THIRD AMENDMENT

                                TO

                   AGREEMENT FOR FACILITIES LEASE

                             between


                      BRAZOS RIVER LEASING L.P.

                                and

            DIAMOND SHAMROCK REFINING AND MARKETING COMPANY

                  Dated as of September 16, 1994















This Third Amendment to Agreement for Facilities Lease has been manually
executed in 8 counterparts, numbered consecutively from 1 through 8, of which
this is No. ____.  To the extent, if any, that this Third Amendment to Agreement
for Facilities Lease constitutes chattel paper (as such term is defined in the
Uniform Commercial code as in effect in any jurisdiction), no security interest
in this Third Amendment to Agreement for Facilities Lease may be created or
perfected through the transfer or possession of any counterpart other than the
original counterpart which shall be the counterpart identified as counterpart
No. 1.



            THIRD AMENDMENT TO AGREEMENT FOR FACILITIES LEASE

       This Third Amendment to Agreement for Facilities Lease is made and   
entered into as of September 16, 1994, by and between BRAZOS RIVER LEASING   
L.P. ("Brazos") and DIAMOND SHAMROCK REFINING AND MARKETING COMPANY ("Diamond   
Shamrock R & M").

                         W I T N E S S E T H:

       WHEREAS, Brazos and Diamond Shamrock R & M have heretofore entered into
an Agreement for Facilities Lease, dated as of April 23, 1992 (the "Agreement
for Facilities Lease"); and

       WHEREAS, Brazos and Diamond Shamrock R & M desire to amend the Agreement 
for Facilities Lease to increase the permitted expenditure amount for Facilities
and to otherwise set forth their mutual agreement; and

       WHEREAS, Brazos and Diamond Shamrock R & M agree that the provisions of
this amendment shall apply, to the extent provided by law, to each Facility
acquired by Brazos under the Agreement for Facilities Lease.

       NOW, THEREFORE, in consideration of the mutual covenants herein contained
and other valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, Brazos and Diamond Shamrock R & M agree that the Agreement
for Facilities Lease is hereby amended as follows:

        1.  Section 2.02 of the Agreement for Facilities Lease is hereby amended
by deleting the reference to "$1,000,000" andinserting in lieu thereof
$1,200,000."

        2.  Brazos and Diamond Shamrock R & M agree that this Third Amendment to
Agreement for Facilities Lease shall not be effective until the approvals
required by Section 9.01 of the Credit Agreement have been obtained as evidenced
by the execution of Amendment No. 3 to the Credit Agreement by the necessary
parties under the Credit Agreement.

        3.  Defined terms used in this Third Amendment to Agreement for
Facilities Lease and not otherwise defined herein have the meanings ascribed to
those terms in the Agreement for Facilities Lease.

       IN WITNESS WHEREOF, Brazos and Diamond Shamrock R & M have caused this
Third Amendment to Agreement for Facilities Lease to be executed and delivered
by their duly authorized officers as of the day and year first above written.

                                BRAZOS RIVER LEASING L.P.

                                By:  Headwater Investments L.P.,
                                     its General Partner

                                     By: Headwater Holdings, Inc.,
                                         its General Partner


                                     By: /S/ GREGORY C. GREENE
                                             President



                                DIAMOND SHAMROCK REFINING
                                     AND MARKETING COMPANY


                                By: /S/ R.C. BECKER
                                        Vice President and Treasurer

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