**EXHIBIT 4.A**   **EL PASO CORPORATION****as Issuer****and****HSBC BANK USA, NATIONAL ASSOCIATION****as Trustee****ELEVENTH SUPPLEMENTAL INDENTURE****Dated as of August 31, 2006****to****INDENTURE****Dated as of May 10, 1999****Reopening of 7.750% Medium Term Notes**  
 

 
**TABLE OF CONTENTS**       **Page**ARTICLE 1 Relation to Indenture; Definitions  2 SECTION 1.01. Relation to Indenture, January 2001 BoardResolutions and January 2002 Officer’s Certificate  2 SECTION 1.02. Definitions  2 SECTION 1.03. General References  2      ARTICLE 2 The Additional Medium Term Notes  2 SECTION 2.01. The Form and Terms of the Additional Medium Term Notes  2 SECTION 2.02. Amount of Additional Medium Term Notes  2      ARTICLE 3 Miscellaneous  3 SECTION 3.01. Certain Trustee Matters  3 SECTION 3.02. Continued Effect  3 SECTION 3.03. Governing Law  3 SECTION 3.04. Counterparts  3 
 

 
     **ELEVENTH SUPPLEMENTAL INDENTURE**, dated as of August 31, 2006 (this “SupplementalIndenture”), between **EL PASO CORPORATION**, a Delaware corporation (the“Company”), and **HSBC BANK USA****, NATIONAL ASSOCIATION**, a national bankingassociation, as successor-in-interest to JPMorgan Chase Bank (formerly The Chase Manhattan Bank),as trustee under the Indenture referred to below (in such capacity, the “Trustee”).**RECITALS OF THE COMPANY**     WHEREAS, the Company and the Trustee are parties to an Indenture dated as of May 10, 1999 (the“Original Indenture”), such Original Indenture, as amended and supplemented from time totime (including without limitation pursuant to this Supplemental Indenture), being referred toherein as the “Indenture;” and     WHEREAS, on January 11, 2002, the Company issued $1,100,000,000 aggregate principal amount ofits 7.750% Medium Term Notes, CUSIP No. 28368E AE 6 (the “Original Medium Term Notes”),pursuant to and in accordance with (i) the Indenture, (ii) the resolutions of the Company’s boardof directors (the “Board of Directors”) adopted pursuant to a unanimous written consent ofthe Board of Directors dated as of January 29, 2001 (the “January 2001 Board Resolutions”)and (iii) the Officer’s Certificate of the Company dated as of January 11, 2002 (the “January2002 Officer’s Certificate”), setting forth the terms and provisions of the Original MediumTerm Notes (including the form of note certificate therefor); and     WHEREAS, Section 301 of the Indenture provides that all Securities of any one series need notbe issued at the same time and that a series of Securities may be reopened, without the consent ofthe Holders, for increases in the aggregate principal amount of such series of Securities andissuances of additional Securities of such series; and     WHEREAS, in connection with the consummation of the exchange offers contemplated by theCompany’s Registration Statement on Form S-4 (Registration No. 333-134099) (including theprospectus dated July 24, 2006 and forming a part thereof), in exchange for the surrender of theCompany’s outstanding 7.75% Senior Notes due 2032 and the Company’s outstanding 7.75% SeniorDebentures due October 15, 2035, the Company desires to issue up to $150,000,000 in additionalaggregate principal amount of notes (the “Additional Medium Term Notes” and collectivelywith the Original Medium Term Notes, the “Medium Term Notes”) having substantially the sameterms as, having the same CUSIP number as, to be issued using substantially the same form of notecertificate as, and constituting a part of the same series as, the Original Medium Term Notes; and     WHEREAS, pursuant to Section 901 of the Indenture, without the consent of any Holders, theCompany and the Trustee, at any time and from time to time, may enter into one or more indenturessupplemental to the Indenture to establish the form or terms of securities of any series aspermitted by Sections 201 and 301 of the Indenture; and     WHEREAS, all action on the part of the Company necessary to authorize the issuance of theAdditional Medium Term Notes under the Original Indenture, the January 2001 Board Resolutions, theJanuary 2002 Officer’s Certificate and this Supplemental Indenture has been duly taken; and     WHEREAS, all acts and things necessary to make the Additional Medium Term Notes, when executedby the Company and authenticated and delivered by the Trustee as provided in the Indenture, thevalid and binding obligations of the Company and to make this Supplemental Indenture a valid andbinding agreement in accordance with the Original Indenture have been done or performed;     NOW, THEREFORE, in consideration of the premises, agreements and obligations set forth hereinand for other good and valuable consideration, the receipt and sufficiency of which are herebyacknowledged, the parties hereto hereby agree, for the equal and proportionate benefit of allHolders of the Medium Term Notes, as follows:
 

