Document:

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                                                                   EXHIBIT 10.24

                  SECOND AMENDED AND RESTATED CREDIT AGREEMENT

     THIS SECOND AMENDED AND RESTATED CREDIT AGREEMENT (this "Amendment") dated
as of the 1/st/ day of December, 1999, by and among PLAINS MARKETING, L.P.
("Borrower"), ALL AMERICAN PIPELINE, L.P. ("All American"), PLAINS ALL AMERICAN
PIPELINE, L.P. ("Plains MLP"), and BANKBOSTON, N.A., as Administrative Agent (in
such capacity, "Administrative Agent"), First Union National Bank, as
Syndication Agent, and Bank of America, N.A., as Documentation Agent, and the
Lenders party hereto.

                             W I T N E S S E T H:

     WHEREAS, Borrower, All American, Plains MLP, Administrative Agent, and
Lenders entered into that certain Amended and Restated Credit Agreement dated as
of November 17, 1998 (as amended, restated, or supplemented to the date hereof,
the "Original Agreement") for the purposes and consideration therein expressed,
pursuant to which Lenders became obligated to make and made loans to Borrower as
therein provided; and

     WHEREAS, Borrower, All American, Plains MLP, Administrative Agent, and
Lenders desire to amend and restate the Original Agreement for the purposes
described herein;

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
and agreements contained herein and in the Original Agreement, as amended and
restated hereby, in consideration of the loans which may hereafter be made by
Lenders to Borrower, and for other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties hereto do hereby
agree as follows:

             ARTICLE I. -- Definitions and References; Restatement
                           ---------------------------------------

     (S) 1.1.  Terms Defined in the Original Agreement.  Unless the context
               ---------------------------------------
otherwise requires or unless otherwise expressly defined herein, the terms
defined in the Original Agreement, as amended and restated hereby, shall have
the same meanings whenever used herein.

     (S) 1.2.  Other Defined Terms.  Unless the context otherwise requires, the
               -------------------
following terms when used herein shall have the meanings assigned to them in
this (S) 1.2.

               "Amendment" means this Second Amended and Restated Credit
                ---------
     Agreement.

               "Credit Agreement" means the Original Agreement as amended and
                ----------------
     restated hereby.

     (S) 1.3.  Restatement.  The Original Agreement is hereby restated in its
               -----------
current form with the amendments set forth herein below. This Amendment,
together with the Original Agreement, shall be deemed to be an amendment and
restatement of the Original Agreement. All references to the Credit Agreement in
any other document, instrument, agreement, or writing shall hereafter
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be deemed to refer to this Amendment and to the Original Agreement as amended
and restated hereby.

     (S) 1.4.  Agents.  First Union National Bank is hereby designated as
               ------
Syndication Agent hereunder and Bank of America, N.A. is hereby designated as
Documentation Agent hereunder; provided, however, that neither First Union
National Bank, as Syndication Agent, nor Bank of America, N.A., as Documentation
Agent (the "Co-Agents"), shall have any duties or responsibilities whatsoever in
such agency capacities (as opposed to its capacity as a Lender) under or in
connection with the Original Agreement, as amended and restated hereby, or under
any of the other Loan Documents. The relationship between Borrower, on the one
hand, and the Co-Agents and Administrative Agent, on the other hand, shall be
solely that of borrower and lender. None of the Co-Agents nor the Administrative
Agent nor any Lender shall have any fiduciary responsibilities to Borrower or
any of its Affiliates. None of the Co-Agents nor the Administrative Agent nor
any Lender undertakes any responsibility to Borrower or any of its respective
Affiliates to review or inform Borrower of any matter in connection with any
phase of Borrower's or such Affiliate's business or operations.

                     ARTICLE II. -- Amendments and Waiver
                                    ---------------------

     (S) 2.1.  Definitions.
               -----------

     (a) Modifications.  References to the "All American Agreement" contained in
         -------------
the Original Credit Agreement shall be deemed to refer to such agreement as
amended from time to time, including as of the date hereof. The definitions of
Base Rate, Borrowing Base, Consolidated EBITDA, Consolidated Funded
Indebtedness, Default Rate, Eurodollar Rate Margin, First Purchase Crude
Payables, Interest Expense, Interest Payment Date, Material Market Open Position
Loss and Maximum Facility Amount contained in Section 1.1 of the Original
Agreement are hereby amended in their entirety to read as follows:

          "Base Rate' means the sum of (a) the Base Rate Margin plus (b) the
           ---------
     higher of (i) the annual rate of interest announced from time to time by
     Administrative Agent at its "base rate" at its head office in Boston,
     Massachusetts, or (ii) the Federal Funds Rate plus one-half percent (0.5%)
     per annum; provided that such rate may not be the lowest rate at which
     funds are made available to customers of Administrative Agent at such time.
     Each change in the Base Rate shall become effective without prior notice to
     Borrower automatically as of the opening of business on the date of such
     change in the Base Rate."

          "Borrowing Base' means the remainder of (a) minus (b) below as of the
           --------------
     date of determination:

     (a) the sum of the following as of the date of determination:

          (i)   100% of Eligible Cash Equivalents; plus

          (ii)  90% of Approved Eligible Receivables; plus

          (iii) 85% of Eligible Margin Deposits; plus

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          (iv)  the lesser of (A) 95% of Hedged Eligible Inventory plus 100% of
                Other Eligible Inventory Value or (B) $40,000,000 prior to
                November 30, 1999, $22,000,000 on and after December 1 and prior
                to January 31, 2000 and zero thereafter; plus

          (v)   80% of Eligible Exchange Balances, plus

          (vi)  100% of all Paid but Unexpired Letters of Credit

     MINUS (b) the following as of the date of determination:

          (i)   100% of First Purchase Crude Payables; plus

          (ii)  100% of Other Priority Claims, plus

          (iii) The Estimate Adjustment Amount as provided in Section 2.13, plus

          (iv)  The amount of any setoff or contra account to any Eligible
                Receivable which could arise from a purchase obligation of crude
                oil in any future month to the extent not otherwise reflected as
                a reduction of Eligible Receivables."

          "Consolidated EBITDA' means, for any four-Fiscal Quarter period, the
           -------------------
     sum of (1) the Consolidated Net Income of Plains MLP and its Subsidiaries
     during such period, plus (2) all interest expense which was deducted in
     determining such Consolidated Net Income for such period, plus (3) all
     income taxes (including any franchise taxes to the extent based upon net
     income) which were deducted in determining such Consolidated Net Income,
     plus (4) all depreciation, amortization (including amortization of good
     will and debt issue costs) and other non-cash charges (including any
     provision for the reduction in the carrying value of assets recorded in
     accordance with GAAP) which were deducted in determining such Consolidated
     Net Income, plus (5) the Identified Loss Adjustment, minus (6) all non-cash
     items of income which were included in determining such Consolidated Net
     Income. The term "Identified Loss Adjustment" means (i) for each four-
                       --------------------------
     Fiscal Quarter period ending on or prior to March 31, 2000, the portion of
     the Identified Loss incurred in such period not to exceed an aggregate
     amount of $180,000,000 and (ii) for each four-Fiscal Quarter period ending
     after March 31, 2000, zero."

          "Consolidated Funded Indebtedness' means as of any date, the sum of
           --------------------------------
     the following (without duplication): (i) all Indebtedness which is
     classified as "long-term indebtedness" on a consolidated balance sheet of
     Plains MLP and its Consolidated Subsidiaries prepared as of such date in
     accordance with GAAP and any current maturities or other principal amount
     in respect of such Indebtedness due within one year but which was
     classified as "long-term indebtedness" at the creation thereof, (ii)
     indebtedness for borrowed money of Plains MLP and its Consolidated
     Subsidiaries outstanding under a revolving credit or similar agreement
     providing for borrowings (and renewals and extensions thereof) over a
     period of more than one year, notwithstanding

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     the fact that any such borrowing is made within one year of the expiration
     of such agreement, and (iii) Indebtedness in respect of Capital Leases of
     Plains MLP and its Consolidated Subsidiaries; provided, however,
     Consolidated Funded Indebtedness shall not include (i) Indebtedness in
     respect of letters of credit or in respect of Cash and Carry Purchases and
     (ii) subordinate Indebtedness referred to in subsection 7.1(g)."

