<PAGE>
 
                                                                   EXHIBIT 10.25

                                                         SERVICE PACKAGE NO. 256
                                                                 AMENDMENT No. 0
                                             

                         GAS TRANSPORTATION AGREEMENT
                      (For Use Under FT-A Rate Schedule)


THIS AGREEMENT is made and entered into as of the 1st day of September, 1993, by
and between TENNESSEE GAS PIPELINE COMPANY, a Delaware Corporation, hereinafter
referred to as "Transporter" and BOSTON GAS CO, a MASSACHUSETTS Corporation,
hereinafter referred to as "Shipper." Transporter and Shipper shall collectively
be referred to herein as the "Parties."

                                   ARTICLE I

                                  DEFINITIONS

1.1  TRANSPORTATION QUANTITY (TQ) - shall mean the maximum daily quantity of gas
     which Transporter agrees to receive and transport on a firm basis, subject
     to Article II herein, for the account of Shipper hereunder on each day
     during each year during the term hereof, which shall be 10,533 dekatherms.
     Any limitations of the quantities to be received from each Point of Receipt
     and/or delivered to each Point of Delivery shall be as specified on Exhibit
     "A" attached hereto.

1.2  EQUIVALENT QUANTITY - shall be as defined in Article I of the General Terms
     and Conditions of Transporter's FERC Gas Tariff.

                                   ARTICLE II

                                 TRANSPORTATION

Transportation Service -  Transporter agrees to accept and receive daily on a
firm basis, at the Point(s) of Receipt from Shipper or for Shipper's account
such quantity of gas as Shipper makes available up to the Transportation
Quantity, and to deliver to or for the account of Shipper to the Point(s) of
Delivery an Equivalent Quantity of gas.

                                  ARTICLE III

                       POINT(S) OF RECEIPT AND DELIVERY

The Primary Point(s) of Receipt and Delivery shall be those points specified on
Exhibit "A" attached hereto.

                                  ARTICLE IV

All facilities are in place to render the service provided for in this
Agreement.

                                       1
<PAGE>
 
                                                         SERVICE PACKAGE NO. 256
                                                                 AMENDMENT NO. 0
                                                


                         GAS TRANSPORTATION AGREEMENT
                      (For Use Under FT-A Rate Schedule) 

                                   ARTICLE V

             QUALITY SPECIFICATIONS AND STANDARDS FOR MEASUREMENT

For all gas received, transported and delivered hereunder the Parties agree to
the Quality Specifications and Standards for Measurement as specified in the
General Terms and Conditions of Transporter's FERC Gas Tariff Volume No. 1. To
the extent that no new measurement facilities are installed to provide service
hereunder, measurement operations will continue in the manner in which they have
previously been handled. In the event that such facilities are not operated by
Transporter or a downstream pipeline, then responsibility for operations shall
be deemed to be Shipper's.

                                  ARTICLE VI

                   RATES AND CHARGES FOR GAS TRANSPORTATION

6.1   TRANSPORTATION RATES - Commencing upon the effective date hereof, the
      rates, charges, and surcharges to be paid by Shipper to Transporter for
      the transportation service provided herein shall be in accordance with
      Transporter's Rate Schedule FT-A and the General Terms and Conditions of
      Transporter's FERC Gas Tariff.

6.2   INCIDENTAL CHARGES - Shipper agrees to reimburse Transporter for any
      filing or similar fees, which have not been previously paid for by
      Shipper, which Transporter incurs in rendering service hereunder.

6.3   CHANGES IN RATES AND CHARGES - Shipper agrees that Transporter shall have
      the unilateral right to file with the appropriate regulatory authority and
      make effective changes in (a) the rates and charges applicable to service
      pursuant to Transporter's Rate Schedule FT-A, (b) the rate schedule(s)
      pursuant to which service hereunder is rendered, or (c) any provision of
      the General Terms and Conditions applicable to those rate schedules.
      Transporter agrees that Shipper may protest or contest the aforementioned
      filings, or may seek authorization from duly constituted regulatory
      authorities for such adjustment of Transporter's existing FERC Gas Tariff
      as may be found necessary to assure Transporter just and reasonable rates.

                                  ARTICLE VII

                             BILLINGS AND PAYMENTS

Transporter shall bill and Shipper shall pay all rates and charges in accordance
with Articles V and VI, respectively, of the General Terms and Conditions of
Transporter's FERC Gas Tariff.

                                       2
<PAGE>
 
                                                        SERVICE  PACKAGE NO. 256
                                                                 AMENDMENT NO. 0



                         GAS TRANSPORTATION AGREEMENT
                      (For Use Under FT-A Rate Schedule)

                                 ARTICLE VIII

                         GENERAL TERMS AND CONDITIONS

This Agreement shall be subject to the effective provisions of Transporter's
Rate Schedule FT-A and to the General Terms and Conditions incorporated therein,
as the same may be changed or superseded from time to time in accordance with
the rules and regulations of the FERC.