 
**ARTICLE 1****Relation to Indenture; Definitions**     **SECTION 1.01.*****Relation to Indenture, January 2001 Board Resolutions and January 2002 Officer’sCertificate.***     With respect to the Medium Term Notes, this Supplemental Indenture constitutes an integralpart of the Indenture and shall also constitute an amendment and supplement to the January 2001Board Resolutions and the January 2002 Officer’s Certificate.     **SECTION 1.02.*****Definitions.***     For all purposes of this Supplemental Indenture, except as otherwise expressly providedherein, capitalized terms used herein and not otherwise defined herein shall have the meaningsassigned thereto in the Original Indenture, the January 2001 Board Resolutions or the January 2002Officer’s Certificate, as appropriate.     **SECTION 1.03.*****General References.***     All references in this Supplemental Indenture to Articles and Sections, unless otherwisespecified, refer to the corresponding Articles and Sections of this Supplemental Indenture; and theterms “*herein*”, “*hereof*”, “*hereunder*” and any other word of similar import refers to thisSupplemental Indenture.**ARTICLE 2****The Additional Medium Term Notes**     **SECTION 2.01.*****The Form and Terms of the Additional Medium Term Notes*****.**     Notwithstanding anything to the contrary set forth in the Original Indenture, the AdditionalMedium Term Notes shall be issued in substantially the form of the form of Medium Term Noteattached to the January 2002 Officer’s Certificate, with such appropriate insertions, omissions,substitutions and other variations as are required or permitted by the Indenture, and may have suchletters, numbers or other marks of identification and such legends or endorsements placed thereonas the Company may deem appropriate or as may be required or appropriate to comply with any laws orwith any rules made pursuant thereto or with the rules of any securities exchange or automatedquotation system on which the Medium Term Notes may be listed or traded, or to conform to generalusage, or as may, consistently with the Indenture, be determined by the officers executing suchAdditional Medium Term Notes, as evidenced by their execution thereof.     Pursuant to and in accordance with the terms and provisions of the Indenture (includingwithout limitation Section 301 thereof), (i) the Additional Medium Term Notes shall havesubstantially the same terms as, shall have the same CUSIP number as, and shall constitute a partof the same series as, the Original Medium Term Notes and (ii) the Company’s issuance of theAdditional Medium Term Notes shall constitute a reopening of the Medium Term Notes. Except asotherwise provided herein, the Additional Medium Term Notes shall be executed, authenticated anddelivered in accordance with the provisions of, and shall in all respects be subject to, the terms,conditions and covenants of the Original Indenture as supplemented by the January 2001 BoardResolutions, the January 2002 Officer’s Certificate (including the form of Medium Term Noteattached thereto (the terms of which are incorporated in and made a part of this SupplementalIndenture for all intents and purposes)) and this Supplemental Indenture. In the event of anyinconsistency between the provisions of this Supplemental Indenture and the provisions of theOriginal Indenture, the provisions of this Supplemental Indenture shall be controlling with respectto the Medium Term Notes.     **SECTION 2.02.*****Amount of Additional Medium Term Notes*****.**     Without limiting the aggregate principal amount of any series of Securities (including withoutlimitation the Medium Term Notes), the aggregate principal amount of Additional Medium Term Noteswhich may be authenticated and delivered pursuant hereto is $150,000,000. The Trustee shallinitially authenticate and deliver Additional Medium Term Notes for original issue in an initialaggregate principal amount of $150,000,000 upon delivery to the Trustee of a Company Order for theauthentication and delivery of such Securities.
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**ARTICLE 3****Miscellaneous**     **SECTION 3.01.*****Certain Trustee Matters*****.**     The recitals contained herein shall be taken as the statements of the Company, and the Trusteeassumes no responsibility for their correctness.     The Trustee makes no representations as to the validity or sufficiency of this SupplementalIndenture or the Additional Medium Term Notes or the proper authorization or the due executionhereof or thereof by the Company.     **SECTION 3.02.*****Continued Effect*****.**     Except as expressly supplemented and amended by this Supplemental Indenture, the OriginalIndenture (as supplemented and amended to date) shall continue in full force and effect inaccordance with the provisions thereof, and the Original Indenture (as so supplemented and amended,and as further supplemented and amended by this Supplemental Indenture) is in all respects herebyratified and confirmed. This Supplemental Indenture and all its provisions shall be deemed a partof the Original Indenture in the manner and to the extent herein and therein provided.     **SECTION 3.03.*****Governing Law.***     This Supplemental Indenture and the Additional Medium Term Notes shall be governed by andconstrued in accordance with the laws of the State of New York.     **SECTION 3.04.*****Counterparts*****.**     This instrument may be executed in any number of counterparts, each of which shall be deemedto be an original, but all such counterparts shall together constitute but one and the sameinstrument.***(Signature Pages Follow)***
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     IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be dulyexecuted and delivered, all as of the day and year first above written.      EL PASO CORPORATION