<PAGE>

                             MASTER TRUST AGREEMENT

                                     Between

--------------------------------------------------------------------------------

             LYONDELL CHEMICAL COMPANY; EQUISTAR CHEMICALS, LP; AND
                      LYONDELL-CITGO REFINING COMPANY LTD.

                                       And

                        FIDELITY MANAGEMENT TRUST COMPANY

--------------------------------------------------------------------------------

       THE LYONDELL CHEMICAL, EQUISTAR CHEMICALS, AND LYONDELL-CITGO PLANS
                                  MASTER TRUST

                           Dated as of March 15, 1999
<PAGE>

                                TABLE OF CONTENTS
                                -----------------
Section                                                                     Page
-------                                                                     ----

 1   Definitions                                                              2

 2   Trust                                                                    4

 3   Exclusive Benefit and Reversion of                                       4
        Sponsor Contributions

 4   Disbursements                                                            5
         (a)  Administrator-Directed Disbursements
         (b)  Participant Withdrawal Requests
         (c)  Limitations

 5   Investment of Trust                                                      5
         (a) Selection of Investment Options
         (b) Available Investment Options
         (c) Participant Direction
         (d) Mutual Funds
         (e) Employer Stock and Common Stock
         (f) Notes
         (g) BrokerageLink
         (h) IDS New Dimensions Fund
         (i) Reliance of Trustee Directions
         (j) Trustee Powers

 6   Recordkeeping and Administrative Services to Be Performed               16
         (a) General
         (b) Accounts
         (c) Inspection and Audit
         (d) Effect of Plan Amendment
         (e) Returns, Reports and Information
         (f) Allocation of Plan Interests

 7   Compensation and Expenses                                               17

                                       2
<PAGE>

 8   Directions and Indemnification                                          18
         (a) Identity of Administrator and Named Fiduciary
         (b) Directions from Sponsor or Administrator
         (c) Directions from Named Fiduciaries
         (d) Co-Fiduciary Liability
         (e) Indemnification
         (f) Survival

 9  Resignation or Removal of Trustee                                        19
         (a) Resignation
         (b) Removal

10   Successor Trustee                                                       20
         (a) Appointment
         (b) Acceptance
         (c) Corporate Action

11   Termination                                                             20

12   Resignation, Removal, and Termination Notices                           20

13   Duration                                                                21

14   Amendment or Modification                                               21

15   Electronic Services                                                     21

16   General                                                                 22
         (a) Performance by Trustee, its Agents or Affiliates
         (b) Delegation by Employer
         (c) Entire Agreement
         (d) Waiver
         (e) Successors and Assigns
         (f) Partial Invalidity
         (g) Section Headings

17   Governing Law                                                           23
         (a) Massachusetts Law Controls
         (b) Trust Agreement Controls

18   Plan Qualification                                                      23

                                       3
<PAGE>

Schedules
---------

A.   Administrative Services
B.   Fee Schedule
C.   Investment Options
D.   Sponsor's Authorization Letter
E.   Named Fiduciary/Administrator's Authorization Letter
F.   IRS Determination Letter or Opinion of Counsel
G.   Telephone Exchange Guidelines
H.   Operational Guidelines for Non-Fidelity Mutual Funds
I.   Plan Designation Form
J.   Securities that may not be purchased under BrokerageLink
K.   BrokerageLink Administrative Procedures
L.   Operating Procedures for the IDS New Dimensions Fund

                                       4
<PAGE>

     TRUST AGREEMENT, dated as of the fifteenth day of March, 1999, between
LYONDELL CHEMICAL COMPANY, a Delaware corporation; EQUISTAR CHEMICALS, LP, a
Delaware limited partnership; and LYONDELL-CITGO REFINING COMPANY LTD., a Texas
limited liability partnership, each having an office at One Houston Center, 1221
McKinney, Suite 1600, Houston, Texas 77253-3646 (individually and collectively
the "Sponsor" as defined in further detail below), and FIDELITY MANAGEMENT TRUST
     ------
COMPANY, a Massachusetts trust company, having an office at 82 Devonshire
Street, Boston, Massachusetts 02109 (the "Trustee").
                                          -------

                                   WITNESSETH:

     WHEREAS, Lyondell Chemical Company is the sponsor of the Lyondell Chemical
Company 401(k) and Savings Plan; Equistar Chemicals, LP is the sponsor of the
Equistar Chemicals, LP Savings and Investment Plan and the Equistar Chemicals,
LP Savings and Investment Plan for Represented Employees; and Lyondell-Citgo
Refining Company Ltd. is the sponsor of the Lyondell-Citgo Refining Company
401(k) and Savings Plan for Non-Represented Employees and the Lyondell-Citgo
Refining Company 401(k) and Savings Plan for Represented Employees. For purposes
of this Agreement "Sponsor" shall refer individually and collectively to the
                   ------
above-referenced plan sponsors unless specifically provided otherwise. Further,
for purposes of this Agreement the term "Plan" shall refer individually and
                                         ----
collectively to the above-referenced plans unless specifically provided
otherwise; and

     WHEREAS, certain affiliates and subsidiaries of the Sponsor maintain, or
may in the future maintain, qualified defined contribution plans for the benefit
of their eligible employees; and

     WHEREAS, the Sponsor desires to establish a single trust to hold all of the
assets of the Plan and such other tax-qualified defined contribution plans
maintained by the Sponsor, or any of its subsidiaries or affiliates, as are
designated by the Sponsor as being eligible to participate in this Trust; and

     WHEREAS, the Trustee shall maintain a separate account reflecting the
equitable share of each Plan in the Trust and in all investments, receipts,
disbursements and other transactions hereunder, and shall report the value of
such equitable share at such times as may be mutually agreed upon by the Trustee
and the Sponsor. Such equitable share shall be used solely for the payments of
benefits,
<PAGE>

expenses and other charges properly allocable to each such Plan and shall not be
used for the payment of benefits, expenses or other charges properly allocable
to any other Plan; and

     WHEREAS, the Trustee will become trustee of certain assets of the Lyondell
Chemical 401(k) and Savings Plan as of the date of this Trust Agreement, and
will become trustee of all remaining Plan assets on April 1, 1999, and prior to
that time, all remaining assets of the Plan will continue to be held by the
current trustee, State Street Bank and Trust Company; and

     WHEREAS, the Trustee, through FIRSCO (as defined below), is willing to hold
and invest the aforesaid Plan assets in trust pursuant to the provisions of this
Trust Agreement, which trust shall constitute a continuation, by means of an
amendment and restatement, of each of the prior trusts from which Plan assets
are transferred to the Trustee; and

     WHEREAS, the Trustee is willing to hold and invest the aforesaid Plan
assets in trust among several investment options selected by the Named
Fiduciary; and

     WHEREAS, the Trustee is willing to perform recordkeeping and administrative
services for the Plan if the services are purely ministerial in nature and are
provided within a framework of Plan provisions, guidelines and interpretations
conveyed in writing to the Trustee by the Administrator.

     NOW, THEREFORE, in consideration of the foregoing premises and the mutual
covenants and agreements set forth below, the Sponsor and the Trustee agree as
follows:

Section 1. Definitions. The following terms as used in this Trust Agreement have
           -----------
the meaning indicated unless the context clearly requires otherwise:

(a)  "Administrator" with respect to the Plan, shall mean the Benefits
      -------------
     Administrative Committee of Lyondell Chemical Company, the "administrator"
     of the Plan within the meaning of section 3(16)(A) of ERISA.

(b)  "Agreement" shall mean this Trust Agreement, as the same may be amended and
      ---------
     in effect from time to time.

(c)  "Code" shall mean the Internal Revenue Code of 1986, as it has been or may
      ----
     be amended from time to time.

                                       2
<PAGE>

(d)  "Common Stock" shall mean ARCO Common Stock, Millennium Petrochemicals,
      ------------
     Inc. Common Stock , and Lyondell Chemical Company Common Stock.

(e)  "Employer" shall mean any employer of a Plan Participant, as defined by
      --------
     ERISA, other than the Sponsor, which authorizes the assets of such plan to
     be deposited in the Trust with the Sponsor's written consent.

(f)  "Employer Stock" shall mean the Common Stock of Lyondell Chemical Company
      --------------
     (as to the Lyondell Chemical Company 401(k) and Savings Plan ONLY)), or
     such other publicly-traded stock of the Sponsor or the Sponsor's affiliates
     as meets the requirements of section 407(d)(5) of ERISA with respect to the
     Plan.

(g)  "ERISA" shall mean the Employee Retirement Income Security Act of 1974, as
      -----
     it has been or may be amended from time to time.

(h)  "Fidelity Mutual Fund" shall mean any investment company advised by
      --------------------
     Fidelity Management & Research Company or any of its affiliates.

(i)  "Mutual Fund" shall refer both to Fidelity Mutual Funds and Non-Fidelity
      -----------
     Mutual Funds.

(j)  "Named Fiduciary" shall mean, with respect to the application of any
      ---------------
     provision of this Agreement to any Plan, the Benefits Administrative
     Committee of Lyondell Chemical Company (within the meaning of section
     402(a) of the Employee Retirement Income Security Act of 1974, as amended);

(k)  "Non-Fidelity Mutual Fund" shall mean certain investment companies not
      ------------------------
     advised by Fidelity Management & Research Company or any of its affiliates.

(l)  "Participant" shall mean, with respect to the Plan, any employee (or former
      -----------
     employee) with an account under the Plan, which has not yet been fully
     distributed and/or forfeited, and shall include the designated
     beneficiary(ies) with respect to the account of any deceased employee (or
     deceased former employee) until such account has been fully distributed
     and/or forfeited.

(m)  "Participant Recordkeeping Reconciliation Period" shall mean the period
      -----------------------------------------------
     beginning on the date of the initial transfer of assets to the Trust and
     ending on the date of the completion of the reconciliation of Participant
     records.

(n)  "Plan" shall mean: the Lyondell Chemical Company 401(k) and Savings Plan;
      ----
     the Equistar Chemicals, LP Savings and Investment Plan; the Equistar
     Chemicals, LP Savings and Investment Plan for Represented Employees; the
     Lyondell-Citgo Refining Company 401(k) and Savings Plan for Non-Represented
     Employees; and the Lyondell-Citgo Refining Company 401(k) and Savings Plan
     for Represented Employees and such other tax-qualified, defined
     contribution plans which are maintained by the Sponsor or any of its
     subsidiaries or affiliates for the benefit of their eligible employees as
     may be designated by the Sponsor in writing to the Trustee as a Plan
     hereunder, such writing to be in the form of the Plan Designation Form
     attached hereto as Schedule "I". Each reference to "a Plan" or "the Plan"
     in this Agreement shall mean and include the Plan or Plans to which the
     particular provision of this Agreement is being applied or all Plans, as
     the context may require.

                                       3
<PAGE>

(o)  "Plan Administrative Manual" shall mean the document that governs the
      --------------------------
     Trustee's processing of Plan transactions in accordance with directions
     from the Administrator.

(p)  "Recordkeeper" shall mean Fidelity Institutional Retirement Services
      ------------
     Company ("FIRSCO"), or its successor, as authorized by the Trustee to
               ------
     perform certain administrative services to the Plan on its behalf.

(q)  "Reporting Date" shall mean the last day of each calendar quarter, the date
      --------------
     as of which the Trustee resigns or is removed pursuant to Section 9 hereof
     and the date as of which this Agreement terminates pursuant to Section 11
     hereof.

(r)  "Sponsor" shall mean Lyondell Chemical Company, a Delaware corporation;
      -------
     Equistar Chemicals, LP, a Delaware limited partnership; and Lyondell-Citgo
     Refining Company Ltd., a Texas limited liability partnership, or any
     successor to all or substantially all of its businesses which, by
     agreement, operation of law or otherwise, assumes the responsibility of the
     Sponsor under this Agreement.

(s)  "Trust" shall mean the Lyondell Chemical, Equistar Chemicals, and
      -----
     Lyondell-Citgo Plans Master Trust, being the trust established by the
     Sponsor and the Trustee pursuant to the provisions of this Agreement and as
     may hereafter be amended from time to time.

(t)  "Trustee" shall mean Fidelity Management Trust Company, a Massachusetts
      -------
     trust company and any successor to all or substantially all of its trust
     business as described in Section 10(c). The term Trustee shall also include
     any successor trustee appointed pursuant to Section 10 to the extent such
     successor agrees to serve as Trustee under this Agreement.

Section 2. Trust. The Sponsor hereby establishes the Trust with the Trustee. The
           -----
Trust shall consist of an initial contribution of money or other property
acceptable to the Trustee in its sole discretion, made by the Sponsor or
transferred from a previous trustee under a Plan, such additional sums of money,
Employer Stock, and Common Stock as shall from time to time be delivered to the
Trustee under a Plan, all investments made therewith and proceeds thereof, and
all earnings and profits thereon, less the payments that are made by the Trustee
as provided herein, without distinction between principal and income. The
Trustee hereby accepts the Trust on the terms and conditions set forth in this
Agreement. In accepting this Trust, the Trustee shall be accountable for the
assets received by it, subject to the terms and conditions of this Agreement.

Section 3. Exclusive Benefit and Reversion of Sponsor Contributions.
           --------------------------------------------------------
     Except as provided under applicable law, no part of the Trust allocable to
a Plan may be used for, or diverted to, purposes other than the exclusive
benefit of the Participants in a Plan or their beneficiaries prior to the
satisfaction of all liabilities with respect to the Participants and their
beneficiaries.

                                       4
<PAGE>

Section 4. Disbursements.
           -------------

     (a) Administrator Directed Disbursements. The Trustee shall make
         ------------------------------------
disbursements in the amounts and in the manner as provided by the Plan as
communicated by the Sponsor to the Trustee and consistent with the terms of the
Plan Administrative Manual. The Trustee shall have no responsibility to
ascertain such direction's compliance with the terms of the Plan or of any
applicable law or the direction's effect for tax purposes or otherwise; nor
shall the Trustee have any responsibility to see to the application of any
disbursement.

     (b) Participant Withdrawal Requests. Pursuant to the Plan, a Participant
         -------------------------------
withdrawal request (in-service, full withdrawal, or hardship, except as
described below) may be made by the Participant by telephone, or in such other
manner as may be agreed to from time to time by the Administrator and Trustee,
and the Trustee shall process such request only after the identity of the
Participant is verified by use of a personal identification number ("PIN") and
                                                                     ---
social security number. The Trustee shall process such withdrawal in accordance
with the terms of the Plan Administrative Manual.

     For hardship withdrawals for Participants in the Equistar Chemicals, LP
Savings and Investment Plan for Represented Employees only, the Trustee shall
forward the withdrawal document to the Participant for execution and submission
for approval to the Administrator. The Administrator shall have the
responsibility for approving the withdrawal and instructing the Trustee to send
the proceeds to the Participant, if so directed by the Administrator.

     (c) Limitations. The Trustee shall not be required to make any disbursement
         -----------
in excess of the net realizable value of the assets of the Trust at the time of
the disbursement. The Trustee shall be required to make all disbursements in
accordance with terms of the Plan Administrative Manual and the Participant's
distribution directions, unless the Administrator has provided written
directions to the contrary.

Section 5.  Investment of Trust.
            -------------------

     (a) Selection of Investment Options. The Trustee shall have no
         -------------------------------
responsibility for the selection of investment options under the Trust and shall
not render investment advice to any person in connection with the selection of
such options.

     (b) Available Investment Options. The Named Fiduciary with respect to a
         ----------------------------
Plan shall direct the Trustee as to what investment options the Trust shall be
invested during the Participant

                                       5
<PAGE>

Recordkeeping Reconciliation Period, and the investment options in which Plan
Participants may invest in, subject to the following limitations. The Named
Fiduciary may determine to offer as investment options only (i) Mutual Funds,
(ii) Employer Stock, (iii) Common Stock, (iv) notes evidencing loans to
Participants in accordance with the terms of the Plan, (v) Self Directed
Brokerage ("BrokerageLink"), and (vi) IDS New Dimensions Fund.
            -------------

          The investment options initially selected by the Named Fiduciary are
identified on Schedules "A" and "C" attached hereto. The Named Fiduciary may
change, withdraw, or add investment options with the consent of the Trustee and
upon mutual amendment of this Trust Agreement and the Schedules thereto to
reflect such additions.

     (c) Participant Direction. Each Participant shall direct the Trustee in
         ---------------------
which investment option(s) to invest the assets in the Participant's individual
accounts except that, as to the Lyondell Chemical Company 401(k) and Savings
Plan, assets received as company contributions shall be invested in Employer
Stock. Such directions may be made by Participants by use of the telephone
exchange system maintained for such purposes by the Trustee or its agent, in
accordance with written Telephone Exchange Guidelines attached hereto as
Schedule "G". In the event that the Trustee fails to receive a proper direction,
the assets shall be invested in the securities of the Mutual Fund set forth for
such purpose on Schedule "C", until the Trustee receives a proper direction.

     (d) Mutual Funds. The Sponsor hereby acknowledges that it has received from
         ------------
the Trustee a copy of the prospectus for each Fidelity Mutual Fund selected by
the Named Fiduciary as a Plan investment option. All transactions involving
Non-Fidelity Mutual Funds shall be done in accordance with the Operational
                                                               -----------
Guidelines for Non-Fidelity Mutual Funds attached hereto as Schedule "H". Trust
----------------------------------------
investments in Mutual Funds shall be subject to the following limitations:

          (i) Execution of Purchases and Sales. Purchases and sales of Mutual
              --------------------------------
Funds (other than for exchanges) shall be made on the date on which the Trustee
receives from the Sponsor in good order all information and documentation
necessary to accurately effect such purchases and sales (or in the case of a
purchase, the subsequent date on which the Trustee has received a wire transfer
of funds necessary to make such purchase). Exchanges of Mutual Funds shall be
made in accordance with the Telephone Exchange Guidelines attached hereto as
Schedule "G".

