Document:

<PAGE>   1

                                                                   EXHIBIT 4.6.2

                          FIRST SUPPLEMENTAL INDENTURE

                            Dated as of July 31, 2000

                                     Between

                              CALPINE CORPORATION,

                                    AS ISSUER

                                       and

                              THE BANK OF NEW YORK,

                                   AS TRUSTEE

                           Supplementing the Indenture
                           Dated as of March 29, 1999

<PAGE>   2

     FIRST SUPPLEMENTAL INDENTURE, dated as of July 31, 2000 (the "First
Supplemental Indenture"), between Calpine Corporation, a Delaware corporation
(the "Company"), and The Bank of New York, as trustee ("the Trustee").

     WHEREAS, the Company executed and delivered the Indenture dated as of March
29, 1999 (the "Indenture"), to the Trustee to provide for the issuance of
$250,000,000 of the Company's 75/8% Senior Notes due 2006;

     WHEREAS, the Holders (as defined in the Indenture) of a majority in
principal amount of such Senior Notes have approved certain amendments proposed
by the Company to certain provisions of the Indenture, and the Company desires
to supplement and amend the Indenture accordingly as contemplated by Section 8.2
thereof;

     WHEREAS, all things necessary to make this First Supplemental Indenture a
valid agreement of the Company and the Trustee in accordance with its terms and
a valid amendment and supplement to the Indenture, have been done.

     NOW THEREFORE, for and in consideration of the premises and mutual
covenants herein contained, the Company and the Trustee agree as follows:

                                    ARTICLE I
                                   DEFINITIONS

     Section 1.1 Definition of Terms

     Unless the context otherwise requires

     (a)  capitalized terms used herein that are not otherwise defined herein
shall have the meaning assigned to such terms in the Indenture;

     (b)  the singular includes the plural and vice versa;

     (c)  headings are for convenience of reference only and do not affect
interpretation.

                                   ARTICLE II
                           AMENDMENTS TO THE INDENTURE

     Section 2.1 Amendments

     (a)  The following definition in Section 1.1 of the Indenture is amended to
read in its entirety as follows:

     "Non-Recourse Debt" means Indebtedness of the Company or any Restricted
     Subsidiary that is Incurred to finance the exploration, drilling,
     development, construction or purchase of or by, or repairs, improvements

                                       2

<PAGE>   3

     or additions to, property or assets of the Company or any Restricted
     Subsidiary, provided that such Indebtedness is without recourse to the
     Company or any Restricted Subsidiary or to any property or assets of the
     Company or any Restricted Subsidiary other than property or assets
     (including Capital Stock) subject to a Lien permitted pursuant to Section
     3.7 (f) or (p).

     (b)  Clause (vii) of Section 3.4(b) is amended to read in its entirety:

     Non-Recourse Debt of a Restricted Subsidiary.

     (c)  Section 3.7(f) of the Indenture is amended to read in its entirety:

          (1)  Liens incurred by the Company or any Restricted Subsidiary
     securing Indebtedness Incurred by the Company or such Restricted
     Subsidiary, as the case may be, to finance the exploration, drilling,
     development, construction or purchase of or by, or repairs, improvements or
     additions to, property or assets of the Company or such Restricted
     Subsidiary, as the case may be, which Liens may include Liens on the
     Capital Stock of such Restricted Subsidiary or (2) Liens incurred by any
     Restricted Subsidiary that does not own, directly or indirectly, at the
     time of such original incurrence of such a Lien under this clause (2) any
     operating properties or assets, securing Indebtedness Incurred to finance
     the exploration, drilling, development, construction or purchase of or by,
     or repairs, improvements or additions to, property or assets of any
     Restricted Subsidiary that does not, directly or indirectly, own any
     operating properties or assets at the time of such original incurrence of
     such Lien, which Liens may include Liens on the Capital Stock of one or
     more Restricted Subsidiaries that do not, directly or indirectly, own any
     operating properties or assets at the time of such original incurrence of
     such Lien, provided, however, that the Indebtedness secured by any such
     Lien may not be issued more than 365 days after the later of the
     exploration, drilling, development, completion of construction, purchase,
     repair, improvement, addition or commencement of full commercial operation
     of the property or asset being so financed;

     (d)  Section 3.7(l) is deleted in its entirety and the term "[Deleted]" is
inserted in lieu thereof.

     (e)  Section 3.7(p) is amended to read in its entirety:

     Liens to secure any refinancing, refunding, extension, renewal or
     replacement (or successive refinancings, refundings, extensions, renewals
     or replacements) as a whole, or in part, of any Indebtedness secured by any
     Lien referred to in the foregoing clauses (f), (g), (h) and (i), provided,
     however, that (x) such new Lien shall be limited to

                                       3

<PAGE>   4

     all or part of the same property or assets that secured the original Lien
     (plus repairs, improvements or additions to such property or assets and
     Liens on the stock or other ownership interest in one or more Restricted
     Subsidiaries beneficially owning such property or assets) and (y) the
     amount of the Indebtedness secured by such Lien at such time (or, if the
     amount that may be realized in respect of such Lien is limited, by contract
     or otherwise, such limited lesser amount) is not increased (other than by
     an amount necessary to pay fees and expenses, including premiums, related
     to the refinancing, refunding, extension, renewal or replacement of such
     Indebtedness);

                                   ARTICLE III
                                  MISCELLANEOUS

     Section 3.1 Notification to Holders.