                                  ARTICLE IX

                                  REGULATION

9.1   This Agreement shall be subject to all applicable and lawful governmental
      statutes, orders, rules and regulations and is contingent upon the receipt
      and continuation of all necessary regulatory approvals or authorizations
      upon terms acceptable to Transporter. This Agreement shall be void and of
      no force and effect if any necessary regulatory approval is not so
      obtained or continued. All Parties hereto shall cooperate to obtain or
      continue all necessary approvals or authorizations, but no Party shall be
      liable to any other Party for failure to obtain or continue such approvals
      or authorizations.

9.2   The transportation service described herein shall be provided subject to
      Subpart G, Part 284, of the FERC Regulations.

                                   ARTICLE X

                     RESPONSIBILITY DURING TRANSPORTATION

Except as herein specified, the responsibility for gas during transportation
shall be as stated in the General Terms and Conditions of Transporter's FERC Gas
Tariff Volume No. 1.

                                  ARTICLE XI

                                  WARRANTIES

11.1  In addition to the warranties set forth in Article IX of the General Terms
      and Conditions of Transporter's FERC Gas Tariff, Shipper warrants the
      following:

      (a)  Shipper warrants that all upstream and downstream transportation
           arrangements are in place, or will be in place as of the requested
           effective date of service, and that it has advised the upstream and
           downstream transporters of the receipt and delivery points under this
           Agreement and any quantity limitations for each point as specified on
           Exhibit "A" attached hereto. Shipper agrees to indemnify and hold
           Transporter harmless for refusal to transport gas hereunder in the

                                       3
<PAGE>
 
                                                        SERVICE  PACKAGE NO. 256
                                                                 AMENDMENT NO. 0


                         GAS TRANSPORTATION AGREEMENT
                      (For Use Under FT-A Rate Schedule)

          event any upstream or downstream transporter fails to receive or
          deliver gas as contemplated by this Agreement.
 
     (b)  Shipper agrees to indemnify and hold Transporter harmless from all
          suits, actions, debts, accounts, damages, costs, losses and expenses
          (including reasonable attorneys fees) arising from or out of breach of
          any warranty by Shipper herein.

11.2 Transporter shall not be obligated to provide or continue service hereunder
     in the event of any breach of warranty.

                                  ARTICLE XII

                                     TERM

12.1 This Agreement shall be effective as of the 1st day of September, 1993, and
     shall remain in force and effect until the 14th day of January, 2003,
     ("Primary Term") and on a month to month basis thereafter unless terminated
     by either Party upon at least thirty (30) days prior written notice to the
     other Party; provided, however, that if the Primary Term is one year or
     more, then unless Shipper elects upon one year's prior written notice to
     Transporter to request a lesser extension term, the Agreement shall
     automatically extend upon the expiration of the Primary Term for a term of
     five years and shall automatically extend for successive five year terms
     thereafter unless Shipper provides notice described above in advance of the
     expiration of a succeeding term; provided further, if the FERC or other
     governmental body having jurisdiction over the service rendered pursuant to
     this Agreement authorizes abandonment of such service, this Agreement shall
     terminate on the abandonment date permitted by the FERC or such other
     governmental body.

12.2 Any portions of this Agreement necessary to resolve or cash-out imbalances
     under this Agreement as required by the General Terms and Conditions of
     Transporter's FERC Gas Tariff Volume No. 1, shall survive the other parts
     of this Agreement until such time as such balancing has been accomplished;
     provided, however, that Transporter notifies Shipper of such imbalance no
     later than twelve months after the termination of this Agreement.

12.3 This Agreement will terminate automatically upon written notice from
     Transporter in the event Shipper fails to pay all of the amount of any bill
     for service rendered by Transporter hereunder in accord with the terms and
     conditions of Article VI of the General Terms and Conditions of
     Transporter's FERC Tariff.

                                       4
<PAGE>
 
                                                        SERVICE  PACKAGE NO. 256
                                                                 AMENDMENT NO. 0


                         GAS TRANSPORTATION AGREEMENT
                      (FOR USE UNDER FT-A RATE SCHEDULE)

                                 ARTICLE XIII

                                    NOTICE

Except as otherwise provided in the General Terms and Conditions applicable to
this Agreement, any notice under this Agreement shall be in writing and mailed
to the post office address of the Party intended to receive the same, as
follows:

            TRANSPORTER:  Tennessee Gas Pipeline Company
                          P. O. Box 2511
                          Houston, Texas  77252-2511
                          Attention:  Transportation Marketing

            SHIPPER:

            NOTICES:      BOSTON GAS CO
                          ONE BEACON STREET 
                          34TH FLOOR

                          BOSTON, MA  02108
                          Attention:  BILL YARDLEY

            BILLING:      BOSTON GAS CO
                          ONE BEACON STREET 
                          34TH FLOOR
 
                          BOSTON, MA  02108
                          Attention:  DON TULCHINSKY

or to such other address as either Party shall designate by formal written
notice to the other.

