POWER OF ATTORNEY
                                    (LIMITED)

        KNOW ALL MEN BY THESE PRESENTS, that I, WILLIAM E. MACAULAY of the
Town/City of GREENWICH, County of FAIRFIELD, State of CONNECTICUT, reposing
special trust and confidence in ANNE E. GOLD, of the Town of RYE, County of
WESTCHESTER, State of NEW YORK and/or, ROBERT J. GALLAGHER, of the Town of RYE,
County of WESTCHESTER, State of NEW YORK, have made, constituted and appointed,
and by these presents do make, constitute and appoint each of the said ANNE E.
GOLD and/or ROBERT J. GALLAGHER, my true and lawful attorney-in-fact and agent,
both FOR ME PERSONALLY and in my name, place and stead, IN MY CAPACITY AS AN
OFFICER OR DIRECTOR OF:

FRC FOUNDERS CORPORATION ("FOUNDERS")
FIRST RESERVE CORPORATION, L.L.C. ("FRC")
FIRST RESERVE PARTNERS LIMITED ("FRPL")
FIRST RESERVE MANAGEMENT LIMITED ("FRML")
FIRST RESERVE GP XII LIMITED ("GP XII")
FIRST RESERVE GP XI, INC. ("GP XI")
FR XI OFFSHORE GP LIMITED ("OFFSHORE XI")
FR HORIZON GP LIMITED ("FR HORIZON")
FIRST RESERVE GP X, INC. ("GP X")
FR X OFFSHORE GP LIMITED ("OFFSHORE X")
FIRST RESERVE ENERGY INFRASTRUCTURE GP LIMITED ("FREI")

or any entity of which any the foregoing is the direct or indirect general
partner or for which any of the foregoing otherwise has the authority to
act (collectively with FOUNDERS, FRC, FRPL, FRML, GP XII, GP XI,
OFFSHORE XI, FR HORIZON, GP X, OFFSHORE X, and FREI the "First Reserve
Entities"), with full power and authority to do and perform each and
every act necessary, as fully as I might do if personally present, to
accomplish and complete the following acts or transactions:

        1. With respect to any entity in which any First Reserve Entities have
an investment (each a "Company"), sign on my behalf, any and all filings
(including filings with the Securities and Exchange Commission), agreements,
notices or documents arising from, or related to any Company, including, (a) any
holdings or investments of any First Reserve Entities in any Company; and (b)
any holdings or investments of mine in any Company.

        2. Seek or obtain, as my representative and on my behalf, from any third
party, including brokers, employee benefit plan administrators and trustees,
information on transactions involving any Company or the securities of any
Company, and I hereby authorize any such persons to release any such information
to either attorney-in-fact designated hereunder and approve and ratify any such
release of information; and

        3. Perform any and all other acts which in the discretion of either such
attorney-in-fact are necessary or desirable for and on my behalf in connection
with the foregoing.

        I acknowledge that:

          (a) this Power of Attorney authorizes, but does not require, either such
attorney-in-fact to act in his or her discretion on information provided to
either such attorney-in-fact without independent verification of such
information;

          (b)    any documents prepared and/or executed by either such
attorney-in-fact on my behalf pursuant to this Power of Attorney will be in such
form and will contain such information and disclosure as either such
attorneys-in-fact, in his or her discretion, deems necessary or desirable;

          (c)    neither such attorney-in-fact nor any Company assumes (i) any
liability for my responsibility to comply with the requirements of any law or
regulation, including without limitation the Securities Act of 1933, as amended
(the "Securities Act") or the Exchange Act of 1934, as amended (the "Exchange
Act"), or (ii) any liability of mine for any failure to comply with such
requirements; and

          (d)    this Power of Attorney does not relieve me from responsibility for
compliance with my obligations under any law or regulation, including without
limitation the requirements under the Securities Act and the Exchange Act.

        I hereby give and grant ANNE E. GOLD and/or ROBERT J. GALLAGHER, in the
capacity set forth above, full power and authority to do and perform all and
every act and thing whatsoever requisite, necessary or appropriate to be done in
and about the foregoing matters as fully to all intents and purposes as I might
or could do if present, hereby ratifying all that either such attorney-in-fact
of, for and on my behalf, shall lawfully do or cause to be done by virtue of
this Power of Attorney.

        This POWER OF ATTORNEY shall remain in effect until revoked and shall
not be affected by disability of the Principal.

EXECUTED this 11th  day of  Arpil, 2012

                          /s/ William E. Macaulay

STATE OF CONNECTICUT       )
                           )SS.
COUNTY OF  FAIRFIELD)

The foregoing instrument was acknowledged before me this 11th day of April, 2012,
by William E. Macaulay, the Principal.

Witness my hand and official seal: MaryAnn Ghirardelli, Notary
My commission expires: January 31, 2017

/s/ Anne E. Gold                 /s/ Robert J. Gallagher
---------------------           -----------------------
Specimen Signature              Specimen Signature of Agent-Attorney
of Agent-Attorney
Anne E. Gold                    Robert J. Gallagher