     The Company shall notify the Holders in accordance with Section 8.2 of the
Indenture of the execution of this First Supplemental Indenture.

     Section 3.2 Ratification of Indenture.

     The Indenture, as supplemented by this First Supplemental Indenture, is in
all respects ratified and confirmed, and this First Supplemental Indenture shall
be deemed part of the Indenture in the manner and to the extent herein and
therein provided.

     Section 3.3 Governing Law.

     This First Supplemental Indenture shall be deemed to be a contract made
under the laws of the State of New York, and for all purposes shall be construed
in accordance with the laws of said State.

     Section 3.4 Separability.

     In case any one or more of the provisions contained in this First
Supplemental Indenture shall for any reason be held to be invalid, illegal or
unenforceable in any respect, such invalidity, illegality or unenforceability
shall not affect any other provisions of this First Supplemental Indenture but
this First Supplemental Indenture shall be construed as if such invalid or
illegal or unenforceable provision had never been contained herein or therein.

     Section 3.5 Counterparts.

     This First Supplemental Indenture may be executed in any number of
counterparts each of which shall be an original; but such counterparts shall
together constitute but one and the same instrument.

     Section 3.6 Effectiveness.

                                        4

<PAGE>   5

     This First Supplemental Indenture shall be effective and binding when
executed by the Company and the Trustee.

     Section 3.7 Trustee Not Responsible for Recitals.

     The recitals herein contained are made by the Company and not by the
Trustee, and the Trustee assumes no responsibility for the correctness thereof.
The Trustee makes no representation as to the validity or sufficiency of this
First Supplemental Indenture.

     Section 3.8 Performance by Trustee.

     The Trustee, for itself and its successors accepts the Trust of the
Indenture as amended by this First Supplemental Indenture and agrees to perform
the same, but only upon the terms and conditions set forth in the Indenture,
including the terms and provisions defining and limiting the liability and
responsibility of the Trustee.

                                      * * *

                                        5

<PAGE>   6

     IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental
Indenture to be duly executed as of the day and year first above written.

                                        CALPINE CORPORATION

                                        By: /s/ ANN B. CURTIS
                                           -------------------------------------
                                           Ann B. Curtis
                                           Executive Vice President and
                                           Chief Financial Officer

                                        THE BANK OF NEW YORK
                                        as Trustee

                                        By: /s/ MICHELE L. RUSSO
                                           -------------------------------------
                                           Name: Michele L. Russo
                                           Title: Assistant Vice President

                                       6<PAGE>   1

                                                                   EXHIBIT 4.7.2

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

                              CALPINE CORPORATION,

                                       and

                        WILMINGTON TRUST COMPANY, Trustee

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

                          FIRST SUPPLEMENTAL INDENTURE

                         Dated as of September 28, 2000

                           Supplementing the Indenture
                           Dated as of August 10, 2000

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

                                 Debt Securities

<PAGE>   2

     FIRST SUPPLEMENTAL INDENTURE, dated as of September 28, 2000, between
Calpine Corporation, a Delaware corporation (the "Company"), and Wilmington
Trust Company, a Delaware banking corporation ("the Trustee").

     WHEREAS, the Company executed and delivered the Indenture, dated as of
August 10, 2000 (the "Indenture"), to the Trustee to provide for the issuance of
debt securities in one or more series from time to time thereunder in an
unlimited aggregate principal amount;

     WHEREAS, pursuant to Section 2.1 of the Indenture, two duly authorized
members of the Board of Directors of the Company executed and delivered to the
Trustee a Directors' Certificate, dated as of August 10, 2000 (the "Directors'
Certificate"), that established the terms of the Company's 8-1/4% Senior Notes
due 2005 (the "8-1/4% Senior Notes") and the Company's 8-5/8% Senior Notes due
2010 (the "8-5/8% Senior Notes" and together with the 8-1/4% Senior Notes, the
"Senior Notes");

     WHEREAS, the Company, when authorized by a Board Resolution, and the
Trustee may amend the Indenture pursuant to Section 8.1 thereof without notice
to or consent of any Holder of the Senior Notes to make any change that does not
adversely affect the rights of any Holder of such Series, including, without
limitation, changing any payment record dates as necessary to conform to the
then-current market practice;

     WHEREAS, the Company desires to supplement and amend the Indenture as
contemplated by Section 8.1 thereof; and

     WHEREAS, all things necessary to make this First Supplemental Indenture a
valid agreement of the Company and the Trustee in accordance with its terms and
a valid amendment and supplement to the Indenture have been done.

