<PAGE>

                                                                   EXHIBIT 10.41

                             AMENDATORY AGREEMENT

     This Amendment is entered into this 1st day of March, 2000, between
Southern Natural Gas Company ("Company") and Chattanooga Gas Company
("Shipper").

                                  WITNESSETH

     WHEREAS, Company and Shipper are parties to Firm Transportation Service
Agreement(s) (collectively referred to as "Contract FSNG130") for the following
Transportation Demands and effective dates under the indicated Rate Schedule(s)
of Company's FERC Gas Tariff, Seventh Revised Volume No. 1:

--------------------------------------------------------------------------
 Original   Package    Rate     Transportation    Effective      Primary
 Contract   Number   Schedule     Demand            Date          Term
 Number                          (Mcf/day)
--------------------------------------------------------------------------
 904470       1         FT         3,300/1/       11/1/1994     4/30/2007
--------------------------------------------------------------------------
 904470       2         FT         4,649          11/1/1994     3/31/2008
--------------------------------------------------------------------------
 904471       3       FT-NN       14,051          11/1/1994     8/31/2003
--------------------------------------------------------------------------
 905660       4         FT         5,000          11/1/1996    10/31/2006
--------------------------------------------------------------------------

     WHEREAS, Company and Shipper are also parties to a Firm Contract Storage
Service Agreement (referred to as "Contract SSNG69") for the following Maximum
Storage Quantity ("MSQ") and Maximum Daily Withdrawal Quantity ("MDWQ") for the
effective dates shown under Rate Schedule CSS of Company's FERC Gas Tariff,
Seventh Revised Volume No. 1:

--------------------------------------------------------------------------
 Original   Package     MSQ       MDWQ      Effective    Primary
 Contract   Number   (Mcf/day)  (Mcf/day)     Date        Term
 Number
--------------------------------------------------------------------------
S20130        1       695,871    14,051     11/1/1994   8/31/2003
--------------------------------------------------------------------------

     WHEREAS, Shipper has chosen to support Company's rate case settlement
filed with the Federal Energy Regulatory Commission ("FERC") on March 10, 2000,
in Docket Nos. RP99-496-000 and RP99-496-001 ("Settlement") in order to receive
the benefit of the lower settlement rates effective March 1, 2000, and the

______________________
/1/ This Transportation Demand is not subject to pregranted abandonment pursuant
to 18 C.F.R. (S) 284.221(d)(3).
<PAGE>


other benefits set forth in the settlement, in exchange for contract extensions
of the above-referenced firm contract(s) for the period(s) specified herein;

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

1.   The primary term(s) set forth in Section 4.1 of each firm Service Agreement
     below is hereby amended to extend the primary term(s) as follows:

--------------------------------------------------------------------------------
  Original     Package      Rate      Transportation    Effective     Extended
  Contract     Number     Schedule    Demand or MSQ       Date         Primary
   Number                               (Mcf/day)                       Term
--------------------------------------------------------------------------------
   904471        3         FT-NN          14,051        11/1/1994     8/31/2006
--------------------------------------------------------------------------------
   S20130        1          CSS          695,871        11/1/1994     8/31/2006
--------------------------------------------------------------------------------


     Each primary term shall continue and remain in force and effect for
     successive terms of one year each after the end of each extended primary
     term for the specified Transportation Demand, unless and until cancelled
     with respect to the associated Transportation Demand by either party giving
     365 days written notice to the other party prior to the end of the extended
     primary term or 270 days written notice prior to the end of any yearly
     extension thereafter.

2.   Company and Shipper agree that Shipper's firm contract(s) 904471 (Package
     3) and S20130 (Package 1) as set forth in Section 1 above shall be subject
     to a right of first refusal by Shipper at the expiration of the extended
     primary term set forth above for such contract(s). Notwithstanding anything
     in Company's FERC Gas Tariff or FERC Order No. 637 to the contrary,
     Shipper's matching bid under the right of first refusal provisions of
     Company's FERC Gas Tariff shall not have to exceed (a) a maximum term of
     five years, and (b) up to 100% of the maximum lawful rolled-in rate under
     the rate schedule that applied to the service as of the expiration of the
     extended primary term of such contract, for Shipper to retain its capacity.
     This contractual right of first refusal shall apply to the firm contracts
     of any replacement shipper that receives a permanent assignment, in whole
     or in part, of Shipper's firm contract(s) set forth above.

     The above-described right of first refusal also shall apply to the
     following firm Transportation Demand(s) that Shipper did not have to extend
     pursuant to the Settlement but which are for a term of one year or longer:

                                       2



<PAGE>

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------
 Original     Package      Rate       Transportation     Effective    Primary
 Contract     Number     Schedule     Demand or MSQ         Date       Term
  Number                                (Mcf/day)
--------------------------------------------------------------------------------
<S>           <C>        <C>          <C>                <C>         <C>
  904470        2           FT            4,649          11/1/1994    3/31/2008
--------------------------------------------------------------------------------
  905660        4           FT            5,000          11/1/1994   10/31/2006
--------------------------------------------------------------------------------
</TABLE>

3.   This Amendment is subject to the conditions subsequent that: (a) the
     Settlement receives final FERC approval in accordance with Article XVI of
     the Settlement; (b) the Settlement is not otherwise terminated as provided
     in Article XVI of the Settlement; and (c) Shipper does not elect to become
     a contesting party pursuant to Article XV, paragraph 6, of the Settlement.
     If any of these conditions occur, either party may terminate this Amendment
     on ten (10) days written notice to the other party, and upon such notice,
     this Amendment shall become null and void ab initio, of no further force
     and effect, and the contract provisions set forth in the contract, absent
     this amendment, shall remain in force and effect.

4.   In the event the rate moratorium under the Settlement is terminated in
     accordance with the terms of Article IV of the Settlement, Shipper shall
     have the right to reduce its Transportation Demand ("TD") under its firm
     transportation contracts during the extension period of any such contract
     and/or reduce the extension period, by giving no less than 90 days written
     notice to Company, to be given no later than one year after the effective
     date of Company's general rate change made pursuant to Article IV,
     paragraph 2, of the Settlement. Any reductions in TDs shall be pro rata
     based on TDs, among Shipper's full rate, discounted, and seasonal TDs, if
     any, and any reduction in the term of the extended contracts shall apply to
     all such contracts.

5.   This Amendment is subject to all applicable, valid laws, orders, rules and
     regulations of any governmental entity having jurisdiction over the parties
     or the subject matter hereof.

6.   This Amendment shall be binding on the parties' respective successors and
     assigns.

                                       3
<PAGE>

     WHEREFORE, the parties have executed this Amendment through their duly
authorized representatives to be effective as of the date first written above.


ATTEST:                                SOUTHERN NATURAL GAS COMPANY

By:_______________________________     By:_____________________________________
Title:____________________________     Title:__________________________________


ATTEST:                                CHATTANOOGA GAS COMPANY

By:________________________________    By:_____________________________________
Title:_____________________________    Title:__________________________________

                                       4