<PAGE>

                                                                 EXHIBIT 10.BB.4



                            LIMESTONE ELECTRON TRUST

                   THIRD AMENDED AND RESTATED TRUST AGREEMENT

                                       BY

                            WILMINGTON TRUST COMPANY,
                     as Trustee and Securities Intermediary


                              EL PASO CORPORATION,
                        as holder of the El Paso Interest

                                 ELECTRON TRUST,
                            as sole Certificateholder

                                       AND

                            LIMESTONE ELECTRON TRUST

                           Dated as of April 12, 2002


<PAGE>

                                TABLE OF CONTENTS

<Table>
<Caption>
                                                                                                           Page Nos.
                                                                                                           ---------
<S>                                                                                                       <C>

ARTICLE I  GENERAL................................................................................................2
         Section 1.01.  Appointment of Wilmington Trust Company...................................................2
         Section 1.02.  Formation of the Trust....................................................................2
         Section 1.03.  Name, Principal Office, and Name and Address of Trustee as
                          Agent for Service of Process............................................................2
         Section 1.04.  Purpose and Powers........................................................................2
         Section 1.05.  Claims Against the Trust..................................................................4
         Section 1.06.  Beneficial Ownership......................................................................4
         Section 1.07.  Certain Covenants Relating to the Separateness of the Trust...............................5

ARTICLE II  DEFINITIONS...........................................................................................7

ARTICLE III  CONTRIBUTIONS.......................................................................................10
         Section 3.01.  Initial Contribution.....................................................................10
         Section 3.02.  Contributions by the Certificateholders..................................................10
         Section 3.03.  Contributions by the Holder of the El Paso Interest......................................11
         Section 3.04.  Holding of the Trust Estate..............................................................12
         Section 3.05.  Limitation on the Liability of the Depositor and the
                          Certificateholders.....................................................................12

ARTICLE IV  THE LIMESTONE CERTIFICATES...........................................................................12
         Section 4.01.  Ownership................................................................................12
         Section 4.03.  Form of Certificates; Denominations; Yield...............................................12
         Section 4.04.  Execution of Certificates................................................................13
         Section 4.05.  Registration of Issuance, Transfer and Exchange of Limestone
                          Certificates...........................................................................13
         Section 4.06.  Mutilated, Destroyed, Lost or Stolen Certificates........................................15
         Section 4.07.  Persons Deemed Owners....................................................................15
         Section 4.08.  Access to List of Certificateholders' Names and Addresses................................16
         Section 4.09.  Maintenance of Office or Agency..........................................................16
         Section 4.10.  Limestone Certificates Held by El Paso...................................................16
         Section 4.11.  ERISA Information........................................................................16
         Section 4.12.  FERC Information.........................................................................16

ARTICLE V  THE EL PASO INTEREST..................................................................................17
         Section 5.01.  The El Paso Interest.....................................................................17
         Section 5.02.  Execution of El Paso Interest............................................................17
         Section 5.03.  Transfer of El Paso Interest.............................................................17
         Section 5.04.  Rights of Holder of El Paso Interest.....................................................17

ARTICLE VI  COLLECTIONS; DISTRIBUTIONS...........................................................................18
         Section 6.01.  Payments From Trust Estate...............................................................18
</Table>



<PAGE>

<Table>
<S>                                                                                                       <C>

         Section 6.02.  Establishment of Limestone Distribution Account and Limestone
                          Collection Account.....................................................................18
         Section 6.03.  Distributions from the Limestone Distribution Account....................................21
         Section 6.04.  Distributions from the Limestone Collection Account......................................22
         Section 6.05.  Limestone Distribution Date Statements...................................................23
         Section 6.06.  Withholding..............................................................................23
         Section 6.07.  Information Provided by the Trustee......................................................24

ARTICLE VII  LIMESTONE CERTIFICATE TRIGGER EVENTS; SPECIFIED EQUITY EVENTS; LIMESTONE
                     CERTIFICATE PURCHASE RIGHT; CERTIFICATE PURCHASE OPTION; EARN-OUT PERIOD;
                     CANCELLATION OF LIMESTONE CERTIFICATES......................................................26
         Section 7.01.  Consequences of a Limestone Certificate Trigger Event or Specified Equity Event..........26
         Section 7.02.  Limestone Certificate Purchase Right; Certificate Purchase Option........................26
         Section 7.03.  Earn-Out Period..........................................................................27
         Section 7.04.  Cancellation of Limestone Certificates...................................................28

ARTICLE VIII  RIGHTS, OBLIGATIONS, POWERS AND STATUS OF THE CERTIFICATEHOLDERS AND THE HOLDER
                     OF THE EL PASO INTEREST.....................................................................28
         Section 8.01.  Management of the Trust..................................................................28
         Section 8.02.  Bankruptcy, Dissolution or Termination of any Certificateholder..........................29
         Section 8.03.  Creditors of the Certificateholders......................................................29
         Section 8.04.  Certain Rights of the Majority Certificateholders........................................29
         Section 8.05.  Voting and Other Rights of the Holder of the El Paso Interest............................29

ARTICLE IX  CONCERNING THE TRUSTEE, THE SECURITIES INTERMEDIARY AND WILMINGTON TRUST COMPANY.....................30
         Section 9.01.  General..................................................................................30
         Section 9.02.  Acceptance of the Trust..................................................................32
         Section 9.03.  Authority and Duties of the Trustee......................................................32
         Section 9.04.  Representations and Warranties of Wilmington Trust Company...............................34
         Section 9.05.  Resignation of the Trustee...............................................................34
         Section 9.06.  Liability................................................................................35
         Section 9.07.  Indemnification..........................................................................35
         Section 9.08.  Fees and Expenses........................................................................36
         Section 9.09.  Litigation, Action Outside Delaware......................................................36
         Section 9.10.  Rights of the Securities Intermediary....................................................37
         Section 9.11.  Resignation; Appointment of Successor Securities Intermediary............................37
         Section 9.12.  Acceptance of Appointment by Successor Securities Intermediary...........................37
         Section 9.13.  Merger or Consolidation of Securities Intermediary.......................................37

ARTICLE X  DISSOLUTION, BANKRUPTCY AND LIQUIDATION OF THE TRUST..................................................38
         Section 10.01.  Dissolution of the Trust................................................................38
         Section 10.02.  Termination.............................................................................39
</Table>


                                       ii
<PAGE>

<Table>
<S>                                                                                                       <C>

ARTICLE XI  NOTICES..............................................................................................39
         Section 11.01.  Notices.................................................................................39

ARTICLE XII  MISCELLANEOUS PROVISIONS............................................................................40
         Section 12.01.  Entire Agreement........................................................................40
         Section 12.02.  Governing Law...........................................................................40
         Section 12.03.  Severability of Provisions..............................................................41
         Section 12.04.  Amendment or Waiver; Effect on Agreement................................................41
         Section 12.05.  Binding Upon Assigns....................................................................41
         Section 12.06.  Survival................................................................................41
         Section 12.07.  Tax Characterization....................................................................41
         Section 12.08.  Counterparts............................................................................42
         Section 12.09.  Effectiveness...........................................................................42
</Table>

Exhibit A         Form of Limestone Certificate
Exhibit B         Form of Certificate of Holder of El Paso Interest
Exhibit C         Form of Investment Certificate


                                      iii
<PAGE>

                            LIMESTONE ELECTRON TRUST

                   THIRD AMENDED AND RESTATED TRUST AGREEMENT


                  This THIRD AMENDED AND RESTATED TRUST AGREEMENT (this
"Agreement") of Limestone Electron Trust, a Delaware statutory business trust
(the "Trust"), is made and entered into as of April 12, 2002 by WILMINGTON TRUST
COMPANY, a Delaware banking corporation (not in its individual capacity but
solely as trustee hereunder, the "Trustee", and as securities intermediary), EL
PASO CORPORATION (formerly El Paso Energy Corporation), a corporation organized
under the laws of Delaware, as holder of the El Paso Interest, ELECTRON TRUST, a
Delaware statutory business trust, as sole Certificateholder, and LIMESTONE
ELECTRON TRUST, the Delaware statutory business trust continued hereby.
Capitalized terms used herein but not defined in Article II hereof have the
meanings assigned to such terms in Annex A to the Participation Agreement dated
as of March 15, 2000, as amended, supplemented, amended and restated or
otherwise modified from time to time (the "Participation Agreement"), among the
Trust, Credit Suisse First Boston (USA), Inc., as successor to DLJ Inc., El
Paso, El Paso Chaparral Holding, El Paso Chaparral Holding II, El Paso
Chaparral, the Management Company, Chaparral, Mesquite, the Share Trust, the
Overfund Trust, Electron, Wilmington Trust Company and The Bank of New York, as
successor to United States Trust Company of New York (each, as defined in the
Participation Agreement).

                  WHEREAS, as of December 22, 1999, Wilmington Trust Company and
El Paso, as Depositor, entered into a Trust Agreement (the "Original Trust
Agreement");

                  WHEREAS, as of December 28, 1999, Wilmington Trust Company,
the Depositor and the Trust amended and restated the Original Trust Agreement in
its entirety (the "First Amended and Restated Trust Agreement");

                  WHEREAS, as of March 27, 2000, Wilmington Trust Company, El
Paso, as holder of the El Paso Interest, Electron, as sole Certificateholder,
and the Trust amended and restated the First Amended and Restated Trust
Agreement in its entirety (the "Second Amended and Restated Trust Agreement");

                  WHEREAS, as of March 27, 2002, Wilmington Trust Company and El
Paso, as holder of the El Paso Interest entered into an amendment to the Second
Amended and Restated Trust Agreement ("Amendment No. 1");

                  WHEREAS, Wilmington Trust Company, El Paso, the sole
Certificateholder and the Trust desire to amend and restate the Second Amended
and Restated Trust Agreement, as amended by Amendment No. 1, in its entirety to
become effective on and as of the Effective Date in accordance with Section
12.09;

                  NOW THEREFORE, in consideration of the premises and the mutual
covenants herein contained, the parties hereto agree that the Second Amended and
Restated Trust Agreement, as amended by Amendment No. 1, is hereby amended and
restated to read in its entirety as set forth herein:



                                       1
<PAGE>

                                    ARTICLE I

                                     GENERAL

                  Section 1.01. Appointment of Wilmington Trust Company.
Pursuant to the Original Trust Agreement, the Depositor appointed Wilmington
Trust Company as Trustee of the Trust effective as of December 22, 1999, to have
all the rights, powers and duties set forth therein and in the Act. Pursuant to
the First Amended and Restated Trust Agreement, the Depositor and Wilmington
Trust Company agreed that Wilmington Trust Company would continue to be the
Trustee of the Trust. Pursuant to the Second Amended and Restated Trust
Agreement, El Paso, all of the Certificateholders and Wilmington Trust Company
agreed that Wilmington Trust Company would continue to be Trustee of the Trust.
Pursuant to this Agreement, El Paso, all of the Certificateholders and
Wilmington Trust Company agree that Wilmington Trust Company shall continue to
be the Trustee of the Trust upon the terms and conditions set forth herein.

                  Section 1.02. Formation of the Trust. The Trust was formed and
continued as a statutory business trust under and pursuant to the Act, the
Original Trust Agreement and the Certificate of Trust of the Trust. It is the
intention of the parties hereto that this Agreement amend, restate and supersede
the Second Amended and Restated Trust Agreement, as amended by Amendment No. 1,
and from and after the Effective Date, constitute the sole governing instrument
of the Trust. All Persons owning or otherwise holding interests of beneficial
ownership in the Trust shall own or otherwise hold such interests of beneficial
ownership pursuant to the provisions of this Agreement.

                  Section 1.03. Name, Principal Office, and Name and Address of
Trustee as Agent for Service of Process. The Trust shall continue to be
conducted under the name "Limestone Electron Trust," in which name the Trust or
the Trustee on behalf of the Trust shall enter into contracts and agreements
with respect to the transactions contemplated hereby. The principal place of
business and office of the Trust shall be c/o Wilmington Trust Company, Rodney
Square North, 1100 North Market Street, Wilmington, Delaware 19890-0001,
Attention: Corporate Trust Administration. The Trustee, who is hereby designated
to accept service of process, shall continue to be Wilmington Trust Company and
its current office is located at the address provided in the preceding sentence.

                  Section 1.04. Purpose and Powers. (a) The purpose of the Trust
shall be limited to engaging in the following activities:

                  (i) entering into, complying with its obligations under,
consummating the transactions and engaging in the activities contemplated by,
(A) the Participation Agreement, (B) the Chaparral LLC Agreement (including
exercising its right to act as Managing Member of Chaparral in accordance with
the Chaparral LLC Agreement), (C) the Indenture, (D) the Security Agreement, (E)
the Remarketing Agreement, (F) this Agreement, (G) the Limestone Account Control
Agreement dated as of March 27, 2000 among the Trust, United States Trust
Company of New York, as indenture trustee, and Wilmington Trust Company, as
securities intermediary, (H) the Closing Agreement, (I) the New Indenture, (J)
the Dealer Manager Agreement and (K) any other Transaction Documents to which it
is to be a party;



                                       2
<PAGE>

                  (ii) (A) entering into any document necessary or appropriate
to commence and/or consummate the Exchange Offer and the transactions
contemplated thereby (including, without limitation, the Closing Agreement and
the Dealer Manager Agreement), (B) entering into any document necessary or
appropriate to amend, supplement or modify any Transaction Document to which the
Trust is a party or by which it is bound to the extent necessary or appropriate
to commence and/or consummate the Exchange Offer and the transactions
contemplated thereby and (C) undertaking any other action necessary or
appropriate to enter into, proceed with, effect and/or consummate the Exchange
Offer, in each case pursuant to the terms and conditions of the Offering
Circular and Consent Solicitation Statement;

                  (iii) owning all the outstanding shares of the Co-Issuer,
which shares shall be registered in the name of the Trust and held by the
Trustee on behalf of the Trust;

                  (iv) issuing the El Paso Interest to El Paso;

                  (v) issuing the Original Certificates pursuant to the First
Amended and Restated Trust Agreement, selling the Original Certificates, issuing
the Subsequent Certificates pursuant to the Second Amended and Restated Trust
Agreement and selling the Subsequent Certificates;

                  (vi) issuing, together with the Co-Issuer, (A) the Limestone
Notes pursuant to the Indenture and selling the Limestone Notes and (B) the New
Limestone Notes pursuant to the New Indenture in exchange for Limestone Notes;

                  (vii) assigning, granting, transferring, pledging, mortgaging
and conveying the Trust Estate to the Indenture Trustee for the benefit of the
holders of the Limestone Notes and holding, managing and distributing to the
Certificateholders and the holder of the El Paso Interest any portion of the
Trust Estate released from the Lien of, and remitted to the Trust pursuant to,
the Indenture in accordance with this Agreement;

                  (viii) making payments to the Indenture Trustee for the
benefit of the holders of the Limestone Notes pursuant to and in accordance with
the Indenture, making payments to the New Indenture Trustee for the benefit of
the holders of the New Limestone Notes pursuant to and in accordance with the
New Indenture and this Agreement (after the repayment in full of the Outstanding
Limestone Notes) and making distributions to the holders of the Limestone
Certificates and the holder of the El Paso Interest pursuant to and in
accordance with this Agreement;

                  (ix) notwithstanding any other provision hereof, repaying the
principal amount of the Limestone Loan with a portion of the proceeds from the
sale of the Limestone Notes and the Subsequent Certificates and paying all
accrued interest on the Limestone Loan with the proceeds of a distribution from
Chaparral, and discharging any obligations of the Trust under the Limestone
Credit Agreement, the security documents related thereto and the Assignment and
Assumption Agreement;

                  (x) (A) holding the Class A Member Interest and (B) upon (I)
the repayment of all of the Limestone Notes on the Maturity Date with Cash
contributed by the holder of the El Paso Interest pursuant to Section 3.03, (II)
the redemption of all or any portion of the Limestone



                                       3
<PAGE>

Notes pursuant to Section 14.01(a)(ii)(A) or 15.01(c)(i) of the Indenture, (III)
the redemption of all or any portion of the New Limestone Notes pursuant to
Section 14.01(a)(ii)(A) or 15.01(c)(i) of the New Indenture, or (IV) a payment
by El Paso, as Guarantor, pursuant to Section 3.09 of the New Indenture,
acquiring an Additional Class B Member Interest and being admitted to Chaparral
as a Class B Member pursuant to Section 3.2(b)(iii) of the Chaparral LLC
Agreement;

                  (xi) making an additional Cash Capital Contribution of
$1,027,250,000 to Chaparral to increase the Class A Member's Capital Account by
such amount;

                  (xii) receiving payments and other distributions from
Chaparral with respect to the Class A Member Interest and any Additional Class B
Member Interest;

                  (xiii) engaging in those activities that are necessary to
accomplish the foregoing or are incidental thereto;

                  (xiv) subject to compliance with the Transaction Documents,
engaging in such other activities as may be required in connection with
conservation of the Trust Estate and making distributions to the
Certificateholders and the holder of the El Paso Interest; and

                  (xv) executing and making, at the request of Chaparral, the
Overfund Trustee or the holder of the El Paso Interest, but at no cost to the
Trust, such filings and registrations, and taking such other actions, as may be
reasonably necessary or appropriate under Applicable Law, Contractual
Obligations to which the Trust is a party, or otherwise, to conduct the business
of Chaparral or its subsidiaries or to transfer member interests in Chaparral or
to comply with, or to consummate the transactions contemplated by, the
Transaction Documents to which the Trust is a party.