          "Default Rate' means, at the time in question, (i) four percent (4%)
           ------------
     per annum plus the Adjusted Eurodollar Rate then in effect for any
     Eurodollar Loan (up to the end of the applicable Interest Period) or (ii)
     two percent (2%) per annum plus the Base Rate for each Base Rate Loan;
     provided, however, the Default Rate shall never exceed the Highest Lawful
     Rate."

          "Eurodollar Rate Margin' means two and one quarter percent (2.25%) per
           ----------------------
     annum."

          "First Purchase Crude Payables' means the unpaid amount of any payable
           -----------------------------
     obligation related to the purchase of crude oil by Borrower which
     Administrative Agent determines will be secured by a statutory Lien,
     including but not limited to the statutory Liens, if any, created under the
     laws of Texas, New Mexico, Wyoming, Kansas, and/or Oklahoma to the extent
     such payable obligation is not at the time in question covered by a Letter
     of Credit."

          "Interest Expense' means, with respect to any period, the sum
           ----------------
     (without duplication) of the following (in each case, eliminating all
     offsetting debits and credits between Plains MLP and its Subsidiaries and
     all other items required to be eliminated in the course of the preparation
     of Consolidated financial statements of Plains MLP and its Subsidiaries in
     accordance with GAAP): (a) all interest and commitment fees in respect of
     Indebtedness of Plains MLP or any of its Subsidiaries (including imputed
     interest on Capital Lease Obligations) which are accrued during such period
     and whether expensed in such period or capitalized; plus (b) all fees,
     expenses and charges in respect of letters of credit issued for the account
     of Plains MLP or any of its Subsidiaries, which are accrued during such
     period and whether expensed in such period or capitalized. Interest which
     is accrued but unpaid on the subordinate Indebtedness referred to in
     subsection 7.1(g), the fees payable pursuant to the letter agreement
     described in Section 2.12(d)(ii), and the amendment fee payable pursuant to
     Section 3.1(f) of the Third Amendment to the All American Agreement shall
     not be treated as Interest Expense.

          "Interest Payment Date' means (a) with respect to each Base Rate
           ---------------------
     the last day of each calendar month, and (b) with respect to each
     Eurodollar Loan, the last day of each calendar month and the last day of
     the Interest Period that is applicable to such Eurodollar Loan."

          "Material Market Open Position Loss' means a cumulative amount of net
           ----------------------------------
     losses resulting from open inventory positions (excluding inventory
     consisting of tank bottoms, pipeline linefill requirements and other
     working inventory of up to 600,000 barrels in the aggregate) of all
     Restricted Persons on a mark to market basis during any period of 12

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     consecutive months in excess of $5,000,000 (exclusive of linefill carried
     in the All American Pipeline), calculated without inclusion of that portion
     of the Identified Loss incurred during such period."

          "Maximum Facility Amount' means the following amounts as such amounts
           -----------------------
     may be reduced by Borrower from time to time as provided in Section 2.12.:

     (a) from November 17, 1998 to and including November 30, 1999,
     $175,000,000;

     (b) from and including December 1, 1999 to and including December 31, 1999,
     $255,000,000 for Letters of Credit, plus an aggregate amount for Loans of
     $40,000,000 of which no more than $22,000,000 shall be for Cash and Carry
     Purchases;

     (c) from and including January 1, 2000 to and including January 31, 2000,
     $301,000,000 for Letters of Credit and Cash and Carry Purchases of which no
     more than $22,000,000 shall be for Cash and Carry Purchases, plus an
     aggregate amount for other Loans of $14,000,000;

     (d) from and including February 1, 2000 to and including April 30, 2000,
     $225,000,000 for Letters of Credit plus an aggregate amount for Loans of
     $14,000,000;

     (e) from and including May 1, 2000 to and including June 30, 2000,
     $225,000,000 for Letters of Credit; and

     (f) from and including July 1, 2000 to the last day of the Commitment
     Period, $200,000,000 for Letters of Credit."

     (b)  Deletions.  The definitions of "Applicable Leverage Ratio" and
          ---------
"Applicable Rating Level" are hereby deleted in their entirety from the Original
Agreement.

     (c)  Additions.  The following definitions are hereby added to Section 1.1
          ---------
of the Original Agreement:

          "Base Rate Margin' three-quarters of one percent (0.75%) per annum."
           ----------------

          "Back to Back Transaction' means a specific transaction for either (i)
           ------------------------
     a specific purchase of crude oil that is matched, alone or with one or more
     other specifically identified purchases, with one or more specifically
     identified sales of crude oil having substantially the same or equivalent
     volume, price basis, delivery location, delivery time and commodity
     specifications so as to represent back to back transactions satisfactory to
     the Administrative Agent or any Person designated by Administrative Agent
     for the purpose of reviewing such transactions, or (ii) a specific exchange
     of equal volumes of crude oil that have the same or substantially
     equivalent price basis, delivery time and commodity specification
     satisfactory to the Administrative Agent or any Person designated by
     Administrative Agent for the purpose of reviewing such transactions."

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          "Identified Loss' means (i) the loss in the aggregate amount of
           ---------------
     $160,000,000 arising from unauthorized trading activity by Borrower during
     the period of January 1, 1999 to November 20, 1999 plus (ii) the fees and
     expenses of lawyers, accountants and other professionals and fees
     associated with amendments and waivers by lenders, in each case associated
     with such loss in an aggregate amount up to $20,000,000."

          "Maximum Loan Amount' means:
           -------------------

     (a) from November 17, 1998 to and including November 30, 1999, $40,000,000;

     (b) from and including December 1, 1999 to and including December 31, 1999,
     $40,000,000;

     (c) from and including January 1, 2000 to and including January 31, 2000,
     $36,000,000;

     (c) from and including February 1, 2000 to and including April 30, 2000,
     $14,000,000; and

     (d) from and including May 1, 2000 to the last day of the Commitment
     Period, zero."

     (S) 2.2. Commitments to Lend; Notes.  Section 2.1 of the Original Agreement
              --------------------------
is hereby amended in its entirety to read as follows:

          "Section 2.1.  Loans; Notes.  Subject to the terms and conditions
                         ------------
     hereof, each Lender agrees to make loans to Borrower (herein called such
     Lender's "Loans") upon Borrower's request from time to time prior to
     January 1, 2000, provided that (a) subject to Sections 3.3, 3.4 and 3.6,
     all Lenders are requested to make Loans of the same Type in accordance with
     their respective Percentage Shares and as part of the same Borrowing, (b)
     after giving effect to such loans, the aggregate principal amount of
     outstanding Loans will not exceed the Maximum Loan Amount, and (c) after
     giving effect to such Loans, the Facility Usage does not exceed the lesser
     of (i) the Maximum Facility Amount and (ii) the Borrowing Base determined
     as of the date on which the requested Loans are to be made. The aggregate
     amount of all Loans in any Borrowing must be equal to $2,000,000 or any
     higher integral multiple of $250,000. Borrower may have no more than five
     Borrowings of Eurodollar Loans outstanding at any time. The obligation of
     Borrower to repay to each Lender the aggregate amount of all Loans made by
     such Lender, together with interest accruing in connection therewith, shall
     be evidenced by a single promissory note (herein called such Lender's
     "Note") made by Borrower payable to the order of such Lender in the form of
     Exhibit A with appropriate insertions. The amount of principal owing on any
     Lender's Note at any given time shall be the aggregate amount of all Loans
     theretofore made by such Lender minus all payments of principal theretofore
     received by such Lender on such Note. Interest on each Note shall accrue
     and be due and payable as provided herein and therein. Each Note shall be
     due and payable as provided herein and therein. Prior to November 30, 1999,
     subject to the terms and conditions of this Agreement, Borrower may borrow,
     repay and reborrow hereunder. Notwithstanding anything to the contrary
     contained in this Agreement or in any Note, Borrower shall pay the
     principal amount of the Loan on each day to the extent that the aggregate
     Loans

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     exceed the Maximum Loan Amount on such day and shall pay all Loans on April
     30, 2000.

