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" and inserting 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