EX-24

                                                                      EXHIBIT 24
                                                                      ----------

                                 POWER OF ATTORNEY
                         For Executing Forms 3, 4 and 5


         Know all by these presents,  that the undersigned,  Don Nickles, hereby
constitutes  and appoints  Jennifer M.  Grigsby,  signing  singly,  his true and
lawful attorney-in-fact to:

                  (1)  execute for and on behalf of the  undersigned  Forms 3, 4
and 5 in accordance  with Section 16(a) of the  Securities  Exchange Act of 1934
and the rules thereunder;

                  (2) do and  perform  any and all acts for and on behalf of the
undersigned which may be necessary or desirable to complete the execution of any
such Form 3, 4 or 5 and the timely  filing of such form with the  United  States
Securities and Exchange Commission and any other authority; and

                  (3) take any other action of any type whatsoever in connection
with the foregoing,  including the execution of a Form ID, which, in the opinion
of such  attorney-in-fact,  may be of benefit  to, in the best  interest  of, or
legally  required by, the  undersigned,  it being  understood that the documents
executed by such  attorney-in-fact on behalf of the undersigned pursuant to this
Power of  Attorney  shall be in such  form and  shall  contain  such  terms  and
conditions as such attorney-in-fact may approve, in her discretion.

         The undersigned hereby grants to such  attorney-in-fact  full power and
authority  to do and perform all and every act and thing  whatsoever  requisite,
necessary  and proper to be done in the exercise of any of the rights and powers
herein  granted,  as fully to all intents and purposes as such  attorney-in-fact
might or could do if  personally  present,  with full power of  substitution  or
revocation,  hereby ratifying and confirming all that such attorney-in-fact,  or
her substitute or  substitutes,  shall lawfully do or cause to be done by virtue
of this  power of  attorney  and the  rights  and  powers  herein  granted.  The
undersigned acknowledges that the foregoing attorney-in-fact, in serving in such
capacity  at  the  request  of  the  undersigned,  is  not  assuming  any of the
undersigned's  responsibilities  to comply  with  Section  16 of the  Securities
Exchange Act of 1934.

         IN WITNESS  WHEREOF,  the undersigned has caused this Power of Attorney
to be executed as of this 5th day of January, 2005.



                                                  /s/  Don Nickles
                                           ------------------------------------
                                                  Don Nickles

EX-24

                                                                      EXHIBIT 24
                                                                      ----------

                                 POWER OF ATTORNEY
                         For Executing Forms 3, 4 and 5


     Know all by these  presents,  that the  undersigned,  Don  Nickles,  hereby
constitutes and appoints Martha A. Burger,  signing singly,  his true and lawful
attorney-in-fact to:

                  (1)  execute for and on behalf of the  undersigned  Forms 3, 4
and 5 in accordance  with Section 16(a) of the  Securities  Exchange Act of 1934
and the rules thereunder;

                  (2) do and  perform  any and all acts for and on behalf of the
undersigned which may be necessary or desirable to complete the execution of any
such Form 3, 4 or 5 and the timely  filing of such form with the  United  States
Securities and Exchange Commission and any other authority; and

                  (3) take any other action of any type whatsoever in connection
with the foregoing,  including the execution of a Form ID, which, in the opinion
of such  attorney-in-fact,  may be of benefit  to, in the best  interest  of, or
legally  required by, the  undersigned,  it being  understood that the documents
executed by such  attorney-in-fact on behalf of the undersigned pursuant to this
Power of  Attorney  shall be in such  form and  shall  contain  such  terms  and
conditions as such attorney-in-fact may approve, in her discretion.

         The undersigned hereby grants to such  attorney-in-fact  full power and
authority  to do and perform all and every act and thing  whatsoever  requisite,
necessary  and proper to be done in the exercise of any of the rights and powers
herein  granted,  as fully to all intents and purposes as such  attorney-in-fact
might or could do if  personally  present,  with full power of  substitution  or
revocation,  hereby ratifying and confirming all that such attorney-in-fact,  or
her substitute or  substitutes,  shall lawfully do or cause to be done by virtue
of this  power of  attorney  and the  rights  and  powers  herein  granted.  The
undersigned acknowledges that the foregoing attorney-in-fact, in serving in such
capacity  at  the  request  of  the  undersigned,  is  not  assuming  any of the
undersigned's  responsibilities  to comply  with  Section  16 of the  Securities
Exchange Act of 1934.

         IN WITNESS  WHEREOF,  the undersigned has caused this Power of Attorney
to be executed as of this 5th day of January, 2005.



                                                  /s/  Don Nickles
                                           ------------------------------------
                                                  Don Nickles