Document:

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                                                                   Exhibit 10.56

                         AMENDMENT TO SERVICE AGREEMENT

         THIS AMENDMENT ("Amendment") is entered into this 30 day of August,
1996, by and between TRANSCONTINENTAL GAS PIPE LINE CORPORATION, a Delaware
corporation, hereinafter referred to as "Seller", first party, and PIEDMONT
NATURAL GAS COMPANY, INC., a New York corporation, hereinafter referred to as
"Buyer", second party.

                                   WITNESSETH:

         WHEREAS, Seller and Buyer entered into that certain Service Agreement,
dated January 1, 1971 under Seller's Rate Schedule LG-A ("Service Agreement")
pursuant to which Seller provides liquefied natural gas storage service for
Buyer up to a total volume of 72,770 Mcf of natural gas which is Buyer's
Liquefaction Capacity Volume; and

         WHEREAS, Seller and Buyer now desire to renew and extend the primary
term of the Service Agreement.

         NOW THEREFORE, Seller and Buyer hereby agree to renew and amend the
Service Agreement as follows:

1.       Article IV of the Service agreement is hereby deleted in its entirety
         and replaced by the following:

                                   "ARTICLE IV
                                TERM OF AGREEMENT

         This agreement shall be effective as of November 1, 1971 and shall
         remain in force and effect until 8:00 a.m. Eastern Standard Time
         October 31, 2001, and thereafter until terminated by Seller or Buyer
         upon at least one hundred eighty (180) days prior written notice."

2.       As herein amended, the Service Agreement is hereby renewed in full
         force and effect pursuant to the terms thereof.

3.       This Amendment shall be effective as of the date first above written.

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
signed by their respective officers or representatives thereunto duly
authorized.

TRANSCONTINENTAL GAS PIPE LINE               PIEDMONT NATURAL GAS COMPANY,
CORPORATION ("Seller")                       INC. ("Buyer")

By /s/ Frank J. Ferazzi                      By /s/ Thomas E. Skains
   --------------------                         --------------------
Frank J. Ferazzi                             Title Senior Vice President
Vice President                                     ---------------------
Customer Service<PAGE>   1
                                                                   Exhibit 10.57

                                SERVICE AGREEMENT

            THIS AGREEMENT entered into this 29th day of January, 1997, by and
between PINE NEEDLE LNG COMPANY, LLC, a North Carolina limited liability
company, hereinafter referred to as "Pine Needle," and PIEDMONT NATURAL GAS
COMPANY, INC., hereinafter referred to as "Customer,"

                                   WITNESSETH

          WHEREAS, by order issued November 27, 1996, in Docket No. CP96-52, the
Federal Energy Regulatory Commission granted a certificate of public convenience
and necessity to Pine Needle to construct and operate a liquefied natural gas
storage facility in Guilford County, North Carolina; and

          WHEREAS, Pine Needle's LNG storage facility, which is proposed to be
in service by May 1, 1999, will have a total storage capacity of 4 Bcf of gas,
with the ability to vaporize 400 MMcf/day and to liquefy at a net rate of 20
MMcf/day; and

          WHEREAS, Customer has requested firm storage service at Pine Needle's
LNG storage facility under Pine Needle's Rate Schedule LNG-1 and has executed
with Pine Needle a Precedent Agreement dated September 22, 1995 for such
service; and

          WHEREAS, Pine Needle is willing to provide the requested firm storage
service for Customer pursuant to the terms and provisions of this Service
Agreement, Rate Schedule LNG-1, and the Precedent Agreement.

          NOW, THEREFORE, Pine Needle and Customer agree as follows:

                                    ARTICLE I
                             SERVICE TO BE RENDERED

          Subject to the terms and provisions of this agreement and of Pine
Needle's Rate Schedule LNG1, as amended from time to time, Pine Needle agrees to
liquefy natural gas; store such gas in liquefied form; and vaporize and deliver
such gas to Customer or for Customer's account as follows:

          To withdraw from storage and vaporize the gas stored in liquefied form
by Pine Needle for Customer's account up to a maximum quantity on any day of the
dekatherm equivalent of 200,000 Mcf, which quantity shall be Customer's
Vaporization Quantity. 1/

         To liquefy natural gas for Customer up to a maximum quantity on any day
of the dekatherm equivalent of 10,000 Mcf, which shall be Customer's
Liquefaction Quantity. 1/

          To store in liquefied form for Customer's account up to a total
quantity of the dekatherm equivalent of 2,000,000 Mcf, which quantity shall be
Customer's Storage Capacity.

