SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, DC 20549
                                SCHEDULE TO
                               (RULE 14D-100)
        TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF
                    THE SECURITIES EXCHANGE ACT OF 1934.
                           (AMENDMENT NO. 1 )
                                         ---
                         TRIGEN ENERGY CORPORATION
- ---------------------------------------------------------------------------
                     (Name of Subject Company (Issuer))
                          T ACQUISITION CORP. (OFFEROR)
                                    ELYO
                          SUEZ LYONNAISE DES EAUX
- ---------------------------------------------------------------------------
     (Names of Filing Persons (identifying status as offeror, issuer or
                               other person))
                       COMMON STOCK, $0.01 PAR VALUE
- ---------------------------------------------------------------------------
                       (Title of Class of Securities)
                                 895930105
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                   (CUSIP Number of Class of Securities)
                              MICHEL BLEITRACH
                                    ELYO
                       235 AVENUE GEORGES CLEMONCEAU
                                  BP 4601
                        92746 NANTERRE CEDEX, FRANCE
                            011-331-41-20-10-10

                              WITH A COPY TO:
                               JEFFREY BAGNER
                  FRIED, FRANK, HARRIS, SHRIVER & JACOBSON
                             ONE NEW YORK PLAZA
                       NEW YORK, NEW YORK 10004-1980
                               (212) 859-8000
- ---------------------------------------------------------------------------
       (Name, address, and telephone numbers of person authorized to
      receive notices and communications on behalf of filing persons)

                         CALCULATION OF FILING FEE

- ---------------------------------------------------------------------------
Transaction Valuation* $173,487,223         Amount Of Filing Fee $34,698
- ---------------------------------------------------------------------------

*    ESTIMATED  FOR  PURPOSES OF  CALCULATING  THE AMOUNT OF THE FILING FEE
     ONLY.  THIS AMOUNT ASSUMES THE PURCHASE OF 7,382,435  SHARES OF COMMON
     STOCK,  PAR VALUE  $.01 PER SHARE  (THE  "SHARES"),  OF TRIGEN  ENERGY
     CORPORATION,  A DELAWARE  CORPORATION (THE  "COMPANY"),  AT THE TENDER
     PRICE OF $23.50 PER SHARE NET TO THE SELLER IN CASH,  WITHOUT INTEREST
     THEREON.  PURSUANT TO THE AAGREEMENT  AND PLAN OF MERGER,  DATED AS OF
     JANUARY 19, 2000, AMONG ELYO ("PARENT"),  T ACQUISITION  CORP. AND THE
     COMPANY,  THE  COMPANY  REPRESENTED  THAT  AS OF  SUCH  DATE,  IT  HAD
     12,416,297 SHARES OUTSTANDING AND 849,210 SHARES RESERVED FOR ISSUANCE
     UPON EXERCISE OF ALL OUTSTANDING  OPTIONS UNDER THE COMPANY'S EMPLOYEE
     BENEFIT PLANS.  PARENT ALREADY  BENEFICIALLY OWNS 6,507,944 SHARES, OF
     WHICH THE  1,637,274  SHARES HELD BY COMPAGNIE  PARISENNE DE CHAUFFAGE
     URBAIN  ("CPCU"),  A  NON-WHOLLY-OWNED  SUBSIDIARY OF PARENT,  WILL BE
     TENDERED.  PARENT HAS SEPARATELY  AGREED TO PURCHASE  1,012,402 SHARES
     FROM  THOMAS R.  CASTEN  ON MARCH 29,  2000,  PURSUANT  TO A  PURCHASE
     AGREEMENT, DATED JANUARY 19, 2000 BETWEEN PARENT AND MR. CASTEN. BASED
     ON THE FOREGOING, THE TRANSACTION VALUE IS EQUAL TO THE PRODUCT OF (I)
     (A)  12,416,297  SHARES (THE NUMBER OF SHARES  OUTSTANDING),  PLUS (B)
     849,210  SHARES  (THE  NUMBER OF SHARES  RESERVED  FOR  ISSUANCE  UPON
     EXERCISE OF OPTIONS),  MINUS (C) THE  DIFFERENCE OF (1) 6,507,944 (THE
     NUMBER OF SHARES  BENEFICIALLY  OWNED BY PARENT)  MINUS (2)  1,637,274
     (THE  NUMBER  OF  SHARES  HELD  BY CPCU  BEING  TENDERED),  MINUS  (D)
     1,012,402  (THE NUMBER OF SHARES HELD BY MR.  CASTEN),  MULTIPLIED  BY
     (II) $23.50.  THE AMOUNT OF THE FILING FEE,  CALCULATED  IN ACCORDANCE
     WITH RULE 0-11 UNDER THE SECURITIES  EXCHANGE ACT OF 1934, AS AMENDED,
     EQUALS 1/50 OF ONE PERCENT OF THE AGGREGATE OF THE CASH OFFERED BY THE
     BIDDER.

