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                                                                   EXHIBIT 4.L.1

                         GULFTERRA ENERGY PARTNERS, L.P.
                      GULFTERRA ENERGY FINANCE CORPORATION,
                                   AS ISSUERS

                                       AND

                         THE SUBSIDIARIES NAMED HEREIN,
                            AS SUBSIDIARY GUARANTORS

                                       AND

                     WELLS FARGO BANK, NATIONAL ASSOCIATION,

                                   as Trustee
                         -------------------------------

                             SUPPLEMENTAL INDENTURE

                           Dated as of August 17, 2004

                                       to

                                    Indenture

                            Dated as of July 3, 2003

                      6-1/4% Series A Senior Notes due 2010

                      6-1/4% Series B Senior Notes due 2010

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      THIS SUPPLEMENTAL INDENTURE, dated as of August 17, 2004, is by and among
GulfTerra Energy Partners, L.P., a Delaware limited partnership (the
"PARTNERSHIP"), GulfTerra Energy Finance Corporation, a Delaware corporation
("GULFTERRA FINANCE", and collectively with the Partnership, the "ISSUERS"), the
Subsidiary Guarantors listed on the signature pages hereof, and Wells Fargo
Bank, National Association, a national banking association, as trustee (the
"TRUSTEE").

      WHEREAS, the Trustee, the Issuers and certain subsidiaries of the
Partnership have heretofore executed and delivered that certain Indenture dated
as of July 3, 2003 (as amended, supplemented or otherwise modified from time to
time, the "INDENTURE"), providing for the issuance of 6-1/4% Series A Senior
Notes due 2010 and 6-1/4% Series B Senior Notes due 2010;

      WHEREAS, on July 3, 2004, the Issuers issued $250,000,000 aggregate
principal amount of their 6-1/4% Series A Senior Notes due 2010 and subsequently
exchanged them for an equal aggregate principal amount of their 6-1/4% Series B
Senior Notes due 2010 (collectively, the "NOTES"), all of which Notes are
currently outstanding;

      WHEREAS, Section 9.02 of the Indenture provides that, with the consent of
Holders representing a majority in aggregate principal amount of the Notes then
outstanding, the Issuers, when authorized by a resolution of the Board of
Directors of the General Partner (in the case of the Partnership) and of the
board of Directors of GulfTerra Finance, and the Subsidiary Guarantors, when
authorized by a resolution of their respective Board of Directors, and the
Trustee may enter into an indenture supplemental to the Indenture for the
purpose of amending or supplementing the Indenture or the Notes (subject to
certain exceptions);

      WHEREAS, the Issuers desire and have requested the Trustee to join with
them in entering into this Supplemental Indenture for the purpose of amending
the Indenture in certain respects as permitted by Section 9.02 of the Indenture;

      WHEREAS, in connection with the acquisition by Enterprise Products
Partners L.P. of the Partnership by merger, Enterprise Products Operating L.P.,
a Delaware limited partnership ("ENTERPRISE") and a wholly-owned subsidiary of
Enterprise Products Partners L.P., has been soliciting consents to this
Supplemental Indenture upon the terms and subject to the conditions set forth in
its Offer to Purchase and Consent Solicitation Statement dated August 4, 2004
and the related Consent and Letter of Transmittal (which together, including any
amendments, modifications or supplements thereto, constitute the "TENDER
OFFER");

      WHEREAS, the execution and delivery of this Supplemental Indenture has
been authorized by resolutions of the Board of Directors of the General Partner
(in the case of the Partnership) and of the Boards of Directors of GulfTerra
Finance and each of the Subsidiary Guarantors;

      WHEREAS, (1) the consent of the Holders of more than a majority in
principal amount of the outstanding Notes has been received, as certified by an
Officers' Certificate of the General Partner delivered to the Trustee
simultaneously with the execution and delivery of this Supplemental Indenture,
(2) the Partnership has delivered to the Trustee simultaneously with the
execution and delivery of this Supplemental Indenture an Officers' Certificate
and an Opinion of Counsel relating to this Supplemental Indenture as
contemplated by Section 9.06 of the Indenture and (3) the Issuers and the
Subsidiary Guarantors have satisfied all other conditions required under Article
9 of the Indenture to enable the Issuers, the Subsidiary Guarantors and the
Trustee to enter into this Supplemental Indenture.