                  (b) The Trust is hereby authorized to engage in the foregoing
activities. The Trust shall not engage in any activity other than (i) the
activities described in clause (a) above or (ii) subject to the terms of this
Agreement, as the Certificateholders and, where appropriate, the holder of the
El Paso Interest, may from time to time direct.

                  Section 1.05. Claims Against the Trust. All Persons extending
credit to, contracting with or having any claim against the Trust shall look
only to the Trust for payment under such credit, contract or claim. None of the
Trustee (including in its individual capacity), the Depositor, the
Certificateholders, the holder of the El Paso Interest or any of the Trust's
officers, employees or agents, whether past, present or future, shall be
personally liable therefor.

                  Section 1.06. Beneficial Ownership. The beneficial ownership
interests in the Trust will be evidenced by (i) the Limestone Certificates
issued on December 28, 1999 pursuant to the First Amended and Restated Trust
Agreement and exchanged for new Limestone Certificates on March 27, 2000
pursuant to the Second Amended and Restated Trust Agreement, (ii) the Limestone
Certificates issued in accordance with Article IV of the Second Amended and
Restated Trust Agreement and (iii) the El Paso Interest issued on December 28,
1999 pursuant to the First Amended and Restated Trust Agreement, each of which
shall constitute undivided beneficial interests in the Trust Estate, provided,
that the rights of the holder of the El Paso Interest are limited as set forth
in Sections 5.04 and 8.05.



                                       4
<PAGE>

                  Section 1.07. Certain Covenants Relating to the Separateness
of the Trust. The Trust shall maintain its separate existence and, specifically,
shall conduct its affairs in accordance with, and El Paso agrees that it will
not take any actions in its dealings with the Trust that are inconsistent with,
the following:

                  (a) The Trust shall: (i) maintain and prepare separate
financial reports (if any) and financial statements (if any) in accordance with
GAAP, showing its assets and liabilities separate and apart from those of any
other Person (other than the Co-Issuer), and will not have its assets listed on
the financial statement of any other Person (provided, however, that the Trust's
assets may be included in a consolidated financial statement of the
Certificateholders if inclusion on such consolidated financial statement is
required to comply with the requirements of GAAP, but only if (a) such
consolidated financial statement shall be appropriately footnoted to the effect
that the Trust's assets are owned by the Trust and that they are being included
on the consolidated financial statement of the Certificateholders solely to
comply with the requirements of GAAP, and (b) such assets shall be listed on the
Trust's own separate balance sheet); (ii) maintain its books, records and bank
accounts separate from those of its Affiliates, any constituent party and any
other Person; and (iii) not permit any Affiliate or constituent party (other
than the Trustee in its capacity as Trustee) independent access to its bank
accounts.

                  (b) The Trust shall not commingle or pool any of its funds or
other assets with those of any Affiliate or constituent party or any other
Person, and it shall, through the Trustee, hold all of its assets in its own
name, except as provided in the Indenture.

                  (c) The Trust, through the Trustee, shall conduct its own
business in its own name and shall not operate, or purport to operate,
collectively as a single or consolidated business entity with respect to any
Person (other than the Co-Issuer).

                  (d) The Trust shall, insofar as is consistent with commercial
and business circumstances affecting its business and financial condition,
remain solvent and pay its own debts, liabilities and expenses (including
overhead expenses, if any) only out of its own assets as the same shall become
due (other than, if at all, pursuant to Section 6.06 and except for certain
legal fees, accounting fees and other out-of-pocket costs and expenses incurred
by the Trust in connection with the formation, administration and activities of
the Trust, which items may be paid by the holder of the El Paso Interest or an
Affiliate of the holder of the El Paso Interest, and except for certain costs
and liabilities of the Trust indemnified against by the holder of the El Paso
Interest pursuant to the Transaction Documents) (provided, that this covenant
shall not constitute a guaranty or "keep well" obligation by the Trustee, any
administrator of or with respect to the Trust or any other Person in respect of
the Trust or its debts, liabilities or expenses, or any financial or balance
sheet condition or ratio of or relating to the Trust).

                  (e) The Trust has done, or caused to be done, and shall do,
all things necessary to observe all Delaware statutory business trust
formalities and other organizational formalities, and preserve its existence
(subject to Article X and the other express provisions hereof), and it shall
not, nor will it permit any Affiliate or constituent party to, amend, modify or
otherwise change this Agreement in a manner which would adversely affect the
existence of the Trust as a special purpose entity.



                                       5
<PAGE>

                  (f) The Trust shall not have any employees.

                  (g) The Trust does not, and shall not, (i) guarantee, become
obligated for, or hold itself or its credit out to be responsible for or
available to satisfy, the debts or obligations of any other Person or (ii)
control the decisions or actions respecting the daily business or affairs of any
other Person.

                  (h) The Trust shall, to the extent it utilizes stationery,
invoices and checks, maintain and utilize separate stationery, invoices and
checks bearing its own name.

                  (i) The Trust shall, at all times, hold itself out to the
public as a legal entity separate and distinct from any other Person and shall
correct any known misunderstanding regarding its separate identity.

                  (j) The Trust shall not identify itself as a division of any
other Person.

                  (k) The Trust shall maintain its assets in such a manner that
it will not be costly or difficult to segregate, ascertain or identify its
individual assets from those of any Affiliate, constituent party or any other
Person, except as provided in the Indenture.

                  (l) The Trust shall not use its separate existence to abuse
creditors or to perpetrate a fraud, injury, or injustice on creditors in
violation of Applicable Law.

                  (m) The Trust shall not, in connection with the Transaction
Documents, act with an intent to hinder, delay, or defraud any of its creditors
in violation of Applicable Law.

                  (n) The Trust shall not be consensually merged or legally
consolidated with any other Person (other than certain Affiliates for financial
reporting and federal tax purposes), but without prejudice to the right to
dissolve, liquidate or wind up in accordance with its Organizational Documents
or Applicable Law.

                  (o) The Trust's ability to enter into transactions with
Affiliates is limited only to transactions on an arms' length basis and on
commercially reasonable terms (the parties hereto each agreeing that the
Transaction Documents satisfy the aforementioned standard).

                  (p) The Trust shall not acquire Equity Interests of any
Affiliate (except Chaparral and the Co-Issuer).

                  (q) The Trust shall not incur any Relevant Indebtedness other
than any Relevant Indebtedness incurred in connection with or pursuant to the
Transaction Documents.

                  (r) The Trust shall not make loans or advances to any Person,
other than pursuant to Section 6.06 and except as permitted by the Transaction
Documents.

                  (s) The issuance of the Limestone Certificates and the El Paso
Interest to the Certificateholders and the holder of the El Paso Interest,
respectively, was and is intended to be, and shall be accounted for on the
books, records, and financial statements of the Trust, the Certificateholders
and the holder of the El Paso Interest, as applicable, as the issuance of equity



                                       6
<PAGE>

capital and not as a loan by the Certificateholders and the holder of the El
Paso Interest, as applicable, to the Trust.

                  (t) The Trust shall make no transfer of its assets except in
accordance with the Transaction Documents.

                  (u) The Trust shall not pledge its assets for the benefit of
any Person, except pursuant to the Transaction Documents.

                  (v) The Trust shall not, nor will it permit any Affiliate or
constituent party to, amend this Section 1.07 in a manner which would adversely
affect the existence of the Trust as a special purpose entity.

                                   ARTICLE II

                                   DEFINITIONS

                  "Amendment No. 1" has the meaning set forth in the preliminary
statements hereto.

                  "Available Funds" means, with respect to any Limestone
Distribution Date, the aggregate amount of Cash on deposit in the Limestone
Distribution Account or the Limestone Collection Account, as the case may be.

                  "Bankruptcy Action" has the meaning set forth in Section
10.01.

                  "Benefit Plan Investor" means a "benefit plan investor" as
defined in the Plan Asset Regulations.

                  "Certificate Face Amount" means, with respect to each
Limestone Certificate, the portion of the aggregate face amount of Limestone
Certificates outstanding corresponding to such Limestone Certificate.

                  "Certificate of Trust" means the Certificate of Trust of the
Trust filed under the Act with the Secretary of State on December 22, 1999, as
such Certificate of Trust may be amended or restated from time to time.

                  "Certificate Purchase Option" has the meaning assigned to such
term in Section 7.02(b).

                  "Certificate Record Date" has the meaning set forth in Section
6.03(d).

                  "Certificate Register" has the meaning set forth in Section
4.05(a).

                  "Certificate Registrar" has the meaning set forth in Section
4.05(a).



                                       7
<PAGE>

                  "Certificateholder" means, with respect to any date, the
Person or Persons in whose name Limestone Certificates (other than Limestone
Certificates that have been cancelled or deemed cancelled pursuant to Section
7.04) are registered in the Certificate Register.

                  "Competitor of El Paso" means any Person who conducts any
significant operations in energy and energy related businesses, including
businesses relating to Energy Assets, except for Persons whose primary business
is banking, insurance, investment banking, investment management or other
investing and financial services.

                  "Depositor" means El Paso, as depositor pursuant to the
Original Trust Agreement.

                  "El Paso Interest" means the Class B beneficial ownership
interest in the Trust issued and authenticated pursuant to the First Amended and
Restated Trust Agreement.

                  "EP Purchase Option Deposit Amount" has the meaning set forth
in Section 7.02(a).

                  "Equity Event Notice" has the meaning set forth in Section
6.07(g).

                  "First Amended and Restated Trust Agreement" has the meaning
set forth in the preliminary statements hereto.

                  "Indemnified Trustee Person" has the meaning set forth in
Section 9.07.

                  "Limestone Certificate Purchase Right" has the meaning set
forth in Section 7.02(a).

                  "Limestone Collection Account" has the meaning set forth in
Section 6.02.

                  "Limestone Distribution Account" has the meaning set forth in
Section 6.02.

                  "Limestone Distribution Date" means each Business Day on which
there are Available Funds in the Limestone Distribution Account or the Limestone
Collection Account; provided that after the satisfaction and discharge of the
Indenture and the New Indenture, "Limestone Distribution Date" shall mean
"Distribution Date" as defined in Annex A.

                  "Limestone Distribution Date Statement" has the meaning set
forth in Section 6.05.

                  "Majority Certificateholders" means at any time
Certificateholders holding, collectively, Limestone Certificates evidencing more
than 50% of the aggregate Certificate Face Amount of all Limestone Certificates
outstanding. At any time when there are no Certificateholders, the holder of the
El Paso Interest shall constitute the "Majority Certificateholders."



                                       8
<PAGE>
                  "Original Certificates" means the Limestone Certificates
issued on December 28, 1999 pursuant to the First Amended and Restated Trust
Agreement having an original Certificate Face Amount, in the aggregate, of
$50,000,000.

                  "Operating Account" means Limestone's account (account number
49273-0) at Wilmington Trust Company.

                  "Periodic Filings" means any tax filings or submissions that
the Trust is required to make with any Federal, state or local taxing authority
or regulatory agency.

                  "Plan Asset Regulations" means the U.S. Department of Labor
regulations at 29 C.F.R. Section 2510.3-101, as in effect from time to time.

                  "Proportionate Interest" at any time, means the proportion
that each Certificateholder's Certificate Face Amount bears to the aggregate
Certificate Face Amount of the Limestone Certificates.

                  "PTP Relevant Person" means each Tax Matters Representing
Purchaser and each Indirect Tax Matters Representing Purchaser that, in each
case, is able to make the representations described in clauses (B)(1) or (B)(2)
of the definition of Tax Matters Representing Purchaser.

                  "Required Certificateholders" means at any time
Certificateholders holding, collectively, Limestone Certificates evidencing more
than 25% of the aggregate Certificate Face Amount of all Limestone Certificates
outstanding. At any time when there are no Certificateholders, the holder of the
El Paso Interest shall constitute the "Required Certificateholders."

                  "Second Amended and Restated Trust Agreement" has the meaning
set forth in the preliminary statements hereto.

                  "Secretary of State" means the office of the Secretary of
State of the State of Delaware.

                  "Subsequent Certificates" means the $100,000,000 aggregate
Certificate Face Amount of Limestone Certificates issued on the Closing Date
pursuant to the Second Amended and Restated Trust Agreement.

                  "Tax Matters Representing Purchaser" means a Person that is
able to represent that (A) it is acting for its own account and not as the
nominee or agent of any other Person, (B) either (1) it is not a partnership,
grantor trust, or S corporation for United States Federal income tax purposes (a
"Flowthrough Entity"), (2) it is a Flowthrough Entity, but less than 50% of the
assets of the Flowthrough Entity will be represented, directly or indirectly, by
Limestone Certificates or (3) it is a Flowthrough Entity (x) whose nominal
owners are able to make the representations in (A) and either (B)(1) or (B)(2)
or, (y) to the extent that any of its direct or indirect nominal owners cannot
make the representations in (B)(1) or (B)(2) and is itself a Flowthrough Entity
(an "Upper Tier Flowthrough Entity"), the nominal owners of any such Upper Tier
Flowthrough Entity are able to make the representations in (A) and either (B)(1)
or



                                       9
<PAGE>

(B)(2) (each such nominal owner described in clause (3) that makes the
representations in either (B)(1) or (B)(2), an "Indirect Tax Matters
Representing Purchaser"), and (C) it has not acquired, and will not transfer any
Limestone Certificates (or any derivative interest therein) on or through an
established securities market within the meaning of Section 7704(b)(1) of the
Code (and Treasury regulations thereunder).

                  "Trust" means the Delaware statutory business trust known as
"Limestone Electron Trust" which was formed on December 22, 1999, under the Act
pursuant to the Original Trust Agreement and the filing of the Certificate of
Trust and continued pursuant to the First Amended and Restated Trust Agreement,
the Second Amended and Restated Trust Agreement, as amended by Amendment No. 1,
as amended and restated by this Agreement.

                  "Trust Estate" means all right, title and interest of the
Trust in, to and under the Class A Member Interest, any Additional Class B
Member Interest, any Transaction Document to which the Trust is a party
(including all rights of the Trust to any amounts payable to the Trust under any
Transaction Document) and any other property contributed to the Trust or
otherwise acquired by the Trust, together with all distributions, payments,
revenues, issues, profits or proceeds thereof and therefrom, and all
appurtenances thereto.

                  "Trustee" means Wilmington Trust Company, not in its
individual capacity but solely as a trustee hereunder, and any successor trustee
appointed in accordance with Section 3807 of the Act and Section 9.05.

                  The rules of construction set forth in Annex A to the
Participation Agreement shall apply to this Agreement as if set forth herein.

                                   ARTICLE III

                                  CONTRIBUTIONS

                  Section 3.01. Initial Contribution. On December 22, 1999, the
Depositor assigned, transferred, conveyed and set over to the Trustee the sum of
one dollar, which initial contribution shall constitute part of the Trust
Estate.