                                       6
<PAGE>

          (ii) Voting. At the time of mailing of notice of each annual or
               ------
special stockholders' meeting of any Mutual Fund, the Trustee shall send a copy
of the notice and all proxy solicitation materials to each Participant who has
shares of the Mutual Fund credited to the Participant's accounts, together with
a voting direction form for return to the Trustee or its designee. The Sponsor
shall have the right to direct the Trustee as to the manner in which the Trustee
is to vote the Mutual Fund shares held in any short-term investment fund or
liquidity reserve. The Participant shall have the right to direct the Trustee as
to the manner in which the Trustee is to vote the shares credited to the
Participant's accounts (both vested and unvested). The Trustee shall vote the
shares as directed by the Participant. The Trustee shall not vote shares for
which it has received no directions from the Participant. During the Participant
Recordkeeping Reconciliation Period, the Sponsor shall have the right to direct
the Trustee as to the manner in which the Trustee is to vote the shares of the
Mutual Funds in the Trust including Mutual Fund shares held in any short-term
investment fund liquidity reserve. With respect to all rights other than the
right to vote, the Trustee shall follow the directions of the Participant and if
no such directions are received, the directions of the Named Fiduciary. The
Trustee shall have no duty to solicit directions from Participants or the
Sponsor.

     (e) Employer Stock and Common Stock. Plan Participants are not permitted to
         -------------------------------
exchange into Common Stock, except that, Participants in the Lyondell Chemical
Company 401(k) and Savings Plan may exchange into Lyondell Chemical Company
Common Stock. All Plan Participants may exchange out of Common Stock. For
purposes of the remainder of this Section 5(e) only, "Stock" shall refer to
Employer Stock and Common Stock, collectively. Investments in Stock shall be
subject to the following limitations:

          (i) Acquisition Limit. Pursuant to the Plan, the Trust may be invested
              -----------------
in Stock to the extent necessary to comply with investment directions under this
Agreement.

          (ii) Fiduciary Duty of Named Fiduciary. The Named Fiduciary shall
               ---------------------------------
continually monitor the suitability under the fiduciary duty rules of section
404(a)(1) of ERISA (as modified by section 404(a)(2) of ERISA) of acquiring and
holding Stock. The Trustee shall not be liable for any loss, or by reason of any
breach, which arises from the directions of the Named Fiduciary with respect to
the acquisition and holding of Stock, unless it is clear on their face that the
actions to be taken under those directions would be prohibited by the foregoing
fiduciary duty rules or would be contrary to the terms of this Agreement or the
Plan as communicated by the Sponsor to the Trustee.

                                       7
<PAGE>

          (iii) Execution of Purchases and Sales.
                --------------------------------

               (A) Purchases and sales of Stock (other than for exchanges) shall
be made in the open market on the date on which the Trustee receives from the
Administrator in good order all information, documentation, and wire transfer of
funds (if applicable), necessary to accurately effect such transactions and
shall be made at the 4:00 p.m. NYSE closing price of the Stock on the trading
date. Exchanges of Stock shall be made in accordance with the Telephone Exchange
Guidelines attached hereto as Schedule "G". Such general rules shall not apply
in the following circumstances:

                    (1) If the Trustee is unable to purchase or sell the total
number of shares required to be purchased or sold on such day as a result of
market conditions; or

                    (2) If the Trustee is prohibited by the Securities and
Exchange Commission, the New York Stock Exchange ("NYSE"), or any other
                                                   ----
regulatory body from purchasing or selling any or all of the shares required to
be purchased or sold on such day.

In the event of the occurrence of the circumstances described in (1) or (2)
above, the Trustee shall purchase or sell such shares as soon as possible
thereafter and shall determine the price of such purchases or sales to be the
average purchase or sales price of all such shares purchased or sold,
respectively as determined over the period in which the purchases or sales
occurred. The Trustee may follow directions from the Named Fiduciary to deviate
from the above purchase and sale procedures provided that such direction is made
in writing by the Named Fiduciary.

               (B) Purchases and Sales from or to Sponsor. If directed by the
                   --------------------------------------
Sponsor in writing prior to the trading date, the Trustee may purchase or sell
Stock from or to the Sponsor if the purchase or sale is for adequate
consideration (within the meaning of section 3(18) of ERISA) and no commission
is charged. If Sponsor contributions (employer) or contributions made by the
Sponsor on behalf of the Participants (employee) under the Plan are to be
invested in Stock, the Sponsor may transfer Stock in lieu of cash to the Trust.
In either case, the number of shares to be transferred will be determined by
dividing the total amount of Stock to be purchased, sold, or contributed by the
4:00 p.m. NYSE closing price of the Stock on the trading date.

               (C) Use of an Affiliated Broker. The Named Fiduciary hereby
                   ---------------------------
directs the Trustee to use Fidelity Capital Markets and its affiliates ("Capital
                                                                        --------
Markets") to provide brokerage services in connection with any purchase or sale
--------
of Stock in accordance with directions from Plan

                                       8
<PAGE>

Participants or pursuant to the terms of the Plan, for the Lyondell Chemical
Company 401(k) and Savings Plan. Capital Markets shall execute such directions
directly or through its affiliate, National Financial Services Company ("NFSC").
                                                                         ----
The provision of brokerage services shall be subject to the following:

                    (1) Except for purchases or sales to or from the Sponsor
under subsection (B), as consideration for such brokerage services, the Named
Fiduciary agrees that Capital Markets shall be entitled to remuneration under
this direction in the amount of five cents ($.05) commission on each share of
Stock up to 10,000 shares in a singular transaction, four cents ($.04)
commission on each share of Stock from 10,001 to 20,000 shares in a singular
transaction, and three and one-half cents ($.035) commission on each share of
Stock in excess of 20,000 shares in a singular transaction. Any change in such
remuneration may be made only by a signed agreement between the Named Fiduciary
and Trustee.

                    (2) The Trustee will provide the Named Fiduciary with a
description of Capital Markets' brokerage placement practices and a form by
which the Named Fiduciary may terminate this direction to use a broker
affiliated with the Trustee. The Trustee will provide the Named Fiduciary with
this termination form annually, as well as monthly and annual reports which
summarize all securities transaction-related charges incurred by the Plan.

                    (3) Any successor organization of Capital Markets, through
reorganization, consolidation, merger or similar transactions, shall, upon
consummation of such transaction, become the successor broker in accordance with
the terms of this direction.

                    (4) The Trustee and Capital Markets shall continue to rely
on this direction until notified to the contrary. The Named Fiduciary reserves
the right to terminate this direction at any time upon written notice to Capital
Markets (or its successor) and the Trustee, in accordance with Section 11 of
this Agreement.

          (iv) Securities Law Reports. The Sponsor shall be responsible for
               ----------------------
filing all reports required under Federal or state securities laws with respect
to the Trust's ownership of Stock, including, without limitation, any reports
required under section 13 or 16 of the Securities Exchange Act of 1934, and
shall immediately notify the Trustee in writing of any requirement to stop
purchases or sales of Stock pending the filing of any report. The Trustee shall
provide to the Sponsor such information on the Trust's ownership of Stock as the
Sponsor may reasonably request in order to comply with Federal or state
securities laws.

                                       9
<PAGE>

          (v) Voting and Tender Offers. Notwithstanding any other provision of
              ------------------------
this Agreement, the provisions of this Section shall govern the voting and
tendering of Stock. The Sponsor, after consultation with the Trustee, shall pay
for all printing, mailing, tabulation and other costs associated with the voting
and tendering of Stock.

               (A) Voting.
                   ------

                    (1) When the issuer of Stock notifies the Sponsor of any
annual or special meeting, the Sponsor shall timely notify the Trustee and shall
cause a copy of all proxy solicitation materials to be sent to the Trustee. If
requested by the Trustee, the Sponsor shall certify to the Trustee that the
aforementioned materials represent the same information distributed to
shareholders of Stock. Based on these materials the Trustee shall prepare a
voting instruction form and shall provide a copy of all proxy solicitation
materials to each Plan Participant, together with the foregoing voting
instruction form, to be returned to the Trustee or its designee. The form shall
show the number of full and fractional shares of Stock credited to the
Participant's accounts.

                    (2) Each Participant shall have the right to direct the
Trustee as to the manner in which the Trustee is to vote the shares of Stock
credited to the Participant's accounts (both vested and unvested). Directions
from a Participant to the Trustee concerning the voting of Stock shall be
communicated in writing, or by mailgram or similar means as agreed upon by the
Trustee and the Sponsor. These directions shall be held in confidence by the
Trustee and shall not be divulged to the Sponsor, or any officer or employee
thereof, or any other person except to the extent that the consequences of such
directions are reflected in reports regularly communicated to any such person in
the ordinary course of the performance of the Trustee's services hereunder. Upon
its receipt of the directions, the Trustee shall vote the shares of Stock as
timely directed by the Participant. The Trustee shall not vote shares of Common
Stock (not including Employer Stock) credited to a Participant's account for
which it has received no directions from the Participant except as otherwise
required by law, unless the Trustee shall have received directions from the
Administrator as to the voting of such Common Stock (not including Employer
Stock). Except as otherwise required by law, the Trustee shall vote shares of
Employer Stock credited to a Participant's account for which it has received no
direction from the Participant in the same proportion on each issue as it votes
those shares credited to Participants' account for which it received voting
directions from Participants.

                                       10
<PAGE>

               (B) Tender Offers.
                   -------------

                    (1) Upon commencement of a tender offer for any securities
held in the Trust that are Stock, the Sponsor shall timely notify the Trustee in
advance of the intended tender date and shall cause a copy of all materials to
be sent to the Trustee. If requested by the Trustee, the Sponsor shall certify
to the Trustee that the aforementioned materials represent the same information
distributed to shareholders of Stock. Based on these materials and after
consultation with the Sponsor, the Trustee shall prepare a tender instruction
form and shall provide a copy of all tender materials to each Plan Participant,
together with the foregoing tender instruction form, to be returned to the
Trustee or its designee. The tender instruction form shall show the number of
full and fractional shares of Stock credited to the Participants account (both
vested and unvested).

                    (2) Each Participant shall have the right to direct the
Trustee to tender or not to tender some or all of the shares of Stock credited
to the Participant's accounts (both vested and unvested). Directions from a
Participant to the Trustee concerning the tender of Stock shall be communicated
in writing, or by mailgram or such similar means as is agreed upon by the
Trustee and the Sponsor. These directions shall be held in confidence by the
Trustee and shall not be divulged to the Sponsor, or any officer or employee
thereof, or any other person except to the extent that the consequences of such
directions are reflected in reports regularly communicated to any such persons
in the ordinary course of the performance of the Trustee's services hereunder.
The Trustee shall tender or not tender shares of Stock as timely directed by the
Participant. Except as otherwise required by law, the Trustee shall not tender
shares of Stock credited to a Participant's accounts for which it has received
no directions from the Participant.

                    (3) Except as otherwise required by law, the Trustee shall
tender that number of shares of Stock not credited to Participants' accounts in
the same proportion as the total number of shares of Stock credited to
Participants' accounts for which it received instructions from Participants.

                    (4) A Participant who has directed the Trustee to tender
some or all of the shares of Stock credited to the Participant's accounts may,
at any time prior to the tender offer withdrawal date, direct the Trustee to
withdraw some or all of the tendered shares, and the Trustee shall withdraw the
directed number of shares from the tender offer prior to the tender offer
withdrawal date. Prior to the withdrawal date, if any shares of Stock not
credited to Participants' accounts have been tendered, the Trustee shall
redetermine the number of shares of Stock that would be tendered under

                                       11
<PAGE>

Section 5(e)(v)(B)(3) if the date of the foregoing withdrawal were the date of
determination, and withdraw from the tender offer the number of shares of Stock
not credited to Participants' accounts necessary to reduce the amount of
tendered Stock not credited to Participants' accounts to the amount so
redetermined. A Participant shall not be limited as to the number of directions
to tender or withdraw that the Participant may give to the Trustee.

                    (5) A direction by a Participant to the Trustee to tender
shares of Stock credited to the Participant's accounts shall not be considered a
written election under the Plan by the Participant to withdraw from the Plan, or
have distributed, any or all of his withdrawable shares. The Trustee shall
credit to each account of the Participant from which the tendered shares were
taken the proceeds received by the Trustee in exchange for the shares of Stock
tendered from that account. Pending receipt of directions from the Participant
or the Named Fiduciary, as provided in the Plan, as to which of the remaining
investment options the proceeds should be invested in, the Trustee shall invest
the proceeds in the Mutual Fund set forth for such purpose on Schedule "C" until
the Trustee receives a proper direction.

          (vi) General. With respect to all rights other than the right to vote,
               -------
the right to tender, and the right to withdraw shares previously tendered, in
the case of Stock credited to a Participant's accounts, the Trustee shall follow
the directions of the Participant and if no such directions are received, the
directions of the Named Fiduciary. The Trustee shall have no duty to solicit
directions from Participants. With respect to all rights other than the right to
vote and the right to tender, in the case of Stock not credited to Participants'
accounts, the Trustee shall follow the directions of the Named Fiduciary.

          (vii) Conversion. All provisions in this Section 5(e) shall also apply
                ----------
to any securities received as a result of a conversion of Stock.

     (f) Participant Loans. The Sponsor shall act as the Trustee's agent for
         -----------------
Participant loans and as such shall (i) separately account for repayments
transmitted to the Trustee and (ii) clearly identify loan repayments as Plan
assets and (iii) collect and remit all principal and interest payments to the
Trustee. The Trustee shall determine, based on the current value of the
Participant's account on the date of the request and guidelines provided by the
Named Fiduciary, as indicated in the Plan Administrative Manual, the amount
available for the loan. The interest rate shall be supplied by the Administrator
in accordance with the terms of the Plan. To facilitate recordkeeping, the
Administrator has been advised that the Trustee may destroy the original of any
promissory note made in connection with a loan to a Participant

                                       12
<PAGE>

under the Plan, provided that the Trustee first creates a duplicate by a
photographic or optical scanning or other process yielding a reasonable
facsimile of the promissory note and the Plan Participant's signature thereon,
which duplicate may be reduced or enlarged in size from the actual size of the
original promissory note.

     (g) BrokerageLink. Under the BrokerageLink option, the Named Fiduciary
         -------------
hereby directs the Trustee to use Fidelity Brokerage Services, Inc. and its
affiliates ("FBSI") to purchase or sell individual securities for Plan
             ----
Participant accounts in accordance with investment directions provided by the
Plan Participants. The provision of brokerage services shall be subject to the
following:

          (i) The Trustee will provide the Named Fiduciary with a description of
FBSI's brokerage placement practices and a form by which the Named Fiduciary may
terminate this direction to use a broker affiliated with the Trustee. The
Trustee will provide the Named Fiduciary with this termination form annually, as
well as quarterly and annual reports which summarize all securities
transaction-related charges incurred by the Plan.

          (ii) Any successor organization of FBSI, through reorganization,
consolidation, merger or similar transactions, shall, upon consummation of such
transaction, become the successor broker in accordance with the terms of this
direction provision.

          (iii) The Trustee and FBSI shall continue to rely on this direction
provision until notified to the contrary. The Named Fiduciary reserves the right
to terminate this direction at any time upon written notice to FBSI (or its
successor) and the Trustee, in accordance with Section 12 of this Agreement.

          (iv) The types of securities which may not be purchased under this
BrokerageLink Option are listed on Schedule "J". Administrative procedures
governing investment in and withdrawals from BrokerageLink are attached hereto
as Schedule "K".

          (v) Participants may authorize the use of an agent to have limited
trading authority over assets in their BrokerageLink account provided that the
Participant completes and files with FBSI the Brokerage Services Limited Trading
Authorization and Indemnification Form or a comparable form.

          (vi) A copy of the notice and all proxy solicitation materials,
together with a voting direction form, will be sent to each Participant with
BrokerageLink account balances.

                                       13
<PAGE>

     (h) IDS New Dimensions Fund. All transactions involving the IDS New
         -----------------------
Dimensions Fund shall be done in accordance with the Operating Procedures
attached hereto as Schedule "L".

     (i) Reliance of Trustee on Directions.
         ---------------------------------

          (i) The Trustee shall not be liable for any loss, or by reason of any
breach, which arises from any Participant's exercise or non-exercise of rights
under this Section 5 over the assets in the Participant's accounts except to the
extent that a loss or breach results from the Trustee's action or inaction
ultimately determined to be a breach of fiduciary duty by a court of competent
jurisdiction.

          (ii) The Trustee shall not be liable for any loss, or by reason of any
breach, which arises from the Named Fiduciary's exercise or non-exercise of
rights under this Section 5, unless it was clear on their face that the actions
to be taken under the Named Fiduciary's directions were prohibited by the
fiduciary duty rules of Section 404(a) of ERISA or were contrary to the terms of
the Plan or this Agreement, or are ultimately determined to be a co-fiduciary
liability pursuant to ERISA.

     (j) Trustee Powers. The Trustee shall have the following powers and
         --------------
authority:

          (i) Subject to paragraphs (b), (c) and (d) of this Section 5, to sell,
exchange, convey, transfer, or otherwise dispose of any property held in the
Trust, by private contract or at public auction. No person dealing with the
Trustee shall be bound to see to the application of the purchase money or other
property delivered to the Trustee or to inquire into the validity, expediency,
or propriety of any such sale or other disposition.

          (ii) Subject to paragraphs (b) and (c) of this Section 5, to invest in
investment contracts and short term investments (including interest bearing
accounts with the Trustee or money market mutual funds advised by affiliates of
the Trustee) and in collective investment funds maintained by the Trustee for
qualified plans, in which case the provisions of each collective investment fund
in which the Trust is invested shall be deemed adopted by the Named Fiduciary
and the provisions thereof incorporated as a part of this Trust as long as the
fund remains exempt from taxation under Sections 401(a) and 501(a) of the Code.