                                  ARTICLE XIV

                                  ASSIGNMENTS

14.1  Either Party may assign or pledge this Agreement and all rights and
      obligations hereunder under the provisions of any mortgage, deed of trust,
      indenture, or other instrument which it has executed or may execute
      hereafter as security for indebtedness. Either Party may, without
      relieving itself of its obligation under this Agreement, assign any of its
      rights hereunder to a company with which it is affiliated. Otherwise,
      Shipper shall not assign this Agreement or any of its rights hereunder,
      except in accord with Article III, Section 11 of the General Terms and
      Conditions of Transporter's FERC Gas Tariff.

14.2  Any person which shall succeed by purchase, merger, or consolidation to
      the properties, substantially as an entirety, of either Party hereto shall
      be entitled to the rights and shall be subject to the obligations of its
      predecessor in interest under this Agreement.

                                       5
<PAGE>
 
                                                         SERVICE PACKAGE NO. 256
                                                                 AMENDMENT NO. 0



                         GAS TRANSPORTATION AGREEMENT
                      (For Use Under FT-A Rate Schedule)

                                  ARTICLE XV

                                 MISCELLANEOUS

15.1  The interpretation and performance of this Agreement shall be in
      accordance with and controlled by the laws of the State of Texas, without
      regard to the doctrines governing choice of law.

15.2  If any provisions of this Agreement is declared null and void, or
      voidable, by a court of competent jurisdiction, then that provision will
      be considered severable at either Party's option; and if the severability
      option is exercised, the remaining provisions of the Agreement shall
      remain in full force and effect.

15.3  Unless otherwise expressly provided in this Agreement or Transporter's Gas
      Tariff, no modification of or supplement to the terms and provisions
      stated in this agreement shall be or become effective until Shipper has
      submitted a request for change through the TENN-SPEED(R) 2 System and
      Shipper has been notified through TENN-SPEED 2 of Transporter's agreement
      to such change.

15.4  Exhibit "A" attached hereto is incorporated herein by reference and made a
      part hereof for all purposes.

    IN WITNESS WHEREOF, the Parties hereto have caused this Agreement to be duly
executed as of the date first hereinabove written.



                                        TENNESSEE GAS PIPELINE COMPANY

                                        BY: /s/ Randall G. Schorre 
                                           ---------------------------
                                              Randall G. Schorre
                                           Agent and Attorney-in-Fact


                                        BOSTON GAS COMPANY

                                        BY: William R. Luthern    
                                           ---------------------------
                                        TITLE:  Vice President
                                               -----------------------
                                        DATE:   3, Dec 94
                                               -----------------------

                                       6
<PAGE>
 
                         GAS TRANSPORTATION AGREEMENT
                      (For Use Under FT-A Rate Schedule)

                                  EXHIBIT "A"
                        TO GAS TRANSPORTATION AGREEMENT
                           DATED September 1st, 1993
                                    BETWEEN
                        TENNESSEE GAS PIPELINE COMPANY
                                      AND
                                 BOSTON GAS CO

<TABLE> 
<CAPTION> 
SERVICE PACKAGE: 256

SERVICE PACKAGE TQ: 10,533

METER   AMD  METER NAME                    INTERCONNECT PARTY NAME    COUNTY      ST   ZONE  R/D   LEG   METER-TQ   MINIMUM PRESSURE
-----------------------------------------------------------------------------------------------------------------------------------
<S>     <C>  <C>                           <C>                        <C>         <C>  <C>   <C>   <C>   <C>        <C> 
010902  0    TRANS-NIAGARA RIVER PURCHASE   TRANS CANADA PIPELINE LTD  NIAGARA     NY    OS    R    230    10,533         700 LBS
020111  0    BOSTON-LEOMINSTER MASS         BOSTON GAS CO              WORCESTER   MA    06    D    200     1,025         100 LBS
020115  0    BOSTON-ARLINGTON MASS          BOSTON GAS CO              MIDDLESEX   MA    86    D    200    10,533         100 LBS
020192  0    BOSTON-LEXINGTON MASS          BOSTON GAS CO              MIDDLESEX   MA    86    D    200       513         100 LBS
</TABLE>

      NUMBER OF RECEIPT  POINTS: 1
      NUMBER OF DELIVERY POINTS: 3

                                       7