THIRD AMENDMENT

                                     TO

                         FACILITIES LEASE AGREEMENT

                                  between

                         BRAZOS RIVER LEASING L.P.

                                    and

              DIAMOND SHAMROCK REFINING AND MARKETING COMPANY

                       Dated as of September 16, 1994













This Third Amendment to Facilities Lease Agreement 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 Facilities
Lease Agreement 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 Facilities Lease Agreement 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 FACILITIES LEASE AGREEMENT

    This Third Amendment to Facilities Lease Agreement 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 a
Facilities Lease Agreement, dated as of April 23, 1992, the "Facilities Lease
Agreement"); and

    WHEREAS, Brazos and Diamond Shamrock R & M desire to amend the Facilities
Lease Agreement to  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
leased by Brazos under the Facilities Lease Agreement.

    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
Facilities Lease Agreement is hereby amended as follows:

    1.  Section 3.02 of the Facilities Lease Agreement is hereby amended to
add in the first sentence of paragraph (a) of such Section 3.02 immediately
after the words "if the terms of (b)" the additional reference to "or (c)"
and to add to such Section 3.02, a paragraph (c) which shall read as follows:
"(c) Upon the release or disposition of a Facility or any portion thereof and
the application of proceeds therefrom in accordance with Section
9.01(a)(viii) of the Credit Agreement, Brazos and Diamond Shamrock R&M shall
execute a Revised Facility Leasing Record to reflect the change in
Acquisition Cost for such Facility caused by such release or disposition."

     2.  Brazos and Diamond Shamrock R & M agree that this Third Amendment to
Facilities Lease Agreement 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 Facilities Lease
Agreement and not otherwise defined herein have the meanings ascribed to
those terms in the Facilities Lease Agreement.

    IN WITNESS WHEREOF, Brazos and Diamond Shamrock R & M have caused this
Third Amendment to Facilities Lease Agreement 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