THIRD AMENDMENT

                                     TO

                           GROUND 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 Ground 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 Ground 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 Ground 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 GROUND LEASE AGREEMENT

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

    WHEREAS, Brazos and Diamond Shamrock R & M desire to amend
the Ground 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 Property leased by Brazos under the Ground 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 Ground Lease Agreement is
hereby amended as follows:

     1.  Section 3.02 of the Ground 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 Property 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 Property Leasing Record to
reflect the change in Acquisition Cost for such Property caused
by such release or disposition."

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

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