                  Section 3.02. Contributions by the Certificateholders. (a) On
December 28, 1999, Electron purchased the Original Certificates for $50,000,000,
which contribution constituted (and shall continue to constitute) a part of the
Trust Estate and was used by the Trust to make a Capital Contribution to
Chaparral to increase the Class A Member's Capital Account by such amount.

                  (b) Each Certificateholder purchasing Subsequent
Certificates, simultaneously with the delivery thereto of a Limestone
Certificate issued by the Trust in accordance with the provisions of the Second
Amended and Restated Trust Agreement, paid to the Trust or the account
designated by the Trust an amount equal to the applicable Certificate Face
Amount, which contribution on the Closing Date constituted a part of the Trust
Estate and was used by the Trust to make an additional Capital Contribution to
Chaparral to increase the Capital Account of the Trust, as Class A Member of
Chaparral.



                                       10
<PAGE>

                  (c) Reserved.

                  (d) The Certificateholders may, at any time and from time
to time, contribute Cash to the Trust for the purpose of causing an Optional
Redemption of all or a portion of the Limestone Notes or, if such contribution
occurs following a Limestone Note Trigger Event but prior to the Asset Remedy
Standstill Expiration Date, a Mandatory Redemption of all of the Limestone
Notes. The Trustee shall, immediately upon its receipt of any such contribution,
irrevocably deposit such contribution into the Indenture Collection Account with
the Indenture Trustee to cause (a) an Optional Redemption of all or a portion of
the Limestone Notes pursuant to and in accordance with Section 14.01(a)(ii)(B)
of the Indenture or (b) a Mandatory Redemption of all of the Limestone Notes
pursuant to and in accordance with Section 15.01(c)(ii) of the Indenture.

                  Section 3.03. Contributions by the Holder of the El Paso
Interest.

                  (a) The holder of the El Paso Interest may, at any time
and from time to time, contribute Cash to the Trust for the purpose of causing
(x) an Optional Redemption of all or a portion of the Limestone Notes if no
Limestone Note Trigger Event has occurred, (y) if such contribution occurs prior
to the 120th day before the Maturity Date and no Limestone Note Trigger Event
has occurred, the repayment of the Limestone Notes on the Maturity Date, or (z)
if such contribution occurs following a Limestone Note Trigger Event but prior
to the Asset Remedy Standstill Expiration Date, a Mandatory Redemption of all of
the Limestone Notes. Simultaneously with such contribution, if made prior to the
occurrence of a Limestone Note Trigger Event, the holder of the El Paso Interest
shall notify the Trustee and the Indenture Trustee in writing as to the purpose
to which such contribution is to be applied. The Trustee shall, immediately upon
its receipt of any such contribution, irrevocably deposit such contribution into
the Indenture Collection Account with the Indenture Trustee to cause (in
accordance with the notice received from the holder of the El Paso Interest, if
such contribution is received prior to the occurrence of a Limestone Note
Trigger Event) (a) an Optional Redemption of all or a portion of the Limestone
Notes pursuant to and in accordance with Section 14.01(a)(ii)(A) of the
Indenture, (b) repayment of the Limestone Notes on the Maturity Date in
accordance with Section 5.04(b) of the Indenture or (c) a Mandatory Redemption
of all of the Limestone Notes pursuant to and in accordance with Section
15.01(c)(i) of the Indenture.

                  (b) If any proceeds from the Asset Remedy, any Asset
Disposition or asset sales (in connection with an enforcement proceeding
following a judgment against the Issuers) are distributed to the New Noteholders
pursuant to Section 5.04 of the New Indenture, the holder of the El Paso
Interest shall, no later than the earlier of (x) 12:00 noon New York City time
on the 10th Business Day following the repayment in full of the New Limestone
Notes and (y) the occurrence of an "Event of Default" described in Section
7.1(e) of the June 11 Agreement with respect to El Paso, regardless of whether
notice is given by the Trustee under Section 6.07(f), contribute Cash to the
Trust for deposit into the Limestone Distribution Account in an amount equal to
the lesser of (i) the amount of such proceeds used to repay the New Limestone
Notes and (ii) the Certificate Purchase Amount as of such date (net of any funds
or the proceeds of the sale of any investments then held for the benefit of the
Limestone Certificateholders in the Limestone Distribution Account, Limestone
Collection Account or, to the extent such amounts



                                       11
<PAGE>

are available for distribution by the Indenture Trustee to Limestone for the
benefit of the Limestone Certificateholders under the Indenture, the Indenture
Accounts).

                  (c) Any payments by El Paso, as Guarantor, pursuant to
Section 3.09 of the New Indenture shall be deemed to constitute a contribution
by the holder of the El Paso Interest of Cash to the Trust in respect of the El
Paso Interest in the amount of such payment.

                  Section 3.04. Holding of the Trust Estate. In furtherance of
Sections 1.01 and 1.02, the Trustee hereby declares and agrees that it will hold
all estate, right, title and interest in and to the Trust Estate until this
Agreement terminates pursuant to the terms of this Agreement, in trust under and
subject to the conditions and agreements hereinafter set forth, for the use and
benefit of the Certificateholders from time to time and the holder of the El
Paso Interest.

                  Section 3.05. Limitation on the Liability of the Depositor and
the Certificateholders. None of the Depositor, any Certificateholder or the
holder of the El Paso Interest shall be liable for any debt, claim, demand,
judgment or obligation of any kind of, against or with respect to the Trust by
reason of its being the Depositor, a Certificateholder or the holder of the El
Paso Interest, nor shall the Depositor, any Certificateholder or the holder of
the El Paso Interest, by reason of its status as such, be subject to any
personal liability whatsoever, in tort, contract or otherwise, to any Person in
connection with the property, liabilities or affairs of the Trust.

                                   ARTICLE IV

                           THE LIMESTONE CERTIFICATES

                  Section 4.01. Ownership. (a) On December 28, 1999, the Trust
issued (i) the Original Certificates to Electron and (ii) the El Paso Interest
to El Paso, in accordance with the First Amended and Restated Trust Agreement.

                  (b) On the Closing Date, the Trust issued the Subsequent
Certificates to Electron in accordance with the Second Amended and Restated
Trust Agreement.

                  (c) The holders of the Limestone Certificates and the
holder of the El Paso Interest are the beneficiaries and beneficial owners
(within the meaning of the Act) of the Trust. All outstanding Limestone
Certificates shall share pari passu in the Trust Estate to the extent set forth
herein and any payments distributable to the Certificateholders therefrom, each
in accordance with its Proportionate Interest.

                  Section 4.02. Reserved.

                  Section 4.03. Form of Certificates; Denominations; Yield. The
Limestone Certificates shall be offered and sold in their initial distribution
to a number of institutions that are Qualified Purchasers that make the
representations set forth in Exhibit C hereto, in transactions exempt from
registration under the Securities Act, and shall be issued in definitive fully
registered form, without interest coupons, in substantially the form attached as
Exhibit A



                                       12
<PAGE>

hereto, with such applicable legends as are provided for in Exhibit A. The
Limestone Certificates shall be issued in minimum denominations of $100,000 and
integral multiples of $1,000 in excess thereof. The Limestone Certificates shall
be executed on behalf of the Trust by manual or facsimile signature of any
authorized signatory of the Trustee having such authority. Limestone
Certificates bearing the manual or facsimile signatures of individuals who were,
at the time when such signatures were affixed, authorized to sign on behalf of
the Trustee shall be validly issued and entitled to the benefits of this
Agreement, notwithstanding that such individuals or any of them have ceased to
be so authorized prior to the authentication and delivery of such Limestone
Certificates. The Limestone Certificates shall accrue yield as set forth in each
such Limestone Certificate.

                  Section 4.04. Execution of Certificates. No Limestone
Certificate shall entitle its holder to any benefit under this Agreement, or
shall be valid for any purpose, unless such certificate is executed by the
Trustee, by manual or facsimile signature. All Limestone Certificates shall be
dated the date of their execution. The Original Certificates and the Subsequent
Certificates shall be treated as a single class for all purposes under this
Agreement, including, without limitation, with respect to waivers, amendments,
redemptions and offers to purchase.

                  Section 4.05. Registration of Issuance, Transfer and Exchange
of Limestone Certificates. (a) The Certificate Registrar shall maintain, or
cause to be maintained, at the office or agency maintained pursuant to Section
4.09, a certificate register (the "Certificate Register") in which, subject to
such reasonable regulations as it may prescribe, the Trustee shall provide for
the registration of Limestone Certificates and of transfers and exchanges of
Limestone Certificates as provided in this Agreement. Pursuant to the Second
Amended and Restated Trust Agreement, Wilmington Trust Company was appointed
"Certificate Registrar" for the purpose of registering Limestone Certificates
and transfers and exchanges of Limestone Certificates as provided in this
Agreement.

                  (b) Upon surrender for registration of transfer of any
Limestone Certificate at the office or agency maintained pursuant to Section
4.09, the Trustee, on behalf of the Trust, shall execute and deliver, in the
name of the designated transferee or transferees, one or more new Limestone
Certificates in authorized denominations of a like Certificate Face Amount dated
the date of execution by the Trustee, subject to the applicable restrictions on
transfer set forth herein. At the option of a Certificateholder, the Limestone
Certificates may be exchanged for other Limestone Certificates in authorized
denominations of a like Certificate Face Amount upon surrender of the Limestone
Certificates to be exchanged at the office or agency maintained pursuant to
Section 4.09.

                  (c) Every Limestone Certificate presented or surrendered
for registration of transfer or exchange shall be accompanied by a written
instrument of transfer in form satisfactory to the Trustee and the Certificate
Registrar duly executed by the Certificateholder or its attorney duly authorized
in writing, including the representations set forth in Section 4.12. Each
Limestone Certificate surrendered for registration of transfer or exchange shall
be cancelled and subsequently disposed of by the Trustee in accordance with its
customary practice.



                                       13
<PAGE>

                  (d) No service charge shall be made for any registration of
transfer or exchange of Limestone Certificates, but the Trustee or the
Certificate Registrar may require payment of a sum sufficient to cover any tax
(other than income taxes) or governmental charge that may be imposed in
connection with any transfer or exchange of Limestone Certificates.

                  (e) Each Limestone Certificate shall be subject to the
restrictions on transfer provided in the applicable legends required to be set
forth in the face of each Limestone Certificate pursuant to Exhibit A hereto.
Whenever any Limestone Certificate is presented or surrendered to the Trustee
for registration of transfer or for exchange for a Limestone Certificate
registered in a name other than that of the Certificateholder, such Limestone
Certificate must be accompanied by, and each proposed transferee, as a condition
to the issuance to such transferee by the Trust of any Limestone Certificate,
shall deliver to the Trustee (A) an appropriately completed certificate of the
proposed transferee (an "Investment Certificate") substantially in the form set
forth in Exhibit C hereto to stating, among other things, (1) that such proposed
transferee is (x) a Qualified Purchaser that has acquired the Limestone
Certificates in compliance with the restrictions on transfer provided in the
applicable legends required to be set forth on the face of each Limestone
Certificate and (y) a Tax Matters Representing Purchaser, (2) that the
representations set forth in Section 4.12 are true and correct with respect to
such proposed transferee, (3) whether the proposed transferee is (x) a Benefit
Plan Investor (and/or if such proposed transferee is an insurance company and it
is using assets of its general account to acquire such Limestone Certificates,
the proportion of its general account that constitutes plan assets for purposes
of the determination described in clause (A) of paragraph (f) below) and/or (y)
a Person who has discretionary authority or control with respect to the assets
of the Trust or provides investment advice with respect to such assets for a fee
(direct or indirect) or an Affiliate of any such Person and (4) if the proposed
transferee is a Benefit Plan Investor subject to ERISA and/or Section 4975 of
the Code, that the transfer will not result in a non-exempt prohibited
transaction within the meaning of Section 406 or 407 of ERISA or Section 4975 of
the Code, and (B) a completed Tax Information Schedule (in the form attached to
the Investment Certificate) for itself and each of its direct or indirect
nominal owners that are Indirect Tax Matters Representing Purchasers. The
Trustee shall forward a copy of each Investment Certificate to the Depositor for
its records.

                  (f) No transfer of a Limestone Certificate shall be effective,
and the Trustee will not recognize any such transfer if, immediately after
giving effect to such transfer, (A) Limestone Certificates corresponding to 25%
or more (as determined under the Plan Asset Regulations) of (i) the aggregate
face amount of Limestone Certificates outstanding and (ii) any other beneficial
ownership interest in the Trust would be held by Benefit Plan Investors or (B)
there would be more than 99 PTP Relevant Persons. For purposes of making the
determination in clause (A) of the immediately preceding sentence, Limestone
Certificates held by or for the benefit of any Person (other than a Benefit Plan
Investor) that has discretionary authority or control over the assets of the
Trust or that provides investment advice for a fee (direct or indirect) with
respect to such assets, or an Affiliate of any such Person, shall be
disregarded.

                  (g) Unless and until (i) a Limestone Note Trigger Event has
occurred, (ii) a Specified Equity Event has occurred or (iii) the Earn-Out
Period Commencement Date has occurred, no Limestone Certificate may be
transferred (except in connection with the exercise of



                                       14
<PAGE>

the Limestone Certificate Purchase Right or the Certificate Purchase Option
hereunder or the Purchase Option under the Chaparral LLC Agreement) unless the
transferor provides the Trustee with a certificate of transfer stating that (x)
the transferee is not a Competitor of El Paso or (y) the consent of El Paso to
such transfer has been obtained.

                  (h) If the holder of the El Paso Interest or its designee or
assignee has given notice of the exercise of its rights under Section 7.02(a) or
(b) and has duly made the deposit of the EP Purchase Option Deposit Amount
referred to in Section 7.02, no transfer of a Limestone Certificate shall be
effective, and the Trustee shall not recognize any such transfer, unless the
holder of the El Paso Interest shall have given prior written consent to such
transfer.

                  (i) Notwithstanding anything contained herein to the contrary,
the Trustee shall not be responsible for ascertaining whether any transfer
complies with the registration provisions or exemptions from the PUHCA, the FPA,
the Securities Act, the Exchange Act, applicable state securities law or the
Investment Company Act; provided, however, that if a certificate is specifically
required to be delivered by the Trustee by a purchaser or a transferee of a
Limestone Certificate, the Trustee shall be obligated to examine such
certificate to determine whether it conforms to the requirements of this
Agreement.

                  Section 4.06. Mutilated, Destroyed, Lost or Stolen
Certificates. In case any Limestone Certificate becomes mutilated or defaced or
lost, destroyed or stolen, then on the terms herein set forth, and not
otherwise, the Trustee on behalf of the Trust shall execute, authenticate and
deliver to the registered Certificateholder a new Limestone Certificate of like
tenor and date, and bearing such identifying number or designation as the
Trustee may determine, in exchange and substitution for, and upon cancellation
of, the mutilated or defaced Limestone Certificate, or in lieu of and in
substitution for the same if lost, destroyed or stolen. The applicant for a new
Limestone Certificate pursuant to this Section 4.06 shall, in the case of any
mutilated or defaced Limestone Certificate, surrender such Limestone Certificate
to the Trustee and furnish to the Trustee, in the case of any lost, destroyed or
stolen Limestone Certificate, evidence satisfactory to the Trustee of such loss,
destruction or theft and, in each case, evidence satisfactory to the Trustee of
the ownership and authenticity of such Limestone Certificate and shall pay all
expenses and charges of such substitution and furnish such security or indemnity
as may be reasonably required by the Trustee to indemnify and defend and save
the Trustee and the Trust harmless (provided, that the unsecured agreement of
indemnity of any Certificateholder shall be deemed satisfactory, it being
understood, that the Trustee may reasonably request information necessary to
establish that any such holder is a Qualified Purchaser). Any defaced or
mutilated Limestone Certificate shall be destroyed by the Trustee, or retained
in accordance with its standard retention policy, upon delivery by it of a new
Limestone Certificate to the Certificateholder.

                  Section 4.07. Persons Deemed Owners. Prior to due presentation
of a Limestone Certificate for registration of transfer, the Trustee, the
Certificate Registrar, and any agent of the Trustee or the Certificate Registrar
may treat the Person in whose name any Limestone Certificate is registered as
the owner of such Limestone Certificate for the purpose of receiving
distributions pursuant to Section 6.03 and for all other purposes whatsoever,
and neither the Trustee, the Certificate Registrar, nor any agent of the Trustee
or the Certificate Registrar shall be affected by any notice to the contrary.



