<PAGE>

                                                                   Exhibit 10.31

                                                              Contract #: 820015

                                SERVICE AGREEMENT
                              FOR RATE SCHEDULE CDS

      This Service Agreement, made and entered into this 29th day of October,
1999, by and between TEXAS EASTERN TRANSMISSION CORPORATION, a Delaware
Corporation (herein called "Pipeline") and BOSTON GAS COMPANY (herein called
"Customer", whether, one or more),

                              W I T N E S S E T H:

      WHEREAS, Customer desires Pipeline to transport natural gas for Customer's
account on a firm basis pursuant to the terms and conditions of Pipeline's Rate
Schedule CDS; and

      WHEREAS, Pipeline and Customer desire to enter into this Service Agreement
under Rate Schedule CDS;

      NOW, THEREFORE, in consideration of the premises and of the mutual
covenants and agreements herein contained, the parties do covenant and agree as
follows:

                                    ARTICLE I

                               SCOPE OF AGREEMENT

      Subject to the terms, conditions and limitations hereof, of Pipeline's
Rate Schedule CDS, and of the General Terms and Conditions, transportation
service hereunder will be firm. Subject to the terms, conditions and limitations
hereof and of Sections 2.3 and 2.4 of Pipeline's Rate Schedule CDS, Pipeline
shall deliver to those points on Pipeline's system as specified in Article IV
herein or available to Customer pursuant to Section 14 of the General Terms and
Conditions (hereinafter referred to as Point(s) of Delivery), for Customer's
account, as requested for any day, natural gas quantities up to Customer's MDQ.
Customer's MDQ is as follows:

                     Maximum Daily Quantity (MDQ)      3,177 dth
<PAGE>

                                SERVICE AGREEMENT
                              FOR RATE SCHEDULE CDS
                                   (Continued)

      Subject to variances as may be permitted by Sections 2.4 of Rate Schedule
CDS or the General Terms and Conditions, Customer shall deliver to Pipeline and
Pipeline shall receive, for Customer's account, at those points on Pipeline's
system as specified in Article IV herein or available to Customer pursuant to
Section 14 of the General Terms and Conditions (hereinafter referred to as
Point(s) of Receipt) daily quantities of gas equal to the daily quantities
delivered to Customer pursuant to this Service Agreement up to Customer's MDQ,
plus Applicable Shrinkage as specified in the General Terms and Conditions.

      Pipeline shall not be obligated to, but may at its discretion, receive at
any Point of Receipt on any day a quantity of gas in excess of the applicable
Maximum Daily Receipt Obligation (MDRO), plus Applicable Shrinkage, but shall
not receive in the aggregate at all Points of Receipt on any day a quantity of
gas in excess of the applicable MDQ, plus Applicable Shrinkage. Pipeline shall
not be obligated to, but may at its discretion, deliver at any Point of Delivery
on any day a quantity of gas in excess of the applicable Maximum Daily Delivery
Obligation (MDDO), but shall not deliver in the aggregate at all Points of
Delivery on any day a quantity of gas in excess of the MDQ.

      In addition to the MDQ and subject to the terms, conditions and
limitations hereof, Rate Schedule CDS and the General Terms and Conditions,
Pipeline shall deliver within the Access Area under this and all other service
agreements under Rate Schedules CDS, FT-1, and/or SCT, quantities up to
Customer's Operational Segment Capacity Entitlements, excluding those
Operational Segment Capacity Entitlements scheduled to meet Customer's MDQ, for
Customer's account, as requested on any day.


