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                                SECOND AMENDMENT
                                     TO THE
                      SECOND AMENDED AND RESTATED AGREEMENT
                  AND CERTIFICATE OF LIMITED PARTNERSHIP OF
            PENOBSCOT ENERGY RECOVERY COMPANY, LIMITED PARTNERSHIP

This Second Amendment dated as of September 29, 1997 amends the Second Amended
and Restated Agreement and Certificate of Limited Partnership of Penobscot
Energy Recovery Company, Limited Partnership originally entered into as of May
15, 1986 and amended by First Amendment dated June 14, 1991 (the "Partnership
Agreement"). The purpose of this Second Amendment is to provide for the partial
transfer of the limited partnership interest held by The Prudential Insurance
Company of America ("PRU") to PERC Management Company Limited Partnership
("PERC") pursuant to a Purchase and Option Agreement between PRU and PERC dated
September, 1997 (the "Purchase Agreement") and to make certain conforming
changes to the Partnership Agreement.

      The Partners hereby agree as follows:

      1. The Partners confirm that effective May 18, 1994 the Partnership name
was changed to Penobscot Energy Recovery Company, Limited Partnership.

      2. The Partners consent to the transfer by PRU to PERC of a Seventy-Seven
Percent (77%) interest in PRU's right, title and interest as a Limited Partner
in the Partnership and under the Partnership Agreement, which constitutes a
49.50002% interest in the entire Partnership in accordance with the Purchase
Agreement and in granting such consent the Partners hereby (a) waive the
provisions of subsections 10.2 (a) (ii), (a) (iv) and (b) (i) to the extent such
provisions may still be applicable to, or binding upon, PRU and (b) consent to
the admission of PERC as a new Limited Partner under Section 10.4. PERC
represents that the transfer of all of PRU's interests to PERC shall not prevent
the Project from being owned and operated as a Qualifying Facility.

      3. Section 1.56 of the Partnership Agreement is hereby amended and
restated to read in its entirety as follows:

            1.56. LP Sharing Ratios. "LP Sharing Ratios" shall mean, with
            respect to each Limited Partner, the following percentages:

                  ENI    28.5714%
                  PRU    16.4286%
                  PERC   55.0000%

      4. Section 2.1 of the Partnership Agreement is amended by adding thereto
the following sentence:


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In furtherance of the foregoing, the General Partners are authorized
            and directed to execute and deliver a Restated Certificate of
            Limited Partnership for the Partnership in the form attached at
            Exhibit A and to file the Restated Certificate with the Maine
            Secretary of State.

      5. Section 2.3 of the Partnership Agreement is amended by changing the
Partnerships address to PERC Management Company Limited Partnership, 110 Main
Street, Suite 1308, Saco, Maine 04072.

      6. Section 2.8 of the Partnership Agreement is amended by adding the
following name and address of a Limited Partner:

                  PERC Management Company Limited Partnership
                  110 Main Street, Suite 1308
                  Saco, Maine 04072

      7. Article 3 of the Partnership Agreement is amended by adding thereto new
Sections 3.16 and 3.17:

                  3.16 No Capital Contributions Due from PRU. The Partners,
            jointly and severally, acknowledge that upon the effective date of
            this Second Amendment, PRU shall have no further obligation to make
            Capital Contributions, Subordinated Loans or other advances to the
            Partnership and shall be, and hereby is, released of any and all
            obligations to the Partnership under Sections 3.1, 3.2, 3.3 and 3.4
            of the Partnership Agreement. PRU and PERC have each entered into a
            separate Assignment and Assumption Agreement (the "Assumption
            Agreement") whereby PERC has assumed all of PRU's obligations under
            the separate PRU Capital Contribution Agreement as defined in
            Section 1.74 of the Partnership Agreement and PRU has been released
            from those obligations.

                  3.17 Assumption of Obligations of PRU. From and after the
            effective date of the Assumption Agreement, PERC shall assume and be
            responsible for any and all obligations to the Partnership of PRU
            under Sections 3.2 and 3.4 of the Partnership Agreement.

      8. Article 8 of the Partnership Agreement is amended by adding thereto the
following new Section 8.3:

                  8.3 Preservation of Indemnification. The rights of PRU to
            indemnification under Article 8 are vested and shall survive and
            remain binding on the Partnership notwithstanding consummation of
            the transfer affected pursuant to this Second Amendment and
            notwithstanding consummation of the anticipated complete withdrawal
            of PRU as a Limited Partner pursuant the exercise by PERC of the
            Option granted to PERC under the Purchase Agreement.


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      9. The Partners hereby consent to the further transfer by PRU of up to all
of its remaining limited partnership interest to PERC pursuant to the Option
granted in the Purchase Agreement, and in connection therewith, hereby consent
to the complete withdrawal of PRU as a limited partner and authorize and direct
the General Partners to execute and deliver any and all documents reasonably
deemed necessary or appropriate to give effect to such withdrawal, including
such amendments as are necessary to reflect accurately the LP Sharing Ratios
applicable from and after such withdrawal.

      10. PERC, in its capacity a new Limited Partner, agrees to be bound by all
of the terms, provisions and conditions of the Partnership Agreement, as amended
hereby.

      11. The terms used herein, unless otherwise specifically defined, shall
have the meanings provided in the Partnership Agreement. Except as amended
hereby, the Partnership Agreement remains in full force and effect.

      Dated: , 1997

                                          THE GENERAL PARTNERS:

                                          PERC MANAGEMENT COMPANY LIMITED
                                          PARTNERSHIP

                                          BY: PERC, INC.
                                              General Partner


                                          /s/ Martin J. Sergi
                                          ------------------------------
                                          Its:  President

                                          
                                          ENERGY NATIONAL, INC.

                                          /s/ Franklin D. Wareham
                                          ------------------------------
                                          Its: Vice President


                                          THE LIMITED PARTNERS:

                                          THE PRUDENTIAL INSURANCE 
                                          COMPANY OF AMERICA

                                          /s/ John Wand
                                          ------------------------------
                                          Its: Vice President


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                                          ENERGY NATIONAL, INC.

                                          /s/ Franklin D. Wareham
                                          ------------------------------
                                          Its: Vice President

                                          PERC MANAGEMENT COMPANY LIMITED
                                          PARTNERSHIP

                                          BY:   PERC, INC.
                                                General Partner

                                          /s/ Martin J. Sergi
                                          ------------------------------
                                          Its: Vice  President


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