EX-24

                               POWER OF ATTORNEY



     KNOW ALL PERSONS BY THESE  PRESENTS that GS  INFRASTRUCTURE  ADVISORS 2006,
L.L.C. (the "Company") does hereby make, constitute and appoint each of Roger S.
Begelman, Yvette Kosic, Andrea Louro DeMar, John M. O'Rourke, Felicia J. Rector,
Michael T.  Seeley,  and Stephen  Wong,  (and any other  employee of The Goldman
Sachs Group,  Inc. or one of its affiliates  designated in writing by one of the
attorneys-in-fact),  acting  individually,  its true  and  lawful  attorney,  to
execute and deliver in its name and on its behalf  whether the Company is acting
individually or as representative of others,  any and all filings required to be
made by the Company under the Securities Exchange Act of 1934, (as amended,  the
"Act"),  with respect to securities which may be deemed to be beneficially owned
by  the   Company   under  the  Act,   giving  and   granting   unto  each  said
attorney-in-fact  power and authority to act in the premises as fully and to all
intents and purposes as the Company might or could do if  personally  present by
one of its authorized signatories, hereby ratifying and confirming all that said
attorney-in-fact shall lawfully do or cause to be done by virtue hereof.

     THIS POWER OF ATTORNEY  shall remain in full force and effect  until either
revoked  in  writing  by the  undersigned  or until  such time as the  person or
persons to whom power of  attorney  has been  hereby  granted  cease(s) to be an
employee of The Goldman Sachs Group, Inc. or one of its affiliates.

     IN WITNESS WHEREOF,  the undersigned has duly subscribed  these presents as
of August 30, 2006.



GS INFRASTRUCTURE ADVISORS 2006, L.L.C.



By:/s/ Renee Beaumont
- ------------------------------------
Name:  Renee Beaumont
Title: Vice President

EX-24

                               POWER OF ATTORNEY



     KNOW ALL PERSONS BY THESE PRESENTS that GS GLOBAL  INFRASTRUCTURE  PARTNERS
I, L.P. (the "Company")  does hereby make,  constitute and appoint each of Roger
S. Begelman,  Yvette Kosic,  Andrea Louro DeMar,  John M.  O'Rourke,  Felicia J.
Rector,  Michael T. Seeley,  and Stephen  Wong,  (and any other  employee of The
Goldman Sachs Group, Inc. or one of its affiliates  designated in writing by one
of the attorneys-in-fact), acting individually, its true and lawful attorney, to
execute and deliver in its name and on its behalf  whether the Company is acting
individually or as representative of others,  any and all filings required to be
made by the Company under the Securities Exchange Act of 1934, (as amended,  the
"Act"),  with respect to securities which may be deemed to be beneficially owned
by  the   Company   under  the  Act,   giving  and   granting   unto  each  said
attorney-in-fact  power and authority to act in the premises as fully and to all
intents and purposes as the Company might or could do if  personally  present by
one of its authorized signatories, hereby ratifying and confirming all that said
attorney-in-fact shall lawfully do or cause to be done by virtue hereof.

     THIS POWER OF ATTORNEY  shall remain in full force and effect  until either
revoked  in  writing  by the  undersigned  or until  such time as the  person or
persons to whom power of  attorney  has been  hereby  granted  cease(s) to be an
employee of The Goldman Sachs Group, Inc. or one of its affiliates.

     IN WITNESS WHEREOF,  the undersigned has duly subscribed  these presents as
of August 30, 2006.



GS GLOBAL INFRASTRUCTURE PARTNERS I, L.P.
By: GS Infrastructure Advisors 2006, L.L.C.


By:/s/ Renee Beaumont
- ------------------------------------
Name:  Renee Beaumont
Title: Vice President