                                       2
<PAGE>

                                SERVICE AGREEMENT
                              FOR RATE SCHEDULE CDS
                                   (Continued)

                                   ARTICLE II

                                TERM OF AGREEMENT

      The term of this Service Agreement shall commence on November 1, 1999, and
shall continue in force and effect until October 31, 2000, and year to year
thereafter unless this Service Agreement is terminated as hereinafter provided.
This Service Agreement may be terminated by either Pipeline or Customer upon one
(1) year prior written notice to the other specifying a termination date of any
October 31 of any year occurring on or after the expiration of the primary term.
Subject to Section 22 of Pipeline's General Terms and Conditions and without
prejudice to such rights, this Service Agreement may be terminated at any time
by Pipeline in the event Customer fails to pay part or all of the amount of any
bill for service hereunder and such failure continues for thirty (30) days after
payment is due; provided, Pipeline gives thirty (30) days prior written notice
to Customer of such termination and provided further such termination shall not
be effective if, prior to the date of termination, Customer either pays such
outstanding bill or furnishes a good and sufficient surety bond guaranteeing
payment to Pipeline of such outstanding bill.

      THE TERMINATION OF THIS SERVICE AGREEMENT WITH A FIXED CONTRACT TERM OR
THE PROVISION OF A TERMINATION NOTICE BY CUSTOMER TRIGGERS PREGRANTED
ABANDONMENT UNDER SECTION 7 OF THE NATURAL GAS ACT AS OF THE EFFECTIVE DATE OF
THE TERMINATION. PROVISION OF A TERMINATION NOTICE BY PIPELINE ALSO TRIGGERS
CUSTOMER'S RIGHT OF FIRST REFUSAL UNDER SECTION 3.13 OF THE GENERAL TERMS AND
CONDITIONS ON THE EFFECTIVE DATE OF THE TERMINATION.

      Any portions of this Service Agreement necessary to correct or cash-out
imbalances under this Service Agreement as required by the General Terms and
Conditions of Pipeline's FERC Gas Tariff, Volume No. 1, shall survive the other
parts of this Service Agreement until such time as such balancing has been
accomplished.


                                       3
<PAGE>

                                SERVICE AGREEMENT
                              FOR RATE SCHEDULE CDS
                                   (Continued)

                                   ARTICLE III

                                  RATE SCHEDULE

      This Service Agreement in all respects shall be and remain subject to the
applicable provisions of Rate Schedule CDS and of the General Terms and
Conditions of Pipeline's FERC Gas Tariff on file with the Federal Energy
Regulatory Commission, all of which are by this reference made a part hereof.

      Customer shall pay Pipeline, for all services rendered hereunder and for
the availability of such service in the period stated, the applicable prices
established under Pipeline's Rate Schedule CDS as filed with the Federal Energy
Regulatory Commission, and as same may hereafter be legally amended or
superseded.

      Customer agrees that Pipeline shall have the unilateral right to file with
the appropriate regulatory authority and make changes effective in (a) the rates
and charges applicable to service pursuant to Pipeline's Rate Schedule CDS, (b)
Pipeline's Rate Schedule CDS pursuant to which service hereunder is rendered or
(c) any provision of the General Terms and Conditions applicable to Rate
Schedule CDS. Notwithstanding the foregoing, Customer does not agree that
Pipeline shall have the unilateral right without the consent of Customer
subsequent to the execution of this Service Agreement and Pipeline shall not
have the right during the effectiveness of this Service Agreement to make any
filings pursuant to Section 4 of the Natural Gas Act to change the MDQ specified
in Article I, to change the term of the agreement as specified in Article II, to
change Point(s) of Receipt specified in Article IV, to change the Point(s) of
Delivery specified in Article IV, or to change the firm character of the service
hereunder. Pipeline agrees that Customer may protest or contest the
aforementioned filings, and Customer does not waive any rights it may have with
respect to such filings.


                                       4
<PAGE>

                                SERVICE AGREEMENT
                              FOR RATE SCHEDULE CDS
                                   (Continued)

                                   ARTICLE IV

                  POINT(S) OF RECEIPT AND POINT(S) OF DELIVERY

      The Point(s) of Receipt and Point(s) of Delivery at which Pipeline shall
receive and deliver gas, respectively, shall be specified in Exhibit(s) A and B
of the executed service agreement. Customer's Zone Boundary Entry Quantity and
Zone Boundary Exit Quantity for each of Pipeline's zones shall be specified in
Exhibit C of the executed service agreement.

      Exhibit(s) A, B and C are hereby incorporated as part of this Service
Agreement for all intents and purposes as if fully copied and set forth herein
at length.