     (S) 2.3. Use of Proceeds.  Section 2.4 of the Original Agreement is hereby
              ---------------
amended in its entirety to read as follows:

               "Section 2.4.  Use of Proceeds.  Borrower shall use the
                              ---------------
     proceeds of all Loans (a) made prior to November 30, 1999, to make
     Qualified Inventory Purchases and to refinance Matured LC Obligations and
     (b) made on or after December 1, 1999 solely for those Cash and Carry
     Purchases not to exceed 2,000,000 barrels committed by Borrower prior to
     November 30, 1999 and to pay transaction costs incurred in connection with
     the Third Amendment to this Agreement, the Third Amendment to the All
     American Agreement, and related transactions, including without limitation
     the fees and expenses of lawyers, accountants and other professionals, in
     each case limited as set forth in the definition of Maximum Facility
     Amount. In no event shall any Loan or any Letter of Credit be used (i) to
     fund distributions by Plains MLP, (ii) directly or indirectly by any Person
     for personal, family, household or agricultural purposes, (iii) for the
     purpose, whether immediate, incidental or ultimate, of purchasing,
     acquiring or carrying any "margin stock" (as such term is defined in
     Regulation U promulgated by the Board of Governors of the Federal Reserve
     System) or (iv) to extend credit to others directly or indirectly for the
     purpose of purchasing or carrying any such margin stock. Borrower
     represents and warrants that Borrower is not engaged principally, or as one
     of Borrower's important activities, in the business of extending credit to
     others for the purpose of purchasing or carrying such margin stock."

     (S) 2.4. Letters of Credit.  Section 2.7 of the Original Agreement is
              -----------------
hereby amended in its entirety to read as follows:

               "Section 2.7  Letters of Credit.  Subject to the terms and
                             -----------------
     conditions hereof, Borrower may during the Commitment Period request LC
     Issuer to issue, amend, or extend the expiration date of, one or more
     Letters of Credit, provided that:

          (a)  after taking such Letter of Credit into account the Facility
     Usage does not exceed the lesser of (i) the Maximum Facility Amount at such
     time or (ii) the Borrowing Base at such time;

          (b)  the expiration date of such Letter of Credit is prior to the
     earlier of (i) 70 days (or 100 days, if the beneficiary thereof is Exxon
     Company U.S.A.) after the date of issuance of such Letter of Credit (or 180
     days after the date of issuance in the case of a Surety Letter of Credit)
     or (ii) 30 days prior to the end of the Commitment Period;

          (c)  the issuance of such Letter of Credit will be in compliance with
     all applicable governmental restrictions, policies, and guidelines and will
     not subject LC Issuer to any cost which is not reimbursable under Article
     III;

          (d)  either (i) such Letter of Credit is related to the purchase or
     exchange by Borrower of crude oil and is in the Form of Exhibit D hereto or
     such other form and terms

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<PAGE>

     as shall be acceptable to LC Issuer in its sole and absolute discretion and
     Currently Approved by Majority Lenders; provided, however, that on and
     after December 1, 1999 such Letter of Credit may only be issued to support
     a Back to Back Transaction, or (ii) such Letter of Credit is a Surety
     Letter of Credit and after taking such Letter of Credit into account the
     aggregate amount of LC Obligations in respect to all Surety Letters of
     Credit does not exceed $1,000,000;

          (e)  from and after December 1, 1999, LC Issuer shall have received
     all reports and other information, in form and substance satisfactory to LC
     Issuer, required under Section 6.2, and all such reports and other
     information confirm to LC Issuer's satisfaction that such Letter of Credit
     is a Back to Back Transaction Letter of Credit; and

          (f)  all other conditions in this Agreement to the issuance of such
     Letter of Credit have been satisfied.

     LC Issuer will honor any such request if the foregoing conditions (a)
     through (f) (in the following Section 2.8 called the "LC Conditions") have
                                                           -------------
     been met as of the date of issuance, amendment, or extension of such Letter
     of Credit. The outstanding letters of credit issued by LC Issuer under the
     Existing Agreement shall be deemed to be Letters of Credit issued
     hereunder; Borrower hereby represents and warrants that the LC Conditions
     have been met as of the date hereof with respect to each such Letter of
     Credit."

     (S) 2.5.  Requesting Letters of Credit.  Section 2.8 of the Original
               ----------------------------
Agreement is hereby amended in its entirety to read as follows:

               "Section 2.8.  Requesting Letters of Credit.  Borrower must make
                              ----------------------------
     application electronically transmitted by means of Administrative Agent's
     Trade Key System for any Letter of Credit at least two Business Days (other
     than Letters of Credit issued on December 1 or 2, 1999) before the date on
     which Borrower desires for LC Issuer to issue such Letter of Credit. By
     making any such application, unless otherwise expressly stated therein,
     Borrower shall be deemed to have represented and warranted that the LC
     Conditions described in Section 2.7 will be met as of the date of issuance
     of such Letter of Credit and to have agreed to all terms and provisions of
     the application for a letter of credit in the form of Exhibit E, the terms
     and provisions of which are hereby incorporated herein by reference. If all
     LC Conditions for a Letter of Credit have been met as described in Section
     2.7 on any Business Day before 11:00 a.m., Boston, Massachusetts time, LC
     Issuer will issue such Letter of Credit on the same Business Day at LC
     Issuer's office in Boston, Massachusetts. If the LC Conditions are met as
     described in Section 2.7 on any Business Day on or after 11:00 a.m.,
     Boston, Massachusetts time, LC Issuer will issue such Letter of Credit on
     the next succeeding Business Day at LC Issuer's office in Boston,
     Massachusetts. If any provisions of any LC Application conflict with any
     provisions of this Agreement, the provisions of this Agreement shall govern
     and control."

     (S) 2.6.  Letters of Credit.  Subsections (a) and (b) of Section 2.9 of the
               -----------------
Original Agreement are hereby amended in their entirety to read as follows:

     "Section 2.9.  Reimbursement and Participations.
                    --------------------------------

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<PAGE>

               (a)  Reimbursement by Borrower.  Each Matured LC Obligation shall
                    -------------------------
     constitute a loan by LC Issuer to Borrower.  Borrower promises to pay to LC
     Issuer, or to LC Issuer's order, on demand, the full amount of each Matured
     LC Obligation, together with interest thereon at the Default Rate.

               (b)  [Intentionally deleted]"

     (S) 2.7.  Interest Rates and Fees.  Subsections (b), (c), and (d) of
               -----------------------
Section 2.12. of the Original Agreement are hereby amended in their entirety to
read as follows, and the following Section 2.12(e) is hereby added to the
Original Agreement as follows:

               "(b)  Commitment Fees.  In consideration of each Lender's
                     ---------------
     commitment to make Loans and to participate in Letters of Credit, Borrower
     will pay to Administrative Agent for the account of each Lender a
     commitment fee determined on a daily basis by applying a rate of one half
     of one percent (0.50%) per annum to such Lender's Percentage Share of the
     unused portion of the Maximum Facility Amount on each day during the
     Commitment Period, determined for each such day by deducting from the
     amount of the Maximum Facility Amount at the end of such day the Facility
     Usage. This commitment fee shall be due and payable in arrears on the last
     day of each Fiscal Quarter and at the end of the Commitment Period.
     Borrower shall have the right from time to time to permanently reduce the
     Maximum Facility Amount, provided that (i) notice of such reduction is
     given not less than 2 business Days prior to such reduction, (ii) the
     resulting Maximum Facility Amount is not less than the Facility Usage, and
     (iii) each partial reduction shall be in an amount at least equal to
     $500,000 and in multiples of $100,000 in excess thereof.