                                       15
<PAGE>

                  Section 4.08. Access to List of Certificateholders' Names and
Addresses. The Trustee shall furnish or cause to be furnished to each
Certificateholder or the holder of the El Paso Interest, within 15 days after
receipt by the Trustee of a written request therefor from such Certificateholder
or the holder of the El Paso Interest, a list, in such form as such party may
reasonably require, of the names and addresses of the Certificateholders as of
the most recent practicable date. Every Certificateholder, by receiving and
holding a Limestone Certificate, agrees that neither the Trustee nor any agent
thereof, shall be held accountable by reason of the disclosure of any such
information as to the names and addresses of the Certificateholders under this
Agreement, regardless of the source from which such information was derived.

                  Section 4.09. Maintenance of Office or Agency. The Trustee
shall maintain in Wilmington, Delaware, an office or offices or agency or
agencies where Limestone Certificates may be surrendered for registration of
transfer or exchange and where notices and demands to or upon the Trustee in
respect of the Limestone Certificates and the Transaction Documents may be
served. The Trustee initially designates Wilmington Trust Company, Rodney Square
North, 1100 North Market Street, Wilmington, Delaware 19890-0001 as its
principal corporate trust office for such purposes. The Trustee shall give
prompt written notice to the Certificateholders and the holder of the El Paso
Interest of any change in the location of the Certificate Register or any such
office of agency.

                  Section 4.10. Limestone Certificates Held by El Paso. For the
purposes of determining whether the Certificateholders of the requisite
Certificate Face Amount have taken any action authorized by this Agreement with
respect to the giving of instruction, consents or approvals or with respect to
any other matter, any Limestone Certificates actually known by a Responsible
Officer of the Trustee to be directly or indirectly owned by El Paso or any of
its Affiliates shall be disregarded and deemed not to be outstanding, unless El
Paso is the sole Certificateholder.

                  Section 4.11. ERISA Information For purposes of the
determination described in Section 4.05(f)(A), each Certificateholder that is an
insurance company will be required to promptly provide a written statement to
the Trustee setting forth (a) the then current proportion of its general account
that constitutes such plan assets and (b) other relevant information, in each
case, at any time requested by the Trustee in connection with a proposed
transfer or exchange of any Limestone Certificate and/or any proposed transfer
or exchange of any other beneficial ownership interest in the Trust. If so
requested by any Certificateholder or the holder of the El Paso Interest, the
Trustee shall request the statements referred to in the preceding sentence.
Promptly upon its receipt of any statement described in the second sentence of
this Section 4.11 or any Investment Certificate, the Trustee shall provide a
complete copy of such statement or certificate to the person making such request
and the Depositor.

                  Section 4.12. FERC Information. Each Certificateholder and any
transferee thereof will be required to provide a written statement to the
Trustee representing that:

                  (a) it is not in the business of producing, transmitting or
selling electric power;



                                       16
<PAGE>

                  (b) its principal business is other than that of a "public
utility" as that term is defined by Section 201 of the FPA and the orders of the
FERC interpreting such section; and

                  (c) it is not a "holding company" as that term is defined by
Section 2 of the PUHCA.

                                    ARTICLE V

                              THE EL PASO INTEREST

                  Section 5.01. The El Paso Interest. The El Paso Interest
represents an undivided, beneficial ownership interest in the Trust Estate;
provided, that the rights of the holder of the El Paso Interest are limited as
set forth in Sections 1.06, 5.04 and 8.05.

                  Section 5.02. Execution of El Paso Interest. On December 28,
1999, the Trustee issued and authenticated the El Paso Interest on behalf of the
Trust and delivered the certificate evidencing the El Paso Interest to El Paso.

                  Section 5.03. Transfer of El Paso Interest. The holder of the
El Paso Interest may not transfer or otherwise dispose of the El Paso Interest
without the consent of the Majority Certificateholders, except that no such
consent shall be required in connection with the transfer to a designee with
respect to, or an assignee of, the Limestone Certificate Purchase Right or the
Certificate Purchase Option. Each transferee of the El Paso Interest shall
deliver to the Trustee an appropriately completed certificate of the proposed
transferee substantially in the form set forth in Exhibit C (or in the case of
any transferee who is an Affiliate of El Paso, Exhibit B) hereto.

                  Section 5.04. Rights of Holder of El Paso Interest. (a) Until
the cancellation of all Limestone Certificates outstanding pursuant to Section
7.04, the El Paso Interest shall entitle the holder thereof only to the specific
voting rights set forth in Section 8.05 and to the Limestone Certificate
Purchase Right and the Certificate Purchase Option (and, in each case, rights of
designation and assignment with respect thereto), the other rights set forth in
Section 3.03, Section 8.05 and Article VII, and the right to receive
distributions in the circumstances set forth in Sections 5.04(b) and 5.04(c).
Notwithstanding the foregoing, the holder of the El Paso Interest shall have the
right to direct the Trustee to take any action required to be taken by Limestone
for El Paso to comply with El Paso's obligations under Section 5.1 of the
Participation Agreement. The holder of the El Paso Interest agrees to provide
the indemnities and defenses and pay the costs and expenses described in
Sections 9.07, 9.08 and 9.09.

                  (b) Immediately upon the cancellation or deemed cancellation
of all Limestone Certificates outstanding pursuant to Section 7.04, but not
before, the El Paso Interest shall be entitled to distributions from the Trust
as provided in Sections 6.03(a)(iv), 6.04(c)(v) and 10.01.

                  (c) Once (i) the holder of the El Paso Interest makes a
contribution pursuant to Section 3.03(a) and, as a result thereof, all or a
portion of the Limestone Notes have been



                                       17
<PAGE>

repaid or redeemed pursuant to the Indenture or (ii) the holder of the El Paso
Interest is deemed to make a contribution pursuant to Section 3.03(c) and all or
a portion of the New Limestone Notes have been repaid or redeemed pursuant to
the New Indenture, the El Paso Interest shall entitle the holder to the right to
receive all allocations and distributions to which the Additional Class B Member
Interest held by the Trust (pursuant to Section 3.2(b)(iii) of the Chaparral LLC
Agreement) is entitled under the Chaparral LLC Agreement; provided that no such
distribution shall be made to the holder of the El Paso Interest prior to the
cancellation or deemed cancellation of the Limestone Certificates pursuant to
Section 7.04.

                                   ARTICLE VI

                           COLLECTIONS; DISTRIBUTIONS

                  Section 6.01. Payments From Trust Estate. All payments to be
made by the Trustee on behalf of the Trust or otherwise under this Agreement or
any of the documents to which the Trust is a party shall be made only from the
income and proceeds of the Trust Estate or, in the event that the holder of the
El Paso Interest shall have made a contribution pursuant to Section 3.03 or the
Limestone Certificate Purchase Right or the Certificate Purchase Option shall
have been exercised by the holder of the El Paso Interest or its designee or
transferee, from the funds deposited with the Trustee in connection with such
contribution or exercise and only to the extent that the Trust shall have
received income or proceeds from the Trust Estate, or such deposit of a
contribution under Section 3.03 or the EP Purchase Option Deposit Amount,
respectively, as aforesaid, to make such payments in accordance with the terms
hereof.

                  Section 6.02. Establishment of Limestone Distribution Account
and Limestone Collection Account. (a)(i) The Securities Intermediary hereby
acknowledges and agrees that it has established, on the books and records of its
office in Delaware, the "Limestone Distribution Account" and the "Limestone
Collection Account" in the name of the Trust, each of which are under the
"control" (as defined in Sections 8-106 and 9-106 of the Delaware UCC) of the
Trust. In addition, the Securities Intermediary hereby agrees that (A) each of
the Limestone Distribution Account and the Limestone Collection Account is and
shall be maintained by the Securities Intermediary as, a "securities account"
(within the meaning of Section 8-501 of the Delaware UCC), (B) the "securities
intermediary's jurisdiction" (within the meaning of Article 8 of the Delaware
UCC) of the Securities Intermediary is the State of Delaware, (C) all cash and
other property in each of the Limestone Distribution Account and the Limestone
Collection Account will be treated by the Securities Intermediary as a
"financial asset" (as defined in Section 8-102(a)(9) of the Delaware UCC) for
the purposes of Article 8 of the Delaware UCC, (D) the "entitlement holder" (as
such term is defined in Section 8-102(a)(7) of the Delaware UCC) for the
purposes of Article 8 of the Delaware UCC shall be the Trust, and (E) the
Securities Intermediary shall act as a "securities intermediary" (within the
meaning of Section 8-102(a)(14) of the Delaware UCC) in maintaining the
Limestone Distribution Account and the Limestone Collection Account and shall
credit to each of the Limestone Distribution Account and the Limestone
Collection Account each financial asset to be held in or credited to each of the
Limestone Distribution Account and the Limestone Collection Account pursuant to
this Agreement. To the extent, if any, that the Trust is deemed to hold
directly, as opposed to having a security entitlement in, any financial asset
held by the Securities Intermediary for the Trust, the



                                       18
<PAGE>

Securities Intermediary hereby agrees that it is holding such financial asset as
the agent of the Trust and hereby expressly acknowledges and agrees that it has
received notification of the Trust's security interest in such financial asset
and that it is holding possession of such financial asset for the benefit of the
Trust.

                           (ii) Each of the Limestone Distribution Account and
         the Limestone Collection Account shall remain at all times with a
         securities intermediary (within the meaning of Section 8-102(a)(14) of
         the Delaware UCC) having a combined capital and surplus of at least
         $150,000,000 and having a long-term debt rating of at least "A3" by
         Moody's and at least "A-" by S&P or otherwise acceptable to such rating
         agencies. The Securities Intermediary shall give notice to the Trust of
         the location of the Limestone Distribution Account and the Limestone
         Collection Account and of any change thereof (provided that, subject to
         Section 9.10, no such change shall be made without the prior approval
         of the Trust), prior to the use thereof. Any income received by the
         Trust with respect to the balance from time to time on deposit in each
         of the Limestone Distribution Account and the Limestone Collection
         Account, including any interest or capital gains on investments in
         overnight securities made with amounts on deposit in each of the
         Limestone Distribution Account and the Limestone Collection Account,
         shall be credited to the Limestone Distribution Account or the
         Limestone Collection Account, as applicable. All right, title and
         interest in and to the cash amounts on deposit from time to time in
         each of the Limestone Distribution Account and the Limestone Collection
         Account together with any investments in overnight securities from time
         to time made pursuant to this Article VI shall constitute part of the
         Trust Estate and shall be held for the benefit of the Trust as its
         interests shall appear hereunder and shall not constitute payment of
         any obligations to which such funds are provided hereunder to be
         applied until applied thereto as hereinafter provided.

                           (iii) In the event that the Securities Intermediary
         has or subsequently obtains by agreement, operation of law or otherwise
         a security interest in the Limestone Distribution Account or the
         Limestone Collection Account, or any "financial asset" (as defined in
         Section 8-102(a)(9) of the Delaware UCC) credited thereto, or any
         "securities entitlement" (as defined in Section 8-102(a)(17) of the
         Delaware UCC) with respect thereto, the Securities Intermediary hereby
         agrees that such security interest shall be subordinate to the security
         interest of the Trust. The financial assets (as defined in Section
         8-102(a)(9) of the Delaware UCC) or any "securities entitlement" (as
         defined in Section 8-102(a)(17) of the Delaware UCC) with respect
         thereto, standing to the credit of the Limestone Distribution Account
         and the Limestone Collection Account will not be subject to deduction,
         set-off, banker's lien, or any other right in favor of any Person other
         than the Trust (except the face amount of any checks which have been
         credited to any of the Limestone Distribution Account or the Limestone
         Collection Account but are subsequently returned unpaid because of
         uncollected or insufficient funds).

                           (iv) There are no other agreements entered into
         between the Securities Intermediary and the Trust with respect to the
         Limestone Distribution Account and the Limestone Collection Account. In
         the event of any conflict between this Section 6.02(a) (or any portion
         thereof), any other provision of this Agreement or any other agreement
         now existing or hereafter entered into, the terms of this Section
         6.02(a) shall prevail.



                                       19
<PAGE>

                           (v) The Trustee shall make or direct the Securities
         Intermediary to make, to the extent required or authorized hereunder,
         withdrawals from each of the Limestone Distribution Account and the
         Limestone Collection Account: (i) to withdraw any amount deposited in
         each of the Limestone Distribution Account and the Limestone Collection
         Account and not required to be deposited therein; (ii) to make required
         payments to the parties entitled thereto pursuant to Sections 6.03 and
         6.04; and (iii) to clear and terminate each of the Limestone
         Distribution Account and the Limestone Collection Account pursuant to
         Article X.

                  (b) Unless otherwise instructed by the holder of the El Paso
Interest pursuant to Section 8.05(c) prior to the occurrence of an El Paso Debt
Obligation Repayment Event, the Trustee shall invest all funds deposited in the
Limestone Distribution Account (which shall be funds received from (i) the
Indenture Trustee pursuant to the Indenture, (ii) the New Indenture Trustee
pursuant to the New Indenture, (iii) El Paso pursuant to the Tax Indemnification
Agreement, (iv) Chaparral in respect of any Special Class A Tax Distribution
pursuant to Section 5.1(c) of the Chaparral LLC Agreement, (v) the holder of the
El Paso Interest or its designee or assignee pursuant to Section 7.02, (vi)
Chaparral in respect of the Additional Class B Member Interest, if any, held by
the Trust, (vii) the Remarketing Agents, El Paso or the Share Trust pursuant to
the Remarketing Agreement following the payment in full of the Limestone Notes,
(viii) the holder of the El Paso Interest pursuant to Section 3.03(b), (ix) the
Overfund Trust pursuant to Section 5.5(b) of the Participation Agreement upon
and after the discharge of the Indenture and (x) the Share Trust in respect of
any Redemption Proceeds pursuant to Section 4.03(a) of the Share Trust Agreement
following the payment in full of the Limestone Notes) in Financial Investments
consisting of overnight repurchase obligations for underlying securities of the
type described in clause (b) of the definition of Financial Investments that are
otherwise consistent with Financial Investments described in clause (d) of the
definition thereof until withdrawn in accordance with this Agreement. Only the
Trustee, on behalf of and for the benefit of the Trust, shall be entitled to
withdraw funds from the Limestone Distribution Account and only the Trustee
shall be an authorized signatory on the Limestone Distribution Account. The
Trustee shall withdraw funds from the Limestone Distribution Account only
pursuant to and in accordance with this Agreement.

                  (c) Unless otherwise instructed by the holder of the El Paso
Interest pursuant to Section 8.05(c) prior to the occurrence of an El Paso Debt
Obligation Repayment Event, the Trustee shall invest all funds deposited in the
Limestone Collection Account (which shall be funds received from (i) Electron in
respect of the Subsequent Certificates on the Closing Date, (ii) Chaparral in
respect of the Class A Member Interest (including in respect of any Additional
Financing Costs, any proceeds of the Asset Remedy, any proceeds of an Asset
Disposition or any proceeds of an asset sale (in connection with an enforcement
proceeding following a judgment against the Issuers) distributed to the holder
of the Class A Member Interest) other than any Special Class A Tax Distribution,
(iii) the Primary Class B Member or its designee or assignee, as Electing
Purchasers pursuant to Section 11.2 of the Chaparral LLC Agreement, (iv)
Chaparral pursuant to Section 11.1 of the Chaparral LLC Agreement, (v) the
Certificateholders pursuant to Section 3.02(d), and (vi) the holder of the El
Paso Interest pursuant to Section 3.03(a)) in Financial Investments consisting
of overnight repurchase obligations for underlying securities of the type
described in clause (b) of the definition of Financial Investments that are
otherwise consistent with Financial Investments described in clause (d) of the
definition thereof until



                                       20
<PAGE>

withdrawn in accordance with this Agreement. Only the Trustee, on behalf of and
for the benefit of the Trust, shall be entitled to withdraw funds from the
Limestone Collection Account and only the Trustee shall be an authorized
signatory on the Limestone Collection Account. The Trustee shall withdraw funds
from the Limestone Collection Account only pursuant to and in accordance with
this Agreement.