                                    ARTICLE V

                                     QUALITY

      All natural gas tendered to Pipeline for Customer's account shall conform
to the quality specifications set forth in Section 5 of Pipeline's General Terms
and Conditions. Customer agrees that in the event Customer tenders for service
hereunder and Pipeline agrees to accept natural gas which does not comply with
Pipeline's quality specifications, as expressly provided for in Section 5 of
Pipeline's General Terms and Conditions, Customer shall pay all costs associated
with processing of such gas as necessary to comply with such quality
specifications. Customer shall execute or cause its supplier to execute, if such
supplier has retained processing rights to the gas delivered to Customer, the
appropriate agreements prior to the commencement of service for the
transportation and processing of any liquefiable hydrocarbons and any PVR
quantities associated with the processing of gas received by Pipeline at the
Point(s) of Receipt under such Customer's service agreement. In addition,
subject to the execution of appropriate agreements, Pipeline is willing to
transport liquids associated Pith the gas produced and tendered for
transportation hereunder.


                                       5
<PAGE>

                                SERVICE AGREEMENT
                              FOR RATE SCHEDULE CDS
                                   (Continued)

                                   ARTICLE VI

                                    ADDRESSES

      Except as herein otherwise provided or as provided in the General Terms
and Conditions of Pipeline's FERC Gas Tariff, any notice, request, demand,
statement, bill or payment provided for in this Service Agreement, or any notice
which any party may desire to give to the other, shall be in writing and shall
be considered as duly delivered when mailed by registered, certified, or regular
mail to the post office address of the parties hereto, as the case may be, as
follows:

       (a)  Pipeline:       TEXAS EASTERN TRANSMISSION CORPORATION
                            5400 Westheimer Court
                            Houston, TX 77056-5310

       (b)  Customer:       BOSTON GAS COMPANY
                            One Beacon Street
                            Boston, MA 02108

or such other address as either party shall designate by formal written notice.

                                   ARTICLE VII

                                   ASSIGNMENTS

      Any Company which shall succeed by purchase, merger, or consolidation to
the properties, substantially as an entirety, of Customer, or of Pipeline, as
the case may be, shall be entitled to the rights and shall be subject to the
obligations of its predecessor in title under this Service Agreement; and either
Customer or Pipeline may assign or pledge this Service Agreement under the
provisions of any mortgage, deed of trust, indenture, bank credit agreement,
assignment, receivable sale, or similar instrument which it has executed or may
execute hereafter; otherwise, neither Customer nor Pipeline shall assign this
Service Agreement or any of its rights hereunder unless it first shall have
obtained the consent thereto in writing of the other; provided further, however,
that neither Customer nor Pipeline shall be released from its obligations
hereunder without the consent of the


                                       6
<PAGE>

                                SERVICE AGREEMENT
                              FOR RATE SCHEDULE CDS
                                   (Continued)

other. In addition, Customer may assign its rights to capacity pursuant to
Section 3.14 of the General Terms and Conditions. To the extent Customer so
desires, when it releases capacity pursuant to Section 3.14 of the General Terms
and Conditions, Customer may require privity between Customer and the
Replacement Customer, as further provided in the applicable Capacity Release
Umbrella Agreement.

                                  ARTICLE VIII

                                 INTERPRETATION

      The interpretation and performance of this Service Agreement shall be in
accordance with the laws of the State of Texas without recourse to the law
governing conflict of laws.

      This Service Agreement and the obligations of the parties are subject to
all present and future valid laws with respect to the subject matter, State and
Federal, and to all valid present and future orders, rules, and regulations of
duly constituted authorities having jurisdiction.

                                   ARTICLE IX

                        CANCELLATION OF PRIOR CONTRACT(S)

      This Service Agreement supersedes and cancels, as of the effective date of
this Service Agreement, the contract(s) between the parties hereto as described
below:

                                 Not Applicable


                                       7
<PAGE>

                                SERVICE AGREEMENT
                              FOR RATE SCHEDULE CDS
                                   (Continued)

      IN WITNESS WHEREOF, the parties hereto have caused this Service Agreement
to be signed by their respective Presidents, Vice Presidents or other duly
authorized agents and their respective corporate seals to be hereto affixed and
attested by their respective Secretaries or Assistant Secretaries, the day and
year first above written.

