PAGE>

                                  ARTICLE TWO

                   REDEMPTION OF THE COLLATERAL SERIES H BONDS

                  SECTION 1. Each Collateral Series H 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 H Bonds,
except that (a) no publication of notice of redemption of the Collateral Series
H Bonds shall be required and (b) if less than all the Collateral Series H Bonds
are to be redeemed, the Collateral Series H 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 H
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 H 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 H 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 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.

                                       4

<PAGE>

                                  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 H
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 Assistant Vice
Presidents and attested by one of its Trust Officers, for and in its behalf, all
as of the day and year first above written.

                                         PUBLIC SERVICE COMPANY OF
                                         COLORADO

                                         By: /s/ Paul E. Pender
                                             -----------------------------------
                                             Name:  Paul E. Pender
                                             Title: Vice President and Treasurer

ATTEST: /s/ Nancy Haley
        ----------------------------
        Name:  Nancy Haley
        Title: Assistant Secretary

STATE OF MINNESOTA                   )
                                     )  ss.:
CITY OF MINNEAPOLIS                  )

                  On this 17th day of September, 2002, before me, Sharon M.
Quellhorst, a duly authorized Notary Public in and for said City in the State
aforesaid, personally appeared Paul E. Pender and Nancy Haley to me known to be
a Vice President and Treasurer and the Assistant 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 Vice President and Treasurer 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.

                                         /s/ Sharon M. Quellhorst
                                         -----------------------------------
                                         Name: Sharon M. Quellhorst
                                         Notary Public, State of Colorado

                                         Commission Expires: January 31, 2005

                                       6

<PAGE>

                                         U.S. BANK TRUST
                                            NATIONAL ASSOCIATION,
                                                  as Trustee

                                         By: /s/ Ignazio Tamburello
                                             -----------------------------------
                                             Name: Ignazio Tamburello
                                             Title: Assistant Vice President

ATTEST: /s/ Adam Berman
       ------------------------------
           Name:     Adam Berman
           Title:    Trust Officer

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

                  On this 17th day of September, 2002, before me, Rouba Fakih, a
duly authorized Notary Public in and for said City and County in the State
aforesaid, personally appeared Ignazio Tamburello and Adam Berman to me known to
be an Assistant Vice President and a Trust Officer, 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
Assistant Vice President and Trust Officer 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.

                                          /s/ Rouba Fakih
                                          --------------------------------
                                          Name:  Rouba Fakih
                                          Notary Public, State of New York

                                          Commission Expires:  February 20, 2003

                                       7
<PAGE>

                                                                       EXHIBIT A

                        FORM OF COLLATERAL SERIES H 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 H

                                    DUE 2012

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 October 1, 2012, 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

                                   Exhibit A-1

<PAGE>

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 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 September
1, 2002 (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 H, 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

                                   Exhibit A-2

<PAGE>

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 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:
       ----------------------------
        [Assistant 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

                                   Exhibit A-3

<PAGE>

                                                                       SCEDULE A

                             SUPPLEMENTAL INDENTURES

<Table>
<Caption>
         DATE OF                      SERIES OF BONDS                    PRINCIPAL               PRINCIPAL
      SUPPLEMENTAL                    ---------------                  AMOUNT ISSUED               AMOUNT
        INDENTURE                                                      -------------            OUTSTANDING
        ---------                                                                               -----------
<S>                            <C>                               <C>                     <C>
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                             --                      --
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                  None
April 25, 1969                              None                             --                      --
</TABLE>

                                  Schedule A-1

<PAGE>

<Table>
<Caption>
         DATE OF                      SERIES OF BONDS                    PRINCIPAL               PRINCIPAL
      SUPPLEMENTAL                    ---------------                  AMOUNT ISSUED               AMOUNT
        INDENTURE                                                      -------------            OUTSTANDING
        ---------                                                                               -----------
<S>                            <C>                               <C>                     <C>
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                  None
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
November 1, 1986*                Pollution Control Series F             27,250,000                  None
May 1, 1987*                       8.95% Series due 1992                75,000,000                  None
July 1, 1990*                      9-7/8% Series due 2020               75,000,000                  None
December 1, 1990*           Secured Medium-Term Notes, Series A        191,500,000**           15,000,000
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            146,340,000
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                  None
                                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
</TABLE>

                                  Schedule A-2

<PAGE>

<Table>
<Caption>
         DATE OF                      SERIES OF BONDS                    PRINCIPAL               PRINCIPAL
      SUPPLEMENTAL                    ---------------                  AMOUNT ISSUED               AMOUNT
        INDENTURE                                                      -------------            OUTSTANDING
        ---------                                                                               -----------
<S>                            <C>                               <C>                     <C>
November 1, 1996                    Collateral Series D                250,000,000              175,000,000
February 1, 1997                    Collateral Series E                150,000,000                  None
April 1, 1998                       Collateral Series F                 250,000,000             250,000,000
August 15, 2002                     Collateral Series G                  48,750,000              48,750,000
</Table>

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

                                  Schedule A-3

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00043-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00043-of-00352.parquet"}]]