          1/        In addition to these quantities, Pine Needle shall retain
                    quantities of gas for fuel and gas otherwise used or lost
                    and unaccounted for pursuant to Rate Schedule LNG-1.

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                          SERVICE AGREEMENT (CONTINUED)

                          POINT OF RECEIPT AND DELIVERY

                    1. The Point of Receipt for all gas tendered to Pine Needle
for liquefaction hereunder shall be at the following point(s):

                    Gas Pipe Line Corporation's ("Transco") mainline system at
                    milepost 1356.95 on Transco's mainline in Guilford County,
                    North Carolina.

         2.         The Point of Delivery for all gas delivered by Pine Needle
                    to Customer or for the account of Customer shall be at the
                    following point(s):

                    The interconnection between Pine Needle's 24-inch outlet
                    pipeline and Transco's mainline system at milepost 1356.95
                    on Transco's mainline in Guilford County, North Carolina.

                                   ARTICLE III
                                TERM OF AGREEMENT

          This agreement shall be effective as of the date that Pine Needle's
facilities necessary to provide service hereunder to Customer have been
constructed and are ready for liquefaction of gas, as determined by Pine Needle
in its sole opinion, hereinafter referred to as the "In-Service Date," and shall
remain in force and effect for a primary term of twenty (20) years from and
after the In-Service Date, and year to year thereafter, subject to termination
by either party upon two (2) years prior written notice to the other.

                             RATE SCHEDULE AND PRICE

          1. Customer shall pay Pine Needle for service rendered hereunder in
accordance with Pine Needle's Rate Schedule LNG-1 and the applicable provisions
of the General Terms and Conditions of Pine Needle's FERC Gas Tariff as filed
with the Federal Energy Regulatory Commission, and as the same may be amended or
superseded from time to time. Such rate schedule and General Terms and
Conditions are by this reference made a part hereof.

          2. Pine Needle shall have the unilateral right to propose, file, and
make effective with the Federal Energy Regulatory Commission, or other
regulatory authority having jurisdiction, changes and revisions to the rates and
rate design proposed pursuant to Section 4 of the Natural Gas Act, or to
propose, file and make effective superseding rates or rate schedules, for the
purposes of changing the rates, charges, rate design, terms and conditions of
service and other provisions thereof effective as to Customer; provided however
that the (i )firm character of service, (ii) term of agreement (as set forth in
Article III above), (iii) quantities, and (iv) points of receipt and delivery
shall not be subject to unilateral change under this paragraph. Customer shall
have the right to file with the Commission or other regulatory authority in
opposition to any such filings or proposals by Pine Needle.

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<PAGE>   3

                          SERVICE AGREEMENT (CONTINUED)

                                  MISCELLANEOUS

          1. The subject headings of the Articles of this agreement are inserted
for the purpose of convenient reference and are not intended to be a part of
this agreement nor to be considered in the interpretation of the same.

          2. This agreement supersedes and cancels as of the effective date
hereof the following contracts between the parties hereto: None.

          3. No waiver by either party of any one or more defaults by the other
in the performance of any provisions of this agreement shall operate or be
construed as a waiver of any future default or defaults, whether of alike or
different character.

          4. This agreement shall be interpreted, performed and enforced in
accordance with the laws of the State of North Carolina.

          5. This agreement shall be binding upon, and inure to the benefit of
the parties hereto and their respective successors and assigns.

          6. Notices to either party shall be in writing and shall be considered
as duly delivered when mailed to the other party at the following address:

                  (a)     If to Pine Needle:
                          Pine Needle LNG Company, LLC
                          c/o Pine Needle Operating Company
                          P.O. Box 1396
                          (2800 Post Oak Boulevard 77056)
                          Houston, Texas 77251-1396
                          Attention: Director - Customer Services and Scheduling

                  (b)     If to Customer:
                          Piedmont Natural Gas Company, Inc.
                          P.O. Box 33068
                          (1915 Rexford Road 28211)
                          Charlotte, North Carolina 28233
                          Attention: Senior Vice President, Gas Supply

Such addresses may be changed from time to time by mailing appropriate notice
thereof to the other party.

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<PAGE>   4

                          SERVICE AGREEMENT (CONTINUED)

         IN WITNESS WHEREOF, the parties hereto have caused this agreement to be
signed by their respective officers or representatives thereunto duly
authorized.

                                           PINE NEEDLE LNG COMPANY, LLC
                                           by its agent
                                           PINE NEEDLE OPERATING COMPANY

                                           By: /s/ Frank J. Ferazzi
                                               ---------------------------------
                                               Vice President

                                           PIEDMONT NATURAL GAS COMPANY, INC.

                                           By: /s/ Thomas E. Skains
                                               ---------------------------------

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