          (iii) To cause any securities or other property held as part of the
Trust to be registered in the Trustee's own name, in the name of one or more of
its nominees, or in the Trustee's

                                       14
<PAGE>

account with the Depository Trust Company of New York, but the books and records
of the Trustee shall at all times show that all such investments are part of the
Trust.

          (iv) To keep that portion of the Trust in cash or cash balances as the
Named Fiduciary may, from time to time, deem to be in the best interest of the
Trust.

          (v) To make, execute, acknowledge, and deliver any and all documents
of transfer or conveyance and to carry out the powers herein granted.

          (vi) To borrow funds from a bank not affiliated with the Trustee in
order to provide sufficient liquidity to process Plan transactions in a timely
fashion, provided that the cost of borrowing shall be allocated in a reasonable
fashion to the investment fund(s) in need of liquidity.

          (vii) To settle, compromise, or submit to arbitration any claims,
debts, or damages due to or arising from the Trust; to commence or defend suits
or legal or administrative proceedings; to represent the Trust in all suits and
legal and administrative hearings; and to pay all reasonable expenses arising
from any such action, from the Trust if not paid by the Sponsor.

          (viii) To employ legal, accounting, clerical, and other assistance as
may be required in carrying out the provisions of this Agreement and to pay
their reasonable expenses and compensation from the Trust if not paid by the
Sponsor in a timely manner upon thirty (30) days notice from the Trustee.

          (ix) To invest all of any part of the assets of the Trust in any
collective investment trust or group trust which then provides for the pooling
of the assets of Plans described in Section 401(a) and exempt from tax under
Section 501(a) of the Code, or any comparable provisions of any future
legislation that amends, supplements, or supersedes those sections, provided
that such collective investment trust or group trust is exempt from tax under
the Code or regulations or rulings issued by the Internal Revenue Service; the
provisions of the document governing such collective investment trusts or group
trusts, as it may be amended from time to time, shall govern any investment
therein and are hereby made a part of this Trust Agreement.

          (x) To do all other acts although not specifically mentioned herein,
as the Trustee may deem necessary to carry out any of the foregoing powers and
the purposes of the Trust.

                                       15
<PAGE>

Section 6. Recordkeeping and Administrative Services to Be Performed.
           ---------------------------------------------------------

     (a) General. The Trustee shall perform those recordkeeping and
         -------
administrative functions described in Schedule "A" attached hereto and as
detailed in the Plan Administrative Manual. These recordkeeping and
administrative functions shall be performed within the framework of the Named
Fiduciary's written directions regarding the Plan's provisions, guidelines and
interpretations.

     (b) Accounts. The Trustee shall keep accurate accounts of all investments,
         --------
receipts, disbursements, and other transactions hereunder, and shall report the
value of the assets held in the Trust as of each Reporting Date. Within thirty
(30) days following each Reporting Date or within sixty (60) days in the case of
a Reporting Date caused by the resignation or removal of the Trustee or the
termination of this Agreement, the Trustee shall file with the Sponsor a written
account setting forth all investments, receipts, disbursements, and other
transactions effected by the Trustee between the Reporting Date and the prior
Reporting Date, and setting forth the value of the Trust as of the Reporting
Date. Except as otherwise required under ERISA, upon the expiration of one (1)
year from the date of filing such account with the Sponsor, the Trustee shall
have no liability or further accountability to anyone with respect to the
propriety of its acts or transactions shown in such account, except with respect
to such acts or transactions as to which the Sponsor shall within such one (1)
year period file with the Trustee written objections.

     (c) Inspection and Audit. All records generated by the Trustee in
         --------------------
accordance with paragraphs (a) and (b) shall be open to inspection and audit
during the Trustee's regular business hours, prior to the termination of this
Agreement, by the Named Fiduciary, the Sponsor or any person designated by the
Sponsor or Named Fiduciary. Upon the resignation or removal of the Trustee or
the termination of this Agreement, the Trustee shall provide to the Sponsor, at
no expense, in the format regularly provided to the Sponsor, a statement of each
Participant's accounts as of the resignation, removal, or termination, and the
Trustee shall provide, on a timely basis, to the Sponsor or the Plan's new
recordkeeper such further records as are reasonable, at the Sponsor's expense.
Notwithstanding the above, all records and accounts maintained or prepared by
the Trustee with respect to the Trust shall be preserved for such period as may
be required under any applicable law.

     (d) Effect of Plan Amendment. A representation as to the current qualified
         ------------------------
status of each Plan (including the most recent IRS determination letter for each
Plan) and a representation as to the Sponsor's intent to submit or resubmit the
Plan to the IRS for a new determination letter no later than

                                       16
<PAGE>

December 1999, is attached hereto as Schedule "F". The Trustee's provision of
the recordkeeping and administrative services set forth in this Section 6 shall
be conditioned on the Sponsor delivering to the Trustee a copy of any amendment
to the Plan as soon as administratively feasible following the amendment's
adoption, with, if requested, an IRS determination letter or representation
substantially in the form of Schedule "F" covering such amendment, and on the
Sponsor providing the Trustee on a timely basis with all the information the
Sponsor deems necessary for the Trustee to perform the recordkeeping and
administrative services and such other information as the Trustee may reasonably
request.

     (e) Returns, Reports and Information. The Sponsor or the Administrator
         --------------------------------
shall be responsible for the preparation and filing of all returns, reports, and
information required of the Trust or Plan by law, other than Participant reports
provided pursuant to Schedule "A". The Trustee shall provide the Sponsor or
Administrator with such information as reasonably requested to make these
filings. The Sponsor shall also be responsible for making any other disclosures
to Participants required by law, except such disclosure as may be required under
federal or state truth-in-lending laws with regard to Participant loans as
provided on Schedule "A", or as required for tax purposes following a
distribution from the Trust as provided on Schedule "A".

     (f) Allocation of Plan Interests. All transfers to, withdrawals from, or
         ----------------------------
other transactions regarding the Trust shall be conducted in such a way that the
proportionate interest in the Trust of each Plan and the fair market value of
that interest may be determined at any time. Whenever the assets of more than
one Plan are commingled in the Trust or in any investment option, the undivided
interest therein of each such Plan shall be debited or credited (as the case may
be) (i) for the entire amount of every contribution received on behalf of such
Plan, every benefit payment, or other expense attributable solely to such Plan,
and every other transaction relating only to such Plan; and (ii) for its
proportionate share of every item of collected or accrued income, gain or loss,
and general expense, and of any other transactions attributable to the Trust or
that investment option as a whole.

Section 7. Compensation and Expenses. Within thirty (30) days of receipt of the
           -------------------------
Trustee's bill, which shall be computed and billed in accordance with Schedule
"B" attached hereto and made a part hereof, as amended from time to time, the
Sponsor shall send to the Trustee a payment in such amount or the Sponsor may
direct the Trustee to deduct such amount from Participants' account, if
applicable. All expenses of the Trustee relating directly to the acquisition and
disposition of investments constituting

                                       17
<PAGE>

part of the Trust, and all taxes of any kind whatsoever that may be levied or
assessed under existing or future laws upon or in respect of the Trust or the
income thereof, shall be a charge against and paid from the appropriate
Participants' accounts.

Section 8. Directions and Indemnification.
           ------------------------------

     (a) Identity of Sponsor and Named Fiduciaries. The Trustee shall be fully
         -----------------------------------------
protected in relying on the fact that the Sponsor and the Named Fiduciaries
under a Plan are the individuals or persons named as such on the Authorization
Letters in the form of Schedules "D" and "E" attached hereto or on a Plan
Designation Form in accordance with Schedule "I" attached hereto or such other
individuals or persons as the Sponsor may notify the Trustee in writing.

     (b) Directions from Sponsor. Whenever the Sponsor or Administrator provides
         -----------------------
a direction to the Trustee, the Trustee shall not be liable for any loss, or by
reason of any breach, arising from the direction if the direction is contained
in a writing (or is oral and immediately confirmed in a writing) signed by any
individual whose name and signature have been submitted (and not withdrawn) in
writing to the Trustee by the Sponsor in the form attached hereto as Schedule
"D", provided the Trustee reasonably believes the signature of the individual to
be genuine. Such direction may also be made via Electronic Data Transfer ("EDT")
                                                                           ---
in accordance with procedures agreed to by the Sponsor and the Trustee;
provided, however, that the Trustee shall be fully protected in relying on such
direction as if it were a direction made in writing by the Sponsor. The Trustee
shall have no responsibility to ascertain any direction's (i) accuracy, (ii)
compliance with the terms of the Plan or any applicable law, or (iii) effect for
tax purposes or otherwise, unless it is clear on the direction's face that the
actions to be taken under the direction would be prohibited by the fiduciary
duty rules of section 404(a) of ERISA or the terms of this Agreement.

     (c) Directions from Named Fiduciary/Administrator. Whenever a Named
         ---------------------------------------------
Fiduciary provides a direction to the Trustee, the Trustee shall not be liable
for any loss, or by reason of any breach, arising from the direction (i) if the
direction is contained in a writing (or is oral and immediately confirmed in a
writing) signed by any individual whose name and signature have been submitted
(and not withdrawn) in writing to the Trustee by the Named Fiduciary or the
Administrator in the form attached hereto as Schedule "E" and (ii) if the
Trustee reasonably believes the signature of the individual to be genuine,
unless it is clear on the direction's face that the actions to be taken under
the direction would be

                                       18
<PAGE>

prohibited by the fiduciary duty rules of section 404(a) of ERISA or would be
contrary to the terms of the Plan or this Agreement.

     (d) Co-Fiduciary Liability. In any other case, the Trustee shall not be
         ----------------------
liable for any loss, or by reason of any breach, arising from any act or
omission of another fiduciary under the Plan except as provided in section
405(a) of ERISA. Without limiting the foregoing, the Trustee shall have no
liability for the acts or omissions of any predecessor or successor trustee.

     (e) Indemnification.
         ---------------

          (i) The Sponsor shall indemnify the Trustee against, and hold the
Trustee harmless from, any and all loss, damage, penalty, liability, cost, and
expense, including without limitation, reasonable attorneys' fees, that may be
incurred by, imposed upon, or asserted against the Trustee by reason of any
claim, regulatory proceeding, or litigation arising from any act done or omitted
to be done by any individual or person with respect to the Plan or Trust,
excepting only any and all loss, etc., arising solely from the Trustee's
negligence, bad faith or breach of any statutory or other duty owed to the Plan,
the Sponsor or the Named Fiduciary.

          (ii) The Trustee shall indemnify the Sponsor against and hold the
Sponsor harmless from any and all such loss, damage, penalty, liability, cost,
and expense, including without limitation, reasonable attorneys' fees and
disbursements, that may be incurred by, imposed upon, or asserted against the
Sponsor resulting from the Trustee's negligence or bad faith.

     (f) Survival. The provisions of this Section 8 shall survive the
         --------
termination of this Agreement.

Section 9. Resignation or Removal of Trustee.
           ---------------------------------

     (a) Resignation. The Trustee may resign at any time upon sixty (60) days'
         -----------
notice in writing to the Sponsor, unless a shorter period of notice is agreed
upon by the Sponsor.

     (b) Removal. The Sponsor may remove the Trustee at any time upon sixty (60)
         -------
days' notice in writing to the Trustee, unless a shorter period of notice is
agreed upon by the Trustee.

                                       19
<PAGE>

Section 10. Successor Trustee.
            -----------------

     (a) Appointment. If the office of Trustee becomes vacant for any reason,
         -----------
the Sponsor may in writing appoint a successor trustee under this Agreement. The
successor trustee shall have all of the rights, powers, privileges, obligations,
duties, liabilities, and immunities granted to the Trustee under this Agreement.
The successor trustee and predecessor trustee shall not be liable for the acts
or omissions of the other with respect to the Trust.

     (b) Acceptance. When the successor trustee accepts its appointment under
         ----------
this Agreement, title to and possession of the Trust assets shall immediately
vest in the successor trustee without any further action on the part of the
predecessor trustee. The predecessor trustee shall execute all instruments and
do all acts that reasonably may be necessary or reasonably may be requested in
writing by the Sponsor or the successor trustee to vest title to all Trust
assets in the successor trustee or to deliver all Trust assets to the successor
trustee.

     (c) Corporate Action. Any successor of the Trustee or successor trustee,
         ----------------
through sale or transfer of the business or trust department of the Trustee or
successor trustee, or through reorganization, consolidation, or merger, or any
similar transaction, shall, upon consummation of the transaction, become the
successor trustee under this Agreement.

Section 11. Termination. This Agreement may be terminated at any time by the
            -----------
Sponsor upon sixty (60) days' notice in writing to the Trustee. On the date of
the termination of this Agreement, the Trustee shall forthwith transfer and
deliver to such individual or entity as the Sponsor shall designate, all cash
and assets then constituting the Trust. If, by the termination date, the Sponsor
has not notified the Trustee in writing as to whom the assets and cash are to be
transferred and delivered, the Trustee may bring an appropriate action or
proceeding for leave to deposit the assets and cash in a court of competent
jurisdiction. The Trustee shall be reimbursed by the Sponsor for all costs and
expenses of the action or proceeding including, without limitation, reasonable
attorneys' fees.

Section 12. Resignation, Removal, and Termination Notices. All notices of
            ---------------------------------------------
resignation, removal, or termination under this Agreement must be in writing and
mailed to the party to which the notice is being given by certified or
registered mail, return receipt requested, to Lyondell Chemical Company,
Benefits Administrative Committee, One Houston Center, 1221 McKinney, Suite
1600, Houston, Texas 77253-3646, and to the Trustee c/o John M. Kimpel, Fidelity
Investments, 82 Devonshire Street, Boston,

                                       20
<PAGE>

Massachusetts 02109, or to such other addresses as the parties have notified
each other of in the foregoing manner.

Section 13. Duration. This Trust shall continue in effect without limit as to
            --------
time, subject, however, to the provisions of this Agreement relating to
amendment, modification, and termination thereof.

Section 14. Amendment or Modification. This Agreement may be amended or modified
            -------------------------
at any time and from time to time only by an instrument in writing executed by
both the Sponsor and the Trustee. Notwithstanding the foregoing, to reflect
increased operating costs only (and not as a result in any change in projections
less than those specified in Schedule "B") the Trustee may once each calendar
year amend Schedule "B" without the Sponsor's consent upon seventy-five (75)
days' prior written notice to the Sponsor.

Section 15. Electronic Services.
            -------------------

     (a) The Trustee may provide communications and services via electronic
medium ("Electronic Services"), including, but not limited to, Fidelity Plan
         -------------------
Sponsor WebStation, Client Intranet, Client e-mail, interactive software
products or any other information provided in an electronic format. The Sponsor
agrees to keep confidential and not publish, copy, broadcast, retransmit,
reproduce, commercially exploit or otherwise redisseminate the data,
information, software or services without the Trustee's written consent.

     (b) The Sponsor shall be responsible for installing and maintaining all
Electronic Services on its computer network and/or Intranet upon receipt in a
manner so that the information provided via the Electronic Service will appear
in the same form and content as it appears on the form of delivery, and for any
programming required to accomplish the installation. If applicable, materials
provided for Plan Sponsor's intranet web sites shall be installed by the Sponsor
and shall be clearly identified as originating from Fidelity. The Sponsor shall
remove, as soon as practicable, Electronic Services from its computer network
and/or Intranet, or replace the Electronic Service with an updated service
provided by the Trustee, upon written notification (including written
notification via facsimile) by the Trustee.

     (c) All Electronic Services shall be provided to the Sponsor without any
express or implied legal warranties or acceptance of legal liability by the
Trustee relative to the use of material or Electronic

                                       21
<PAGE>

Services by the Sponsor. No rights are conveyed to any property, intellectual or
tangible, associated with the contents of the Electronic Services and related
material.

     (d) To the extent that any Electronic Services utilize Internet services to
transport data or communications, the Trustee will take, and Sponsor agrees to
follow, reasonable security precautions; however, the Trustee disclaims any
liability for interception of any such data or communications if such reasonable
security precautions were taken and the Trustee was not negligent or acting in
bad faith. The Trustee shall not be responsible for, and makes no warranties
regarding access, speed or availability of Internet or network services. The
Trustee shall not be responsible for any loss or damage related to or resulting
from any changes or modifications to the electronic material after delivering it
to the Sponsor.

Section 16. General.
            -------

     (a) Performance by Trustee, its Agents or Affiliates. The Sponsor
         ------------------------------------------------
acknowledges and authorizes that the services to be provided under this
Agreement shall be provided by the Trustee, its agents or affiliates, including
Fidelity Investments Institutional Operations Company and/or Fidelity
Institutional Retirement Services Company or its successor, and that certain of
such services may be provided pursuant to one or more other contractual
agreements or relationships.

     (b) Delegation by Employer. By authorizing the assets of any Plan as to
         ----------------------
which it is an Employer to be deposited in the Trust, each Employer, other than
the Sponsor, hereby irrevocably delegates and grants to the Sponsor full and
exclusive power and authority to exercise all of the powers conferred upon the
Sponsor and each Employer by the terms of this Agreement, and to take or refrain
from taking any and all action which such Employer might otherwise take or
refrain from taking with respect to this Agreement, including the sole and
exclusive power to exercise, enforce or waive any rights whatsoever which such
Employer might otherwise have with respect to the Trust, and irrevocably
appoints the Sponsor as its agent for all purposes under this Agreement. The
Trustee shall have no obligation to account to any such Employer or to follow
the instructions of or otherwise deal with any such Employer, the intention
being that the Trustee shall deal solely with the Sponsor.

     (c) Entire Agreement. This Agreement contains all of the terms agreed upon
         ----------------
between the parties with respect to the subject matter hereof.

                                       22
<PAGE>

     (d) Waiver. No waiver by either party of any failure or refusal to comply
         ------
with an obligation hereunder shall be deemed a waiver of any other or subsequent
failure or refusal to so comply.