|X|  CHECK  THE BOX IF ANY PART OF THE FEE IS OFFSET  AS  PROVIDED  BY RULE
     0-11(A)(2)  AND IDENTIFY THE FILING WITH WHICH THE  OFFSETTING FEE WAS
     PREVIOUSLY   PAID.   IDENTIFY  THE  PREVIOUS  FILING  BY  REGISTRATION
     STATEMENT NUMBER, OR THE FORM OR SCHEDULE AND THE DATE OF ITS FILING.

Amount Previously Paid:     $34,698
Form or Registration No.:   Schedule TO-T
Filing Party:               T Acquisition Corp., Elyo, Suez Lyonnaise des Eaux
Date Filed:                 February 28, 2000

|_|  Check  the  box  if  the   filing   relates   solely  to   preliminary
     communications made before the commencement of a tender offer.

Check the  appropriate  boxes below to designate any  transactions to which
the statement relates:

|X|  third-party tender offer subject to Rule 14d-1.
|_|  issuer tender offer subject to Rule 13e-4.
|X|  going-private transaction subject to Rule 13e-3.
|_|  amendment to Schedule 13D under Rule 13d-2.

Check the  following box if the filing is a final  amendment  reporting the
results of the tender offer: |_|





                                INTRODUCTION

     This Amendment No. 1 (this  "Amendment")  amends and  supplements  the
Tender  Offer  Statement  on  Schedule  TO filed  with the  Securities  and
Exchange  Commission  on February  28,  2000,  by T  Acquisition  Corp.,  a
Delaware corporation  ("Purchaser"),  Elyo, a societe anonyme organized and
existing  under  the laws of the  Republic  of France  ("Parent")  and Suez
Lyonnaise des Eaux, a societe anonyme organized and existing under the laws
of the Republic of France. The Schedule TO relates to the offer to purchase
any and all outstanding  shares of Common Stock,  par value $.01 per share,
of Trigen Energy Corporation,  a Delaware corporation (the "Company"), at a
purchase  price of $23.50  per share,  net to the  seller in cash,  without
interest,  upon the terms and  subject to the  conditions  set forth in the
Offer to Purchase dated February 28, 2000 (the "Offer to Purchase"), and in
the related Letter of Transmittal  (which,  together with any amendments or
supplements thereto,  collectively constitute the "Offer"), copies of which
are filed as Exhibits  (a)(1)(i) and (a)(1)(ii) hereto,  respectively,  and
which are incorporated herein by reference.  Capitalized terms used and not
defined herein shall have the meanings  assigned to such terms in the Offer
to Purchase and the Schedule TO.

ITEM 12. Exhibits.

     Item 12 is hereby amended to add the following exhibit:

(a)(1)(v)  Notice to the  Company  401k  Plan  Participants  from  Fidelity
           Management Trust Company.





                                 SIGNATURE

     After  due  inquiry  and to the best of my  knowledge  and  belief,  I
certify that the information set forth in this statement is true,  complete
and correct.

                              T ACQUISITION CORP.


