POWER OF ATTORNEY


         KNOW ALL MEN  BY THESE PRESENTS, that  I, the  undersigned,  do  hereby
constitute and appoint Susan S. Keith,  John M. Allen and Bruce A. Metzinger, or
any of them acting  alone, my true and lawful attorneys-in-fact and agents, with
full power of substitution and  resubstitution, to prepare and sign  for me, and
in my name,  place and stead, in any and all capacities, any  and all reports as
may from time to time be required under Section 16(a) of the Securities Exchange
Act of  1934, as amended,  and the rules,  regulations and  requirements  of the
Securities and Exchange Commission in respect thereof, and to file the same with
the Securities and Exchange Commission, granting unto said attorneys-in-fact and
agents  full power and authority to  do and perform each and every act and thing
requisite and necessary  to be done  (with full power  to each  of  them to  act
alone),  as fully and to  all intents and  purposes as I  might or  could  do in
person, hereby ratifying  and  confirming all  that said  attorneys-in-fact  and
agents or any of them, or their substitutes, may lawfully do or cause to be done
by virtue hereof.
         This  Power of Attorney  shall remain  in full  force  and effect until
revoked by me in writing.
         IN WITNESS WHEREOF, I hereto set my hand this 6th day of August, 2001.

                                       /s/  Douglas L. Foshee
                                       -----------------------------------
                                            Douglas L. Foshee


                                POWER OF ATTORNEY


         KNOW ALL MEN BY  THESE PRESENTS,  that I, the  undersigned,  do  hereby
constitute and appoint Susan S. Keith, John M. Allen and Bruce A. Metzinger,  or
any of them acting alone, my true and lawful  attorneys-in-fact and agents, with
full power of substitution and  resubstitution,  to prepare and sign for me, and
in my name,  place and stead, in any and all capacities,  any and all reports as
may from time to time be required under Section 16(a) of the Securities Exchange
Act of 1934, as amended,  and the rules,  regulations  and  requirements  of the
Securities and Exchange Commission in respect thereof, and to file the same with
the Securities and Exchange Commission, granting unto said attorneys-in-fact and
agents full power and  authority  to do and perform each and every act and thing
requisite  and  necessary  to be done  (with  full  power to each of them to act
alone),  as fully  and to all  intents  and  purposes  as I might or could do in
person,  hereby  ratifying and  confirming all that said  attorneys-in-fact  and
agents or any of them, or their substitutes, may lawfully do or cause to be done
by virtue hereof.
         This Power of  Attorney shall  remain in  full force and  effect  until
revoked by me in writing.
         IN WITNESS WHEREOF, I hereto set my hand this 7th day of August, 2001.

                                       /s/  Robert R. Harl
                                       ---------------------------
                                            Robert R. Harl



                                POWER OF ATTORNEY


         KNOW ALL MEN  BY THESE PRESENTS,  that I,  the  undersigned,  do hereby
constitute and appoint Lester L. Coleman,  Susan S. Keith and John M. Allen,  or
any of them acting alone, my true and lawful  attorneys-in-fact and agents, with
full power of substitution and  resubstitution,  to prepare and sign for me, and
in my name,  place and stead, in any and all capacities,  any and all reports as
may from time to time be required under Section 16(a) of the Securities Exchange
Act of 1934, as amended,  and the rules,  regulations  and  requirements  of the
Securities and Exchange Commission in respect thereof, and to file the same with
the Securities and Exchange Commission, granting unto said attorneys-in-fact and
agents full power and  authority  to do and perform each and every act and thing
requisite  and  necessary  to be done  (with  full  power to each of them to act
alone),  as fully  and to all  intents  and  purposes  as I might or could do in
person,  hereby  ratifying and  confirming all that said  attorneys-in-fact  and
agents or any of them, or their substitutes, may lawfully do or cause to be done
by virtue hereof.
         This Power of  Attorney shall remain  in full force  and  effect  until
revoked by me in writing.
         IN WITNESS WHEREOF, I hereto set my hand this 24th day of May, 2001.

                                       /s/ Edgar J. Ortiz
                                       -------------------------------------
                                           Edgar J. Ortiz