     NOW, THEREFORE, for and in consideration of the premises and mutual
covenants herein contained, the Company and the Trustee agree as follows:

                                    ARTICLE I
                                   DEFINITIONS

     Section 1.1 Definition of Terms

     Unless the context otherwise requires:

     (a)  capitalized terms used herein that are not otherwise defined herein
shall have the meaning assigned to such terms in the Indenture or the Directors'
Certificate, as the case may be;

     (b)  the singular includes the plural and vice versa;

     (c)  headings are for convenience of reference only and do not affect
interpretation.

<PAGE>   3

                                   ARTICLE II
                           AMENDMENTS TO THE INDENTURE

     Section 2.1 Amendments

     (a)  Paragraph 4 of the Directors' Certificate relating to the 8-1/4%
Senior Notes is hereby deleted in its entirety and the following paragraph is
inserted in lieu thereof to conform the payment record dates in respect of the
8-1/4% Senior Notes to current market practice:

          4.   The 8-1/4% Senior Notes shall bear interest from August 10, 2000
     at the rate of 8-1/4% per annum, payable on February 15 and August 15,
     commencing February 15, 2001, for payment to Holders of record on the
     immediately preceding February 1 and August 1, respectively;

     (b)  Paragraph 4 of the Directors' Certificate relating to the 8-5/8%
Senior Notes is hereby deleted in its entirety and the following paragraph is
inserted in lieu thereof to conform the payment record dates in respect of the
8-5/8% Senior Notes to current market practice:

          4.   The 8-5/8% Senior Notes shall bear interest from August 10, 2000
     at the rate of 8-5/8% per annum, payable on February 15, and August 15,
     commencing February 15, 2001, for payment to the Holders of record on the
     immediately preceding February 1 and August 1, respectively;

                                   ARTICLE III
                                  MISCELLANEOUS

     Section 3.1 Notification to Holders.

     The Company shall notify the Holders in accordance with Section 8.1 of the
Indenture of the execution of this First Supplemental Indenture.

     Section 3.2 Notation on Senior Notes.

     All Senior notes authenticated and delivered after the date hereof shall
bear the following notation, which may be stamped or imprinted thereon:

     "In accordance with the First Supplemental Indenture dated as of September
     28, 2000, to the Indenture, dated as of August 10, 2000, each between
     Calpine Corporation and Wilmington Trust Company, as Trustee, the interest
     payable on this Security on each February 15 and August 15 shall be payable
     to the Holders of record on the immediately preceding February 1 and August
     1, respectively."

                                       2

<PAGE>   4

     The Company shall arrange for and pay all expenses related to such
notation.

     Section 3.3 Ratification of Indenture.

     The Indenture (including, without limitation, the Directors' Certificate),
as supplemented by this First Supplemental Indenture, is in all respects
ratified and confirmed, and this First Supplemental Indenture shall be deemed
part of the Indenture in the manner and to the extent herein and therein
provided.

     Section 3.4 Governing Law.

     This First Supplemental Indenture shall be deemed to be a contract made
under the laws of the State of New York, and for all purposes shall be construed
in accordance with the laws of said State.

     Section 3.5 Separability.

     In case any one or more of the provisions contained in this First
Supplemental Indenture shall for any reason be held to be invalid, illegal or
unenforceable in any respect, such invalidity, illegality or unenforceability
shall not affect any other provisions of this First Supplemental Indenture but
this First Supplemental Indenture shall be construed as if such invalid or
illegal or unenforceable provision had never been contained herein or therein.

     Section 3.6 Counterparts.

     This First Supplemental Indenture may be executed in any number of
counterparts each of which shall be an original; but such counterparts shall
together constitute but one and the same instrument.

     Section 3.7 Effectiveness.

     This First Supplemental Indenture shall be effective and binding when
executed and delivered by the Company and the Trustee.

     Section 3.8 Trustee Not Responsible for Recitals.

     The recitals herein contained are made by the Company and not by the
Trustee, and the Trustee assumes no responsibility for the correctness thereof.
The Trustee makes no representation as to the validity or sufficiency of this
First Supplemental Indenture.

     Section 3.9 Performance by Trustee.

     The Trustee, for itself and its successors accepts the trusts under the
Indenture as amended by this First Supplemental Indenture, and agrees to perform
the same, but only upon the terms and conditions set forth in the Indenture,
including, without limitation, the terms and provisions defining and limiting
the liability and responsibility of the Trustee.

                                       3

<PAGE>   5

     IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental
Indenture to be duly executed as of the day and year first above written.

                                        CALPINE CORPORATION

                                        By: /s/ ANN B. CURTIS
                                           -------------------------------------
                                           Name: Ann B. Curtis
                                           Title: Executive Vice President and
                                                  Chief Financial Officer

                                        WILMINGTON TRUST COMPANY,
                                        as Trustee

                                        By: /s/ BRUCE L. BISSON
                                           -------------------------------------
                                           Name: Bruce L. Bisson
                                           Title: Vice President

                                       4

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00021-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00021-of-00352.parquet"}]]