      NOW, THEREFORE, in consideration of the above premises, each party hereby
agrees, for the benefit of the others and for the equal and ratable benefit of
the Holders of the Notes, as follows:

                                        1

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                                    ARTICLE I

                                   DEFINITIONS

      SECTION 1.1 DELETION OF DEFINITIONS AND RELATED REFERENCES. Section 1.01
of Article 1 of the Indenture is hereby amended to delete in their entirety all
terms and their respective definitions for which all references are eliminated
in the Indenture as a result of the amendments set forth in Article II of this
Supplemental Indenture.

                                   ARTICLE II

                             AMENDMENTS TO INDENTURE

      SECTION 2.1 AMENDMENTS TO ARTICLES 3, 4, 5 AND 6. The Indenture is hereby
amended by deleting the following provisions of the Indenture and all references
thereto in their entirety:

Section 3.09 (Offer to Purchase by Application of Net Proceeds);
Section 4.03(b) and (c) (Compliance Certificate);
Section 4.04 (Taxes);
Section 4.05 (Stay, Extension and Usury Laws);
Section 4.06 (Change of Control);
Section 4.07 (Asset Sales);
Section 4.08 (Restricted Payments);
Section 4.09 (Incurrence of Indebtedness and Issuance of Disqualified Equity);
Section 4.10 (Liens);
Section 4.11 (Dividend and Other Payment Restrictions Affecting Subsidiaries);
Section 4.12 (Transactions with Affiliates);
Section 4.13 (Additional Subsidiary Guarantees);
Section 4.14 (Designation of Restricted and Unrestricted Subsidiaries);
Section 4.15 (Business Activities);
Section 4.16 (Sale and Leaseback Transactions);
Section 4.17 (Payments for Consent);
Section 4.18 (Reports);
Section 4.19 (Elimination of Covenants);
Section 5.01(a)(iii) and clauses (A) and (B) of Section 5.01(a)(iv) (Merger,
Consolidation, or Sale of Assets); and
Section 6.01(c), (d), (e) and (f) (Events of Default).

                                   ARTICLE III

                            MISCELLANEOUS PROVISIONS

      SECTION 3.1 DEFINED TERMS. For all purposes of this Supplemental
Indenture, except as otherwise defined or unless the context otherwise requires,
terms used in capitalized form in this Supplemental Indenture and defined in the
Indenture have the meanings specified in the Indenture.

      SECTION 3.2 INDENTURE. Except as amended hereby, the Indenture and the
Notes are in all respects ratified and confirmed and all the terms shall remain
in full force and effect. This Supplemental Indenture shall form a part of the
Indenture for all purposes, and every Holder of Notes heretofore or hereafter
authenticated and delivered under the Indenture shall be bound hereby and all
terms and conditions of both shall be read together as though they constitute a
single instrument, except that in the case of conflict the provisions of this
Supplemental Indenture shall control.

      SECTION 3.3 GOVERNING LAW. THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED
BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

                                        2

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      SECTION 3.4 SUCCESSORS. All agreements of the Issuers and the Subsidiary
Guarantors in this Supplemental Indenture and the Notes shall bind their
respective successors. All agreements of the Trustee in this Supplemental
Indenture shall bind its successors.

      SECTION 3.5 DUPLICATE ORIGINALS. All parties may sign any number of copies
of this Supplemental Indenture. Each signed copy shall be an original, but all
of them together shall represent the same agreement. It is the express intent of
the parties to be bound by the exchange of signatures on this Supplemental
Indenture via telecopy.

      SECTION 3.6 SEVERABILITY. In case any one or more of the provisions in
this Supplemental Indenture or in the Notes shall be held invalid, illegal or
unenforceable, in any respect for any reason, the validity, legality and
enforceability of any such provision in every other respect and of the remaining
provisions shall not in any way be affected or impaired thereby, it being
intended that all of the provisions hereof shall be enforceable to the full
extent permitted by law.

      SECTION 3.7 TRUSTEE DISCLAIMER. The Trustee accepts the amendment of the
Indenture effected by this Supplemental Indenture and agrees to execute the
trust created by the Indenture as hereby amended, but on the terms and
conditions set forth in the Indenture, including the terms and provisions
defining and limiting the liabilities and responsibilities of the Trustee, which
terms and provisions shall in like manner define and limit its liabilities and
responsibilities in the performance of the trust created by the Indenture as
hereby amended, and without limiting the generality of the foregoing, the
Trustee shall not be responsible in any manner whatsoever for or with respect to
any of the recitals or statements contained herein, all of which recitals or
statements are made solely by the Issuers and the Subsidiary Guarantors, and the
Trustee makes no representation with respect to any such matters. Additionally,
the Trustee makes no representations as to the validity or sufficiency of this
Supplemental Indenture.