     (e) Successors and Assigns. The stipulations in this Agreement shall inure
         ----------------------
to the benefit of, and shall bind, the successors and assigns of the respective
parties.

     (f) Partial Invalidity. If any term or provision of this Agreement or the
         ------------------
application thereof to any person or circumstances shall, to any extent, be
invalid or unenforceable, the remainder of this Agreement, or the application of
such term or provisions to persons or circumstances other than those as to which
it is held invalid or unenforceable, shall not be affected thereby, and each
term and provision of this Agreement shall be valid and enforceable to the
fullest extent permitted by law.

     (g) Section Headings. The headings of the various sections and subsections
         ----------------
of this Agreement have been inserted only for the purposes of convenience and
are not part of this Agreement and shall not be deemed in any manner to modify,
explain, expand or restrict any of the provisions of this Agreement.

Section 17. Governing Law.
            -------------

     (a) Massachusetts Law Controls. This Agreement is being made in the
         --------------------------
Commonwealth of Massachusetts, and the Trust shall be administered as a
Massachusetts trust. The validity, construction, effect, and administration of
this Agreement shall be governed by and interpreted in accordance with the laws
of the Commonwealth of Massachusetts, except to the extent those laws are
superseded under section 514 of ERISA.

     (b) Trust Agreement Controls. The Trustee is not a party to the Plan, and
         ------------------------
in the event of any conflict between the provisions of the Plan and the
provisions of this Agreement, the provisions of this Agreement shall control.

Section 18. Plan Qualification. The Sponsor shall be responsible for verifying
            ------------------
that while any assets of a particular Plan are held in the Trust, the Plan (i)
is qualified within the meaning of section 401(a) of the Code; (ii) is permitted
by existing or future rulings of the United States Treasury Department to pool
its funds in a group trust; and (iii) permits its assets to be commingled for
investment purposes with the assets of other such plans by investing such assets
in this Trust. If any Plan ceases to be qualified within

                                       23
<PAGE>

the meaning of section 401(a) of the Code, the Sponsor shall notify the Trustee
as promptly as is reasonable. Upon receipt of such notice, the Trustee shall
promptly segregate and withdraw from the Trust, the assets which are allocable
to such disqualified Plan, and shall dispose of such assets in the manner
directed by the Sponsor.

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their duly authorized officers as of the day and year first above
written.

                                       24
<PAGE>


<TABLE>
<CAPTION>
                                            LYONDELL CHEMICAL COMPANY

<S>                                         <C>
Attest:  /s/ JoAnn L. Beck                  By:    /s/ Jeffrey R. Pendergraft   /s/ JLB
         ---------------------                     ---------------------------------------------
         Asst. Secretary
                                            Name:  Jeffrey R. Pendergraft
                                                   ---------------------------------------------
                                            Title: Executive VP and Chief Administrative Officer
                                                   ---------------------------------------------
                                            Date:  March 12, 1999
                                                   ---------------------------------------------


                                            EQUISTAR CHEMICALS, LP


Attest:  /s/ Gerald A. O'Brien              By:    /s/ Myra J. Perkinson   /s/ JLB
         ---------------------                     -----------------------------
         Secretary
                                            Name:  VP, Human Resources
                                                   ------------------------------

                                            Title: Myra J. Perkinson
                                                   ----------------------------

                                            Date:  March 12, 1999
                                                   ------------------------------


                                            LYONDELL-CITGO REFINING COMPANY LTD


Attest:  /s/ Steven B. Strauss              By:    /s/ Rose Nenni   /s/ JLB
         ---------------------                     ------------------------------
         Secretary
                                            Name:  Rose Nenni
                                                   ------------------------------

                                            Title: VP, Human Resources
                                                   ------------------------------

                                            Date:  March 15, 1999
                                                   ------------------------------


                                            FIDELITY MANAGEMENT TRUST
                                            COMPANY


Attest:  /s/ Douglas O. Kent                By:   /s/ Carolyn Redden
         ---------------------                    ------------------------------
         Assistant Clerk
                                            Name:  Carolyn Redden
                                                   -----------------------------

                                            Title: Vice President
                                                   -----------------------------

                                            Date:  March 30, 1999
                                                   -----------------------------
</TABLE>

                                       25
<PAGE>

                                  Schedule "A"

                             ADMINISTRATIVE SERVICES
                             -----------------------

Administration
--------------

..    Establishment and maintenance of Participant account and election
     percentages.

..    Maintenance of the following Plan investment options:

     .    Fidelity Fund
     .    Fidelity Intermediate Bond Fund
     .    Fidelity Retirement Money Market Fund
     .    Spartan U.S. Equity Index Fund
     .    Dodge & Cox Balanced Fund
     .    PBHG Growth Fund
     .    Neuberger & Berman Genesis Trust
     .    American EuroPacific Growth Fund
     .    IDS New Dimensions Fund
     .    Lyondell DPO Stock (frozen EXCEPT as to Participants in Lyondell
          Chemical Company 401(k) and Savings Plan)
     .    Lyondell DR Stock (frozen EXCEPT as to Participants in Lyondell
          Chemical Company 401(k) and Savings Plan)
     .    ARCO Stock (frozen)
     .    Millenium Stock (frozen)
     .    BrokerageLink

Mutual Fund Window investment options as follows:

     .    Alger Capital Appreciation Retirement
     .    Alger Mid Cap Growth Retirement
     .    Alger Small Cap Retirement
     .    AMR Balanced Fund
     .    AMR International Equity
     .    AMR Large Cap Value
     .    AMR Limited-Term Income
     .    Ariel Appreciation Fund
     .    Ariel Premier Bond - Investor
     .    Fidelity Balanced Fund
     .    Baron Asset Fund
     .    Baron Growth & Income
     .    Blue Chip Growth
     .    Calvert Capital Accumulation Fund - Class A
     .    Calvert New Africa Fund - Class A
     .    Calvert New Vision Small Cap Fund - Class A
     .    Calvert Social Investment Fund: Managed Growth Portfolio - Class A
     .    Calvert World Values: International Equity
     .    Fidelity Canada Fund
<PAGE>

     .    Fidelity Capital & Income Fund
     .    Fidelity Capital Appreciation Fund
     .    Fidelity Contrafund II
     .    Fidelity Convertible Securities Fund
     .    Fidelity Diversified International Fund
     .    Fidelity Dividend Growth Fund
     .    Domini Social Equity Fund
     .    Founders Balanced Fund
     .    Founders Blue Chip Fund
     .    Founders Frontier Fund
     .    Founders Growth Fund
     .    Founders Passport Fund
     .    Founders Special Fund
     .    Founders Worldwide Growth Fund
     .    INVESCO Dynamics Fund
     .    INVESCO Growth Fund
     .    INVESCO High Yield Fund
     .    INVESCO Industrial Income
     .    INVESCO Multi- Asset Allocation
     .    INVESCO Select Income
     .    INVESCO Small Company Growth Fund
     .    INVESCO Total Return Fund
     .    INVESCO Value Equity Fund
     .    Janus Flexible Income Fund
     .    Fidelity Emerging Growth Fund
     .    Fidelity Emerging Markets
     .    Fidelity Equity Income
     .    Fidelity Equity Income II
     .    Fidelity Europe
     .    Fidelity Europe Capital Apprec.
     .    Fidelity Export and Multinat'l
     .    Fidelity Asset Manager
     .    Fidelity Asset Mg. Gro.
     .    Fidelity Asset Mg. Inc.
     .    Fidelity Fifty
     .    Fidelity Fund
     .    Fidelity Intermediate Bond Fund
     .    Fidelity Retirement Money Market Fund
     .    Fidelity Freedom 2000
     .    Fidelity Freedom 2010
     .    Fidelity Freedom 2020
     .    Fidelity Freedom 2030
     .    Fidelity Freedom Income Fund
     .    Fidelity Ginnie Mae
     .    Fidelity Global Balanced
     .    Fidelity Govt. Securities
     .    Fidelity Growth Company

                                       ii
<PAGE>

     .    Fidelity Institutional Short-Intermediate Govt.
     .    Fidelity Intermediate Bond
     .    Fidelity International Value
     .    Fidelity Int'l Growth & Income
     .    Fidelity Investment Grade Bond
     .    Fidelity Mid Cap Stock
     .    Fidelity Japan
     .    Fidelity Large Cap Stock
     .    Fidelity Latin America
     .    Franklin Small Cap Growth I
     .    MAS Balanced Portfolio - Adviser Class
     .    MAS Fixed Income - Adviser Class
     .    MAS High Yield Portfolio - Adviser Class
     .    MAS Mid Cap Growth Portfolio- Adviser Class
     .    Montgomery International Small Cap
     .    Montgomery Select 50
     .    Morgan Stanley Active Country Allocation B
     .    Morgan Stanley Emerging Markets
     .    Morgan Stanley Global Equity Portfolio B
     .    Morgan Stanley International Magnum Class B
     .    Morgan Stanley Emerging Growth Class B
     .    Morgan Stanley Equity Growth B
     .    Templeton Mutual Discovery Fund I
     .    Templeton Mutual Shares Fund Class I
     .    Neuberger & Berman Focus Trust
     .    Neuberger & Berman Guardian Trust
     .    Neuberger & Berman Manhattan Trust
     .    Neuberger & Berman Partners Trust
     .    Neuberger & Berman Socially Responsible
     .    Fidelity New Markets Income Fund
     .    Fidelity OTC Portfolio
     .    Fidelity Overseas Fund
     .    Fidelity Pacific Basin Fund
     .    PBHG Emerging Growth
     .    PIMCO Capital Appreciation Fund
     .    PIMCO Global Bond Fund
     .    PIMCO High Yield Fund
     .    PIMCO Low Duration Fund
     .    PIMCO Long-Term US Government
     .    PIMCO Mid-Cap Growth
     .    PIMCO Total Return - Admin.
     .    Fidelity Puritan Fund
     .    Fidelity Real Estate Investment Portfolio
     .    Fidelity Retirement Growth Fund
     .    Fidelity Short-Intermediate Govt. Fund
     .    Fidelity Short-Term Bond Fund
     .    Fidelity Small Cap Selector

                                      iii
<PAGE>

     .    Fidelity Southeast Asia Fund
     .    Spartan Market Index Fund
     .    Fidelity Stock Selector
     .    Strong Total Return Fund
     .    Strong Advantage Fund
     .    Strong Common Stock Fund
     .    Strong Discovery Fund
     .    Strong Government Securities Fund
     .    Strong Growth Fund
     .    Strong Opportunity Fund
     .    Strong Schafer Value
     .    Strong Short-Term Bond Fund
     .    Fidelity Target Timeline 1999
     .    Fidelity Target Timeline 2001
     .    Fidelity Target Timeline 2003
     .    Fidelity TechnoQuant Growth
     .    Templeton Foreign Smaller Companies I
     .    Templeton Developing Markets Trust I
     .    Templeton Foreign Fund I
     .    Templeton Global Bond Fund I
     .    Templeton Growth Fund I
     .    Templeton World Fund I
     .    Fidelity Trend Fund
     .    UAM/FMA Small Company Institutional
     .    UAM/FPA Crescent Institutional
     .    UAM/McKee Int'l Equity Institutional
     .    UAM/Rice Hall Small Cap Institutional
     .    UAM/Sterling Equity Institutional
     .    Fidelity U.S. Bond Index Fund
     .    USAA Emerging Markets Fund
     .    USAA GNMA Fund
     .    USAA Growth Fund
     .    USAA Income Fund
     .    USAA Income Stock Fund
     .    USAA International Fund
     .    Fidelity Utilities Fund
     .    Fidelity Value Fund
     .    Warburg Capital Appreciation Fund
     .    Warburg Growth & Income Fund
     .    Warburg Global Fixed Income Fund
     .    Warburg International Equity Fund
     .    Warburg Small Company Value Fund
     .    Warburg Emerging Growth Fund
     .    Fidelity Worldwide Fund

                                       iv
<PAGE>

..    Maintenance of the following money classifications for the Lyondell
     Chemical Company 401(k) and Savings Plan:

     01   Pre-tax
     02   After-tax
     03   Company Match
     04   Transferable Shares
     05   Prior ESOP Post-Tax
     06   Prior ESOP Company Match
     07   Company Match on Post-tax
     08   Old Company Match
     09   Rollover

..    Maintenance of the following money classifications for the Equistar
     Chemicals, LP Savings and Investment Plan:

     01   Pre-tax
     02   After-tax
     03   Company Match
     04   Prior Plan
     05   Prior ESOP
     06   ARCO ESOP
     07   Prior After-tax
     08   ARCO Match
     09   Rollover
     10   GR - Pre-tax (GR=Grandfathered and is subject to QJSA)
     11   GR - Post-tax
     12   GR - Company Match
     13   GR - Rollover

..    Maintenance of the following money classifications for the Equistar
     Chemicals, LP Savings and Investment Plan for Represented Employees:

     01   Pre-tax
     02   After-Tax
     03   Company Match
     04   Prior Plan
     05   Prior ESOP
     06   Rollover

..    Maintenance of the following money classifications for the Lyondell-Citgo
     Refining Company 401(k) and Savings Plan for Non-Represented Employees:

     01   Pre-tax
     02   After-tax
     03   Company Match
     04   ARCO ESOP After-tax
     05   Prior After-tax
     06   ARCO ESOP Match

                                       v
<PAGE>

     07   Rollover

..    Maintenance of the following money classifications for the Lyondell-Citgo
     Refining Company 401(k) and Savings Plan for Represented Employees:

     01   Pre-tax
     02   After-tax
     03   Company Match
     04   ARCO ESOP After-tax
     05   Prior After-tax
     06   ARCO ESOP Match
     07   Rollover

..    The Trustee will provide the recordkeeping and administrative services set
     forth on this Schedule "A" and as detailed in the Plan Administrative
     Manual. The Plan Administrative Manual shall be completed by Fidelity and
     the Sponsor after the effective date of this Agreement and shall contain
     detailed information and processes regarding the recordkeeping and
     administrative services set forth on this Schedule "A". The content of the
     Plan Administrative Manual shall be mutually agreed to by Fidelity and the
     Sponsor. To the extent that the terms of the Plan Administrative Manual
     differ from the terms of this Schedule "A" or this Agreement, this Schedule
     "A" and this Agreement shall be amended accordingly and the Plan
     Administrative Manual is incorporated by reference herein.

A)   Provide Participant Telephone Services

     1. Fidelity registered representatives are available from 8:30 a.m. - 12:00
     midnight ET each business day to provide toll free telephone service for
     Participant inquiries and transactions. Additionally, Participants have 24
     hour account balance and transaction inquiry access utilizing our automated
     voice response system and the Internet.

     2. For security purposes, all calls are recorded. In addition, several
     levels of security are available including the verification of a Personal
     Identification Number (PIN) and/or any other indicative data resident on
     the system.

     3. Through our telephone services, Fidelity provides the following
     services:

          .    Provide Plan investment option information.
          .    Maintain Plan specific provisions.
          .    Process exchanges (transfers) between investment options on a
               daily basis.
          .    Maintain and process changes to Participants' contribution
               allocations for all money sources.
          .    Allow Participants to change their deferral and after-tax
               percentages and provide updates via EDT for customer to apply to
               its payrolls accordingly.
          .    Consult with Participants in various loan scenarios and generate
               all documentation.
          .    Process all Participant loan and withdrawal requests via
               Fidelity's toll-free telephone service according to Plan
               provisions on a daily basis.
          .    Process in-service withdrawals via telephone due to certain
               circumstances previously approved by the Administrator, if any.

                                       vi
<PAGE>

          .    Process hardship withdrawals via telephone according to
               procedures approved by the Named Fiduciary and in accordance with
               the procedures set forth in Exhibit "A" attached hereto..
          .    Enroll new Participants via telephone; provide confirmation of
               enrollment within five (5) days of the request.

B)   Plan Accounting

     1. Process payroll contributions according to payroll frequency via
     electronic data transfer (EDT), consolidated magnetic tape or diskette. The
                               ---
     data format will be provided by Fidelity.

     2. Provide Plan and Participant level accounting for the money
     classifications for the Plan.

     3. Audit and reconcile the Plan and Participant accounts daily.

     4. Provide daily Plan and Participant level accounting for the Plan
     investment options.

     5. Reconcile and process Participant withdrawal requests as approved and
     directed by the Sponsor. All requests are paid based on the current market
     values of Participants' accounts, not advanced or estimated values. A
     distribution report will accompany each check.

     6. Track individual Participant loans; process loan withdrawals; re-invest
     loan repayments; and prepare and deliver comprehensive reports to the
     Sponsor to assist in the administration of Participant loans.

     7. Maintain and process changes to Participants' prospective and existing
     investment mix elections via Fidelity's toll-free telephone service.

C)   Participant Reporting

     1. Mail confirmation to Participants of all transactions initiated via
     Fidelity Telephone Services within three (3) calendar days of the
     transaction.

     2. Prepare and mail via first class to each Plan Participant a quarterly
     detailed Participant statement reflecting all activity for the period.
     Statements will be mailed no later than twenty (20) calendar days after
     each quarter end.

     3. Mail required 402(f) notification for distribution from the Plan. This
     notice advises Participants of the tax consequences of their Plan
     distributions.

D)   Plan Reporting

     1. Prepare, reconcile and deliver a monthly Trial Balance Report presenting
     all money classes and investments. This report is based on the market value
     as of the last business day of the month. The report will be delivered not
     later than twenty (20) days after the end of each month in the absence of
     unusual circumstances.

                                      vii
<PAGE>

     2. Prepare, reconcile and deliver a Quarterly Administrative Report
     presenting both on a Participant and a total Plan basis all money classes,
     investment positions and a summary of all activity of the Participant and
     Plan as of the last business day of the quarter. The report will be
     delivered not later than twenty (20) days after the end of each quarter in
     the absence of unusual circumstances.