                  (d) If on any Limestone Distribution Date the Trustee
ascertains that the Available Funds in the Limestone Distribution Account or the
Limestone Collection Account, as applicable, are then insufficient to pay in
full the amount required to be paid from the Limestone Distribution Account or
the Limestone Collection Account, as applicable, then, if any investments are
held in the Limestone Distribution Account and/or the Limestone Collection
Account, as applicable, the Trustee shall sell or otherwise liquidate all or
such portion of such investments as is necessary to pay in full the required
amount. If at any time the Trustee is required to certify as to the Available
Funds in the Limestone Distribution Account and the Limestone Collection Account
in connection with the calculation of the Share Trust Amount (including any
certification pursuant to Section 6.07(c)), then the Trustee shall liquidate the
investments, if any, then held in the Limestone Distribution Account or
Limestone Collection Account up to an amount that, in the aggregate with all
other funds then held in the Limestone Distribution Account and Limestone
Collection Account, shall cause the Share Trust Amount to equal zero.

                  Section 6.03. Distributions from the Limestone Distribution
Account. The Trustee shall direct the Securities Intermediary to withdraw and
distribute all Available Funds held in the Limestone Distribution Account
pursuant to and in accordance with this Section 6.03.

                  (a) To the extent funds are received by the Trust on or prior
to 12:00 noon (New York City time) on any Limestone Distribution Date, then, on
or before 2:00 p.m. New York City time on such date, the Trustee, on behalf of
and for the benefit of the Trust, shall distribute or cause to be distributed
all Available Funds (other than funds received as a result of a distribution or
payment described in Section 6.03(b) and without duplication of payments made
under Section 6.04) then on deposit in the Limestone Distribution Account in the
following order of priority, with the amount of each such distribution (and the
components thereof) being determined by the Trustee and set forth in the related
Limestone Distribution Date Statement:

                           (i) first, pro rata to the Certificateholders, the
         accrued and unpaid Limestone Certificate Yield then due and payable in
         respect of the Limestone Certificates held by such Certificateholders
         and accrued and unpaid Default Yield with respect to any overdue
         payment of Limestone Certificate Yield, if any;

                           (ii) second, pro rata to the Certificateholders, all
         amounts the Trust is entitled to receive in respect of the Class A
         Member Interest or, when the EP Purchase Option Deposit Amount has been
         paid under Section 7.02, an amount equal to the EP Purchase Option
         Deposit Amount (in each case less any amounts distributed in accordance
         with priority first above);

                           (iii) third, until the cancellation or deemed
         cancellation of all Limestone Certificates pursuant to Section 7.04,
         any amounts remaining in the Limestone



                                       21
<PAGE>

         Distribution Account to be invested in Financial Investments; provided
         that if an El Paso Debt Obligation Repayment Event has occurred, such
         amounts shall be invested in Financial Investments other than El Paso
         Debt Obligations and commercial paper issued by El Paso; and

                           (iv) fourth, following the cancellation or deemed
         cancellation of all Limestone Certificates pursuant to Section 7.04, to
         the holder of the El Paso Interest, any remainder.

                  (b) (i) If Chaparral makes a Special Class A Tax
Distribution pursuant to Section 5.1(c) of the Chaparral LLC Agreement, (ii) El
Paso makes any payments pursuant to the Tax Indemnification Agreement, (iii) the
Trust receives any payment in respect of the Share Trust Amount from any of the
Indenture Trustee, the Share Trust, the Remarketing Agents or El Paso, or (iv)
the Trust receives any payment from the holder of the El Paso Interest pursuant
to Section 3.03(b), in each case, to the extent funds are received by the Trust
on or prior to 12:00 noon New York City time on any such date, on or before 2:00
p.m. New York City time on such date, the Trustee, on behalf of and for the
benefit of the Trust, shall distribute or cause to be distributed all Available
Funds then on deposit in the Limestone Distribution Account to the
Certificateholders (in the case of amounts described in clauses (iii) or (iv),
on a pro rata basis and first to the payment of yield as described in Section
6.03(a)(i)), with the amount of each such distribution (and the components
thereof) being determined by the Trustee and set forth in the related Limestone
Distribution Date Statement.

                  (c) Each Certificateholder shall be deemed to agree, by its
acceptance of a Limestone Certificate, that it shall promptly remit to the
Trustee for payment in accordance with this Section 6.03 any excess payment it
has received.

                  (d) All payments made to the Certificateholders on any
Limestone Distribution Date shall be made to the Certificateholders of record as
of the close of business on the last Business Day of the calendar month
immediately preceding such Limestone Distribution Date (the "Certificate Record
Date").

                  (e) The Certificateholders shall be entitled to receive
distributions hereunder on any Limestone Distribution Date or on such other date
as provided for in Section 6.03(b), by wire transfer to the account specified in
writing by the applicable Certificateholder to the Trustee. In each case, the
account must be specified in writing no later than the Certificate Record Date
for the Limestone Distribution Date on which wire transfers will commence.

                  Section 6.04. Distributions from the Limestone Collection
Account. The Trustee shall direct the Securities Intermediary to withdraw and
distribute all Available Funds on deposit from time to time in the Limestone
Collection Account pursuant to and in accordance with this Section 6.04.

                  (a) To the extent funds are received by the Trust on or prior
to 12:00 noon New York City time, on any Limestone Distribution Date prior to
the date upon which the Limestone Notes are repaid in full, then, on or before
2:00 p.m. New York City time on such date, the Trustee, on behalf of and for the
benefit of the Trust, shall distribute or cause to be



                                       22
<PAGE>

distributed all Available Funds then on deposit in the Limestone Collection
Account to the Indenture Trustee for deposit into the Indenture Collection
Account.

                  (b) Following the repayment in full of the Outstanding
Limestone Notes, but prior to the repayment in full of the New Limestone Notes,
to the extent funds are received by the Trust on or prior to 12:00 noon New York
City time, on any Limestone Distribution Date, then, on or before 2:00 p.m. New
York City time on such date, the Trustee, on behalf of and for the benefit of
the Trust, shall distribute or cause to be distributed all Available Funds then
on deposit in the Limestone Collection Account to the New Indenture Trustee for
deposit into the New Notes Account.

                  (c) Following the repayment in full of the Outstanding
Limestone Notes and the New Limestone Notes, to the extent funds are received by
the Trust on or prior to 12:00 noon New York City time on any Limestone
Distribution Date, then, on or before 2:00 p.m. New York City time on such date,
the Trustee, on behalf of and for the benefit of the Trust, shall distribute all
Available Funds then on deposit in the Limestone Collection Account in the
following order of priority, with the amount of each such distribution (and the
components thereof) being determined by the Trustee and set forth in the related
Limestone Distribution Date Statement:

                  (i) first, pro rata to the Certificateholders, the accrued and
unpaid Limestone Certificate Yield then due and payable in respect of the
Limestone Certificates held by such Certificateholders and accrued and unpaid
Default Yield, if any;

                  (ii) second, pro rata to the Certificateholders, all amounts
the Trust is entitled to receive in respect of the Class A Member Interest (less
any amounts distributed in accordance with priority first above);

                  (iii) third, to the Trustee for the payment of Administrative
Expenses;

                  (iv) fourth, until the cancellation or deemed cancellation of
all Limestone Certificates pursuant to Section 7.04, any amounts remaining in
the Limestone Collection Account to be invested in Financial Investments;
provided that if an El Paso Debt Obligation Repayment Event has occurred, such
amounts shall be invested in Financial Investments other than El Paso Debt
Obligations and commercial paper issued by El Paso; and

                  (v) fifth, following the cancellation or deemed cancellation
of all Limestone Certificates pursuant to Section 7.04, to the holder of the El
Paso Interest, any remainder.

                  Section 6.05. Limestone Distribution Date Statements. On each
Limestone Distribution Date, the Trustee shall prepare and deliver to the
Certificateholders and the holder of the El Paso Interest a statement (the
"Limestone Distribution Date Statement") setting forth for the period since the
preceding Limestone Distribution Date, as applicable (i) the amount, nature and
origin of all income, proceeds, payments and collections received in the
Limestone Distribution Account or the Limestone Collection Account, as
applicable, and (ii) the amounts to be paid or distributed pursuant to Section
6.03(a) or (b) or Section 6.04(a), (b) or (c).

                  Section 6.06. Withholding. Notwithstanding any other provision
of this Agreement to the contrary, each Certificateholder hereby authorizes the
Trustee to withhold and



                                       23
<PAGE>

to pay over any taxes (including any interest or penalties related thereto)
payable by the Trust as a result of such Certificateholder's participation in
the Trust. The Trustee will give each such Certificateholder at least five (5)
days notice prior to any such withholding. If and to the extent that the Trust
shall be required to withhold any such taxes (including any interest or
penalties related thereto), such Certificateholder shall, in the sole discretion
of the Trustee, (i) pay the amount of such withholding to the Trust within five
(5) days of being notified in writing of the amount to be withheld by the Trust
or (ii) be deemed for all purposes of this Agreement to have received a payment
from the Trust as of the time such withholding is required to be paid, which
payment shall be deemed to be a distribution to the extent that the
Certificateholder is then entitled to receive a distribution. To the extent that
the aggregate of such payments to a Certificateholder for any fiscal period
exceeds the distributions to which such Certificateholder is entitled for such
period, the amount of such excess shall be considered a loan from the Trust to
such Certificateholder, with interest at 10.35% per annum (which interest shall
be treated as an item of Trust income), until discharged by such
Certificateholder by repayment directly or out of distributions to which such
Certificateholder would otherwise subsequently be entitled. The withholdings
referred to in this Section 6.06 shall be made at the maximum applicable
statutory rate under the applicable tax law unless the Trustee shall have
received an opinion of counsel or other evidence, satisfactory to the Trustee,
to the effect that a lower rate is applicable, or that no withholding is
applicable.

                  Section 6.07. Information Provided by the Trustee. (a) The
Trustee shall provide to the Indenture Trustee and the New Indenture Trustee, if
applicable, promptly upon receipt any information which the Trust receives from
Chaparral in connection with any distribution in accordance with the Chaparral
LLC Agreement, including notice with respect to the use of any such distribution
to cause an Optional Redemption or Mandatory Redemption of the Limestone Notes
or the New Limestone Notes, or both.

                  (b) The Trustee shall provide to the Managing Member, promptly
upon receipt of written notice from Electron, written notice of any reduction in
the amount of the Limestone Equity Cash Component or Limestone Equity PIK
Component.

                  (c) The Trustee shall, upon the written request of the
Remarketing Agents or El Paso, promptly (but in any event within five Business
Days of such request) deliver to the Remarketing Agents, the Indenture Trustee
and El Paso an Officer's Certificate setting forth the amount of Available Funds
then on deposit in the Limestone Collection Account and the Limestone
Distribution Account (after giving effect to any liquidation of investments that
is required to be made pursuant to the last sentence of Section 6.02(d)), which
certification shall be used in connection with the calculation of the Share
Trust Amount, and hereby undertakes to notify the Remarketing Agents, the
Indenture Trustee and El Paso if any such amount should change prior to the Rate
Reset Date.

                  (d) The Trustee shall provide to the holder of the El Paso
Interest and the Share Trustee written notice of (i) the receipt by the
Certificateholders of proceeds of Collections received by the Trustee from the
Share Trust in an aggregate amount equal to the amount of the aggregate proceeds
received by the Noteholders from the Asset Remedy, any Asset Disposition or
asset sales (in connection with an enforcement proceeding following a judgment
against the Issuers) (in each case, as such amounts are certified by the
Indenture Trustee), (ii) the occurrence



                                       24
<PAGE>

of the Final Payment Date, if such date occurs after the satisfaction and
discharge of the Indenture, and (iii) the date on which the Share Trust Amount
equals zero, if such date occurs after the satisfaction and discharge of the
Indenture, in each case, promptly upon such receipt by the Certificateholders or
such occurrence, as the case may be (but in any event within five Business Days
after such receipt or occurrence).

                  (e) Upon the distribution to the Indenture Trustee of any
contributions received by the Trust pursuant to Sections 3.02(d) and 3.03(a)
which the Trustee has been notified are to be used to cause an Optional
Redemption of the Limestone Notes, the Trustee shall provide notice to the
Indenture Trustee that such amounts distributed to the Indenture Trustee are to
be used to cause an Optional Redemption of the Limestone Notes.

                  (f) Upon the repayment in full of the New Limestone Notes, if
any proceeds from the Asset Remedy, an Asset Disposition or asset sales (in
connection with an enforcement proceeding following a judgment against the
Issuers) were used to repay the New Limestone Notes, the Trustee shall provide
to the holder of the El Paso Interest a notice requesting payment pursuant to
Section 3.03(b), which notice shall include, to the extent applicable, (i) the
amount of proceeds from the Asset Remedy, Asset Disposition or asset sales (in
connection with an enforcement proceeding following a judgment against the
Issuers) received by the Trustee from Chaparral pursuant to the Chaparral LLC
Agreement, (ii) the amount of such proceeds distributed to the New Indenture
Trustee pursuant to Section 6.04(b) and (iii) any amounts received from the New
Indenture Trustee and deposited into the Limestone Distribution Account after
the repayment in full of the New Limestone Notes.

                  (g) Upon the occurrence of a Specified Equity Event and the
Trustee's receipt of written notice thereof from any Certificateholder, the
Trustee shall deliver a written notice (an "Equity Event Notice") to El Paso,
the Indenture Trustee (so long as any Limestone Notes are outstanding) and the
New Indenture Trustee (so long as any New Limestone Notes are outstanding),
which shall specifically state that it is an Equity Event Notice and that upon
the Trustee's receipt of proceeds from an Asset Disposition or, after the
satisfaction and discharge of the Indenture, proceeds from the exercise of the
Asset Remedy in connection with such Specified Equity Event, the Limestone Notes
and the New Limestone Notes will be subject to a Special Redemption in
accordance with Article XV of the Indenture and Article XV of the New Indenture,
as applicable.

                  Section 6.08. Limitations on Distributions to the
Certificateholders. For the avoidance of doubt, in no event shall the
Certificateholders receive distributions from the Trust in an amount exceeding
the Certificate Purchase Amount at any time; provided that, for purposes of this
Section 6.08, such distributions shall be deemed to exclude any indemnity or
expense reimbursement payments to which any Indemnified Persons are entitled
pursuant to any of the Transaction Documents.



                                       25
<PAGE>

                                   ARTICLE VII

         LIMESTONE CERTIFICATE TRIGGER EVENTS; SPECIFIED EQUITY EVENTS;
       LIMESTONE CERTIFICATE PURCHASE RIGHT; CERTIFICATE PURCHASE OPTION;
                                EARN-OUT PERIOD;
                     CANCELLATION OF LIMESTONE CERTIFICATES

                  Section 7.01. Consequences of a Limestone Certificate Trigger
Event or Specified Equity Event. (a) Until the Limestone Notes have been repaid
in full, upon the occurrence of a Limestone Certificate Trigger Event, the
Required Certificateholders shall have the right to direct the Indenture Trustee
to commence the Asset Remedy. Such Asset Remedy shall be exercised in accordance
with (i) Section 9.04(g) of the Indenture and (ii) Section 11.3 of the Chaparral
LLC Agreement, and any proceeds therefrom received by the Trust, as Class A
Member of Chaparral, shall be deposited into the Limestone Collection Account
and applied in accordance with Section 6.04 of this Agreement.

                  (b) After the Limestone Notes have been repaid in full, upon
the occurrence of a Specified Equity Event, the Required Certificateholders
shall have the right to direct the Trustee to commence the Asset Remedy;
provided that the Trustee may pursue the Asset Remedy only if (i) the Required
Certificateholders shall have directed the Trustee to commence the Asset Remedy
and delivered a copy of such direction to El Paso, (ii) the Special Management
Standstill Expiration Date shall have occurred without the Specified Equity Cure
occurring on or before the 30th day after the relevant Specified Equity Event
and (iii) the holder of the El Paso Interest has not consummated the Certificate
Purchase Option pursuant to Section 7.02(b). Such Asset Remedy shall be
exercised in accordance with Section 11.3 of the Chaparral LLC Agreement, and
any proceeds therefrom received by the Trust, as Class A Member of Chaparral,
shall be deposited into the Limestone Collection Account and applied in
accordance with Section 6.04(b) or Section 6.04(c), as applicable, of this
Agreement.

