July 13, 1999 Mobley Environmental Services, Inc. 111 Congress Avenue, Suite 1400 Austin, Texas 78701 Attention: John Mobley Re: Extension of the Offer Dear John: GAP Capital, L.L.C. (the "Purchaser") exercises its right under Section 1.1 of the...

                                                                  July 13, 1999



Xxxxxx Environmental Services, Inc.
000 Xxxxxxxx Xxxxxx, Xxxxx 0000
Xxxxxx, Xxxxx 00000
Attention: Xxxx Xxxxxx


     Re:  Extension of the Offer


Dear Xxxx:

     GAP Capital, L.L.C. (the "Purchaser") exercises its right under Section 1.1
of the Tender Offer Agreement dated June 4, 1999 (the "Tender Offer
Agreement") between the Purchaser and Xxxxxx Environmental Services, Inc. to
extend the Expiration Date of the Offer to 12:00 Midnight, New York City
time, on Tuesday, July 27, 1999.

      Capitalized terms used but not defined herein have the meanings
assigned to such terms in the Tender Offer Agreement.

                                       Sincerely,
                                       GAP CAPITAL, L.L.C.

                                       By: /s/ Xxxxx X. Xxxxx
                                           -----------------------------------
                                           Xxxxx X. Xxxxx, Manager


cc:  Xxxxxx Xxxx
     Xxxxx XxXxxxxxx & Oaks Xxxxxxxx
     000 Xxxxxxxx Xxxxxx, Xxxxx 0000
     Xxxxxx, Xxxxx 00000