E)   Government Reporting

     1. Process year-end tax reports for Participants - 1099R, as well as
     financial reporting to assist in the preparation of Form 5500 for each
     participating Plan.

F)   Communication Services

     1. Employee communications describing available investment options,
     including multimedia informational materials and group presentations.

G)   Other

     1. Performance of non-discrimination limitation testing pursuant to the
     terms of a separate agreement between Fidelity and the Sponsor. In order to
     obtain this service, the client shall be required to provide the
     information identified in the Fidelity Discrimination Testing Package
     Guidelines.

     2. Monitor and process required minimum distribution amounts (MRD) in
                                                                   ---
     accordance with the Plan document as follows: the Trustee will notify the
     MRD Participant and, upon notification from the MRD Participant, will use
     the MRD Participant's information to process their distributions. If the
     MRD Participant does not respond to the Trustee's notification, the Sponsor
     directs the Trustee to automatically begin the required distributions for
     the Participant in a timely fashion.

     3. The Fidelity Recordkeeping System is available on-line to the Sponsor
     via our Plan Sponsor Webstation ("PSW"). PSW is a graphical, Windows-based
                                       ---
     application that provides current Plan and Participant-level information,
     including indicative data, account balances, activity and history.

BENEFITS ADMINISTRATIVE COMMITTEE           FIDELITY MANAGEMENT TRUST
OF LYONDELL CHEMICAL COMPANY                COMPANY


By: /s/ Myra J. Perkinson  3/16/99          By: /s/ Carolyn Redden     3/30/99
    -------------------------------------       --------------------------------
                           Date                   Vice President       Date

                                      viii
<PAGE>

                                   Exhibit "A"

             OPERATING PROCEDURES FOR HARDSHIP WITHDRAWALS BY PHONE
             ------------------------------------------------------

1.   The participant calls Fidelity to request a hardship withdrawal.

2.   Assuming the participant has met the initial plan requirements, the
     Participant Services representative enters the hardship request.

     Plan requirements are as follows:

     .    The individual is an active participant with an available pre-tax
          balance;
     .    All loanable assets have been exhausted;
     .    All in-service after-tax withdrawal assets have been exhausted;
     .    The participant declares that the hardship withdrawal meets one of the
          four safe-harbor provisions.

3.   Fidelity mails the hardship withdrawal application and procedures to the
     participant's home.

4.   The participant adheres to the following procedures in order to execute the
     transaction:

     .    Reviews the application carefully and notes the expiration date.
     .    Signs the application and procedures page.
     .    Submits the required documentation noted on the second page of the
          procedures.
     .    Submits the signed application, signed procedures and any supporting
          documentation to:

          Regular Mail
          Fidelity Investments
          P.O. Box 9029
          Boston, MA  02205-8631

          Overnight Mail
          Fidelity Institutional Retirement Services Company
          300 Puritan Way, MM2M
          Marlborough, MA 01752

5.   Fidelity receives the participant's application and reviews it for
     participant signature and required documentation.

     The  required documentation includes one of the following:

          .    Purchase (excluding mortgage payments) of primary residence A
               copy of the Purchase and Sale Agreement signed by both buyer and
               seller, or a copy of the Construction Contract for new
               construction

                                       ix
<PAGE>

          .    Payment of tuition for the next year of post-secondary education
               for the participant, his/her spouse, children or dependents A
               copy of the bill from the educational institution or a letter
               from the education institution (must be on school's letterhead)
               attesting to the fact that the student is enrolled for the next
               12 months and providing the costs for tuition, room and board,
               and books.

          .    Payment of deductible medical or dental expenses not covered by
               insurance for the participant, his/her spouse, children or
               dependents An Explanation of Benefits (EOB) form from the
               participant's insurance carrier, or a copy of the letter from the
               participant's HMO, detailing any out of pocket deductibles,
               co-payments or denial of coverage for services rendered.

          .    Payment needed to prevent eviction under the terms of a lease
               agreement or foreclosure on the mortgage of the participant's
               primary residence A Notice of Eviction or Foreclosure in writing
               from the landlord or mortgage holder, including the amount in
               arrears that must be paid in order to avoid eviction or
               foreclosure.

6.   If the application and documentation meet the requirements, Fidelity will
     execute the transaction and mail the check directly to the participant's
     home.

7.   If the application and documentation do not meet t he requirements,
     Fidelity will send a letter to the participant indicating that the hardship
     request was rejected and the reason for such rejection (i.e.: no signature,
     insufficient documentation).

8.   If Fidelity is unsure whether the participant's documentation meets the
     requirements, Fidelity will forward the hardship request to the Named
     Fiduciary for direction (written approval or rejection).

BENEFITS ADMINISTRATIVE COMMITTEE
OF LYONDELL CHEMICAL COMPANY


By: /s/ Myra J. Perkinson         3/16/99   /s/ JLB
    -----------------------------------------------
                                  Date

                                       x
<PAGE>

                                  Schedule "B"

                                  FEE SCHEDULE
                                  ------------

<TABLE>
<S>                                     <C>
Enrollments by Phone:                   $5.00 per year per non-active employee residing on
                                        Fidelity's Participant recordkeeping system.

Loan Fee:                               Establishment fee of $35.00 per loan account;
                                        annual fee of $15.00 per loan account.

Minimum Required Distribution:          $25.00 per Participant per MRD withdrawal.

In-Service Withdrawals by Phone:        $20.00 per withdrawal.

Plan Sponsor Webstation (PSW):          Two (2) user IDs provided free of charge, each
                                        additional user ID, $500 per year.

Return of Excess Contribution Fee:      $25.00 per Participant, one-time charge per
                                        calculation and check generation.

Non-Fidelity Mutual Funds:              .15% annual fee on the assets in the IDS New
                                        Dimensions Fund; .10% annual administration fee on
                                        the Dodge & Cox Balanced Fund; .35% annual
                                        administration fee on the following Non-Fidelity
                                        Mutual Fund assets which are equity/balanced
                                        funds:  AMR Funds, Calvert Funds,
                                        Franklin/Templeton Funds, Founders Funds, Pilgrim
                                        Baxter Funds and Warburg Pincus Funds.  .25% annual
                                        administration fee on all other Non-Fidelity Mutual
                                        Fund assets (all Non-Fidelity Mutual Fund fees to
                                        be paid by the Non-Fidelity Mutual Fund vendor.)

Self Directed Brokerage:                Fidelity BrokerageLink Account Fee:
                                        ----------------------------------
                                        Annual Account Fee of $75.00 per account within
                                        each Plan per year. Fidelity BrokerageLink Plan
                                        Account minimum initial investment is $2,500
                                        (minimum initial investment not applicable to
                                        existing accounts transferred from prior
                                        recordkeeper); subsequent transfer minimum is
                                        $1,000.  Fees for individual trades will be charged
                                        in accordance with a separate commission schedule..

Proxy Services:                         The cost of proxy administration, mailing and
                                        tabulation services is passed through to the
                                        Sponsor (currently, approximately $3.42 per
</TABLE>

                                       xi
<PAGE>

<TABLE>
<S>                                     <C>
                                        Participant).  The Trustee shall not charge any
                                        additional fee for these proxy services.
</TABLE>

..    Other Fees: separate charges for corporate actions, optional
     non-discrimination testing, extraordinary expenses resulting from large
     numbers of simultaneous manual transactions, from errors not caused by
     Fidelity, reports not contemplated in this Agreement, or extraordinary
     and/or duplicative expenses associated with electronic services. The
     Administrator may withdraw reasonable administrative fees from the Trust by
     written direction to the Trustee.

Trustee Fee
-----------

..    To the extent that assets are invested in Company Stock, .10 % of such
     assets in the Trust payable pro rata quarterly on the basis of such assets
     as of the calendar quarter's last valuation date, but no less than $10,000
     nor more than $125,000 per year.

Note: These fees have been negotiated and accepted based on the following Plan
----
characteristics: 5 Plans in the relationship, current Plan assets of $638
million, current participation of 9,486 Participants, current stock assets of
$ 142.9 million, total Fidelity actively managed Mutual Fund assets of $ 243.4
million, total Fidelity non-actively managed Mutual Fund assets of $58.0
million, total FundsNet/Outside Fund assets of $193.7 million and projected
net cash flows of $4.7 million per year. Fees contingent on the liquidation of
the IDS New Dimensions Fund no later than 12/31/99. Fees will be subject to
revision if these Plan characteristics change significantly by either falling
below or exceeding current or projected levels by an amount in excess of 10%.

BENEFITS ADMINISTRATIVE COMMITTEE           FIDELITY MANAGEMENT TRUST
OF LYONDELL CHEMICAL COMPANY                COMPANY


By: /s/ Myra J. Perkinson  3/16/99          By: /s/ Carolyn Redden     3/30/99
    -------------------------------------       --------------------------------
                           Date                   Vice President       Date

                                      xii
<PAGE>

                                  Schedule "C"

                               INVESTMENT OPTIONS
                               ------------------

     In accordance with Section 5(b), the Named Fiduciary hereby directs the
Trustee that Participants' individual accounts may be invested in the following
investment options:

     .    Fidelity Fund
     .    Fidelity Intermediate Bond Fund
     .    Fidelity Retirement Money Market Fund
     .    Spartan U.S. Equity Index Fund
     .    Dodge & Cox Balanced Fund
     .    PBHG Growth Fund
     .    Neuberger & Berman Genesis Trust
     .    American EuroPacific Growth Fund
     .    IDS New Dimensions Fund
     .    Lyondell DPO Stock (frozen EXCEPT as to Participants in Lyondell
          Chemical Company 401(k) and Savings Plan)
     .    Lyondell DR Stock (frozen EXCEPT as to Participants in Lyondell
          Chemical Company 401(k) and Savings Plan)
     .    ARCO Stock (frozen)
     .    Millenium Stock (frozen)
     .    BrokerageLink

Mutual Fund Window investment options as follows:

     .    Alger Capital Appreciation Retirement
     .    Alger Mid Cap Growth Retirement
     .    Alger Small Cap Retirement
     .    AMR Balanced Fund
     .    AMR International Equity
     .    AMR Large Cap Value
     .    AMR Limited-Term Income
     .    Ariel Appreciation Fund
     .    Ariel Premier Bond - Investor
     .    Fidelity Balanced Fund
     .    Baron Asset Fund
     .    Baron Growth & Income
     .    Blue Chip Growth
     .    Calvert Capital Accumulation Fund - Class A
     .    Calvert New Africa Fund - Class A
     .    Calvert New Vision Small Cap Fund - Class A
     .    Calvert Social Investment Fund: Managed Growth Portfolio - Class A
     .    Calvert World Values: International Equity
     .    Fidelity Canada Fund

                                      xiii
<PAGE>

     .    Fidelity Capital & Income Fund
     .    Fidelity Capital Appreciation Fund
     .    Fidelity Contrafund II
     .    Fidelity Convertible Securities Fund
     .    Fidelity Diversified International Fund
     .    Fidelity Dividend Growth Fund
     .    Domini Social Equity Fund
     .    Founders Balanced Fund
     .    Founders Blue Chip Fund
     .    Founders Frontier Fund
     .    Founders Growth Fund
     .    Founders Passport Fund
     .    Founders Special Fund
     .    Founders Worldwide Growth Fund
     .    INVESCO Dynamics Fund
     .    INVESCO Growth Fund
     .    INVESCO High Yield Fund
     .    INVESCO Industrial Income
     .    INVESCO Multi- Asset Allocation
     .    INVESCO Select Income
     .    INVESCO Small Company Growth Fund
     .    INVESCO Total Return Fund
     .    INVESCO Value Equity Fund
     .    Janus Flexible Income Fund
     .    Fidelity Emerging Growth Fund
     .    Fidelity Emerging Markets
     .    Fidelity Equity Income
     .    Fidelity Equity Income II
     .    Fidelity Europe
     .    Fidelity Europe Capital Apprec.
     .    Fidelity Export and Multinat'l
     .    Fidelity Asset Manager
     .    Fidelity Asset Mg. Gro.
     .    Fidelity Asset Mg. Inc.
     .    Fidelity Fifty
     .    Fidelity Fund
     .    Fidelity Intermediate Bond Fund
     .    Fidelity Retirement Money Market Fund
     .    Fidelity Freedom 2000
     .    Fidelity Freedom 2010
     .    Fidelity Freedom 2020
     .    Fidelity Freedom 2030
     .    Fidelity Freedom Income Fund
     .    Fidelity Ginnie Mae
     .    Fidelity Global Balanced
     .    Fidelity Govt. Securities
     .    Fidelity Growth Company

                                      xiv
<PAGE>

     .    Fidelity Institutional Short-Intermediate Govt.
     .    Fidelity Intermediate Bond
     .    Fidelity International Value
     .    Fidelity Int'l Growth & Income
     .    Fidelity Investment Grade Bond
     .    Fidelity Mid Cap Stock
     .    Fidelity Japan
     .    Fidelity Large Cap Stock
     .    Fidelity Latin America
     .    Franklin Small Cap Growth I
     .    MAS Balanced Portfolio - Adviser Class
     .    MAS Fixed Income - Adviser Class
     .    MAS High Yield Portfolio - Adviser Class
     .    MAS Mid Cap Growth Portfolio- Adviser Class
     .    Montgomery International Small Cap
     .    Montgomery Select 50
     .    Morgan Stanley Active Country Allocation B
     .    Morgan Stanley Emerging Markets
     .    Morgan Stanley Global Equity Portfolio B
     .    Morgan Stanley International Magnum Class B
     .    Morgan Stanley Emerging Growth Class B
     .    Morgan Stanley Equity Growth B
     .    Templeton Mutual Discovery Fund I
     .    Templeton Mutual Shares Fund Class I
     .    Neuberger & Berman Focus Trust
     .    Neuberger & Berman Guardian Trust
     .    Neuberger & Berman Manhattan Trust
     .    Neuberger & Berman Partners Trust
     .    Neuberger & Berman Socially Responsible
     .    Fidelity New Markets Income Fund
     .    Fidelity OTC Portfolio
     .    Fidelity Overseas Fund
     .    Fidelity Pacific Basin Fund
     .    PBHG Emerging Growth
     .    PIMCO Capital Appreciation Fund
     .    PIMCO Global Bond Fund
     .    PIMCO High Yield Fund
     .    PIMCO Low Duration Fund
     .    PIMCO Long-Term US Government
     .    PIMCO Mid-Cap Growth
     .    PIMCO Total Return - Admin.
     .    Fidelity Puritan Fund
     .    Fidelity Real Estate Investment Portfolio
     .    Fidelity Retirement Growth Fund
     .    Fidelity Short-Intermediate Govt. Fund
     .    Fidelity Short-Term Bond Fund
     .    Fidelity Small Cap Selector

                                       xv
<PAGE>

     .    Fidelity Southeast Asia Fund
     .    Spartan Market Index Fund
     .    Fidelity Stock Selector
     .    Strong Total Return Fund
     .    Strong Advantage Fund
     .    Strong Common Stock Fund
     .    Strong Discovery Fund
     .    Strong Government Securities Fund
     .    Strong Growth Fund
     .    Strong Opportunity Fund
     .    Strong Schafer Value
     .    Strong Short-Term Bond Fund
     .    Fidelity Target Timeline 1999
     .    Fidelity Target Timeline 2001
     .    Fidelity Target Timeline 2003
     .    Fidelity TechnoQuant Growth
     .    Templeton Foreign Smaller Companies I
     .    Templeton Developing Markets Trust I
     .    Templeton Foreign Fund I
     .    Templeton Global Bond Fund I
     .    Templeton Growth Fund I
     .    Templeton World Fund I
     .    Fidelity Trend Fund
     .    UAM/FMA Small Company Institutional
     .    UAM/FPA Crescent Institutional
     .    UAM/McKee Int'l Equity Institutional
     .    UAM/Rice Hall Small Cap Institutional
     .    UAM/Sterling Equity Institutional
     .    Fidelity U.S. Bond Index Fund
     .    USAA Emerging Markets Fund
     .    USAA GNMA Fund
     .    USAA Growth Fund
     .    USAA Income Fund
     .    USAA Income Stock Fund
     .    USAA International Fund
     .    Fidelity Utilities Fund
     .    Fidelity Value Fund
     .    Warburg Capital Appreciation Fund
     .    Warburg Growth & Income Fund
     .    Warburg Global Fixed Income Fund
     .    Warburg International Equity Fund
     .    Warburg Small Company Value Fund
     .    Warburg Emerging Growth Fund
     .    Fidelity Worldwide Fund

                                      xvi
<PAGE>

     The investment option referred to in Section 5(c) and Section
5(e)(v)(B)(5)shall be the Fidelity Retirement Money Market Fund.

BENEFITS ADMINISTRATIVE COMMITTEE           FIDELITY MANAGEMENT TRUST
OF LYONDELL CHEMICAL COMPANY                COMPANY


By: /s/ Myra J. PerkinsoN  3/16/99 /s/ JLB      By: /s/ Carolyn Redden  3/30/99
    --------------------------------------      --------------------------------
                           Date                   Vice President         Date

                                      xvii
<PAGE>

                                 Schedule "D"

[LYONDELL - LETTERHEAD]







March 12, 1999



Ms. Kimberly McCausland
Fidelity Investments Institutional Operations Company, Inc.
82 Devonshire Street -- MM3H
Boston, Massachusetts 02109

Dear Ms. McCausland:

This letter is sent to you in accordance with Section 8(b) of the Trust
Agreement, dated as of March 12, 1999, between Lyondell Chemical Company,
Equistar Chemicals, LP, LYONDELL-CITGO Refining Company, Ltd. and Fidelity
Management Trust Company. We hereby designate Edward W. Rich, Dennis D. Veal,
and Katherine W. McDonald, as the individuals who may provide directions, on
behalf of the Sponsor, upon which Fidelity Management Trust Company shall be
fully protected in relying. Only one such individual need provide any direction.
The signature of each designated individual is set forth below and certified to
be such.