                  (c) Upon the occurrence of a Specified Equity Event, the
Required Certificateholders shall have the right to direct the Trustee to
exercise the rights of Limestone under Section 6.1(a) of the Chaparral LLC
Agreement in connection with such Specified Equity Event; provided that the
Trustee may exercise the rights of Limestone under Section 6.1(a) of the
Chaparral LLC Agreement only if (i) the Required Certificateholders shall have
directed the Trustee to exercise the rights of Limestone under Section 6.1(a) of
the Chaparral LLC Agreement in connection with such Specified Equity Event and
delivered a copy of such direction to El Paso, (ii) the Special Management
Standstill Expiration Date shall have occurred without the Specified Equity Cure
occurring on or before the 30th day after the relevant Specified Equity Event
and (iii) the holder of the El Paso Interest has not consummated the Certificate
Purchase Option pursuant to Section 7.02(b). If, as a result of or following
such exercise, an Asset Disposition has been consummated, any proceeds therefrom
received by the Trust, as Class A Member of Chaparral, shall be deposited into
the Limestone Collection Account and applied in accordance with Section 6.04(b)
or Section 6.04(c), as applicable, of this Agreement.

                  Section 7.02. Limestone Certificate Purchase Right;
Certificate Purchase Option. (a) The holder of the El Paso Interest or its
designees or assigns shall have the right (the "Limestone Certificate Purchase
Right"), concurrently with the repayment, at maturity or



                                       26
<PAGE>

otherwise, of the principal of the Limestone Notes and the New Limestone Notes
(in each case, to the extent then Outstanding), to purchase or cause a third
party to purchase the outstanding Limestone Certificates at a purchase price
(the "EP Purchase Option Deposit Amount") equal to the Certificate Purchase
Amount. The holder of the El Paso Interest or its designees or assigns shall
exercise such right by providing written notice of such exercise to the
Certificateholders and the Trustee within 10 days of the event giving rise to
the Limestone Certificate Purchase Right, which notice shall be irrevocable, and
by depositing or causing the deposit of the EP Purchase Option Deposit Amount
within 90 days of such notice in the Limestone Distribution Account to be
distributed to the Certificateholders in accordance with Section 6.03(a).

                  (b) The holder of the El Paso Interest or its designees
or assigns shall have the option at any time (the "Certificate Purchase Option")
to purchase or cause a third party to purchase the outstanding Limestone
Certificates at a price equal to the EP Purchase Option Deposit Amount. The
holder of the El Paso Interest or its designees or assigns shall exercise such
right by (i) providing written notice of such exercise to the Certificateholders
and the Trustee, which notice shall be irrevocable, no later than the earliest
to occur of (A) if a Specified Equity Event has occurred, the earlier of the
Special Management Replacement Date and the date on which Limestone, as Class A
Member, shall have delivered an Asset Remedy Notice pursuant to Section 11.3 of
the Chaparral LLC Agreement and such Asset Remedy Notice shall have become
effective pursuant to Section 11.3(a)(i) of the Chaparral LLC Agreement and (B)
the date on which Limestone, as Class A Member, shall have delivered a
Liquidation Notice pursuant to Section 12.10 of the Chaparral LLC Agreement and
such Liquidation Notice shall have become effective pursuant to Section 12.10(a)
of the Chaparral LLC Agreement and (ii) depositing or causing the deposit of the
EP Purchase Option Deposit Amount in the Limestone Distribution Account on or
prior to 12:00 noon New York City time on the date that is not more than five
Business Days after the earliest to occur of the dates referred to in clauses
(A) and (B) herein, to be distributed to the Certificateholders in accordance
with Section 6.03(a).

                  Section 7.03. Earn-Out Period. If the holder of the El Paso
Interest or its designee or assign has not (i) deposited the EP Purchase Option
Deposit Amount on or prior to the 90th day following notice of its exercise of
the Limestone Certificate Purchase Right in accordance with Section 7.02(a),
(ii) given notice of its exercise of the Limestone Certificate Purchase Right
within 10 days after the occurrence of the Earn-Out Period Commencement Date or
(iii) prior to the Earn-Out Period Commencement Date but after the satisfaction
and discharge of the Indenture and the New Indenture, and after the occurrence
of a Specified Equity Event, deposited the EP Purchase Option Deposit Amount on
or prior to the Special Management Standstill Expiration Date for such Specified
Equity Event, the Required Certificateholders shall have the right to direct the
Trustee to exercise the rights of the Trust as holder of the Class A Member
Interest, including, to cause an Asset Remedy Notice to be delivered to
Chaparral from time to time in accordance with Section 11.3(b) of the Chaparral
LLC Agreement and to cause the liquidation and sale of the assets of Chaparral
pursuant to Section 12.10(b) of the Chaparral LLC Agreement. Any proceeds from
the sale of the assets of Chaparral paid to the Trust as holder of the Class A
Member Interest and any distributions from Chaparral in respect of the Class A
Member Interest during the Earn-Out Period shall be deposited in the Limestone
Collection Account and applied in accordance with Section 6.04(b) or Section
6.04(c), as applicable.



                                       27
<PAGE>

                  Section 7.04. Cancellation of Limestone Certificates. (a)
Subject to Section 7.04(b) below, after the repayment in full of the Outstanding
Limestone Notes and the New Limestone Notes, upon the receipt by any
Certificateholder of such Certificateholder's Proportionate Interest of the
Certificate Purchase Amount, either as a result of distributions pursuant to
this Agreement or payments to which such Certificateholder is entitled pursuant
to any other Transaction Document, in each case attributable to the Limestone
Certificate(s) held by such Certificateholder, (i) such Limestone Certificate(s)
shall be deemed to be no longer outstanding for purposes of this Agreement, (ii)
such Certificateholder's right to receive distributions under Article VI shall
immediately terminate and (iii) such Certificateholder shall, within five
Business Days after request by the holder of the El Paso Interest, deliver its
original Limestone Certificate(s) to the Trustee, and such Limestone
Certificate(s) shall be immediately cancelled by the Trustee; provided that, for
all purposes of this Agreement, such Limestone Certificate(s) shall be deemed to
have been cancelled on the date on which the applicable Certificateholder
received its Proportionate Interest of the Certificate Purchase Amount; provided
further that such cancellation or deemed cancellation shall not affect such
Certificateholder's rights to indemnity or reimbursement. Upon cancellation (or
deemed cancellation) of any Limestone Certificate pursuant to this Section 7.04,
the Trustee shall promptly (but in any event, within five Business Days after
request therefor by the holder of the El Paso Interest) deliver a certificate of
the Trustee to each of the Indenture Trustee, the Share Trustee, the Overfund
Trustee, the Management Company and the holder of the El Paso Interest,
certifying (x) as to the aggregate Certificate Face Amount of the Limestone
Certificate(s) so cancelled and (y) as to the aggregate Certificate Face Amount
of all outstanding Limestone Certificates (after giving effect to such
cancellation) (or, if all outstanding Limestone Certificates shall have been
cancelled or deemed cancelled, certifying as to such cancellation).

                  (b) Notwithstanding Section 7.04(a) above, a
Certificateholder's Limestone Certificates shall not be cancelled upon receipt
by such Certificateholder of its Proportionate Interest of the Certificate
Purchase Amount if such receipt was as a result of the exercise of the Limestone
Certificate Purchase Right or the Certificate Purchase Option; provided that if
El Paso or any Affiliate of El Paso acquires any Limestone Certificates through
the exercise of the Limestone Certificate Purchase Right or the Certificate
Purchase Option, such Person shall have the option to deliver its Limestone
Certificates to the Trustee for cancellation.

                                  ARTICLE VIII

                     RIGHTS, OBLIGATIONS, POWERS AND STATUS
                            OF THE CERTIFICATEHOLDERS
                     AND THE HOLDER OF THE EL PASO INTEREST

                  Section 8.01. Management of the Trust. It is the intention of
the parties hereto and the Certificateholders by their acceptance thereof shall
be deemed to agree, that the Trustee's duties are to be ministerial in nature
only. Subject to Article VII, Sections 8.05 and 10.01(a) hereof, the
Certificateholders (or the portion thereof as provided herein) shall have the
exclusive right and obligation to determine the matters herein referenced to be
determined by the Certificateholders and to direct the Trustee to carry out and
accomplish such matters, and the Certificateholders, in that capacity, subject
to the provisions of the Act, the other provisions of



                                       28
<PAGE>

this Agreement and the Transaction Documents, shall direct the management of the
business and affairs of the Trust, in a manner consistent with the provisions of
this Agreement and the Act in order best to carry out the Trust's purposes.

                  Section 8.02. Bankruptcy, Dissolution or Termination of any
Certificateholder. The incapacity, dissolution, termination or bankruptcy of any
Certificateholder shall not result in the termination or dissolution of the
Trust.

                  Section 8.03. Creditors of the Certificateholders. As is
provided in paragraph (b) of Section 3805 of the Act, no creditor of a
Certificateholder shall have any right to obtain possession of, or otherwise
exercise legal or equitable remedies with respect to, the Trust Estate.

                  Section 8.04. Certain Rights of the Majority
Certificateholders. Subject to Section 8.05, the Majority Certificateholders
shall have the right to direct the following matters on behalf of all
Certificateholders:

                  (a) directing the Trustee in accordance with Sections 8.01 and
9.01(d) (including directing the Trustee to exercise the rights of the
beneficial owner of the Class A Member Interest under Section 7.4 of the
Chaparral LLC Agreement);

                  (b) instructing the Trustee to amend the Certificate of Trust
or this Agreement in accordance with Sections 9.03(a) or 12.04;

                  (c) appointing a replacement Trustee pursuant to Section 9.05;
and

                  (d) instructing the Trustee to appear in, prosecute or defend
any action in accordance with Section 9.09(a).

                  Section 8.05. Voting and Other Rights of the Holder of the El
Paso Interest. (a) Notwithstanding anything in this Agreement to the contrary,
the following actions by the Trust will require the prior written consent of the
holder of the El Paso Interest:

                  (i) the dissolution, liquidation, consolidation or merger of
the Trust (with or into any other person) or the sale of all or substantially
all of the Trust Estate;

                  (ii) the taking of any Bankruptcy Action with respect to the
Trust;

                  (iii) the amendment of any Transaction Document to which the
Trust is a party (including any amendment to this Agreement or the Certificate
of Trust);

                  (iv) the repudiation by the Trust of any of the Transaction
Documents (other than any action provided for in Section 7.03, to the extent
such action constitutes a repudiation); and

                  (v) the replacement of the Trustee pursuant to Section 9.05.

                  (b) The holder of the El Paso Interest will have no other
voting rights until the earlier to occur of (i) the purchase of all of the
outstanding Limestone Certificates pursuant to



                                       29
<PAGE>

Section 7.02 or (ii) the cancellation of all of the Limestone Certificates
pursuant to Section 7.04. Upon any such purchase or cancellation of all
outstanding Limestone Certificates, the holder of the El Paso Interest shall
have the exclusive right to exercise all voting rights hereunder and to deliver
all instructions to the Trustee in connection with this Agreement.

                  (c) Until the occurrence of an El Paso Debt Obligation
Repayment Event, the holder of the El Paso Interest shall have the right to
direct, by written notice to the Trustee signed by a Responsible Officer of El
Paso, the investment of the Available Funds in the Limestone Distribution
Account and the Limestone Collection Account, in Financial Investments.

                  (d) The holder of the El Paso Interest shall have the
exclusive right to direct, by written notice to the Trustee signed by an
Authorized Officer of El Paso, the amendment of Sections 7.01(cc), (dd), (ee),
(ff) and (gg) of the New Indenture (provided that such amendments are not
inconsistent with and do not attempt to override any other provision of any
Transaction Document), and the Certificateholders shall have no right to direct
any such amendment or consent to any such amendment.

                                   ARTICLE IX

CONCERNING THE TRUSTEE, THE SECURITIES INTERMEDIARY AND WILMINGTON TRUST COMPANY

                  Section 9.01. General. (a) In the exercise or administration
of the Trust hereunder (and, without limitation, with respect to taking any
action pursuant to the terms of paragraph (a) of Section 10.01), the Trustee at
the expense of the Trust (to be paid as provided in Section 9.08) may (i) act
directly or through agents or attorneys pursuant to agreements entered into with
any of them, and the Trustee shall not be liable for the default or misconduct
of such agents or attorneys if such agents or attorneys shall have been selected
by the Trustee with reasonable care, and (ii) consult with counsel, accountants
and other skilled Persons to be selected with reasonable care and employed by
the Trustee, and it shall not be liable for anything done, suffered or omitted
in good faith by it in accordance with the advice or opinion of any such
counsel, accountants or other skilled Persons.

                  (b) Except as expressly provided herein, (i) in accepting the
Trust hereby continued, Wilmington Trust Company acts solely as Trustee
hereunder and not in its individual capacity, and (ii) all Persons having any
claim against the Trust or the Trustee by reason of the transactions
contemplated by this Agreement shall look only to the Trust's property for
payment or satisfaction thereof.

                  (c) Except in accordance with the written instructions
furnished by the Required Certificateholders or except as provided herein, the
Trustee shall have no duty to (i) see to any recording or filing of any
document, or (ii) see to the payment or discharge of any tax, assessment or
other governmental charge or any lien or encumbrance of any kind owing with
respect to, assessed or levied against any part of the Trust.



                                       30
<PAGE>

                  (d) The Trustee will administer the business and affairs of
the Trust in accordance with the terms of the Act and the Transaction Documents
to which the Trust is a party; provided, however, that the Trustee undertakes to
perform only such duties as are specifically set forth in this Agreement and as
the Trustee may be duly directed from time to time in writing by the Majority
Certificateholders in accordance with and subject to the Transaction Documents
to which the Trust is a party and as the Trustee is required to in order to
comply with the Transaction Documents to which the Trust is a party. The Trustee
shall not have any duty or obligation to manage, control, use, sell, dispose of
or otherwise deal with the Trust or to otherwise take or refrain from taking any
action under this Agreement or the other Transaction Documents to which the
Trust is a party except as expressly required by the terms hereof (or of the
Transaction Documents to which the Trust is a party) or as expressly provided in
written instructions from the Majority Certificateholders, and no implied duties
or obligations shall be read into this Agreement against the Trustee. Wilmington
Trust Company nevertheless agrees that it will, at its own cost and expense (and
not at the expense of the Trust), promptly take all action as may be necessary
to discharge any Liens on any part of the Trust Estate which are attributable to
actions by or claims against Wilmington Trust Company that are not related to
the ownership of any part of the Trust Estate or the administration of the Trust
Estate or the transactions contemplated by this Agreement.

                  (e) The Trustee shall not be required to take any action under
this Agreement if the Trustee shall reasonably determine or shall have been
advised by counsel that such action is contrary to the terms of this Agreement
or is otherwise contrary to Applicable Law.

                  (f) Subject to paragraph (a) of Section 10.01, whenever the
Trustee is unable to decide between alternative courses of action permitted or
required by the terms of this Agreement, or is unsure as to the application,
intent, interpretation or meaning of any provision hereof, the Trustee may give
notice (in such form as shall be appropriate under the circumstances) to the
Certificateholders and, in any circumstance contemplated in Section 8.05, the
holder of the El Paso Interest, requesting written instructions as to the course
of action to be adopted, and, to the extent the Trustee acts in good faith in
accordance with any such appropriate instruction received from the Required
Certificateholders, the Trustee shall not be liable on account of such action or
inaction to any Person. If the Trustee shall not have received appropriate
instructions within ten days of such notice (or within such shorter period of
time as reasonably may be specified in such notice or may be necessary under the
circumstances), it may, but shall be under no duty to, take or refrain from
taking such action which is consistent, in its view, with this Agreement and as
it shall deem to be in the best interests of the Certificateholders and, in any
circumstance contemplated in Section 8.05, the holder of the El Paso Interest,
and the Trustee shall have no liability to any Person for any such action or
inaction.