               (c)  Letter of Credit Fees.  In consideration of LC Issuer's
                    ---------------------
     issuance of any Letter of Credit after December 1, 1999, Borrower agrees to
     pay (i) to Administrative Agent, for the account of all Lenders in
     accordance with their respective Percentage Shares, a letter of credit fee
     at a rate equal to two and one quarter percent (2.25%) per annum, and (ii)
     to such LC Issuer for its own account, a letter of credit fronting fee at a
     rate equal to one eighth of one percent (.125%) per annum. Each such fee
     will be calculated on the face amount of each Letter of Credit outstanding
     on each day at the above applicable rates and will be payable monthly in
     arrears on the last day of each month and upon drawing on or expiration of
     such Letter of Credit, as applicable. In addition, Borrower will pay to LC
     Issuer a minimum administrative issuance fee of $100 for each Letter of
     Credit and such other fees and charges customarily charged by the LC Issuer
     in respect of any amendment or negotiation of any Letter of Credit in
     accordance with the LC Issuer's published schedule of such charges as of
     the date of such amendment or negotiation.

               (d)  Other Fees.  In addition to all other amounts due to
                    ----------
     Administrative Agent under the Loan Documents, Borrower will pay all fees
     (i) to Administrative Agent as described in a letter agreement dated
     December 1, 1999 between Administrative Agent and Borrower, (ii) to certain
     Lenders and their affiliates as described in a letter agreement dated
     December 1, 1999 between such Lenders and Borrower and (iii) to Lenders as
     described in a letter agreement dated December 1, 1999.

                                      -9-
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     (S) 2.8.  Books, Financial Statements, and Reports.  Section 6.2 of the
               ----------------------------------------
Original Agreement is amended by adding thereto the following Subsections
6.2(i), 6.2(j), 6.2(k), 6.2(l),6.2(m), and 6.2(n):

               "(i)   concurrently with the request for the issuance of any
     Letter of Credit, and on or prior to the 28/th/ day of each month, a
     schedule forecasting report by a firm of independent consultants or
     accountants acceptable to Administrative Agent confirming Borrower's
     compliance with (A) the requirements of Back to Back Transactions and (B)
     Section 6.20(b) with regard to transactions described in the most recent
     Borrowing Base Report, in form and substance satisfactory to Administrative
     Agent, which shall list for the immediately succeeding calendar month, each
     purchase, sale or exchange of crude oil, the volumes for each such
     purchase, sale or exchange, the counterparties for each such purchase, sale
     or exchange, and related pricing indices, and shall have attached thereto
     (i) copies of all material purchase, sales or exchange contracts related to
     transactions for which Letters of Credit are requested or issued and (ii)
     calculations of Borrower's estimated gross margin and operating income for
     such calendar month, all in form and substance satisfactory to
     Administrative Agent.

               (j)    On each Business Day, a MERC position report of Restricted
     Persons as of such date.

               (k)    On a daily, weekly, or other periodic basis determined by
     Administrative Agent, a report of inventory positions of Restricted Persons
     in form satisfactory to Administrative Agent.

               (l)    On the last day of each calendar week a report on the
     status of the Borrowing Base in form satisfactory to Administrative Agent
     completed by an authorized officer of General Partner.

               (m)    On or before 1:00 p.m., Boston, Massachusetts time, on the
     10/th/ day of each calendar month, a Consolidated statement of Plains MLP's
     earnings and cash flows for the immediately preceding calendar month in
     form satisfactory to Administrative Agent.

               (n)    On the 15/th/ and the last day of each calendar month,
     Borrower's earnings and cash flow forecast for the current and two
     succeeding months, both including and excluding Plains Scurlock Permian,
     L.P., and accompanying the forecast due on the 15/th/ day of each calendar
     month, a report in form and substance satisfactory to Administrative Agent
     from PricewaterhouseCoopers, Arthur Andersen or other independent certified
     public accountants selected by General Partner and acceptable to Majority
     Lenders, regarding the methodology used by Borrower for its cash flows and
     the reasonableness of the assumptions used by Borrower in connection with
     its forecast."

     (S) 2.9.  Other Information and Inspections.  Section 6.3 of the Original
               ---------------------------------
Agreement is hereby amended to add the following sentence immediately before the
last sentence thereof:

                                     -10-
<PAGE>

     "Borrower shall (i) at all times provide all information and shall provide
     access to all Restricted Persons' books and records to a firm of
     independent public accountants or independent consultants retained by the
     Administrative Agent for purposes of confirming the Borrowing Base,
     Borrower's compliance with all conditions related to Letters of Credit and
     such other matters relating to the Restricted Persons as may be determined
     from time to time by Administrative Agent and (ii) shall pay within 20 days
     after an invoice therefor has been delivered to Borrower all fees and
     expenses of such independent public accountants or independent consultants
     incurred in connection with their activities."

     (S) 2.10. Operating Practices; Linefill Contracts. The following Sections
               ---------------------------------------
6.21 and 6.22 are hereby added to the Original Agreement:

               "Section 6.21. Operating Practices.
                              -------------------

               (a) Borrower shall operate its business in a manner that is
     consistent with the best practices of companies in similar businesses and
     similarly situated. Borrower shall, during the month of December, 1999 and
     from time to time thereafter as requested by Administrative Agent, review
     its policies and procedures regarding its crude oil purchases, sales,
     exchanges and Hedging Contracts, as soon as possible adopt such policies
     and procedures relating thereto as may be recommended by Restricted
     Persons' or Administrative Agent's third party consultants and accountants,
     and provide a report to Lenders regarding such policies and procedures,
     including such policies and procedures which Borrower could adopt and has
     adopted to represent such best practices.

               (b) Borrower shall not enter into any transaction involving any
     crude oil purchase, sale, exchange or Hedging Contract unless such
     transaction is a Back to Back Transaction or is a Cash and Carry
     Transaction described on Schedule 8.

               Section 6.22.  Monetize Linefill Contracts.  On or prior to
                              ---------------------------
     January 20, 2000, Borrower shall monetize all contracts for the sale of
     linefill contained in the All American Pipeline and the linefill related to
     such contracts, with respect to the deliveries to be made in January and
     February, 2000 providing for a discount of not more than 10% of the full
     purchase price, and otherwise in a form and on terms reasonably
     satisfactory to Lenders whose combined Percentage Share is not less than
     80%. The foregoing covenant shall have no grace period as otherwise
     specified in Section 8.1(e). All cash proceeds from such monetization shall
     be used to fund the working capital shortages resulting from the Identified
     Loss. Any such cash proceeds not immediately needed for such working
     capital shortages shall be held as cash collateral in a lockbox maintained
     by Administrative Agent to secure first the obligations of Borrower under
     the All American Agreement and second the obligations of Borrower under
     this Credit Agreement until it is needed for such working capital
     shortages.

     (S) 2.11. Indebtedness. Section 7.1 of the Original Agreement is hereby
               ------------
amended by renumbering clause (g) to be clause (h) and to insert a new clause
(g), to read as follows:

                                      -11-
<PAGE>

               "(g)  Indebtedness in a principal amount not at any time in
     excess of $114,000,000 (plus accrued unpaid interest on such principal
     amount) owing by Borrower to General Partner and subordinated to the
     Obligations under this Agreement and the Indebtedness under the All
     American Agreement on terms and conditions satisfactory to Administrative
     Agent."

     (S) 2.12. Limitation on Dividends and Redemptions. Section 7.6 of the
               ---------------------------------------
Original Agreement is hereby to read as follows:

               "Section 7.6  Limitation on Dividends and Redemptions.  No
                             ---------------------------------------
     Restricted Person will declare or pay any dividends on, or make any other
     distribution in respect of, any class of its capital stock or any
     partnership or other interest in it, nor will any Restricted Person
     directly or indirectly make any capital contribution to or purchase,
     redeem, acquire or retire any shares of the capital stock of or partnership
     interests in any Restricted Person (whether such interests are now or
     hereafter issued, outstanding or created), or cause or permit any reduction
     or retirement of the capital stock of any Restricted Person, while any Loan
     is outstanding. Notwithstanding the foregoing, but subject to Section 7.5,
     (i) Subsidiaries of Plains MLP, Borrower, or of any Guarantor shall not be
     restricted, directly or indirectly, from declaring and paying dividends or
     making any other distributions to Plains MLP, Borrower, or any such
     Guarantor, respectively, (ii) no Restricted Person shall be restricted from
     making capital contributions to a Wholly Owned Subsidiary of such
     Restricted Person that is a Guarantor, and (iii) Plains MLP may make a
     regular quarterly distribution of Available Cash to its partners in
     accordance with the Partnership Agreement if, and only if, all Lenders (or,
     if no Lender shall have a Percentage Share exceeding 25%, Majority Lenders)
     shall have given their prior written consent to such distribution."

