

FOR IMMEDIATE RELEASE      Contact: Guy T. Marcus             Li-San Hwang
October 20, 1997                    V. P.-Inv. Rel.           President & CEO
                                    Halliburton               Tetra Tech
                                    (214)978-2691             (626)351-4664


         HALLIBURTON UNITS AGREE TO SELL ENVIRONMENTAL SERVICES BUSINESS
                               TO TETRA TECH, INC.

         DALLAS,  Texas - Halliburton  Company  (NYSE:HAL) and Tetra Tech,  Inc.
(NASDAQ:WATR)  jointly announced today that Halliburton's Brown & Root, Inc. and
Halliburton NUS Corporation  subsidiaries have signed a definitive  agreement to
sell the assets of their  environmental  services  business to Tetra  Tech.  The
agreement calls for Tetra Tech to pay cash consideration of about $32 million.
         Completion  of the  sale  is  subject  to  Hart-Scott-Rodino  antitrust
clearance.  Both  Halliburton  and Tetra Tech seek to close the  transaction  by
year-end 1997.
         Halliburton's  environmental business provides consulting,  engineering
and design services for the environmental remediation of contaminated air, water
and soil.  Customers include  industrial  clients as well as federal,  state and
local  governments,  primarily in the United States.  In 1996 the  environmental
service business had revenues of about $100 million.
         Tetra Tech provides comprehensive  environmental and telecommunications
support services including research and development, engineering and design,









                               Page 5 of 6 Pages
                      The Exhibit Index Appears on Page 4
<PAGE>


Halliburton Company                     2

construction  management,  and  operation and  maintenance.  Tetra Tech provides
these services to a broad base of customers world-wide.
         Halliburton  Company is one of the world's largest  diversified  energy
services, engineering, maintenance, and construction companies. Founded in 1919,
Halliburton  provides a broad range of energy services and products,  industrial
and marine engineering and construction services.

                                        ###












                               Page 6 of 6 Pages
                      The Exhibit Index Appears on Page 4