                  (g) In no event whatsoever shall the Trustee be liable for any
representation, warranty, covenant, agreement, indebtedness or other obligation
of the Trust; provided, however, the foregoing shall, in no event whatsoever,
relieve the Trustee from any liability resulting from the Trustee's bad faith,
willful misconduct or gross negligence.

                  (h) The Trustee may rely upon and shall incur no liability to
anyone in acting upon any signature, instrument, notice, resolution, request,
consent, order, certificate, report,



                                       31
<PAGE>

opinion, bond or other document or paper reasonably believed by it to be genuine
and reasonably believed by it to be signed by the proper party or parties. The
Trustee may accept a certified copy of a resolution of the board of directors or
other governing body of any corporate party as conclusive evidence that such
resolution has been duly adopted by such body and that the same is in full force
and effect. As to any fact or matter the manner of ascertainment of which is not
specifically prescribed herein, the Trustee may for all purposes hereof rely on
a certificate, signed by the president or any vice president or by the treasurer
or any assistant treasurer or the secretary or any assistant secretary (or
equivalent position) of the relevant party, as to such fact or matter, and such
certificate shall constitute full protection to the Trustee for any action taken
or omitted to be taken by it in good faith reliance thereon.

                  (i) The Trustee shall not be personally liable for any error
of judgment made in good faith by a Responsible Officer of the Trustee.

                  (j) The Trustee shall not be required to take any action that
is inconsistent with the purposes of the Trust set forth in Section 1.04.

                  (k) No provision of this Agreement shall require the Trustee
to expend or risk its personal funds, or otherwise incur any financial liability
in the performance of its rights or powers hereunder, if the Trustee shall have
reasonable grounds for believing that repayment of such funds or adequate
indemnity against such risk or liability is not reasonably assured or provided
to it.

                  (l) The Trustee may fully rely upon and shall have no
liability in connection with calculations or instructions forwarded to the
Trustee by the Certificateholders, unless the Trustee determines that such
calculations or instructions are in error; provided, however, the Trustee shall
have no obligation to make any such determination.

                  (m) The Trustee shall not have any responsibility or liability
for or with respect to the genuineness, value, sufficiency or validity of the
Trust Estate. The Trustee shall in no event assume or incur any liability, duty
or obligation to the Depositor, the Certificateholders or any other Person other
than as expressly provided for herein, and in no event shall the Trustee have
any implied duties or obligations hereunder.

                  (n) The Trustee shall incur no liability if, by reason of any
provision of any future law or regulation thereunder, the Trustee shall be
prevented or forbidden from doing or performing any act or thing which the terms
of this Agreement provide shall or may be done or performed.

                  Section 9.02. Acceptance of the Trust. Wilmington Trust
Company declares that it accepts the Trust hereby continued and agrees to
perform its duties under this Agreement and the Act but only upon the terms of
this Agreement as contemplated by the Transaction Documents.

                  Section 9.03. Authority and Duties of the Trustee. (a) The
Trustee is authorized and directed to execute and deliver this Agreement, the
Participation Agreement, the Chaparral LLC Agreement, the Indenture, the
Security Agreement, the Remarketing Agreement, the Closing Agreement, the Dealer
Manager Agreement, the New Indenture, any other Transaction



                                       32
<PAGE>

Document to which the Trust or the Trustee is a party, and each certificate or
other document attached as an exhibit to or contemplated by any such agreement,
which agreements, or amendments thereto, as applicable (other than the
Commencement Date Documents), may be declared effective by the Trustee upon
receipt of notice from the Certificateholders that all conditions precedent set
forth in Section 5 of the Closing Agreement have been satisfied. The execution
and delivery of, and performance of the terms of, the Participation Agreement,
the Chaparral LLC Agreement, the Indenture, the Security Agreement, the
Remarketing Agreement, the Closing Agreement, the Dealer Manager Agreement, the
New Indenture and each certificate of other document attached as an exhibit to
or otherwise expressly contemplated by any such agreement shall be deemed not to
conflict with or constitute a breach or default under this Agreement. The
Trustee shall have only such authority and duties as are expressly set forth in
this Agreement. Subject to Sections 10.02 and 12.04, the Trustee shall, upon the
written instruction of the Majority Certificateholders (and the holder of the El
Paso Interest with respect to clause (i) below), (i) amend the Certificate of
Trust or this Agreement and (ii) execute, acknowledge, deliver, file or record
any document or instrument necessary or appropriate to carry out the provisions
of this Agreement, the Participation Agreement, the Chaparral LLC Agreement, the
Indenture, the Security Agreement, the Remarketing Agreement, the Closing
Agreement, the Dealer Manager Agreement or the New Indenture in such form as is
provided to it; provided that such action does not alter the rights, powers and
duties of the Trustee as set forth in this Article IX.

                  (b) The Trustee shall have the power and authority to execute,
deliver, acknowledge and file all necessary documents and to maintain all
necessary records of the Trust as required by the Act.

                  (c) In the performance of its duties under this Agreement, the
Trustee may rely on any document believed by it to be genuine and to have been
signed or presented by the proper Person. The Trustee need not investigate any
fact or matter stated in any such document, but the Trustee, in its discretion,
may make further inquiry or investigation.

                  (d) The Trustee shall cause to be prepared and filed, such tax
returns and Periodic Filings relating to the Trust, and make such elections as
may from time to time be required or appropriate under any applicable Federal,
state or local tax statute or rule or regulation thereunder so as to maintain to
the extent possible the Trust's characterization set forth in Section 12.07.

                  (e) Subject to the provisions of any applicable
confidentiality agreement to which the Trust is or becomes a party, the Trustee
shall furnish to the Certificateholders and the holder of the El Paso Interest,
promptly upon receipt thereof, duplicates or copies of all reports, notices,
requests, demands, certificates, financial statements and any other instruments
furnished to the Trustee hereunder, under the Participation Agreement (other
than the information the Trustee is deemed to have received under Section
5.1(e)(i), (ii), (iii), or (iv) of the Participation Agreement), or under any
other Transaction Document to which the Trust is a party, provided that the
Trustee shall not be required to furnish the Certificateholders with a copy of
any such materials if the Trustee determines that such party has otherwise
received such copies, unless such Certificateholder so requests.



                                       33
<PAGE>

                  Section 9.04. Representations and Warranties of Wilmington
Trust Company. Wilmington Trust Company, in its individual capacity, hereby
represents and warrants to the holder of the El Paso Interest and the
Certificateholders from time to time that, as of the date hereof and as of the
Effective Date:

                  (a) it is duly incorporated, validly existing and in good
         standing under the laws of its jurisdiction of incorporation;

                  (b) it is has the corporate power and authority to execute,
         deliver and perform its obligations under this Agreement, and this
         Agreement has been duly authorized by it by all necessary corporate
         action;

                  (c) no authorization, consent or approval of any governmental
         authority, regulatory body or other Person is required for the due
         authorization, execution, delivery or performance by it of this
         Agreement (other than the filing of the Certificate of Trust);

                  (d) this Agreement has been duly executed and delivered by it
         and (subject to the due execution and delivery hereof by the holder of
         the El Paso Interest and the Certificateholders) constitutes a legal
         and binding obligation of it, enforceable against it in accordance with
         its terms, except as enforceability may be limited by applicable
         bankruptcy, insolvency, reorganization, moratorium or other similar
         laws now or hereinafter in effect, relating to the enforcement of
         creditors' rights in general and except as such enforceability may be
         limited by general principles of equity (whether considered in a
         proceeding at law or in equity); and

                  (e) it complies with all the requirements of the Act relating
         to the qualification of a trustee of a Delaware business trust.

                  Section 9.05. Resignation of the Trustee. (a) The Trustee may
resign by giving 60 days' prior written notice to the Certificateholders and the
holder of the El Paso Interest. In the case of the resignation of the Trustee,
the Majority Certificateholders shall, with the consent of the holder of the El
Paso Interest, appoint a Person to serve as successor Trustee, provided, that
such Person shall in all respects satisfy the requirements of Section 3807 of
the Act, or any successor provision, and shall be a bank or trust company
incorporated and doing business within the United States of America, whose
business shall consist at least in part as serving as trustee in asset
securitization transactions and having a combined capital and surplus of at
least $150,000,000, if there be such an institution willing, able and legally
qualified to perform the duties of the Trustee hereunder upon reasonable or
customary terms. The appointment of the successor Trustee shall take effect
concurrently with (i) the resignation of the former Trustee and (ii) the
ratification of the Transaction Documents by the successor trustee, and no
resignation of a Trustee shall be effective absent the concurrent appointment of
a successor Trustee.

                  (b) If a successor Trustee shall not have been appointed
within 60 days after such notice of resignation, the Trustee or the Required
Certificateholders may apply to any court of competent jurisdiction to appoint a
successor Trustee to act until such time as a successor shall have been
appointed as above provided.



                                       34
<PAGE>

                  (c) Any corporation into which the Trustee may be merged or
converted or with which it may be consolidated, or any corporation resulting
from any merger, conversion or consolidation to which the Trustee shall be a
party, or any corporation to which substantially all the corporate trust
business of the Trustee may be transferred, shall, subject to such corporation
satisfying in all respects the requirements set forth in Section 9.05(a), be the
Trustee hereunder without further action.

                  (d) Upon the substitution of the Person serving as Trustee,
the successor Trustee, and, if necessary, the holder of the El Paso Interest and
the Required Certificateholders shall file an amendment to the Certificate of
Trust with the Secretary of State in accordance with the provisions of Section
3810 of the Act, indicating the change in the Trustee.

                  Section 9.06. Liability. Wilmington Trust Company shall not be
personally liable under any circumstances, except (a) for its own bad faith,
willful misconduct or gross negligence, (b) in the case of the inaccuracy of any
representation or warranty contained in Section 9.04, (c) for liabilities
arising from the failure by Wilmington Trust Company to perform obligations
expressly undertaken by it in the last sentence of Section 9.01(d) or (d) for
taxes, fees or other charges on, based on or measured by any fees, commissions
or compensation received by the Trustee in connection with any of the
transactions contemplated by this Agreement. In particular, but not by way of
limitation:

                  (i) the provisions of this Agreement, to the extent that they
         restrict the duties and liabilities of Wilmington Trust Company
         otherwise existing at law or in equity, replace such other duties or
         liabilities of Wilmington Trust Company to the extent permissible under
         law or in equity and

                  (ii) Wilmington Trust Company shall not be personally liable
         for the default or misconduct of the Certificateholders.

                  Section 9.07. Indemnification. The holder of the El Paso
Interest shall indemnify, pay, protect, and hold harmless each of Wilmington
Trust Company, its officers, directors, employees, shareholders and agents
(collectively, the "Indemnified Trustee Persons" or individually an "Indemnified
Trustee Person") from and against any and all liabilities, obligations, losses,
damages, actions, judgments, suits, proceedings, taxes, costs, expenses and
disbursements of any kind or nature whatsoever including, without limitation,
all reasonable legal fees, third party costs and expenses of defense, appeal and
settlement of any and all suits, actions, or proceedings instituted against such
Indemnified Trustee Person or the Trust and all reasonable third party costs of
investigation in connection therewith that may be imposed on, incurred by, or
asserted against an Indemnified Trustee Person relating to or arising out of any
action or inaction on the part of the Trust or an Indemnified Trustee Person in
respect of the Trust. Notwithstanding the foregoing, the holder of the El Paso
Interest shall not be liable to any such Indemnified Trustee Person for any of
the matters set forth in clauses (a) through (d) of the first sentence of
Section 9.06. If any action, suit, or proceeding shall be pending against the
Trust and/or one or more Indemnified Trustee Persons relating to or arising out
of any action or inaction of the Indemnified Trustee Person or Indemnified
Trustee Persons, the holder of the El Paso Interest shall have the right to
assume the defense of the Indemnified Trustee Person or Indemnified Trustee
Persons in which case such defense shall be conducted by counsel chosen



                                       35
<PAGE>

by the holder of the El Paso Interest and reasonably satisfactory to the
Indemnified Trustee Person or Indemnified Trustee Persons; provided, however,
that if an Indemnified Trustee Person is advised by its counsel that due to
actual or potential conflicting interests representation by the same counsel
would be inappropriate under applicable standards of professional conduct, such
Indemnified Trustee Person may, at the expense of the Trust, employ separate
counsel of its choice with respect to which such conflicting interest arise in
any such action. The indemnities contained in this Section 9.07 shall survive
the resignation of the Trustee, the termination of the Trust or the termination
of this Agreement.

                  Section 9.08. Fees and Expenses. All reasonable out-of pocket
expenses, disbursements and advances incurred or made by Wilmington Trust
Company, in its capacity as Trustee or Securities Intermediary hereunder,
including without limitation, costs and expenses of winding up, liquidation and
termination of the Trust shall be paid (a) from the Administrative Expenses
distributed to the Trustee by the Indenture Trustee pursuant to Section 5.04 of
the Indenture; provided that the Trustee shall give notice to the Indenture
Trustee of the amount of such expenses, disbursements and advances due and owing
to the Trustee and the Securities Intermediary no later than three Business Days
prior to each Payment Date, (b) from Additional Financing Costs distributed to
the Trust pursuant to Section 6.10 of the Chaparral LLC Agreement or (c) if the
amounts distributed pursuant to the foregoing clauses (a) and (b) are
insufficient, by the holder of the El Paso Interest. Wilmington Trust Company
shall receive as compensation for its services as Trustee and Securities
Intermediary hereunder such ordinary fees as are separately agreed upon between
Wilmington Trust Company and the holder of the El Paso Interest in a separate
fee agreement. Wilmington Trust Company, in its capacity as Trustee and
Securities Intermediary hereunder, shall be compensated reasonably for any
extraordinary services rendered by it hereunder as agreed to separately by the
holder of the El Paso Interest and Wilmington Trust Company.

                  Section 9.09. Litigation, Action Outside Delaware. (a) The
Trustee shall not be under any obligation to appear in, prosecute or defend any
action that in its opinion may require it to incur any out-of-pocket expense or
any liability, unless it shall be furnished with specific instruction from the
Majority Certificateholders and such reasonable security and indemnity against
such expense or liability as it may require, and any reasonable out-of-pocket
costs of the Trustee as a result of such actions shall be paid by the holder of
the El Paso Interest.

                  (b) Notwithstanding anything contained herein to the contrary,
Wilmington Trust Company shall not be required to take any action in any
jurisdiction other than in the State of Delaware if the taking of such action
will (i) require the consent or approval or authorization or order of or the
giving of notice to, or the registration with or the taking of any other action
in respect of, any state or other governmental authority or agency of any
jurisdiction other than the State of Delaware; (ii) result in any fee, tax or
other governmental charge under the laws of any jurisdiction or any political
subdivisions thereof in existence on the Effective Date other than the State of
Delaware becoming payable by Wilmington Trust Company; or (iii) subject
Wilmington Trust Company to personal jurisdiction in any jurisdiction other than
the State of Delaware for causes of action arising from acts unrelated to the
consummation of the transactions by Wilmington Trust Company contemplated
hereby.



                                       36
<PAGE>

                  Section 9.10. Rights of the Securities Intermediary. The
Securities Intermediary shall be entitled to all of the same rights,
protections, immunities and indemnities as the Trustee under this Agreement and
the other Transaction Documents.

                  Section 9.11. Resignation; Appointment of Successor Securities
Intermediary.

                  (a) The Securities Intermediary shall resign if it fails to
meet the requirements of the first sentence of Section 6.02(a)(ii), and such
resignation shall take effect upon receipt by the Trust of an instrument of
acceptance of appointment executed by a successor Securities Intermediary as
herein provided in Sections 9.12 and 9.13.

                  (b) If at any time the Securities Intermediary shall resign,
the Trust shall use its best efforts to locate and recommend a qualified
successor Securities Intermediary and a successor Securities Intermediary may be
appointed by the Trust (whether or not such successor shall have been located or
recommended by the Trust) upon written notice to the Securities Intermediary. In
the event that no such successor Securities Intermediary is appointed by the
Trust within 30 days after the giving of a notice of resignation, the Securities
Intermediary or the Majority Certificateholders may request a court to make such
appointment. Every successor Securities Intermediary appointed pursuant to this
Section 9.11(b) shall be a corporation or association organized under the law of
the United States or any State thereof having a combined capital and surplus of
at least $150,000,000 and a long-term debt rating of at least "A3" by Moody's
and at least "A-" by S&P, if there be such an institution willing and able to
accept the position upon reasonable or customary terms.