     (S) 2.13. Current Ratio. Section 7.11 of the Original Agreement is hereby
amended in its entirety to read as follows:

               "Section 7.11. Current Ratio. The ratio of (i) the sum of Plains
     MLP's Consolidated current assets plus the All American Revolver
     Availability to (ii) Plains MLP's Consolidated current liabilities will
     never be less than 1.0 to 1.0. For purposes of this section, Plains MLP's
     Consolidated current liabilities will be calculated without including (a)
     any payments of principal on the Notes which are required to be repaid
     within one year from the time of calculation and (b) all Liabilities
     arising under permitted Hedging Contracts. Further, Consolidated current
     liabilities shall be decreased by (x) $105,000,000 for the period from
     December 1, 1999 to and including January 31, 2000 and (y) $10,000,000 for
     the period from January 31, 2000 through and including February 28, 2000."

     (S) 2.14. Debt to Capital Ratio.  Section 7.15 of the Original Agreement
               ---------------------
is hereby amended in its entirety to read as follows:

               "Section 7.15  Debt to Capital Ratio.  On or before April 30,
                              ---------------------
     2000, the ratio of (a) all Consolidated Funded Indebtedness to (b) the sum
     of Consolidated Funded Indebtedness plus Consolidated Net Worth plus one-
     half (50%) of the Identified Loss

                                      -12-
<PAGE>

     will never be greater than .60 to 1.0 at any time. After April 30, 2000,
     the ratio of (a) all Consolidated Funded Indebtedness to (b) the sum of
     Consolidated Funded Indebtedness plus Consolidated Net Worth will never be
     greater than .60 to 1.0 at any time."

     (S) 2.15. Open Inventory Position.  Section 7.16 of the Original Agreement
               -----------------------
is hereby amended in its entirety as follows:

               "Section 7.16  Open Inventory Position.  Borrower shall not at
                              -----------------------
     any time have an Open Position other than inventory consisting of tank
     bottoms, pipeline linefill requirements and other working inventory not to
     exceed at any time 600,000 barrels in the aggregate."

     (S) 2.16. Future Delivery Contracts.  The Agreement is amended to add
               -------------------------
following Sections 7.18 and 7.19  to the Original Agreement:

               "Section 7.18 Future Delivery Contracts.
                             -------------------------

               (a) No contract shall be entered into after December 1, 1999 for
     delivery or receipt of crude oil (including but not limited to a futures
     contract, open market contract or forward sale) other than (i) for delivery
     or receipt during the next succeeding two months after the date of the such
     contract or (ii) involving sales solely on a floating market price basis.

               (b) Once a contract giving rise to an "Eligible Receivable" is
     reflected in a Borrowing Base Report representing the obligation to deliver
     crude oil in the month next succeeding the month in which the Borrowing
     Base Report is delivered, such a contract may not be modified, sold or
     exchanged in any respect which would affect the Borrowing Base without the
     consent of the Administrative Agent and a re-certification of the Borrowing
     Base in a Borrowing Base Report satisfactory to Administrative Agent.

               Section 7.19.  No Contango Transactions.  Borrower shall not
                              ------------------------
     engage in any contango transactions except for (a) the sale of the linefill
     contained in the All American Pipeline permitted hereunder and (b) other
     such transactions to which Borrower is committed as of December 1, 1999,
     which have been disclosed to Lenders in writing, and which do not in the
     aggregate exceed $28,000,000.

     (S) 2.17. Events of Default.  Section 8.1 of the Original Agreement is
               -----------------
hereby amended by adding a new subsection (m) to read as follows:

               (m) General Partner shall fail to make on or after December 2,
     1999, but on or before January 10, 2000, a loan to or other investment in
     Borrower in an amount not less than $50,000,000, which loan shall have been
     subordinated to the Obligations upon terms and conditions satisfactory to
     Administrative Agent, or Borrower shall use any proceeds of such loan or
     investment to pay any portion of the Identified Loss.

                                      -13-
<PAGE>

     (S) 2.18. Schedules.  Schedules 1 and 2 to the Original Agreement are
               ---------
hereby deleted in their entirety and replaced with Schedules 1 and 2 hereto.
Schedule 8 hereto is hereby added to the Original Agreement.

     (S) 2.19. Waiver.  This Amendment, upon its effectiveness as provided in
               ------
(S) 3.1, shall waive (i) the violations of Sections 7.6, 7.11, 7.15, and 7.16 of
the Original Agreement by Borrower on and prior to the date hereof, based upon
unauthorized trading activities disclosed by Plains MLP in its press release of
November 29, 1999, (ii) the Events of Default arising under Sections 8.1(f),
8.1(g), 8.1(l) of the Original Agreement on and prior to the date hereof, based
upon unauthorized trading activities disclosed by Plains MLP in its press
release of November 29, 1999 and (iii) those Defaults and Events of Default
occurring on or before December 1, 1999 resulting from the foregoing, based upon
unauthorized trading activities disclosed by Plains MLP in its press release of
November 29, 1999.

     (S) 2.20. Consent.  Each Lender a party hereto hereby consents to (i) the
               -------
sale by All American of the linefill carried in the All American Pipeline during
the period from December 1, 1999 through February 29, 2000 as is contracted for
on the date of this Amendment, (ii) any earlier monetization of such linefill
and the contracts for the sale thereof (including, without limitation, a sale or
loan with recourse limited to such linefill and contracts), (iii) the retention
of the proceeds of such sale or monetization in a cash collateral account within
the control of "Administrative Agent" under the All American Agreement to
secure, on a first priority basis, the Indebtedness under the All American
Agreement and, on a second priority basis, the Obligations, in accordance with
the Intercreditor Agreement, (iv) the delivery of such proceeds to Borrower by
the Administrative Agent from time to time upon request by Borrower for the
payment of accounts payable of Borrower on the date such payables are actually
paid and (v) the release of the Lien under the Security Documents on such
linefill and such proceeds upon use of such proceeds for such purpose. The
Restricted Persons agree that the portion of such transferred proceeds owned by
All American shall be made as a loan from All American to Borrower, and that
such loan shall be evidenced in a manner satisfactory to the Administrative
Agent and shall be subordinated to the Obligations under the Credit Agreement
and to the Indebtedness under the All American Credit Agreement on terms and
conditions satisfactory to the Administrative Agent.

                  ARTICLE III. -- Conditions of Effectiveness
                                  ---------------------------

     (S) 3.1.  Effective Date.  This Amendment shall become effective as of the
               --------------
date first above written when and only when:

               (a) Administrative Agent shall have received, at Administrative
     Agent's office: (i) a counterpart of this Amendment executed and delivered
     by Borrower, All American, Plains MLP, Administrative Agent, and Majority
     Lenders, (ii) new Notes, renewing and increasing the Notes issued pursuant
     to the Original Agreement, executed and delivered by Borrower to each
     Lender as of the date hereof, (iii) a certificate of a duly authorized
     officer of General Partner (A) stating that all of the representations and
     warranties set forth in Article IV hereof are true and correct at and as of
     the time of such effectiveness, (B) stating that no Material Adverse Change
     shall have occurred other than the Identified Loss, and (C) having attached
     thereto as an exhibit a copy of resolutions

                                      -14-
<PAGE>

     duly adopted by the Board of Directors of General Partner in full force and
     effect at the time that this Amendment is entered into, and containing such
     other certifications as shall be required by Administrative Agent, in form
     and substance acceptable to Administrative Agent, (iv) an opinion of
     Fulbright & Jaworski, L.L.P., special Texas and New York counsel to
     Restricted Persons, in form and substance acceptable to Administrative
     Agent in Administrative Agent's sole and absolute discretion, and (v) an
     opinion of Michael R. Patterson, General Counsel for Restricted Persons.