You may rely upon each designation and certification set forth in this letter
until we deliver to you written notice of the termination of authority of a
designated individual.

Very truly yours,


By:  /s/ Jeffrey R. Pendergraft
   ------------------------------
   Jeffrey R. Pendergraft               /s/ JLB
   Executive Vice President &
   Chief Administrative Officer



     /s/ Edward W. Rich
   ------------------------------
   Edward W. Rich



     /s/ Dennis D. Veal
   ------------------------------
   Dennis D. Veal




     /s/ Katherine W. McDonald
   ------------------------------
   Katherine W. McDonald



                                     xviii

<PAGE>


                                 Schedule "E"

[LYONDELL - LETTERHEAD]







March 12, 1999



Kimberly McCausland, Esq.
Fidelity Investments Institutional Operations Company, Inc.
82 Devonshire Street -- MM3H
Boston, Massachusetts 02109

Dear Ms. McCausland:

This letter is sent to you in accordance with Section 8(c) of the Trust
Agreement, dated as of March 12, 1999, between Lyondell Chemical Company,
Equistar Chemicals, LP., LYONDELL-CITGO Refining Company, Ltd. and Fidelity
Management Trust Company. I hereby designate Allen C. Holmes, Myra J. Perkinson,
and John A. Hollinshead, as the individuals who may provide directions, on
behalf of the Named Fiduciary, upon which Fidelity Management Trust Company
shall be fully protected in relying. Only one such individual need provide any
direction. The signature of each designated individual is set forth below and
certified to be such.

You may rely upon each designation and certification set forth in this letter
until we deliver to you written notice of the termination of authority of a
designated individual.

Very truly yours,


By:  /s/ Jeffrey R. Pendergraft
   ------------------------------
   Jeffrey R. Pendergraft           /s/ JLB
   Executive Vice President &
   Administrative Officer



   ------------------------------
   Allen C. Holmes



     /s/ Myra J. Perkinson
   ------------------------------
   Myra J. Perkinson




     /s/ John A. Hollinshead
   ------------------------------
   John A. Hollinshead



                                      xix


<PAGE>

                                 Schedule "F"


[LYONDELL - LETTERHEAD]




March 12, 1999

Kimberly McCausland, Esq.
Fidelity Investments Institutional Operations Company, Inc.
82 Devonshire Street -- MM3H
Boston, MA 02109

Dear Ms. McCausland:

In accordance with your request, I hereby submit the following:

Copies of the most recent favorable determination letters for:

     (1)  LYONDELL-CITGO Refining Company Ltd. 401(k) and Savings Plan for
          Non-Represented Employees;
     (2)  LYONDELL-CITGO Refining Company 401(k) and Savings Plan for
          Represented Employees;
     (3)  Lyondell Chemical Company 401(k) and Saving Plan (now the Equistar
          Chemicals LP Savings and Investment Plan, effective January 1, 1998);
     (4)  ARCO Chemical Company Capital Accumulation Plan (merged into the
          current Lyondell Chemical Company 401(k) and Savings Plan);
     (5)  ARCO Chemical Company Savings Plan (merged into the current Lyondell
          Chemical Company 401(k) and Savings Plan); and
     (6)  Equistar Savings and Investment Plan for Hourly Represented Employees
          (formerly Quantum).

Nothing has occurred since the date of these letters that could reasonably be
expected to cause a loss of qualification.

Lyondell intends to apply for a determination letter from the Internal Revenue
Service prior to December, 1999, for the new Lyondell 401(k) and Savings Plan
and the Equistar Savings and Investment Plan for former Occidental Employees
(merged into the Equistar Savings and Investment Plan April 1, 1999).

Very truly yours,



By  /s/ Jeffrey R. Pendergraft
   ------------------------------
   Jeffrey R. Pendergraft               /s/ JLB
   Executive Vice President &
   Administrative Officer


                                      xx
<PAGE>

ARCO CHEMICAL COMPANY

        If you have questions concerning this matter, please contact the person
whose name and telephone number are shown above.

                                        Sincerely yours,

                                        /s/ illegible
                                        -----------------------------------
                                        District Director

Enclosures:
Publication 794
Reporting & Disclosure Guide
 for Employee Benefit Plans

                                      xxi
<PAGE>


ARCO CHEMICAL COMPANY

        If you have questions concerning this matter, please contact the person
whose name and telephone number are shown above.

                                        Sincerely yours,

                                        /s/ illegible
                                        -----------------------------------
                                        District Director

Enclosures:
Publication 794
Reporting & Disclosure Guide
 for Employee Benefit Plans

                                      xxii

<PAGE>

INTERNAL REVENUE SERVICE                        DEPARTMENT OF THE TREASURY
DISTRICT DIRECTOR
1100 COMMERCE STREET
DALLAS, TX 75242
                                        Employer Identification Number:
Date: March 6, 1997                        95-4160558
                                        File Folder Number:
LYONDELL PETROCHEMICAL COMPANY             760015162
1221 MCKINNEY, SUITE 1600               Person to Contact:
HOUSTON, TX 77010                          CUSTOMER SERVICE DIVISION
                                        Contact Telephone Number:
                                           (800) 829-1040
                                        Plan Name:
                                           LYONDELL PETROCHEMICAL CO. SAVINGS
                                           PLAN/NON-REPRESENTED EMPLOYEES
                                        Plan Number: 003

Dear Applicant:

        We have made a favorable determination on your plan, identified above,
based on the information supplied. Please keep this letter in your permanent
records.

        Continued qualification of the plan under its present form will depend
on its effect in operation. (See section 1.401-1(b)(3) of the Income Tax
Regulations.) We will review the status of the plan in operation periodically.

        The enclosed document explains the significance of this favorable
determination letter, points out some features that may affect the qualified
status of your employee retirement plan, and provides information on the
reporting requirements for your plan. It also describes some events that
automatically nullify it. It is very important that you read the publication.

        This letter relates only to the status of your plan under the Internal
Revenue Code. It is not a determination regarding the effect of other federal or
local statutes.

        This determination is subject to your adoption of the proposed
amendments submitted in your letter dated Sept. 9, 1996. The proposed amendments
should be adopted on or before the date prescribed by the regulations under Code
section 401(b).

        This determination letter is applicable for the amendment(s) adopted on
June 26, 1995.

        This determination letter does not apply to the merger, consolidation,
or transfer of assets or liabilities of a plan described in Code section 6058(a)
to, or with, another plan, or to whether requirements of the income tax
regulations under Code section 414(l) have been met. This is only a
determination as to the qualification of the plan.

        This plan satisfies the requirements of Code section 4975(e)(7).

        This plan has been mandatorily disaggregated, permissively aggregated,
or restructured to satisfy the nondiscrimination requirements.

        This plan satisfies the nondiscrimination in amount requirement of
section

                                                              Letter 835 (DO/CG)


<PAGE>

                                      -2-

LYONDELL PETROCHEMICAL COMPANY

1.401(a)(4)-1(b)(2) of the regulations on the basis of a design-based safe
harbor described in the regulations.

        This letter is issued under Rev. Proc. 93-39 and considers the
amendments required by the Tax Reform Act of 1986 except as otherwise specified
in this letter.

        This plan satisfies the nondiscriminatory current availability
requirements of section 1.401(a)(4)-4(b) of the regulations with respect to
those benefits, rights, and features that are currently available to all
employees in the plan's coverage group. For this purpose, the plan's coverage
group consists of those employees treated as currently benefitting for purposes
of demonstrating that the plan satisfies the minimum coverage requirements of
section 410(b) of the Code.

        This letter may not be relied upon with respect to whether the plan
satisfies the qualification requirements as amended by the Uruguay Round
Agreements Act, Pub. L. 103-465.

        The information on the enclosed addendum is an integral part of this
determination. Please be sure to read and keep it with this letter.

        We have sent a copy of this letter to your representative as indicated
in the power of attorney.

        If you have questions concerning this matter, please contact the person
whose name and telephone number are shown above.

                                        Sincerely yours,

                                        /s/ Bobby E. Scott
                                        ------------------------------------
                                        Bobby E. Scott
                                        District Director

Enclosures
Publication 794
Reporting & Disclosure Guide
 for Employee Benefit Plans
Addendum

                                                              Letter 835 (DO/CG)



<PAGE>

                                      -3-

LYONDELL PETROCHEMICAL COMPANY

This determination letter is also applicable for the amendments adopted on:

April 25, 1995
Aug. 19, 1993
Oct. 30, 1992
June 26, 1992
Sept. 26, 1991

<PAGE>

                                      -2-

QUANTUM CHEMICAL CORPORATION

satisfies the qualification requirements as amended by the Uruguay Round
Agreements Act, Pub. L. 103-465.

        We have sent a copy of this letter to your representative as indicated
in the power of attorney.

        If you have questions concerning this matter, please contact the person
whose name and telephone number are shown above.

                                        Sincerely yours,

                                        /s/ illegible
                                        ---------------------------------
                                        District Director

Enclosure(s)
Publication 794

<PAGE>

INTERNAL REVENUE SERVICE                        DEPARTMENT OF THE TREASURY
DISTRICT DIRECTOR
1100 COMMERCE STREET
DALLAS, TX 75242
                                        Employer Identification Number:
Date: April 25, 1997                       76-0395303
                                        File Folder Number:
LYONDELL-CITGO REFINING COMPANY LTD        760015962
C/O MINDY G. DAVIDSON                   Person to Contact:
MAYOR DAY CALDWELL & KEETON LLP            CUSTOMER SERVICE DIVISION
700 LOUISIANA, SUITE 1900               Contact Telephone Number:
HOUSTON, TX 77002                          (800) 829-1040
                                        Plan Name:
                                           LYONDELL-CITGO REFINING COMPANY LTD
                                           SAVINGS PLAN/NON-REPR EMPLOYEES
                                        Plan Number: 064

Dear Applicant:

        We have made a favorable determination on your plan, identified above,
based on the information supplied. Please keep this letter in your permanent
records.

        Continued qualification of the plan under its present form will depend
on its effect in operation. (See section 1.401-1(b)(3) of the Income Tax
Regulations.) We will review the status of the plan in operation periodically.

        The enclosed document explains the significance of this favorable
determination letter, points out some events that may affect the qualified
status of your employee retirement plan, and provides information on the
reporting requirements for your plan. It also describes some events that
automatically nullify it. It is very important that you read the publication.

        This letter relates only to the status of your plan under the Internal
Revenue Code. It is not a determination regarding the effect of other federal or
local statutes.

        This determination is subject to your adoption of the proposed
amendments submitted in your letter dated April 25, 1997. The proposed
amendments should be adopted on or before the date prescribed by the regulations
under Code section 401(b).

        This determination letter is applicable for the amendment(s) adopted on
June 22, 1995.

        This determination letter is also applicable for the amendment(s)
adopted on April 21, 1995.

        This determination letter is applicable for the plan adopted on
June 25, 1993.

        This determination letter does not apply to the merger, consolidation,
or transfer of assets or liabilities of a plan described in Code section 6058(a)
to, or with, another plan, or to whether requirements of the income tax
regulations under Code section 414(l) have been met. This is only a
determination as to the qualification of the plan.

                                                              Letter 835 (DO/CG)


<PAGE>

                                      -2-

LYONDELL-CITGO REFINING COMPANY LTD

        This plan satisfies the minimum coverage requirements on the basis of
the average benefit test in section 410(b)(2) of the Code.

        This plan satisfies the nondiscrimination in amount requirement of
section 1.401(a)(4)-1(b)(2) of the regulations on the basis of a design-based
safe harbor described in the regulations.

        This letter is issued under Rev. Proc. 93-39 and considers the
amendments required by the Tax Reform Act of 1986 except as otherwise specified
in this letter.

        This plan satisfies the nondiscriminatory current availability
requirements of section 1.401(a)(4)-4(b) of the regulations with respect to
those benefits, rights, and features that are currently available to all
employees in the plan's coverage group. For this purpose, the plan's coverage
group consists of those employees treated as currently benefitting for purposes
of demonstrating that the plan satisfies the minimum coverage requirements of
section 410(b) of the Code.

        Except as otherwise specified this letter may not be relied upon with
respect to whether the plan satisfies the qualification requirements as amended
by the Uruguay Round Agreements Act, Pub. L. 103-465 and by the Small Business
Job Protection Act of 1996 (SBJPA), Pub. L. 104-108, other than the requirements
of Code section 401(a)(26).

        The information on the enclosed Publication 794 is an integral part of
this determination. Please be sure to read and keep it with this letter.

        We have sent a copy of this letter to your representative as indicated
in the power of attorney.

        If you have questions concerning this matter, please contact the person
whose name and telephone number are shown above.

                                        Sincerely yours,

                                        /s/ Bobby E. Scott
                                        ------------------------------------
                                        Bobby E. Scott
                                        District Director

Enclosures
Publication 794
Reporting & Disclosure Guide
 for Employee Benefit Plans
Addendum

                                                              Letter 835 (DO/CG)

<PAGE>

                                      -3-

LYONDELL-CITGO REFINING COMPANY LTD

This determination letter supercedes the determination letter dated March 6,
1997.

                                                              Letter 835 (DO/CG)

<PAGE>

INTERNAL REVENUE SERVICE                        DEPARTMENT OF THE TREASURY
DISTRICT DIRECTOR
1100 COMMERCE STREET
DALLAS, TX 75242
                                        Employer Identification Number:
Date: April 25, 1997                       76-0395303
                                        File Folder Number:
LYONDELL-CITGO REFINING COMPANY LTD        760015962
C/O MINDY G. DAVIDSON                   Person to Contact:
MAYOR DAY CALDWELL & KEETON LLP            CUSTOMER SERVICE DIVISION
700 LOUISIANA, SUITE 1900               Contact Telephone Number:
HOUSTON, TX 77002                          (800) 829-1040
                                        Plan Name:
                                           LYONDELL-CITGO REFINING COMPANY LTD
                                           SAVINGS PLAN FOR REPRESENTED
                                           EMPLOYEES
                                        Plan Number: 063

Dear Applicant:

     We have made a favorable determination on your plan, identified above,
based on the information supplied. Please keep this letter in your permanent
records.

     Continued qualification of the plan under its present form will depend
on its effect in operation. (See section 1.401-1(b)(3) of the Income Tax
Regulations.) We will review the status of the plan in operation periodically.

     The enclosed document explains the significance of this favorable
determination letter, points out some features that may affect the qualified
status of your employee retirement plan, and provides information on the
reporting requirements for your plan. It also describes some events that
automatically nullify it. It is very important that you read the publication.

     This letter relates only to the status of your plan under the Internal
Revenue Code. It is not a determination regarding the effect of other federal or
local statutes.

     This determination letter is applicable for the amendment(s) dated on
June 22, 1995.

     This determination letter is also applicable for the amendment(s)
dated on April 21, 1995.

     This determination letter is applicable for the plan adopted on
June 25, 1993.

     This determination letter does not apply to the merger, consolidation,
or transfer of assets or liabilities of a plan described in Code section 6058(a)
to, or with, another plan, or to whether requirements of the income tax
regulations under Code section 414(l) have been met. This is only a
determination as to the qualification of the plan.

     This plan satisfies the minimum coverage and nondiscrimination requirements
of sections 410(b) and 401(a)(4) of the Code because the plan benefits only
collectively bargained employees or employees treated as collectively bargained
employees.


                                                              Letter 835 (DO/CG)

<PAGE>

                                     -2-

LYONDELL-CITGO REFINING COMPANY LTD


     This letter is issued under Rev. Proc. 93-39 and considers the amendments
required by the Tax Reform Act of 1986 except as otherwise specified in this
letter.

     Except as otherwise specified this letter may not be relied upon with
respect to whether the plan satisfies the qualification requirements as amended
by the Uruguay Round Agreements Act, Pub. L. 103-465 and by the Small Business
Job Protection Act of 1996 (SBJPA), Pub. L. 104-108, other than the requirements
of Code section 401(a)(26).

     The information on the enclosed Publication 794 is an integral part of
this determination. Please be sure to read and keep it with this letter.

     We have sent a copy of this letter to your representative as indicated
in the power of attorney.

     If you have questions concerning this matter, please contact the person
whose name and telephone number are shown above.


                                        Sincerely yours,

                                        /s/ Bobby E. Scott
                                        ------------------------------------
                                        Bobby E. Scott
                                        District Director

Enclosures:
Publication 794
Reporting & Disclosure Guide
 for Employee Benefit Plans
Addendum

                                                              Letter 835 (DO/CG)

<PAGE>
                                     -3-

LYONDELL-CITGO REFINING COMPANY LTD



This determination letter supercedes the determination letter dated March 6,
1997.






                                                              Letter 835 (DO/CG)



<PAGE>

                                  Schedule "G"

                          TELEPHONE EXCHANGE GUIDELINES
                          -----------------------------

The following telephone exchange guidelines are currently employed by Fidelity
Investments Institutional Operations Company, Inc. ("FIIOC").
                                                     -----

Telephone exchange hours via a Fidelity Representative are 8:30 a.m. (ET) to
12:00 midnight (ET) on each business day. A "business day" is any day on which
the New York Stock Exchange ("NYSE") is open. Exchanges via the Internet and
                              ----
Fidelity's voice response system are intended to be available virtually 24 hours
a day.

FIIOC reserves the right to change these telephone exchange guidelines at its
discretion.

Note: The NYSE's normal closing time is 4:00 p.m. (ET); in the event the NYSE
alters its closing time, all references below to 4:00 p.m. shall mean the NYSE
closing time as altered.

             Exchanges Between Mutual Funds/IDS New Dimensions Fund
             ------------------------------------------------------

Participants may call on any business day to exchange between the Mutual
Funds/IDS New Dimensions Fund. If the request is confirmed before 4:00 p.m.
(ET), it will receive that day's trade date. Requests confirmed after 4:00 p.m.
(ET) will be processed on a next business day basis.