                              By:   /s/  Michel Bleitrach
                                    ---------------------------------------
                                    Name: Michel Bleitrach
                                    Title: President



                              ELYO


                              By:   /s/  Michel Bleitrach
                                    ---------------------------------------
                                    Name: Michel Bleitrach
                                    Title: Chief Executive Officer



                              SUEZ LYONNAISE DES EAUX


                              By:   /s/  M. Patrice Herbet
                                    ---------------------------------------
                                    Name: M. Patrice Herbet*
                                    Title: Authorized Representative


     Dated: March 6, 2000


- ----------
*     A Power of Attorney authorizing M. Patrice Herbet to sign on behalf of
Suez Lyonnaise des Eaux is filed herewith as Exhibit (i).



                               EXHIBIT INDEX
                               -------------
 EXHIBIT
  NUMBER       TITLE
- -----------    -----

(a)(1)(i)      Offer to Purchase, dated February 28, 2000.*

(a)(1)(ii)     Letter of Transmittal.*

(a)(1)(iii)    Notice of Guaranteed Delivery.*

(a)(1)(iv)     Letter to Brokers, Dealers, Commercial Banks, Trust
               Companies and Other Nominees.*

(a)(1)(v)      Notice to the Company 401k Plan Participants from Fidelity
               Management Trust Company.

(a)(2)         Letter to stockholders from Richard E. Kessel, President and
               Chief Executive Officer of the Company.*

(a)(3)         Exhibit (a)(1)(i) is incorporated herein by reference.

(a)(4)         Not applicable.

(a)(5)(i)      Letter from Brokers, Dealers, Commercial Banks, Trust
               Companies and Other Nominees to Clients.*

(a)(5)(ii)     Guidelines for Certification of Taxpayer Identification
               Number on Substitute Form W-9.*

(a)(5)(iii)    Agreement and Plan of Merger dated as of January 19, 2000,
               among Elyo, T Acquisition Corp. and the Company.*

(a)(5)(iv)     Audited financial statements for the Company's 1998 and 1997
               fiscal years, beginning on page F-1 of the Company's Annual
               Report on Form 10-K for the fiscal year ended December 31,
               1998 (incorporated by reference to the Company's Annual
               Report on Form 10-K filed with the Commission on March 31,
               1999).*

(a)(5)(v)      Pages 1 through 8, inclusive, of the Company's Quarterly
               Report on Form 10-Q for the fiscal quarter ended September
               30, 1999 (incorporated by reference to the Company's
               Quarterly Report on Form 10-Q filed with the Commission on
               November 12, 1999).*

(a)(5)(vi)     Joint Press Release, dated January 19, 2000.*

(a)(5)(vi)     Joint Press Release, dated February 28, 2000.*

(b)            Not applicable.

(c)(i)         Summary Presentation prepared for Parent by Lazard Freres &
               Co., LLC, dated January 19, 2000.*

(c)(ii)        Written Presentation prepared for the Special Committee by
               Credit Suisse First Boston Corporation, dated January 19,
               2000.*

(c)(iii)       Opinion of Credit Suisse First Boston Corporation, dated
               January 19, 2000 (incorporated by reference from Annex A of
               the Solicitation/Recommendation Statement on Schedule 14D-9
               of the Company, dated February 28, 2000).*

(d)(i)         Tender and Voting Agreement dated as of January 19, 2000,
               among Elyo, T Acquisition Corp. and the Stockholders.*

(d)(ii)        Letter Agreement between Thomas R. Casten and Elyo, dated
               January 19, 2000.*

(d)(iii)       Separation Agreement and Release dated as of January 19,
               2000, between Trigen Energy Corporation and Thomas R.
               Casten.*

(f)            Section 262 of the Delaware General Corporaiton Law
               (included as Schedule II to the Offer to Purchase filed
               herewith as Exhibit (a)(1)(i)).*

(g)            Not applicable.

(h)            Not applicable.

(i)            Power of Attorney, dated October 27, 1998.*

*    Previously filed