               (b) Each "Underwriter" (as defined in that certain letter
     agreement of even date herewith among certain Lenders and Borrower) shall
     have received a report, in form and substance satisfactory to such Persons,
     prepared by Arthur Andersen & Co. regarding its review of the accounting
     records, loss assessments, transaction reviews, borrowing base reports,
     cash flow methodology, and letter of credit requirements of the Restricted
     Persons.

               (c) Borrower shall have used its best efforts to have pledged all
     of the outstanding limited partnership interests in Plains Scurlock
     Permian, L.P. as Collateral pursuant to Security Documents satisfactory to
     Administrative Agent, such Collateral to be "Marketing Priority Collateral"
     (as such term is defined in the Intercreditor Agreement).

               (d) General Partner shall have made on or after November 21, 1999
     a loan to Borrower in an amount not less than $64,000,000 and each of
     General Partner and Borrower shall have certified the making of such loan,
     which loan shall have been subordinated to the Obligations upon terms and
     conditions satisfactory to Administrative Agent.

               (e) Amendments to the Security Documents amending the description
     of secured indebtedness therein to reflect the Maximum Facility Amount,
     together with favorable opinions of local counsel for the states of
     Arizona, California, New Mexico and Oklahoma, as requested by and
     satisfactory to Administrative Agent.

               (f) Documents satisfactory to Administrative Agent regarding the
     sale of the linefill contained in the All American Pipeline.

               (g) Payment of all underwriting, agency and other fees required
     to be paid to any Lender pursuant to any Loan Documents and all fees and
     expenses of Thompson & Knight LLP, and Vinson & Elkins, L.L.P. counsel to
     Administrative Agent.

               (h) A contemporaneous amendment to the All American Credit
     Agreement executed by all "Lenders" under the All American Agreement
     amending the All American Credit Agreement to permit the increased Maximum
     Facility Amount, amending other provisions therein, and waiving all
     existing Defaults and Events of Default as of the date hereof, in form
     satisfactory to Administrative Agent.

                                      -15-
<PAGE>

               (i) Administrative Agent shall have received all documents and
     instruments which Administrative Agent has then requested, in addition to
     those described in the foregoing (S) 3.1(a) through and including (S)
     3.1(g).

               (j) Administrative Agent shall have received assurances from
     Borrower that Borrower will be able to monetize the Letter of Credit
     contracts for the sale of the linefill contained in the All American
     Pipeline as required by Section 6.21 of the Credit Agreement.

               (k) Administrative Agent shall have received satisfactory
     evidence that the Sempra "rings" transactions (as described to Lenders by
     Borrower) shall have been effectuated and closed on or prior to December 1,
     1999.

                 ARTICLE IV. -- Representations and Warranties
                                ------------------------------

     (S) 4.1.  Representations and Warranties of Plains MLP and Borrower.  In
               ---------------------------------------------------------
order to induce Administrative Agent and Lenders to enter into this Amendment,
Plains MLP and Borrower represent and warrant to Administrative Agent and each
Lender that:

               (a) The representations and warranties contained in Article V of
     the Original Agreement are true and correct at and as of the time of the
     effectiveness hereof, except to the extent that such representation and
     warranty was made as of a specific date.

               (b) Each Restricted Person is duly authorized to execute and
     deliver this Amendment, and Borrower is and will continue to be duly
     authorized to borrow and perform its obligations under the Credit
     Agreement. Each Restricted Person has duly taken all corporate action
     necessary to authorize the execution and delivery of this Amendment and to
     authorize the performance of their respective obligations hereunder.

               (c) The execution and delivery by each Restricted Person of this
     Amendment, the performance by each Restricted Person of its respective
     obligations hereunder, and the consummation of the transactions
     contemplated hereby, do not and will not conflict with any provision of
     law, statute, rule or regulation or of the constituent documents of any
     Restricted Person, or of any material agreement, judgment, license, order
     or permit applicable to or binding upon any Restricted Person, or result in
     the creation of any lien, charge or encumbrance upon any assets or
     properties of any Restricted Person, except in favor of Administrative
     Agent for the benefit of Lenders and other Permitted Liens. Except for
     those which have been duly obtained, no consent, approval, authorization or
     order of any court or governmental authority or third party is required in
     connection with the execution and delivery by any Restricted Person of this
     Amendment or to consummate the transactions contemplated hereby.

               (d) When this Amendment has been duly executed and delivered,
     each of the Loan Documents, as amended by this Amendment, will be a legal
     and binding instrument and agreement of each Restricted Person, enforceable
     in accordance with its terms,

                                      -16-
<PAGE>

     (subject, as to enforcement of remedies, to applicable bankruptcy,
     insolvency and similar laws applicable to creditors' rights generally and
     to general principles of equity).

               (e) No Material Adverse Change has occurred other than the
     Identified Loss.

                          ARTICLE V. -- Miscellaneous
                                        -------------

                                      -17-
<PAGE>

     (S) 5.1.  Ratification of Agreements; Release.  The Original Agreement, as
               -----------------------------------
hereby amended, is hereby ratified and confirmed in all respects. The Loan
Documents (including but not limited to each Guaranty), as they may be amended
or affected by this Amendment, are hereby ratified and confirmed in all respects
by each Restricted Person to the extent a party thereto. Any reference to the
Credit Agreement in any Loan Document shall be deemed to refer to this Amendment
also. The execution, delivery and effectiveness of this Amendment shall not,
except as expressly provided herein, operate as a waiver of any right, power or
remedy of Administrative Agent or any Lender under the Credit Agreement or any
other Loan Document nor constitute a waiver of any provision of the Credit
Agreement or any other Loan Document. As further consideration and to induce
each Lender Party to enter into and grant the accommodations contained in this
Amendment, EACH RESTRICTED PERSON - ON BEHALF OF ITSELF AND, TO THE EXTENT IT IS
PERMITTED BY LAW OR IS OTHERWISE EXPRESSLY AUTHORIZED TO DO SO, ON BEHALF OF ALL
OF ITS AFFILIATES (COLLECTIVELY, "RELEASING PARTIES") -- HEREBY GENERALLY
RELEASE AND FOREVER DISCHARGE EACH LENDER PARTY AND EACH OF THEIR RESPECTIVE
AFFILIATES (COLLECTIVELY, "RELEASED PARTIES"), FROM ANY AND ALL CLAIMS, DEMANDS,
AND CAUSES OF ACTION OF WHATEVER KIND OR CHARACTER WHICH SUCH RELEASING PARTY
HAS, OR MAY HAVE IN THE FUTURE, BASED ON ANY ACTIONS, FAILURES TO ACT, OR EVENTS
THAT HAVE OCCURRED PRIOR TO THE EFFECTIVE DATE HEREOF, WHICH IN ANY WAY RELATE
TO OR ARE BASED UPON (I) ANY TRANSACTIONS OF ANY KIND AMONG THE RELEASING
PARTIES , ON THE ONE HAND, AND THE RELEASED PARTIES, ON THE OTHER HAND, OR (II)
ANY ACTUAL OR ALLEGED NEGOTIATIONS, DISCUSSIONS, REPRESENTATIONS, WARRANTIES,
PROMISES, OR OTHER UNDERTAKINGS BY RELEASED PARTIES IN CONNECTION WITH ANY OF
THE FOREGOING (THE "RELEASED CLAIMS"). THIS RELEASE IS TO BE CONSTRUED AS THE
BROADEST TYPE OF GENERAL RELEASE AND COVERS AND RELEASES ANY AND ALL RELEASED
CLAIMS, WHETHER KNOWN OR UNKNOWN AND HOWEVER OR WHENEVER ARISING, WHETHER BY
CONTRACT OR AGREEMENT, AT LAW OR UNDER ANY STATUTE (INCLUDING WITHOUT LIMITATION
ANY LAW OR STATUTE PERTAINING TO NEGLIGENCE, GROSS NEGLIGENCE, STRICT LIABILITY,
FRAUD, DECEPTIVE TRADE PRACTICES, NEGLIGENT MISREPRESENTATION, SECURITIES
VIOLATIONS, BREACH OF FIDUCIARY DUTY, BREACH OF CONTRACT, TRADE REGULATION,
REGULATION OF BUSINESS OR COMPETITION, CONSPIRACY OR RACKETEERING), OR OTHERWISE
ARISING, AND EXPRESSLY INCLUDING ANY CLAIMS FOR PUNITIVE OR EXEMPLARY DAMAGES,
ATTORNEYS' FEES, OR PENALTIES. TO THE EXTENT THAT ANY RELEASED CLAIMS WITH
RESPECT TO RELEASED PARTIES HAVE NOT BEEN RELEASED BY THIS LETTER AGREEMENT,
EACH RELEASING PARTY HEREBY ASSIGN S SUCH RELEASED CLAIMS TO RELEASED PARTIES.