                           Employer Stock/Common Stock
                           ---------------------------

Participants may call on any business day to exchange between Employer
Stock/Common Stock and any other investment option. If the request is received
before 4:00 p.m. (ET), it will receive that day's trade date. Calls received
after 4:00 p.m. (ET) will be processed on a next day basis. The same process
will be followed for voice response transactions or internet. If a transaction
is submitted on a non-business day, the transaction will occur at the next
available business day scheduled for completion, as if it were received before
4:00p.m. (ET) on that day.

I. Sales of Employer Stock/Common Stock: The Employer Stock/Common Stock is sold
   ------------------------------------
on the following business day and the subsequent purchase into the new
investment options will take place five (5) business days later (call date plus
4). The participant's account will reflect the purchase on the sixth business
day (call date plus 5). This allows for settlement of the stock trade at the
custodian and the corresponding transfer to Fidelity.

II. Purchases of Employer Stock: Mutual Fund shares are sold on the day in which
    ---------------------------
in request is received, subject to the provisions stated above, and Employer
Stock/ Stock is purchased the following business day and will appear in the
participant's account on the third business day (call date plus two).

                                    xxxiii
<PAGE>

III. Restrictions
     ------------

     Participants in the Plan are not permitted to exchange into ARCO Common
     Stock and/or Millenium Petrochemicals, Inc. Common Stock.

     Participants in the Lyondell Chemical, LP 401(k) and Savings Plan ONLY are
     permitted to exchange into Lyondell Chemical Company Common Stock.

                              BrokerageLink Option
                              --------------------

I.   Exchanges from Mutual Funds/ IDS New Dimensions Fund into BrokerageLink
     -----------------------------------------------------------------------
     Option
     ------

     Participants may call on any business day to exchange out of the Mutual
     Funds/IDS New Dimensions Fund into BrokerageLink Account. Participants must
     speak to a participant services representative to exchange into
     BrokerageLink Option. If the call is received before 4:00 p.m. (ET), the
     Standard Plan Option ("SPO") Mutual Fund redemption will receive that day's
     trade date. The purchase into the BrokerageLink Option core account,
     Fidelity Cash Reserves, will receive the next business day's trade date.
     Calls received after 4:00 p.m. (ET) will be processed on a next business
     day basis.

     Although there is a one day lag in the trade date of the purchase into the
     BrokerageLink Option core account, Participants can trade in their
     BrokerageLink account prior to the actual exchanged assets being credited
     to the BrokerageLink Option core account.

II.  Exchanges from BrokerageLink Option into Mutual Funds/IDS New Dimensions
     ------------------------------------------------------------------------
     Fund
     ----

     Each Plan must designate an SPO Option as the default fund to which all
     exchanged assets from BrokerageLink to SPO are credited. Participants will
     have no choice as to where these assets are invested upon transfer from the
     FBSI system. If a Participant wants to reallocate to other investment
     options, he/she must call after they have been credited to Fidelity's
     Participant Recordkeeping System ("FPRS").

     Participant may call on any business day to transfer from their
     BrokerageLink account to their SPO default fund. Participants must speak to
     a brokerage representative to exchange from BrokerageLink account to SPO
     account. The transfer will involve a redemption from the BrokerageLink core
     account (Fidelity Cash Reserves). If the call is received before 4:00 p.m.
     (ET), the BrokerageLink core account redemption will receive that day's
     trade date. The purchase into the SPO default fund will receive that day's
     trade date. Calls received after 4:00 p.m. (ET) will be processed on a next
     business day basis.

     Most trades with the BrokerageLink account require a three business day
     settlement period. When placing the sell order in his/her BrokerageLink
     account, the Participant may request that upon settlement of the sell,
     assets be transferred from BrokerageLink to the SPO default fund.

                                     xxxiv
<PAGE>

BENEFITS ADMINISTRATIVE COMMITTEE           FIDELITY MANAGEMENT TRUST
OF LYONDELL CHEMICAL COMPANY                COMPANY


By: /s/ Myra J. Perkinson 3/16/99           By: /s/ Carolyn Redden 3/30/99
    -------------------------------------       --------------------------------
                           Date                   Vice President       Date

                                     xxxv
<PAGE>

                                  Schedule "H"

              OPERATIONAL GUIDELINES FOR NON-FIDELITY MUTUAL FUNDS
              ----------------------------------------------------

Pricing
-------
By 7:00 p.m. Eastern Time ("ET") each Business Day, the Non-Fidelity Mutual Fund
Vendor (Fund Vendor) will input the following information ("Price Information")
into the Fidelity Participant Recordkeeping System ("FPRS") via the remote
access price screen that Fidelity Investments Institutional Operations Company,
Inc. ("FIIOC"), an affiliate of the Trustee, has provided to the Fund Vendor:
(1) the net asset value for each Fund at the close of trading, (2) the change in
each Fund's net asset value from the close of trading on the prior Business Day,
and (3) in the case of an income fund or funds, the daily accrual for interest
rate factor ("mil rate"). FIIOC must receive Price Information each Business Day
(a "Business Day" is any day the New York Stock Exchange is open). If on any
Business Day the Fund Vendor does not provide such Price Information to FIIOC,
FIIOC shall pend all associated transaction activity in the Fidelity Participant
Recordkeeping System ("FPRS") until the relevant Price Information is made
available by Fund Vendor.

Trade Activity and Wire Transfers
---------------------------------
By 7:00 a.m. ET each Business Day following Trade Date ("Trade Date plus One"),
                                                                    ----
FIIOC will provide, via facsimile, to the Fund Vendor a consolidated report of
net purchase or net redemption activity that occurred in each of the Funds up to
4:00 p.m. ET on the prior Business Day. The report will reflect the dollar
amount of assets and shares to be invested or withdrawn for each Fund. FIIOC
will transmit this report to the Fund Vendor each Business Day, regardless of
processing activity. In the event that data contained in the 7:00 a.m. ET
facsimile transmission represents estimated trade activity, FIIOC shall provide
a final facsimile to the Fund Vendor by no later than 9:00 a.m. ET. Any
resulting adjustments shall be processed by the Fund Vendor at the net asset
value for the prior Business Day.

The Fund Vendor shall send via regular mail to FIIOC transaction confirms for
all daily activity in each of the Funds. The Fund Vendor shall also send via
regular mail to FIIOC, by no later than the fifth Business Day following
calendar month close, a monthly statement for each Fund. FIIOC agrees to notify
the Fund Vendor of any balance discrepancies within twenty (20) Business Days of
receipt of the monthly statement.

                                     xxxvi
<PAGE>

For purposes of wire transfers, FIIOC shall transmit a daily wire for aggregate
purchase activity and the Fund Vendor shall transmit a daily wire for aggregate
redemption activity, in each case including all activity across all Funds
occurring on the same day.

Prospectus Delivery
-------------------
FIIOC shall be responsible for the timely delivery of Fund prospectuses and
periodic Fund reports ("Required Materials") to Plan Participants, and shall
retain the services of a third-party vendor to handle such mailings. The Fund
Vendor shall be responsible for all materials and production costs, and hereby
agrees to provide the Required Materials to the third-party vendor selected by
FIIOC. The Fund Vendor shall bear the costs of mailing annual Fund reports to
Plan Participants. FIIOC shall bear the costs of mailing prospectuses to Plan
Participants.

Proxies
-------
The Fund Vendor shall be responsible for all costs associated with the
production of proxy materials. FIIOC shall retain the services of a third-party
vendor to handle proxy solicitation mailings and vote tabulation. Expenses
associated with such services shall be billed directly to the Fund Vendor by the
third-party vendor.

Participant Communications
--------------------------
The Fund Vendor shall provide internally-prepared fund descriptive information
approved by the Funds' legal counsel for use by FIIOC in its written Participant
communication materials. FIIOC shall utilize historical performance data
obtained from third-party vendors (currently Morningstar, Inc., FACTSET Research
Systems and Lipper Analytical Services) in telephone conversations with Plan
Participants and in quarterly Participant statements. The Sponsor hereby
consents to FIIOC's use of such materials and acknowledges that FIIOC is not
responsible for the accuracy of such third-party information. FIIOC shall seek
the approval of the Fund Vendor prior to retaining any other third-party vendor
to render such data or materials under this Agreement.

Compensation
------------
FIIOC shall be entitled to fees as set forth in a separate agreement with the
Fund Vendor.

                                    xxxvii
<PAGE>

                                  Schedule I

[LETTERHEAD OF LYONDELL APPEARS HERE]

March 12, 1999

Kimberly McCausland, Esq.
Fidelity Investments Institutional Operations Company, Inc.
82 Devonshire Street
Boston, Massachusetts 02109

Dear Ms. McCausland:

This letter is sent to you in accordance with Section 8(a) of the Trust
Agreement dated as of the 12th day of March, 1999 between Lyondell Chemical
Company, Equistar Chemicals, LP, LYONDELL-CITGO Refining Company, Ltd. and
Fidelity Management Trust Company ("Sponsors").

Each of the Plans identified below is a tax-qualified defined contribution plan
which meets the requirements of Section 18 of the Trust Agreement and which is
maintained by the Sponsors, for the benefit of their eligible employees. Each
plan is hereby designated as a "Plan" for purposes of said Trust Agreement.

     (1) Lyondell Chemical Company 401(k) and Savings Plan);
     (2) LYONDELL-CITGO Refining Company Ltd. 401(k) and Savings Plan for
         Non-Represented Employees;
     (3) LYONDELL-CITGO Refining Company 401(k) and Savings Plan for Represented
         Employees;
     (4) Equistar Savings and Investment Plan for Non-Represented Employees; and
     (5) Equistar Savings and Investment Plan for Hourly Represented Employees.

The following individuals or entities are the Administrator and Named Fiduciary
of these Plans.

         Benefits Administrative Committee
         ---------------------------------

              Allen C. Holmes, Chairman
              John A. Hollinshead
              Myra J. Perkinson
              Gerald A. O'Brien
              Rose Nenni
              Edward W. Rich
              Jose L. Rodriguez

Lyondell Chemical Company                                    [LOGO APPEARS HERE]

<PAGE>

We hereby further certify that each Employer with respect to each of the
foregoing Plans has authorized the assets of that Plan to be deposited in the
Trust and, as a result, is bound by Section 16(b) of the Trust Agreement.

You may rely upon the foregoing designations and certifications until we deliver
to you written notice of a change in any of the information set forth therein.

Very truly yours,

By /s/ Jeffrey R. Pendergraft
   --------------------------------
   Jeffrey R. Pendergraft               /s/ JLB
   Executive Vice President &
   Chief Administrative Officer

<PAGE>

                                  Schedule "J"

       Securities that may not be purchased under the BrokerageLink Option

Precious Metals
Tax-Exempt Securities (including mutual funds and UITs)
Limited Partnerships
Level 3,4 and 5 Options (which require margin accounts)
Currencies
Currency Options
Currency Warrants
Commodities
Interest Rate Options
Financial Futures
CAPS
Any Security that may result in a prohibited transaction
Such other Securities as directed by the Sponsor

                                      xl
<PAGE>

                                  Schedule "K"

                     BrokerageLink Administrative Procedures
                     ---------------------------------------

This Schedule spells out the actions that Fidelity Investments Institutional
Operations Company ("FIIOC") will take to rectify various situations that might
                     -----
arise in Participant Self Directed Brokerage ("BrokerageLink") accounts as an
                                               -------------
option in the Plan(s). By signing this Schedule, the Plan agrees to the terms of
this Schedule as standing instructions for FIIOC to take the appropriate action
to comply with the Trust document and to facilitate customer service and
operations processing.

General
-------

As necessary, FIIOC will initiate a transaction in the Participant's
BrokerageLink core account to rectify a situation in the Participant's Standard
Plan Options ("SPO"). FIIOC will only initiate a sell trade in the Participant's
               ---
BrokerageLink security positions if the terms of the Trust Agreement have been
violated. In problem resolution situations that are not violations of the Trust
Agreement, then FIIOC will look to the Sponsor for direction with regard to the
Participant's BrokerageLink account.

Unsecured debit or overdraft
----------------------------

If an unsecured debit or overdraft is identified in a Participant's
BrokerageLink account, FIIOC will first look to the Participant's SPO to cover
the unsecured debit or overdraft. If there are enough assets in SPO, then FIIOC
will initiate a redemption exchange according to the appropriate hierarchy from
SPO and transfer those assets to the Participant's BrokerageLink account. The
Participant will be notified of these transactions by a confirmation.

If there are not ample assets in SPO to cover the unsecured debit or overdraft,
then FIIOC will place a sell trade order(s) in the Participant's BrokerageLink
account to raise enough cash to cover the unsecured debit or overdraft. The
securities that will be sold will be selected on a last in - first out basis.
Only enough shares/par of the security(ies) will be sold to cover the unsecured
debit or overdraft. Any trade related expenses (commissions, other fees) and
realized gain of loss will be borne by the Participant. The Participant will be
notified of these transactions by a confirmation.

Restricted sources
------------------

A Plan may restrict sources from being transferred to BrokerageLink. If FIIOC
identifies any restricted source assets that have been transferred to
BrokerageLink, then FIIOC will take action to return the original transferred
amount related to the restricted source(s) to SPO; any earned or unearned income
generated by these assets will remain in SPO.

If there are enough assets in the Participant's BrokerageLink core account, then
FIIOC will initiate a trade order to transfer the assets from the core account
to SPO. The assets will be credited to the SPO default fund. The Participant
will be notified of these transactions by a confirmation.

If there are not enough assets in the Participant's BrokerageLink core account,
FIIOC will place a sell trade order(s) in the Participant's BrokerageLink
account to raise enough cash to cover the restricted source assets. The
securities that will be sold will be selected on a last in - first out basis.
Only enough shares/par of the security(ies) will be sold to cover the restricted
source assets. Any trade related expenses (commissions, other fees) and realized
gain or loss will be borne by the Participant. The assets

                                      xli
<PAGE>

will be returned to the SPO default fund. The Participant will be notified of
these transactions by a confirmation.

Non-vested assets
-----------------

A Plan may restrict non-vested assets from being transferred to BrokerageLink.
If FIIOC identifies any non-vested assets that have been transferred to
BrokerageLink, then FIIOC will take action to return the original transferred
amount related to the non-vested assets to SPO.

If there are enough assets in the Participant's BrokerageLink core account, then
FIIOC will initiate a trade order to transfer the assets from the core account
to SPO. The assets will be credited to the SPO default fund. The Participant
will be notified of these transactions by a confirmation.

If there are not enough assets in the Participant's BrokerageLink account, FIIOC
will place a sell trade order in the Participant's BrokerageLink account to
raise enough liquid assets to cover the non-vested assets. The securities that
will be sold will be selected on a last in - first out basis. Only enough
shares/par of the security(ies) will be sold to cover the non-vested assets. Any
trade related expenses (commissions, other fees) and realized gain or loss will
be borne by the Participant. The assets will be returned to the SPO default
fund. The Participant will be notified of these transactions by a confirmation.

Restricted or ineligible securities
-----------------------------------

The Plan has designated that certain securities or security types be restricted
from being purchased by Participants. If FIIOC identifies a restricted security
that has been purchased by a Participant, then FIIOC will place a sell trade
order in the Participant's BrokerageLink account to remove that security from
the Plan. Any trade related expenses (commissions, other fees) and realized gain
or loss will be borne by the Participant. The liquidated assets will be credited
to the BrokerageLink core account. The Participant will be notified of these
transactions by a confirmation.

Unauthorized channel deposits
-----------------------------

Participants may deposit money into their BrokerageLink account only through the
SPO recordkeeping system (FPRS). A Participant may not deposit money to the
BrokerageLink account by any other means than payroll deduction or a Fidelity
phone representative assisted transfer. Money that is deposited to the
BrokerageLink account in any other way is considered to be an unauthorized
channel.

If money is deposited to a BrokerageLink account via an unauthorized channel,
then FIIOC will initiate the removal of that money. If there are enough assets
in the Participant's BrokerageLink core account, the FIIOC will request that a
check be cut in the amount of the original deposit. The check will be mailed to
the Participant.

If there are not enough assets in the Participant's BrokerageLink core account,
then FIIOC will place a sell trade order(s) in the Participant's BrokerageLink
account to raise enough liquid assets to cover the unauthorized channel deposit.
The securities that will be sold will be selected on a last in - first out
basis. Only enough shares/par of the security(ies) will be sold to cover the
unauthorized channel deposit. Any trade related expenses (commissions, other
fees) and realized gain or loss will be borne by the Participant. Once the sell
transactions have settled, FIIOC will request that a check be cut for the
original amount of the unauthorized channel deposit. The check will be mailed to
the Participant.

                                     xlii
<PAGE>

Unauthorized channel withdrawals
--------------------------------

Participants may withdraw money from their BrokerageLink account only through
the SPO recordkeeping system (FPRS). A Participant may not withdraw money from
the BrokerageLink account by any other means than by speaking to a Fidelity
phone representative. Money that is withdrawn from the BrokerageLink account in
any other way is considered to be an unauthorized channel.

If money is withdrawn through an unauthorized channel, FIIOC will contact the
Participant and request that the withdrawn assets be returned to FIIOC. FIIOC
will redeposit the assets in the Participant's BrokerageLink account.

Anti-discrimination testing
---------------------------

If a distribution of excess contribution (all are not excess contributions -
this term is meant as catch-all) needs to be made from a Participant's
retirement savings account due to discrimination testing reasons, FIIOC will
first look to SPO for available assets. If there are not enough assets in SPO,
then FIIOC will look to the BrokerageLink account.

If there are ample assets in the Participant's BrokerageLink core account, then
FIIOC will initiate the transfer of the assets to the SPO default fund. The
distribution of excess contributions will then be made from SPO according to the
appropriate hierarchy.

