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                                                                     EXHIBIT 2.3


                               AMENDING AGREEMENT

     THIS AMENDING AGREEMENT made as of March 16, 2001 BETWEEN:

          ENCAL ENERGY LTD., a body corporate incorporated under the laws of the
          Province of Alberta with its head office in Calgary, Alberta
          (hereinafter called "ECo")

                                       AND

          CALPINE CORPORATION, a body corporate incorporated under the laws of
          the State of Delaware with its head office in San Jose, California
          (hereinafter called "CCo")

     WHEREAS ECo and CCo entered into a combination agreement (the "Combination
Agreement") dated effective as of February 7, 2001;

     AND WHEREAS ECo and CCo have agreed to certain technical amendments to the
Combination Agreement and the schedules thereto (the "Amending Agreement");

     NOW THEREFORE THIS AGREEMENT WITNESSETH that in consideration of the
covenants and agreements herein contained and other good and valuable
consideration (the receipt and sufficiency of which are hereby acknowledged),
the parties hereto do hereby covenant and agree as follows:

                                   ARTICLE 1
                                 INTERPRETATION

1.1  Capitalized terms used herein, including the recitals hereto, which are
     defined in the Combination Agreement, shall have the meanings ascribed
     thereto in this Amending Agreement.

1.2  Any provision of this Amending Agreement which may be invalid shall be
     ineffective to the extent of such invalidity only, without affecting the
     validity of the remaining provisions of this Amending Agreement or the
     Combination Agreement as amended hereby, it being the intent and purpose
     that the Combination Agreement, as amended by this Amending Agreement
     should survive and be valid to the maximum extent permitted by applicable
     law.

                                   ARTICLE 2
                                   AMENDMENTS

2.1  The Combination Agreement shall be amended as follows:

     (a)  By adding the word "and" to the end of section 5.1(f) and deleting the
          word "and" at the end of section 5.1(g) and replacing it with a
          period.

     (b)  Section 7.4 shall be deleted and replaced with the following:

          Promptly after the Effective Time, CCo will notify in writing each
          holder of a ECo Option of the exchange of such ECo Option for an
          option to purchase CCo Common Stock (the "New Options") in accordance
          with


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          the Plan of Arrangement, and CCo will confirm its agreement to honour
          such options in accordance with their terms.

     (c)  The second reference to "CCo Common Stock" contained in section 3.4(a)
          shall be replaced with "CCo preferred stock" and a close parenthesis
          mark shall be added after the words "Rights Agent".

2.2  The Plan of Arrangement attached as Exhibit A to the Combination Agreement
     shall be amended as follows:

     (a)  Section 2.1(e) shall be deleted and replaced with the following:

          holders of ECo Common Shares who are residents of Canada for the
          purposes of the ITA and who receive Exchangeable Shares under Section
          2.1(a) shall be entitled to make an income tax election pursuant to
          section 85 of the ITA (and any applicable provicial legislation) with
          respect to the transfer of their ECo Common Shares to CCo Sub by
          providing two signed copies of the necessary election forms to CCo Sub
          within 90 days following the Effective Date, duly completed with the
          details of the number of shares transferred and the applicable agreed
          amounts for the purposes of such elections. Thereafter, subject to the
          election forms complying with the provisions of the ITA (and any
          applicable provincial legislation), the forms will be signed by CCo
          Sub and returned to such holders of ECo Common Shares for filing with
          the Canada Customs and Revenue Agency (and any applicable provincial
          taxation authority).

     (b)  Section 2.2 shall be deleted and replaced with the following:

          A Shareholder who has transferred his ECo Common Shares to CCo Sub as
          contemplated under Section 2.1(a) shall be considered to have received
          any of the ancillary rights and benefits associated with the
          Exchangeable Shares in consideration for the grant by the Shareholder
          to CCo and CCo Sub of certain rights and benefits as against the
          Shareholder in respect of the Exchangeable Shares. To the extent that
          the value of the ancillary rights and benefits received by the
          Shareholder exceeds the value of the rights and benefits given up by
          the Shareholder to CCo and CCo Sub, the Shareholder shall be
          considered to have disposed of a portion of his ECo Common Shares in
          consideration for such excess ancillary rights and benefits, and to
          have disposed of the remaining portion (the "share portion") of such
          ECo Common Shares solely in consideration for Exchangeable Shares. The
          share portion (expressed as a number) shall be equal to the number of
          ECo Common Shares obtained when the total number of ECo Common Shares
          transferred by the Shareholder to CCo Sub is multiplied by the
          aggregate fair market value of the Exchangeable Shares received by the
          Shareholder divided by the sum of such aggregate fair market value and
          the amount, if any, by which the aggregate fair market value of the
          ancillary rights and benefits received by the Shareholder exceeds the
          aggregate fair market value of the rights and benefits granted by the
          Shareholder to CCo and CCo Sub in respect of the Exchangeable Shares.


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2.3  The Exchangeable Share Provisions and Other Provisions to be Included in
     the Articles of Incorporation of CCo Sub attached as Exhibit B to the
     Combination Agreement shall be amended as follows:

     (a)  After section 14.6, the following shall be inserted as section 14.7.

          For the purposes of subsection 191(4) of the Income Tax Act (Canada)
          the "specified amount" in respect of each Exchangeable Share shall be
          $o [with amount to be inserted once the "CCo Average Price" as defined
          in the Plan of Arrangement has been determined, and such amount to be
          the CCo Average Price minus $CDN 5.00].

2.4  The Support Agreement attached as Exhibit C to the Combination Agreement
     shall be amended as follows:

     (a)  The reference to "alone or together with any" contained in section 2.9
          shall be replaced with "or a".

2.5  The Voting and Exchange Trust Agreement attached as Exhibit D to the
     Combination Agreement shall be amended as follows:

     (a)  The definition of "CCo Holdco" shall be removed and replaced with the
          following:

               "Cco Holdco" means a Subsidiary of CCo (other than Cco Sub).

                                   ARTICLE 3I
                                  MISCELLANEOUS

3.1  This Amending Agreement together with the provisions of the Combination
     Agreement and Confidentiality Agreement constitute the entire agreement
     between the parties hereto, and for greater certainty, other than as
     specifically provided in this Amending Agreement, the provisions of the
     Combination Agreement and the Confidentiality Agreement remain in full
     force and effect and unamended.

3.2  Notwithstanding the date of execution hereof, the effective date of this
     amendment to the Combination Agreement and exhibits thereto shall be
     February 7, 2001 and all references to the Combination Agreement and
     exhibits thereto dated February 7, 2001 shall be deemed to include this
     document.

3.3  This Amending Agreement may be executed in one or more counterparts, each
     of which shall be deemed an original, but all of which together shall
     constitute one and the same instrument.

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     IN WITNESS WHEREOF, the parties hereto have executed this Amending
Agreement the 16th day of March, 2001.

                                    ENCAL ENERGY LTD.

                                    Per: /s/ DAVID D. JOHNSON
                                        ----------------------------------------
                                        David D. Johnson
                                        President and Chief Executive Officer



                                    Per: /s/ STEVEN A. ALLAIRE
                                        ----------------------------------------
                                        Steven A. Allaire
                                        Vice President, Finance, Chief Financial
                                        Officer and Corporate Secretary



                                     CALPINE CORPORATION

                                     Per:
                                         ---------------------------------------

                                     Per:
                                         ---------------------------------------