     (S) 5.2.  Ratification of Security Documents.  Restricted Persons,
               ----------------------------------
Administrative Agent, and Lenders each acknowledge and agree that any and all
indebtedness, liabilities or obligations arising under or in connection with the
LC Obligations, as amended hereby, or the Notes, as amended hereby, are
Obligations and are secured indebtedness under, are guarantied by, and are
secured by, each and every Security Document to which any Restricted Person is a
party. Each

                                      -18-
<PAGE>

Restricted Person hereby re-pledges, re-grants and re-assigns a security
interest in and lien on every asset of the such Restricted Person described as
Collateral in any Security Document and re-guaranties all Obligations, as
amended hereby.

     (S) 5.3.  Ratification of Intercreditor Agreement.  Each Lender hereby
               ---------------------------------------
acknowledges and confirms that all Obligations under the Credit Agreement, as
amended hereby, and the "Obligations" under the All American Credit Agreement,
as amended on the date hereof, shall be and shall remain subject to the terms
and entitled to the benefits of the Intercreditor Agreement.

     (S) 5.4.  Survival of Agreements.  All representations, warranties,
               ----------------------
covenants and agreements of the Restricted Persons herein shall survive the
execution and delivery of this Amendment and the performance hereof, including
without limitation the making or granting of each Loan, and shall further
survive until all of the Obligations are paid in full. All statements and
agreements contained in any certificate or instrument delivered by any
Restricted Person hereunder or under the Credit Agreement to Administrative
Agent or any Lender shall be deemed to constitute representations and warranties
by, or agreements and covenants of, such Restricted Person under this Amendment
and under the Credit Agreement.

     (S) 5.5.  Loan Documents.  This Amendment is a Loan Document, and all
               --------------
provisions in the Credit Agreement pertaining to Loan Documents apply hereto.

     (S) 5.6.  GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY AND CONSTRUED
     --------------------------------------------------------------------------
IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK AND ANY APPLICABLE LAWS OF
-------------------------------------------------------------------------------
THE UNITED STATES OF AMERICA IN ALL RESPECTS, INCLUDING CONSTRUCTION, VALIDITY
------------------------------------------------------------------------------
AND PERFORMANCE.
----------------

     (S) 5.7.  Counterparts.  This Amendment may be separately executed in
               ------------
counterparts and by the different parties hereto in separate counterparts, each
of which when so executed shall be deemed to constitute one and the same
Amendment.

     IN WITNESS WHEREOF, this Amendment is executed as of the date first above
written.

                              PLAINS MARKETING, L.P.

                              By:   PLAINS ALL AMERICAN INC.,
                                    its general partner

                                    By: /s/ Phil Kramer
                                       --------------------------------
                                       Phil Kramer
                                       Executive Vice President

                              PLAINS ALL AMERICAN PIPELINE, L.P.

                              By:   PLAINS ALL AMERICAN INC.,
                                    its general partner

                                      -19-
<PAGE>

                                    By: /s/ Phil Kramer
                                       --------------------------------
                                       Phil Kramer
                                       Executive Vice President

                              ALL AMERICAN PIPELINE, L.P.

                              By:   PLAINS ALL AMERICAN INC.,
                                    its general partner

                                    By: /s/ Phil Kramer
                                       --------------------------------
                                       Phil Kramer
                                       Executive Vice President

                                    BANKBOSTON, N.A., as Administrative Agent
                                    and Lender

                                    By: /s/ Terrence Ronan, Director
                                       --------------------------------
                                       Terrence Ronan, Director

                                    FIRST UNION NATIONAL BANK, Lender

                                    By: /s/ Paul N. Riddle
                                       --------------------------------
                                       Name:  Paul N. Riddle
                                       Title: Senior Vice President

                                    WELLS FARGO BANK (TEXAS), NATIONAL
                                    ASSOCIATION, Lender

                                    By: /s/ Ann Rhoads
                                       --------------------------------
                                       Name:  Ann Rhoads
                                       Title: Vice President

                                    BANK OF AMERICA, N.A., Lender

                                    By: /s/ Irene C. Rummell
                                       -----------------------
                                       Name:  Irene C. Rummell
                                       Title: Vice President

                                      -20-<PAGE>

[Pipeline]                                                         EXHIBIT 10.25

                         AMENDMENT AND LIMITED CONSENT

                                   RECITALS:

     Reference is hereby made to that certain Amended and Restated Credit
Agreement dated as of December 1, 1999 (as amended, restated or supplemented to
the date hereof, the "Agreement") by and between All American Pipeline, L.P., as
Borrower ("Borrower"), Plains Marketing, L.P. ("Marketing"), Plains All American
Pipeline, L.P. ("Plains MLP"), and BankBoston, N.A., as Administrative Agent
("Administrative Agent"), and certain financial institutions, as Lenders
(collectively, "Lenders" and each, individually, a "Lender").  Terms used and
not defined herein shall have the meanings given them in the Agreement.

     Borrower has requested that Lenders consent to certain amendments to the
Agreement.

                                 AMENDMENT AND CONSENT:

     Subject to the conditions and limitations set forth hereinbelow, each
Lender signing below hereby consents to the following amendments:

A.   The last sentence of the definition of "Consolidated EBITDA" set forth in
     Section 1.1 of the Agreement is hereby amended in its entirety to read as
     follows:

     The term "Identified Loss Adjustment" means for any four-Fiscal Quarter
     period, the portion of the Identified Loss incurred in such period not to
     exceed an aggregate amount of $180,000,000.

B.   Section 7.15 of the Agreement is hereby amended in its entirety to read as
follows:

           Section 7.15  Debt to Capital Ratio.  The ratio of (a) all
     Consolidated Funded Indebtedness to (b) the sum of Consolidated Funded
     Indebtedness plus Consolidated Net Worth plus one-half (50%) of the
     Identified Loss will never be greater than .60 to 1.0 at any time.