Qualified Domestic Relation Orders (QDRO's)
-------------------------------------------

FIIOC will comply with the terms of the QDRO. If a BrokerageLink account is
involved in a QDRO situation, then FIIOC will take direction from the Sponsor as
to the actions to be taken with regards to potentially splitting the
BrokerageLink account.

Deaths
------

FIIOC will comply with the terms of the applicable legal documents in the event
of a Participant death. If a BrokerageLink account is involved in a death, then
FIIOC will take direction from the Sponsor as to the action to be taken with
regards to any potential activity in the BrokerageLink account.

Systematic Withdrawal Payments/Minimum Required Distributions
-------------------------------------------------------------

All withdrawals, systematic or otherwise, are debited from the Participant's
SPO. If there are not enough assets in SPO to make the distribution, then FIIOC
will look to the BrokerageLink account.

If there are ample assets in the Participant's BrokerageLink core account, then
FIIOC will initiate the transfer to cover the next scheduled systematic
withdrawal.

If there are not ample assets in the Participant's BrokerageLink core account,
then FIIOC will notify the Participant and request that ample assets be
transferred from BrokerageLink to SPO. If the Participant does not take action
to transfer assets from BrokerageLink to SPO, then FIIOC will place a sell trade
order(s) in the Participant's BrokerageLink account to raise enough liquid
assets to cover the next scheduled systematic distribution. The securities that
will be sold will be selected on a last in - first out basis. Only enough
shares/par of the security(ies) will be sold to cover the next scheduled
systematic payment. Any trade related expenses (commissions, other fees) and
realized gain or loss will be borne by

                                     xliii
<PAGE>

the Participant. The assets will be returned to the SPO default fund for
distribution. The Participant will be notified of these transactions by a
confirmation.

Fees
----

All Plan related fees that are paid by the Participant are debited from the
Participant's SPO. If there are not enough assets in SPO to pay fees of any
nature, then FIIOC will look to the BrokerageLink account.

If there are ample assets in the Participant's BrokerageLink core account, then
FIIOC will initiate the transfer of at least $500 to the SPO default fund to
cover current and future fees.

If there are not ample assets in the Participant's BrokerageLink core account,
then FIIOC will bill the Sponsor for the fees and notify/request that the
Participant transfer at least $500 to SPO for future fees.

BENEFITS ADMINISTRATIVE COMMITTEE           FIDELITY MANAGEMENT TRUST
OF LYONDELL CHEMICAL COMPANY                COMPANY


By: /s/ Myra J. Perkinson 3/15/99           By: /s/ Carolyn Redden  3/30/99
    -------------------------------------       --------------------------------
                           Date   /s/ JLB         Vice President       Date

                                      xlv
<PAGE>

                   FIRST AMENDMENT TO TRUST AGREEMENT BETWEEN
        FIDELITY MANAGEMENT TRUST COMPANY AND LYONDELL CHEMICAL COMPANY;
           EQUISTAR CHEMICALS, LP; AND LYONDELL-CITGO REFINING COMPANY LTD.

     THIS FIRST AMENDMENT, dated as of the first day of June, 1999, by and
between Fidelity Management Trust Company (the "Trustee") and Lyondell Chemical
                                                -------
Company, Equistar Chemicals, LP, and Lyondell-Citgo Refining LB (individually
and collectively the "Sponsor");
                                    -------

                                   WITNESSETH:

     WHEREAS, the Trustee and the Sponsor heretofore entered into a Trust
Agreement dated March 15, 1999 with regard to the Lyondell Chemical Company
401(k) and Savings Plan; the Equistar Chemicals, LP Savings and Investment Plan;
the Equistar Chemicals, LP Savings and Investment Plan for Represented
Employees; the Lyondell-Citgo Refining Company 401(k) and Savings Plan for
Non-Represented Employees; and the Lyondell-Citgo Refining Company 401(k) and
Savings Plan for Represented Employees (individually and collectively the
"Plan"); and
 ----

     WHEREAS, the Trustee and the Sponsor now desire to amend said Trust
Agreement as provided for in Section 14 thereof;

     NOW THEREFORE, in consideration of the above premises, the Trustee and the
Sponsor hereby amend the Trust Agreement by:

     (1)  Amending Section 8(e), Indemnification, to add the following
                                 ---------------
          subsection:

          (iii) Special Indemnification for Fidelity PortfolioPlannerSM. The
          Trustee shall indemnify the Sponsor against and hold the Sponsor
          harmless from any and all such loss, damage, penalty, liability, cost,
          and expense, including without limitation, reasonable attorney's fees
          and disbursements, that may be incurred by, imposed upon, or asserted
          against the Sponsor solely as a result of a) any defects in the
          investment methodology embodied in the target asset allocation or
          model portfolio provided through Fidelity PortfolioPlanner, except to
          the extent that any such loss, damage, penalty, liability, cost or
          expense arises from information provided by the participant, the
          Sponsor or third parties; or b) any prohibited transactions resulting
          from the provision by the Trustee of Fidelity PortfolioPlanner.

     (2)  Amending Section F) Communication Services, of Schedule "A" by adding
          the following section:

          2. Fidelity PortfolioPlanner (SM), an internet-based educational
          service for participants that generates target asset allocations and
          recommended model portfolios customized to investment options in the
          Plan based upon methodology provided by Strategic Advisers, Inc., an
          affiliate of the Trustee. The Sponsor acknowledges that it has
          received the ADV Part II for Strategic Advisers, Inc. more than 48
          hours prior to executing the Trust amendment.
<PAGE>

     IN WITNESS WHEREOF, the Trustee and the Sponsor have caused this First
Amendment to be executed by their duly authorized officers effective as of the
day and year first above written.

                                            LYONDELL CHEMICAL COMPANY


Attest: /s/ JoAnn L. Beck                    By:   /s/ Jeffrey R. Pendergraft
       --------------------------                  -----------------------------
         Secretary
                                            Name:   Jeffrey R. Pendergraft
                                                   -----------------------------
                                            Title:  Executive Vice President
                                                    and Chief Administrative
                                                    Officer
                                                   -----------------------------
                                            Date:   November  10, 1999
                                                   -----------------------------

                                            EQUISTAR CHEMICALS, LP


Attest:   /s/ Gerald A. O'Brien             By:     /s/ Eugene R. Allspach
         --------------------------                -----------------------------
         Secretary
                                            Name:   Eugene R. Allspach
                                                   -----------------------------
                                            Title:  President
                                                   -----------------------------
                                            Date:   November 10, 1999
                                                   -----------------------------

                                            LYONDELL-CITGO REFINING LP /s/ JLB


Attest:  /s/ Steven B. Strauss              By:     /s/ Rose Nenni
        ---------------------------                -----------------------------
         Secretary
                                            Name:   Rose Nenni
                                                   -----------------------------
                                            Title:  Vice President
                                                   -----------------------------
                                            Date:   November 12, 1999
                                                   -----------------------------

                                            FIDELITY MANAGEMENT TRUST COMPANY


Attest:   /s/ Douglas O. Kent               By:     /s/ Carolyn Redden
         --------------------------                -----------------------------
         Assistant Clerk
                                            Name:   Carolyn Redden
                                                   -----------------------------
                                            Title:  Vice President
                                                   -----------------------------
                                            Date:   December 3, 1999
                                                   -----------------------------

                                       2
<PAGE>

                   SECOND AMENDMENT TO TRUST AGREEMENT BETWEEN
        FIDELITY MANAGEMENT TRUST COMPANY AND LYONDELL CHEMICAL COMPANY;
             EQUISTAR CHEMICALS, LP; AND LYONDELL-CITGO REFINING, LP

     THIS SECOND AMENDMENT, dated as of the fifteenth day of October, 2000, by
and between Fidelity Management Trust Company (the "Trustee") and Lyondell
Chemical Company, Equistar Chemicals, LP, and Lyondell-Citgo Refining, LP
(individually and collectively the "Sponsor");

                                   WITNESSETH:

     WHEREAS, the Trustee and the Sponsor heretofore entered into a Master Trust
Agreement dated March 15, 1999 with regard to the Lyondell Chemical Company
401(k) and Savings Plan; the Equistar Chemicals, LP Savings and Investment Plan;
the Equistar Chemicals, LP Savings and Investment Plan for Represented
Employees; the Lyondell-Citgo Refining Company 401(k) and Savings Plan for
Non-Represented Employees; and the Lyondell-Citgo Refining Company 401(k) and
Savings Plan for Represented Employees (individually and collectively, the
"Plan"); and

     WHEREAS, the sponsor has informed the Trustee that Lyondell-Citgo Refining
Company Ltd. has changed its name to Lyondell-Citgo Refining, LP and that all
references in the Master Trust Agreement should be changed accordingly; and

     WHEREAS, the Trustee and the Sponsor now desire to amend said Trust
Agreement as provided for in Section 14 thereof;

     NOW THEREFORE, in consideration of the above premises, the Trustee and the
Sponsor hereby amend the Trust Agreement by:

     (1)  Deleting all references to "Lyondell-Citgo Refining Company Ltd." and
          "Lyondell-Citgo Refining Company" and replacing said references with
          "Lyondell-Citgo Refining, LP".

     (2)  Amending the "money classifications" sections of Schedule "A" as
          follows:

          For the Lyondell Chemical Company 401(k) and Savings Plan, by adding
          the following:

               10   QNEC
               11   QMAC

          For the Equistar Chemicals, LP Savings and Investment Plan, by adding
          the following:

               14 QNEC
               15 QMAC

          For the Equistar Chemicals, LP Savings and Investment Plan for
          Represented Employees, by adding the following:

               07 QNEC
               08 QMAC

          For the Lyondell-Citgo Refining, LP Savings Plan for Non-Represented
          Employees, by adding the following:

               09 QNEC
               10 QMAC
<PAGE>

          For the Lyondell-Citgo Refining, LP 401(k) and Savings Plan for
          Represented Employees, by adding the following:

               08 QNEC
               09 QMAC

     (3)  Amending the "Mutual Fund Window investment options" section of
          Schedules "A" and "C" by adding the following:

               Fidelity Freedom 2040 Fund

     IN WITNESS WHEREOF, the Trustee and the Sponsor have caused this Second
Amendment to be executed by their duly authorized officers effective as of the
day and year first above written.

                                            LYONDELL CHEMICAL COMPANY


Attest:  /s/ JoAnn L. Beck                  By:    /s/ Dan F. Smith
         --------------------------                -----------------------------
         Secretary

                                            Name:   Dan F. Smith
                                                   -----------------------------
                                            Title:  President & CEO
                                                   -----------------------------
                                            Date:   April 26, 2001
                                                   -----------------------------

                                            EQUISTAR CHEMICALS, LP


Attest:  /s/ JoAnn L. Beck                  By:    /s/ Eugene L. Allspach
         --------------------------                -----------------------------
         Secretary

                                            Name:   Eugene L. Allspach
                                                   -----------------------------
                                            Title:  President & COO
                                                   -----------------------------
                                            Date:   April 27, 2001
                                                   -----------------------------

                                            LYONDELL-CITGO REFINING, LP


Attest:  /s/ Gordon C. C.                   By:    /s/ William Thompson
         --------------------------                -----------------------------
         Secretary

                                            Name:   William Thompson
                                                   -----------------------------
                                            Title:  V.P.G.M. Operations
                                                   -----------------------------
                                            Date:   May 1, 2001
                                                   -----------------------------

                                            FIDELITY MANAGEMENT TRUST COMPANY


Attest:                                     By:    /s/ Carolyn Redden
         --------------------------                -----------------------------
         Secretary

                                            Name:   Carolyn Redden
                                                   -----------------------------
                                            Title:  Vice President
                                                   -----------------------------
                                            Date:   June 11, 2001
                                                   -----------------------------

                                        2
<PAGE>

                                        3
<PAGE>

                   THIRD AMENDMENT TO TRUST AGREEMENT BETWEEN
        FIDELITY MANAGEMENT TRUST COMPANY AND LYONDELL CHEMICAL COMPANY;
             EQUISTAR CHEMICALS, LP; AND LYONDELL-CITGO REFINING, LP

     THIS THIRD AMENDMENT, dated and effective as of the first day of October,
2001, except as otherwise set out herein, by and between Fidelity Management
Trust Company (the "Trustee") and Lyondell Chemical Company, Equistar Chemicals,
LP, and Lyondell-Citgo Refining, LP (individually and collectively the
"Sponsor");

                                   WITNESSETH:

     WHEREAS, the Trustee and the Sponsor heretofore entered into a Master Trust
Agreement dated March 15, 1999 with regard to the Lyondell Chemical Company
401(k) and Savings Plan; the Equistar Chemicals, LP Savings and Investment Plan;
the Equistar Chemicals, LP Savings and Investment Plan for Represented
Employees; the Lyondell-Citgo Refining, LP 401(k) and Savings Plan for
Non-Represented Employees; and the Lyondell-Citgo Refining, LP 401(k) and
Savings Plan for Represented Employees (individually and collectively, the
"Plan"); and

     WHEREAS, the Trustee and the Sponsor now desire to amend said Trust
Agreement as provided for in Section 14 thereof;

     NOW THEREFORE, in consideration of the above premises, the Trustee and the
Sponsor hereby amend the Trust Agreement by:

     (1)  Amending Section 5(d)(i) by adding the following language at the end
          thereof:

          Provided however, that each day that the Fidelity Select Funds are
          open for business as set forth in the Funds' then current prospectus,
          the Named Fiduciary hereby directs the Trustee to submit for
          processing all instructions for purchases and sales, but not
          exchanges, of shares of Fidelity Select Funds as designated on
          Schedules "A" and "C" only once each business day immediately prior to
          the last time at which the Fidelity Select Funds net asset values are
          calculated on such business day as specified in the Fidelity Select
          Funds' then current prospectuses.

     (2)  Amending the "investment options" listed in Schedules "A" and "C" by
          adding the following:

          Fidelity Select Air Transportation Portfolio
          Fidelity Select Automotive Portfolio
          Fidelity Select Banking Portfolio
          Fidelity Select Biotechnology Portfolio
          Fidelity Select Brokerage and Investment Management Portfolio
          Fidelity Select Business Services and Outsourcing Portfolio
          Fidelity Select Chemicals Portfolio
          Fidelity Select Computers Portfolio
          Fidelity Select Construction and Housing Portfolio
          Fidelity Select Consumer Industries Portfolio
          Fidelity Select Cyclical Industries Portfolio
          Fidelity Select Defense and Aerospace Portfolio
          Fidelity Select Developing Communications Portfolio
          Fidelity Select Electronics Portfolio
          Fidelity Select Energy Portfolio
          Fidelity Select Energy Service Portfolio
          Fidelity Select Environmental Portfolio
          Fidelity Select Financial Services Portfolio
          Fidelity Select Food and Agriculture Portfolio
          Fidelity Select Gold Portfolio
<PAGE>

          Fidelity Select Health Care Portfolio
          Fidelity Select Home Finance Portfolio
          Fidelity Select Industrial Equipment Portfolio
          Fidelity Select Industrial Materials Portfolio
          Fidelity Select Insurance Portfolio
          Fidelity Select Leisure Portfolio
          Fidelity Select Medical Delivery Portfolio
          Fidelity Select Medical Equipment and Systems Portfolio
          Fidelity Select Money Market Portfolio
          Fidelity Select Multimedia Portfolio
          Fidelity Select Natural Gas Portfolio
          Fidelity Select Natural Resources Portfolio
          Fidelity Select Networking and Infrastructure Portfolio
          Fidelity Select Paper and Forest Products Portfolio
          Fidelity Select Pharmaceuticals Portfolio
          Fidelity Select Retailing Portfolio
          Fidelity Select Software and Computer Services Portfolio
          Fidelity Select Technology Portfolio
          Fidelity Select Telecommunications Portfolio
          Fidelity Select Transportation Portfolio
          Fidelity Select Utilities Growth Portfolio
          Fidelity Select Wireless Portfolio

     (3)  Effective August 10, 2001, amending the "money classifications"
          sections of Schedule "A" for the Equistar Chemicals, LP Savings and
          Investment Plan, by adding the following:

                            16 Discr. Profit Sharing

     IN WITNESS WHEREOF, the Trustee and the Sponsor have caused this Third
Amendment to be executed by their duly authorized officers effective as of the
day and year first above written.

                                       2
<PAGE>

                                        LYONDELL CHEMICAL COMPANY


Attest:  /s/ JoAnn L. Beck              By:    /s/ Dan F. Smith
         ------------------------              ---------------------------------
         Asst. Secretary
                                        Name:   Dan F. Smith            /s/ JLB
                                               ---------------------------------
                                        Title:  President & CEO
                                               ---------------------------------
                                        Date:   October 16, 2001
                                               ---------------------------------


                                        EQUISTAR CHEMICALS, LP


Attest:                                 By:    /s/ Eugene R. Allspach
         ------------------------              ---------------------------------
         Secretary
                                        Name:   Eugene R. Allspach      /s/ JLB
                                               ---------------------------------
                                        Title:  President & COO
                                               ---------------------------------
                                        Date:   October 16, 2001
                                               ---------------------------------


                                        LYONDELL-CITGO REFINING, LP


Attest:                                 By:    /s/ William F. Thompson
         ------------------------              ---------------------------------
         Secretary
                                        Name:   William F. Thompson     /s/ JLB
                                               ---------------------------------
                                        Title:  V.P. & G.M. Operations
                                               ---------------------------------
                                        Date:
                                               ---------------------------------


                                        FIDELITY MANAGEMENT TRUST COMPANY


Attest:                                 By:    /s/ Carolyn Redden
         ------------------------              ---------------------------------
         Secretary
                                        Name:   Carolyn Redden
                                               ---------------------------------
                                        Title:  Vice President
                                               ---------------------------------
                                        Date:   November 20, 2001
                                               ---------------------------------

                                       3