                            TEXAS EASTERN TRANSMISSION CORPORATION


                            By
                               ---------------------------------- /s/ PMT

ATTEST:


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

                            BOSTON GAS COMPANY


                            By /s/ William R. Luthern
                               ----------------------------------

ATTEST:


/s/ Elizabeth [ILLEGIBLE]
-------------------------


                                       8
<PAGE>

                                                              Contract #: 820015

                         EXHIBIT A, TRANSPORTATION PATHS
                      FOR BILLING PURPOSES, DATED 10/29/99
                TO THE SERVICE AGREEMENT UNDER RATE SCHEDULE CDS
           BETWEEN TEXAS EASTERN TRANSMISSION CORPORATION ("Pipeline")
               AND BOSTON GAS COMPANY ("Customer"), DATED 10/29/99

(1)   Customer's firm Point(s) of Receipt:

                             Maximum Daily
     Point                Receipt Obligation
      of                    (plus Applicable     Measurement
    Receipt  Description      Shrinkage)      Responsibilities   Owner  Operator
    -------  -----------  ------------------  ----------------   -----  --------

     None

(2)   Customer shall have Pipeline's Master Receipt Point List ("MRPL").
      Customer hereby agrees that Pipeline's MRPL as revised and published by
      Pipeline from time to time is incorporated herein by reference.

Customer hereby agrees to comply with the Receipt Pressure Obligation as set
forth in Section 6 of Pipeline's General Terms and Conditions at such Point(s)
of Receipt.

                                                  Transportation
                         Transportation Path   Path Ouantity (Dth/D)
                         -------------------   ---------------------

                              M2 to M3                3,177

SIGNED FOR IDENTIFICATION


PIPELINE:                            /s/ JMM
         ----------------------------

CUSTOMER: /s/ W. R. Luthern          /s/ ED
         ----------------------------

SUPERSEDES EXHIBIT A DATED:
                            ---------



                                      A-1
<PAGE>

                                                              Contract #: 820015

                 EXHIBIT B, POINT(S) OF DELIVERY, DATED 10/29/99
                TO THE SERVICE AGREEMENT UNDER RATE SCHEDULE CDS
        BETWEEN TEXAS EASTERN TRANSMISSION CORPORATION ("Pipeline"), AND
                        BOSTON GAS COMPANY ("Customer"),
                                 DATED 10/29/99:

<TABLE>
<CAPTION>
                                         Maximum
                                         Daily         Delivery
   Point of                              Delivery      Pressure        Measurement
   Delivery       Description            Obligation    Obligation      Responsibilities    Owner    Operator
   --------       -----------            ----------    ----------      ----------------    -----    --------
                                             (dth)
<S>          <C>                           <C>         <C>             <C>                <C>       <C>
1. 70087     ALGONQUIN - LAMBERTVILLE      3,177       AS REQUESTED    TX EAST TRAN       TX EAST   ALGONQUIN
             NJ HUNTERDON CO., NJ                      BY CUSTOMER,                       TRAN
                                                       NOT TO
                                                       EXCEED 750
                                                       POUNDS PER
                                                       SQUARE INCH
                                                       GUAGE
</TABLE>

provided, however, that until changed by a subsequent Agreement between Pipeline
and Customer, Pipeline's aggregate maximum daily delivery obligations under this
and all other firm Service Agreements existing between Pipeline and Customer,
shall in no event exceed the following:


                                      B-1
<PAGE>

                                                              Contract #: 820015

                   EXHIBIT B, POINT(S) OF DELIVERY (Continued)
                               BOSTON GAS COMPANY

                              Aggregate Maximum Daily
Point of Delivery             Delivery Obligation (dth)
-----------------             -------------------------

No. 1                                 177,070

SIGNED FOR IDENTIFICATION


PIPELINE:                            /s/ JMM
         ----------------------------

CUSTOMER: /s/ W. R. Luthern          /s/ ED
         ----------------------------