                          LIMITATIONS AND CONDITIONS:

1.   Except as expressly waived or agreed herein, all covenants, obligations and
     agreements of Restricted Persons contained in the Agreement shall remain in
     full force and effect in accordance with their terms.  Without limitation
     of the foregoing, the consents, waivers and agreements set forth herein are
     limited precisely to the extent set forth herein and shall not be deemed to
     (a) be a consent or agreement to, or waiver or modification of, any other
     term or condition of the Agreement or any of the documents referred to
     therein, or (b) except as expressly set forth herein, prejudice any right
     or rights which any Lender Party may now have or may have in the future
     under or in connection with the Agreement or any of the documents referred
     to therein.  Except as expressly modified hereby, the terms and

                                       1
<PAGE>

     provisions of the Agreement and any other documents or instruments executed
     in connection with any of the foregoing, are and shall remain in full force
     and effect, and the same are hereby ratified and confirmed by Restricted
     Persons in all respects. As further consideration and to induce each Lender
     Party to enter into and grant the accommodations contained in this
     Amendment and Limited Consent, EACH RESTRICTED PERSON - ON BEHALF OF ITSELF
     AND, TO THE EXTENT IT IS PERMITTED BY LAW OR IS OTHERWISE EXPRESSLY
     AUTHORIZED TO DO SO, ON BEHALF OF ALL OF ITS AFFILIATES (COLLECTIVELY,
     "RELEASING PARTIES") -- HEREBY GENERALLY RELEASE AND FOREVER DISCHARGE EACH
     LENDER PARTY AND EACH OF THEIR RESPECTIVE AFFILIATES (COLLECTIVELY,
     "RELEASED PARTIES"), FROM ANY AND ALL CLAIMS, DEMANDS, AND CAUSES OF ACTION
     OF WHATEVER KIND OR CHARACTER WHICH SUCH RELEASING PARTY HAS, OR MAY HAVE
     IN THE FUTURE, BASED ON ANY ACTIONS, FAILURES TO ACT, OR EVENTS THAT HAVE
     OCCURRED PRIOR TO THE EFFECTIVE DATE HEREOF, WHICH IN ANY WAY RELATE TO OR
     ARE BASED UPON (I) ANY TRANSACTIONS OF ANY KIND AMONG THE RELEASING PARTIES
     , ON THE ONE HAND, AND THE RELEASED PARTIES, ON THE OTHER HAND, OR (II) ANY
     ACTUAL OR ALLEGED NEGOTIATIONS, DISCUSSIONS, REPRESENTATIONS, WARRANTIES,
     PROMISES, OR OTHER UNDERTAKINGS BY RELEASED PARTIES IN CONNECTION WITH ANY
     OF THE FOREGOING (THE "RELEASED CLAIMS"). THIS RELEASE IS TO BE CONSTRUED
     AS THE BROADEST TYPE OF GENERAL RELEASE AND COVERS AND RELEASES ANY AND ALL
     RELEASED CLAIMS, WHETHER KNOWN OR UNKNOWN AND HOWEVER OR WHENEVER ARISING,
     WHETHER BY CONTRACT OR AGREEMENT, AT LAW OR UNDER ANY STATUTE (INCLUDING
     WITHOUT LIMITATION ANY LAW OR STATUTE PERTAINING TO NEGLIGENCE, GROSS
     NEGLIGENCE, STRICT LIABILITY, FRAUD, DECEPTIVE TRADE PRACTICES, NEGLIGENT
     MISREPRESENTATION, SECURITIES VIOLATIONS, BREACH OF FIDUCIARY DUTY, BREACH
     OF CONTRACT, TRADE REGULATION, REGULATION OF BUSINESS OR COMPETITION,
     CONSPIRACY OR RACKETEERING), OR OTHERWISE ARISING, AND EXPRESSLY INCLUDING
     ANY CLAIMS FOR PUNITIVE OR EXEMPLARY DAMAGES, ATTORNEYS' FEES, OR
     PENALTIES. TO THE EXTENT THAT ANY RELEASED CLAIMS WITH RESPECT TO RELEASED
     PARTIES HAVE NOT BEEN RELEASED BY THIS LETTER AGREEMENT, EACH RELEASING
     PARTY HEREBY ASSIGNS SUCH RELEASED CLAIMS TO RELEASED PARTIES.

2.   Borrower agrees to reimburse and save Administrative Agent and each Lender
     Party harmless from and against liabilities for the payment of all out-of-
     pocket costs and expenses arising in connection with the preparation,
     execution, delivery, amendment, modification, waiver and enforcement of, or
     the preservation of any rights under, this Amendment and Limited Consent,
     including, without limitation, the reasonable fees and expenses of legal
     counsel to Administrative Agent which may be payable in respect of, or in
     respect of any modification of, this Amendment and Limited Consent.

                                       2
<PAGE>

3.   This Amendment and Limited Consent and the rights and obligations of the
     parties hereunder shall be construed in accordance with and be governed by
     the laws of the State of New York.

4.   This Amendment and Limited Consent and the documents referred to herein
     represent the entire understanding of the parties hereto regarding the
     subject matter hereof and supersede all prior and contemporaneous oral and
     written agreements of the parties hereto with respect to the subject matter
     hereof.

5.   This Amendment and Limited Consent is a "Loan Document" as defined and
     described in the Agreement and all of the terms and provisions of the
     Agreement relating to Loan Documents shall apply hereto.

6.   This Amendment and Limited Consent may be separately executed in
     counterparts and by the different parties hereto in separate counterparts,
     each of which when so executed shall be deemed to constitute one and the
     same agreement.

     Executed as of February 29, 2000.

     IN WITNESS WHEREOF, the parties hereto have executed and delivered this
Amendment and Limited Consent as of date first written above.

                              ALL AMERICAN PIPELINE, L.P.

                              By: PLAINS ALL AMERICAN INC.,
                                  its general partner

                              By:/s/ Phil Kramer
                                 --------------------------------------
                                  Phil Kramer, Executive Vice President

                              PLAINS MARKETING, L.P.

                              By: PLAINS ALL AMERICAN INC.,
                                    its general partner

                              By:/s/ Phil Kramer
                                 --------------------------------------
                                  Phil Kramer, Executive Vice President

                              PLAINS ALL AMERICAN PIPELINE, L.P.

                              By: PLAINS ALL AMERICAN INC.,
                                    its general partner

                              By:/s/ Phil Kramer
                                 --------------------------------------
                                  Phil Kramer, Executive Vice President

                                       3
<PAGE>

                              BANKBOSTON, N.A.,
                              as Administrative Agent and Lender

                              By:/s/ Terrence Ronan
                                 ---------------------------
                                  Terrence Ronan, Director

                              WELLS FARGO BANK (TEXAS),
                              NATIONAL ASSOCIATION, as Lender

                              By:
                                 ---------------------------
                                  Name:
                                  Title:

                              MEESPIERSON CAPITAL CORP., as Lender

                              By:
                                 ---------------------------
                                  Name:
                                  Title:

                              By:
                                 ---------------------------
                                  Name:
                                  Title:

                              BANK OF SCOTLAND, as Lender

                              By:/s/ Annie Glynn
                                 -------------------------------
                                  Name:  Annie Glynn
                                  Title: Senior Vice President

                              HIBERNIA NATIONAL BANK, as Lender

                              By:/s/ David R. Reid
                                 --------------------------------
                                  Name:  David R. Reid
                                  Title: Senior Vice President

                              BANK OF AMERICA, N.A., as Lender

                              By:/s/ Irene C. Rummel
                                 --------------------------------
                                  Name:  Irene C. Rummel
                                  Title: Vice President

                                       4
<PAGE>

                              FIRST UNION NATIONAL BANK, Lender

                              By:/s/ Robert R. Wetteroff
                                 ----------------------------------------------
                                  Name:  Robert R. Wetteroff
                                  Title: Senior Vice President

                              CREDIT AGRICOLE INDOSUEZ, as Lender

                              By:/s/ Patrick Cocquerel
                                 ----------------------------------------------
                                  Name:  Patrick Cocquerel
                                  Title: First Vice President, Managing Director
                                         Head of Houston Representative Office

                              By:/s/ Douglas A. Whiddon
                                  ---------------------------------------------
                                  Name:  Douglas A. Whiddon
                                  Title: Vice President Senior Relationship
                                         Manager

                              UNION BANK OF CALIFORNIA, N.A., as Lender

                              By:/s/ Dustin Gaspari
                                 ----------------------------------------------
                                  Name:  Dustin Gaspari
                                  Title: Assistant Vice President

                              BANK ONE, TEXAS, N.A., as Lender

                              By:/s/ Charles Kingswell-Smith
                                 -----------------------------------------------
                                  Name:  Charles Kingswell-Smith
                                  Title: First Vice President

                              ELC (CAYMAN) LTD., Lender

                              By:/s/ Joseph H. Towell
                                 -----------------------------------------------
                                  Name:  Joseph T. Howell
                                  Title: Senior Vice President

                                       5

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