                  Section 9.12. Acceptance of Appointment by Successor
Securities Intermediary Any successor Securities Intermediary appointed as
provided in Section 9.11 shall execute, acknowledge and deliver to the Trust and
its predecessor Securities Intermediary an instrument accepting such appointment
hereunder and agreeing to all the provisions regarding the Securities
Intermediary and the Limestone Distribution Account and the Limestone Collection
Account set forth in this Agreement. Subject to the provisions of Section 9.11,
thereupon the resignation of the predecessor Securities Intermediary shall
become effective and such successor Securities Intermediary, without any further
act, deed or conveyance, shall become vested with all the rights, powers, duties
and obligations of its predecessor hereunder, with like effect as if originally
named as Securities Intermediary herein; but, nevertheless, at the written
request of the successor Securities Intermediary, the Securities Intermediary
ceasing to act shall execute and deliver an instrument transferring to such
successor Securities Intermediary all the rights and powers of the Securities
Intermediary so ceasing to act.

                  Section 9.13. Merger or Consolidation of Securities
Intermediary. Any corporation into which the Securities Intermediary may be
merged or converted or with which it may be consolidated or any corporation
resulting from any merger, conversion or consolidation to which the Securities
Intermediary shall be a party shall be the successor of the Securities
Intermediary hereunder; provided that such corporation shall be qualified under
the provisions of




                                       37
<PAGE>

the first sentence of Section 6.02(a)(ii), without the execution or filing of
any paper or any further act on the part of any of the parties hereto or the
Certificateholders, notwithstanding anything contained herein to the contrary.

                                    ARTICLE X

              DISSOLUTION, BANKRUPTCY AND LIQUIDATION OF THE TRUST

                  Section 10.01. Dissolution of the Trust. (a) The Trust shall
be dissolved, wound up and terminated as provided herein upon the Trustee's
determination, in its sole discretion after consultation with such counsel and
other experts as it deems necessary, that the Trust is insolvent. Upon any such
determination, the Trustee shall have the right, in its sole discretion, to (i)
apply for or consent to the appointment of, or the taking of possession by, a
receiver, custodian, trustee, examiner or liquidator of the Trust or of all or a
substantial part of the Trust Estate, (ii) make a general assignment for the
benefit of the Trust's creditors, (iii) file a petition seeking to take
advantage of any other law relating to bankruptcy, insolvency, reorganization,
liquidation, dissolution, arrangement or winding-up, or composition or
readjustment of debts, (iv) take any action for the purpose of effecting any of
the foregoing or (v) do the equivalent of any of the foregoing under the laws of
the United States or of any state or other jurisdiction therein, or of any other
jurisdiction (domestic or foreign) (each action described in (i) through (v), a
"Bankruptcy Action"), each with respect to the Trust upon 90 days' prior written
notice to the Certificateholders and the holder of the El Paso Interest. Neither
the holder of the El Paso Interest nor any Certificateholder shall have any
right to direct the taking of a Bankruptcy Action with respect to the Trust;
provided, however, the Certificateholders shall have the right, subject to the
prior written consent of the holder of the El Paso Interest as provided in
Section 8.05, to liquidate the assets of the Trust on a date that is at least
one year and one day after the Trustee shall have received (x) a certificate
from the Indenture Trustee that all of the obligations under the Indenture have
been satisfied and discharged in full and (y) a certificate from the New
Indenture Trustee that all of the obligations under the New Indenture have been
satisfied and discharged in full. With respect to any determination of
discretion by the Trustee under this Section 10.01(a), the Trustee shall incur
no personal liability to any Person for any determination (or action or inaction
in connection therewith) made in good faith, and in acting (or not in acting as
the case may be) under this Section, the Trustee shall owe no fiduciary duties
to any Person other than the Trust, the Certificateholders, the holder of the El
Paso Interest and any creditors of the Trust. In connection with the Trustee's
determination that the Trust is insolvent, the Trustee shall not be obligated to
follow the instructions of the Certificateholders and shall have no liability to
the Trust or any other Person for its failure to do so.

                  (b) Upon liquidation of the Trust, the Trust's assets shall be
applied in the following order of priority: (i) first, (A) to pay the costs and
expenses of winding up, liquidation and termination of the Trust, including
amounts owed to the Trustee, (B) to creditors of the Trust or (C) to establish
reserves reasonably adequate to meet any and all contingent or unforeseen
liabilities or obligations of the Trust as reasonably determined by the Trustee
in accordance with Applicable Law, in each case, in the order of priority
provided by law; (ii) second, to the Certificateholders, pro rata, until they
have received payments in an aggregate amount equal to the Certificate Purchase
Amount; and (iii) the assets (if any) of the Trust remaining after



                                       38
<PAGE>

distribution as set forth in clauses (i) and (ii) shall, following cancellation
or deemed cancellation of all Limestone Certificates outstanding pursuant to
Section 7.04, be distributed to the holder of the El Paso Interest.

                  Section 10.02. Termination. The Trust shall terminate upon the
earlier of (a) the 10th anniversary of the Closing Date, (b) the date when all
of the Trust's assets shall have been disposed of and distributed as provided
herein and (c) the election of the holder of the El Paso Interest following the
date upon which all Limestone Certificates shall have been cancelled pursuant to
Section 7.04. Upon the winding up of the Trust and its termination, the Trustee
shall cause the Certificate of Trust to be cancelled by filing a certificate of
cancellation with the Secretary of State in accordance with the provisions of
Section 3810 of the Act. Upon such termination, all outstanding Limestone
Certificates shall be cancelled.

                                   ARTICLE XI

                                     NOTICES

                  Section 11.01. Notices. Except as otherwise expressly provided
herein in any particular case, all notices, approvals, consents, requests and
other communications hereunder shall be in writing and shall, if addressed as
provided in the following sentence, be deemed to have been given, (i) when
delivered by hand, (ii) one Business Day after being sent by a private
nationally or internationally recognized overnight courier service, or (iii)
when sent by telecopy, if immediately after transmission the sender's facsimile
machine records in writing the correct answer back. Actual receipt at the
address of an addressee, regardless of whether in compliance with the foregoing
is effective notice hereunder. Until otherwise so notified by the respective
parties, all notices, approvals, consents, requests and other communications
shall be addressed to the following addressees:

                  If to El Paso:

                  1001 Louisiana Street
                  Houston, Texas 77002
                  Attention: Tom Kilgore
                  Telecopier No.: (713) 420-7249
                  Telephone No.: (713) 420-5574

                  with a copy to:

                  1001 Louisiana Street
                  Houston, Texas 77002
                  Attention: Kelly Jameson
                  Telecopier No.: (713) 420-4099
                  Telephone No.: (713) 420-2017



                                       39
<PAGE>

                  If to the Trustee, the Securities Intermediary or the Trust:

                  c/o Wilmington Trust Company
                  Rodney Square North
                  1100 North Market Street
                  Wilmington, Delaware 19890-0001
                  Attention: Corporate Trust Administration
                  Telecopier No.: (302) 651-8882
                  Telephone No.: (302) 651-8681


                  If to the Certificateholders:

                  To the Certificateholders identified as such in the
                  Certificate Register, at the addresses specified in Schedule I
                  to the Participation Agreement or in the Investment
                  Certificate, as applicable.

                                   ARTICLE XII

                            MISCELLANEOUS PROVISIONS

                  Section 12.01. Entire Agreement. This Agreement (including,
without limitation, the exhibits hereto) and the other Transaction Documents,
and each of the parties hereto represents and warrants to the others that this
Agreement constitutes the entire agreement among the parties hereto relating to
the transactions contemplated hereby.

                  Section 12.02. Governing Law. THIS AGREEMENT SHALL BE GOVERNED
BY AND CONSTRUED AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE STATE OF
DELAWARE; PROVIDED THAT THERE SHALL NOT BE APPLICABLE TO THE TRUST, THE PARTIES
HEREUNDER OR THIS AGREEMENT, ANY PROVISION OF THE LAWS (COMMON OR STATUTORY) OF
THE STATE OF DELAWARE PERTAINING TO TRUSTS (OTHER THAN THE ACT) THAT RELATE TO
OR REGULATE, IN A MANNER INCONSISTENT WITH THE TERMS HEREOF, (A) THE FILING WITH
ANY COURT OR GOVERNMENTAL BODY OR AGENCY OF TRUSTEE ACCOUNTS OR SCHEDULES OF
TRUSTEE FEES AND CHARGES, (B) AFFIRMATIVE REQUIREMENTS TO POST BONDS FOR
TRUSTEES, OFFICERS, AGENTS OR EMPLOYEES OF A TRUST, (C) THE NECESSITY FOR
OBTAINING COURT OR OTHER GOVERNMENTAL APPROVAL CONCERNING THE ACQUISITION,
HOLDING OR DISPOSITION OF REAL OR PERSONAL PROPERTY, (D) FEES OR OTHER SUMS
PAYABLE TO TRUSTEES, OFFICERS, AGENTS OR EMPLOYEES OF A TRUST, (E) THE
ALLOCATION OF RECEIPTS AND EXPENDITURES TO INCOME OR PRINCIPAL, (F) RESTRICTIONS
OR LIMITATIONS ON THE PERMISSIBLE NATURE, AMOUNT OR CONCENTRATION OF TRUST
INVESTMENTS OR REQUIREMENTS RELATING TO THE TITLING, STORAGE OR OTHER MANNER OF
HOLDING OR INVESTING TRUST ASSETS OR (G) THE ESTABLISHMENT OF FIDUCIARY OR OTHER
STANDARDS OF RESPONSIBILITY OR LIMITATIONS ON THE ACTS OR POWERS OF THE TRUSTEE



                                       40
<PAGE>

THAT ARE INCONSISTENT WITH THE LIMITATIONS OR AUTHORITIES AND POWERS OF THE
TRUSTEE HEREUNDER AS SET FORTH OR REFERENCED IN THIS AGREEMENT. SECTION 3540 OF
TITLE 12 OF THE DELAWARE CODE SHALL NOT APPLY TO THE TRUST.

                  Section 12.03. Severability of Provisions. If any provision
hereof shall be held invalid or unenforceable by any court of competent
jurisdiction, such holding shall not invalidate or render unenforceable any
other provision hereof. To the extent permitted by Applicable Law, the parties
hereto hereby agree that any provision hereof that renders any other term or
provision hereof invalid or unenforceable in any respect shall be modified, but
only to the extent necessary to avoid rendering such other term or provision
invalid or unenforceable, and such modification shall be accomplished in the
manner that most nearly preserves the benefit of all the parties' bargain
hereunder.

                  Section 12.04. Amendment or Waiver; Effect on Agreement. Any
provision of this Agreement may be amended or waived by an amendment or waiver
which is in writing and signed by the holder of the El Paso Interest and the
Trustee; provided, that the Trustee shall consent to any amendment or waiver
only upon instruction by the Majority Certificateholders; provided, further,
that without the consent of 100% of the Certificateholders at the time, no such
amendment or waiver or any amendment or waiver to any other Transaction Document
to which the Trust is a party shall (1) alter or amend the right of the
Certificateholders to receive payments thereon, or institute suit in respect
thereof, (2) release any portion of the Trust Estate or any portion of the
assets of the Trust, (3) reduce any amount required to be collected or retained
by the Trust or the Trustee or (4) release the Guarantor from any of its
obligations under the El Paso Guarantee or reduce the amount of the Guaranteed
Obligations.

                  Promptly after the execution by all required parties of any
such amendment to, or waiver of, this Agreement, the Trustee shall furnish a
copy of any such amendment or waiver to each Certificateholder and the holder of
the El Paso Interest.

                  Section 12.05. Binding Upon Assigns. Except as otherwise
provided herein, the provisions of this Agreement (including any amendments,
modification and waivers hereof properly adopted) shall be binding upon and
shall inure to the benefit of the parties hereto and their respective successors
and assigns.

                  Section 12.06. Survival. All agreements, representations,
warranties and indemnities contained in this Agreement and in any agreement,
document or certificate delivered pursuant hereto, or in connection herewith,
shall survive and continue in effect following the execution and delivery of
this Agreement and the Closing Date. Upon the repayment in full of the Limestone
Certificates, this Agreement shall terminate except as to those provisions,
including without limitation, Section 9.07 hereof, expressly intended to survive
such termination.

                  Section 12.07. Tax Characterization. (a) Each of the parties
hereto recognizes and intends that, for United States federal, state and local
income tax purposes,

                           (i) the Trust will not be treated as an association
         taxable as a corporation;



                                       41
<PAGE>

                           (ii) the Limestone Certificates will either be
         disregarded or treated as equity interests in the Trust; and

                           (iii) the El Paso Interest will be disregarded until
         such time as the holder of the El Paso Interest exercises its rights,
         makes a contribution or is deemed to make a contribution pursuant to
         Section 3.03.

                  (b) To the extent that any of the parties hereto is required
to report any item of income, gain, loss, deduction or credit relating to the
Trust for United States federal, state or local income tax purposes, such party
shall report such item in a manner consistent with the characterization intended
by this Section 12.07 and shall not take any contrary position on any tax return
or report relating to the United States federal, state or local income taxes or
take any other action which is inconsistent with such characterization.

                  (c) Notwithstanding anything to the contrary herein, no party
shall be obligated to take a position subsequent to (A) a Final Determination to
the contrary or (B) a written opinion of independent, nationally-recognized tax
counsel selected by such party (such counsel and form of opinion to be
reasonably satisfactory to the holder of the El Paso Interest) that no
Reasonable Basis exists to take such position, which opinion shall, solely in
the case of a United States federal income Tax return, be based on a Change in
Law, provided, however, that a court decision described in clause (iii) of the
definition of "Change in Law" shall not constitute a Change in Law if the holder
of the El Paso Interest provides to the relevant party a written opinion of
independent, nationally-recognized tax counsel selected by the holder of the El
Paso Interest (such counsel and form of opinion to be reasonably satisfactory to
such party) that, notwithstanding such decision, such party's position is more
likely than not to prevail if challenged.

                  Section 12.08. Counterparts. This Agreement may be executed in
any number of counterparts, each of which shall be deemed to be an original, but
all such counterparts shall together constitute but one and the same instrument.

                  Section 12.09. Effectiveness. This Agreement shall take effect
on and as of the Effective Date.





                                       42
<PAGE>
                  IN WITNESS WHEREOF, the undersigned have executed this
Agreement as of the date above first written.

                                    WILMINGTON TRUST COMPANY,
                                      as Trustee


                                    By: /s/ Ann E. Roberts
                                        ----------------------------------------
                                        Name:  Ann E. Roberts
                                        Title: Assistant Vice President



                                    ELECTRON TRUST,
                                      as sole Certificateholder

                                    By: Wilmington Trust Company, not in its
                                        individual capacity, but solely as
                                        Trustee



                                    By: /s/ Ann E. Roberts
                                        ----------------------------------------
                                        Name:  Ann E. Roberts
                                        Title: Assistant Vice President



                                    LIMESTONE ELECTRON TRUST

                                    By: Wilmington Trust Company, not in its
                                        individual capacity, but solely as
                                        Trustee


                                        By: /s/ Ann E. Roberts
                                            ------------------------------------
                                            Name:  Ann E. Roberts
                                            Title: Assistant Vice President



                           Limestone Trust Agreement
<PAGE>
                                   WILMINGTON TRUST COMPANY,
                                     as Securities Intermediary for the purposes
                                     of Sections 6.02, 6.03, 6.04, 9.10, 9.11,
                                     9.12 and 9.13 only


                                   By: /s/ Ann E. Roberts
                                       ----------------------------------------
                                       Name:  Ann E. Roberts
                                       Title: Assistant Vice President



                                   EL PASO CORPORATION,
                                   as holder of the El Paso Interest


                                   By: /s/ Thomas G. Kilgore
                                       ----------------------------------------
                                       Name:  Thomas G. Kilgore
                                       Title: Vice President







                           Limestone Trust Agreement