      SECTION 3.8 EFFECTIVENESS. The provisions of this Supplemental Indenture
shall be effective only upon execution and delivery of this instrument by the
parties hereto. Notwithstanding the foregoing sentence, the provisions of this
Supplemental Indenture shall become operative only upon the purchase by
Enterprise of more than a majority in principal amount of the outstanding Notes
pursuant to the Tender Offer, with the result that the amendments to the
Indenture effected by this Supplemental Indenture shall be deemed to be revoked
retroactive to the date hereof if such purchase shall not occur. The Partnership
shall notify the Trustee promptly after the occurrence of such purchase or
promptly after the Partnership shall determine that such purchase will not
occur.

      SECTION 3.9 ENDORSEMENT AND CHANGE OF FORM OF NOTES. Any Notes
authenticated and delivered after the close of business on the date that this
Supplemental Indenture becomes operative in substitution for Notes then
outstanding and all Notes presented or delivered to the Trustee on and after
that date for such purpose shall be stamped, imprinted or otherwise legended by
the Trustee, with a notation as follows:

      "Effective as of        , 2004, certain restrictive covenants of the
Issuers and certain Events of Default have been eliminated or limited, as
provided in the Supplemental Indenture, dated as of August 17, 2004. Reference
is hereby made to said Supplemental Indenture, copies of which are on file with
the Trustee, for a description of the amendments made therein."

      SECTION 3.10 EFFECT OF HEADINGS. The Section headings herein are for
convenience only and shall not affect the construction thereof.

            [THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK]

                                        3

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      IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed as of the day and year written above.

                                      GULFTERRA ENERGY PARTNERS, L.P.

                                      By: GULFTERRA ENERGY COMPANY,
                                          L.L.C., as General Partner

                                      By: William G. Manias
                                          --------------------------------------
                                      Name: William G. Manias
                                      Title: Vice President and Chief Financial
                                             Officer

                                      GULFTERRA ENERGY FINANCE CORPORATION

                                      By: William G. Manias
                                          --------------------------------------
                                      Name: William G. Manias
                                      Title: Vice President and Chief Financial
                                             Officer

                              [SIGNATURE PAGE - 1]

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                                Subsidiary Guarantors:

                                CAMERON HIGHWAY PIPELINE GP, L.L.C.*
                                CAMERON HIGHWAY PIPELINE I, L.P.*
                                CRYSTAL HOLDING, L.L.C.*
                                FIRST RESERVE GAS, L.L.C.*
                                FLEXTREND DEVELOPMENT COMPANY, L.L.C.*
                                GULFTERRA ALABAMA INTRASTATE, L.L.C.*
                                GULFTERRA FIELD SERVICES, L.L.C.*
                                GULFTERRA GC, L.P.*
                                GULFTERRA HOLDING III, L.L.C.*
                                GULFTERRA INTRASTATE, L.P.*
                                GULFTERRA NGL STORAGE, L.L.C.*
                                GULFTERRA OPERATING COMPANY, L.L.C.*
                                GULFTERRA TEXAS PIPELINE, L.P.*
                                HATTIESBURG INDUSTRIAL GAS SALES, L.L.C.*
                                HATTIESBURG GAS STORAGE COMPANY
                                      By: FIRST RESERVE GAS, L.L.C., in its
                                          capacity as 50% general partner of
                                          Hattiesburg Gas Storage Company*
                                      By: HATTIESBURG INDUSTRIAL GAS
                                          SALES, L.L.C., in its capacity as 50%
                                          general partner of Hattiesburg Gas
                                          Storage Company*
                                HIGH ISLAND OFFSHORE SYSTEM, L.L.C.
                                      By: GULFTERRA ENERGY PARTNERS,
                                          L.P., its sole member*
                                MANTA RAY GATHERING COMPANY, L.L.C.*
                                PETAL GAS STORAGE, L.L.C.*
                                POSEIDON PIPELINE COMPANY, L.L.C.*

                                *By: William G. Manias
                                     -------------------------------------------
                                Name: William G. Manias
                                Title: Vice President and Chief Financial
                                       Officer

                              [SIGNATURE PAGE - 2]

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                                WELLS FARGO BANK, NATIONAL ASSOCIATION,
                                as Trustee

                                By: /s/ Melissa Scott
                                    --------------------------------------------
                                    Name: Melissa Scott
                                    Title: Vice President

                              [SIGNATURE PAGE - 3]