SUPERSEDES EXHIBIT B DATED:
                            ---------


                                      B-2
<PAGE>

                                                              Contract #: 820015

    EXHIBIT C, ZONE BOUNDARY ENTRY QUANTITY AND ZONE BOUNDARY EXIT QUANTITY,
        DATED 10/29/99, TO THE SERVICE AGREEMENT UNDER RATE SCHEDULE CDS
         BETWEEN TEXAS EASTERN TRANSMISSION CORPORATION ("PIPELINE") AND
                 BOSTON GAS COMPANY ("CUSTOMER"), DATED 10/29/99

                          ZONE BOUNDARY ENTRY QUANTITY
                                      Dth/D

                                       To

<TABLE>
<CAPTION>
====================================================================================================================
FROM    STX   ETX   WLA   ELA    Ml-24    Ml-30   Ml-TXG   Ml-TGC    M2-24    M2-30    M2-TXG    M2-TGC    M2    M3
--------------------------------------------------------------------------------------------------------------------
<S>     <C>   <C>   <C>   <C>    <C>      <C>     <C>      <C>       <C>      <C>      <C>       <C>       <C>   <C>
STX
--------------------------------------------------------------------------------------------------------------------
ETX
--------------------------------------------------------------------------------------------------------------------
WLA
--------------------------------------------------------------------------------------------------------------------
ELA
--------------------------------------------------------------------------------------------------------------------
M1-24
--------------------------------------------------------------------------------------------------------------------
M1-30
--------------------------------------------------------------------------------------------------------------------
M1-TXG
--------------------------------------------------------------------------------------------------------------------
M1-TGC
--------------------------------------------------------------------------------------------------------------------
M2-24
--------------------------------------------------------------------------------------------------------------------
M2-30
--------------------------------------------------------------------------------------------------------------------
M2-TXG
--------------------------------------------------------------------------------------------------------------------
M2-TGC
--------------------------------------------------------------------------------------------------------------------
M2                                                                                                             3,177
--------------------------------------------------------------------------------------------------------------------
M3
====================================================================================================================
</TABLE>


                                      C-1
<PAGE>

                                                              Contract #: 820015

                              EXHIBIT C (Continued)
                               BOSTON GAS COMPANY

                           ZONE BOUNDARY EXIT QUANTITY
                                      Dth/D

                                       To

<TABLE>
<CAPTION>
====================================================================================================================
FROM    STX   ETX   WLA   ELA    Ml-24    Ml-30   Ml-TXG   Ml-TGC    M2-24    M2-30    M2-TXG    M2-TGC    M2    M3
--------------------------------------------------------------------------------------------------------------------
<S>     <C>   <C>   <C>   <C>    <C>      <C>     <C>      <C>       <C>      <C>      <C>       <C>       <C>   <C>
STX
--------------------------------------------------------------------------------------------------------------------
ETX
--------------------------------------------------------------------------------------------------------------------
WLA
--------------------------------------------------------------------------------------------------------------------
ELA
--------------------------------------------------------------------------------------------------------------------
M1-24
--------------------------------------------------------------------------------------------------------------------
M1-30
--------------------------------------------------------------------------------------------------------------------
M1-TXG
--------------------------------------------------------------------------------------------------------------------
M1-TGC
--------------------------------------------------------------------------------------------------------------------
M2-24
--------------------------------------------------------------------------------------------------------------------
M2-30
--------------------------------------------------------------------------------------------------------------------
M2-TXG
--------------------------------------------------------------------------------------------------------------------
M2-TGC
--------------------------------------------------------------------------------------------------------------------
M2                                                                                                             3,177
--------------------------------------------------------------------------------------------------------------------
M3
====================================================================================================================
</TABLE>

SIGNED FOR IDENTIFICATION:


PIPELINE:                            /s/ JMM
         ----------------------------

CUSTOMER: /s/ W. R. Luthern          /s/ ED
         ----------------------------

SUPERSEDES EXHIBIT c DATED:
                            ---------


                                      C-2