Exhibit 10.58

Execution Version

AMENDMENT

TO EXCHANGE AGREEMENT

(Thomas Hill)

THIS AMENDMENT (this “Amendment”) is dated as of March 8, 2013 and made by and
among Clean Coal Solutions, LLC, a Colorado limited liability company (“CCS”),
AEC-TH, LLC, a Colorado limited liability company (“Lessor”), and GS RC
Investments LLC, a Delaware limited liability company (“Lessee”). CCS, Lessor
and Lessee may be referred to herein individually as a “Party” and collectively
as the “Parties.”

RECITALS:

WHEREAS, the Parties have previously entered into that certain Exchange
Agreement, dated as of December 15, 2011 (the “Exchange Agreement”);

WHEREAS, contemporaneously herewith, Lessor and Lessee are entering into that
certain Amended and Restated Equipment Lease (the “A&R Equipment Lease”),
thereby amending and restating the terms of that certain Equipment Lease between
Lessor and Lessee, dated as of December 15, 2011, as amended as of December 21,
2012 (the “New Equipment Lease”); and

WHEREAS, the Parties desire to amend the Exchange Agreement as set forth herein.

NOW, THEREFORE, in consideration of the foregoing recitals, the promises and
agreements set forth in this Amendment, and other good and valuable
consideration (the receipt and sufficiency of which are hereby acknowledged),
the Parties agree as follows:

ARTICLE I

DEFINITIONS

Section 1.1 Definitions. Unless otherwise defined herein, capitalized terms used
in this Amendment shall have the respective meaning ascribed to such terms in
the Exchange Agreement.

ARTICLE II

AMENDMENTS TO EXCHANGE AGREEMENT

Section 2.1 Amendments to Definitions.

 

  a. The following definitions shall be added to Section 1.1 of the Exchange
Agreement:

“A&R Equipment Lease” means the Amended and Restated Equipment Lease, dated as
of March 8, 2013, by and between Lessor and Lessee, as the same may be modified,
amended or restated from time to time.

“Term” has the meaning set forth in the New Equipment Lease or the A&R Equipment
Lease, as the context requires.

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  b. The definition of “Loss” or “Losses” shall be deleted in its entirety and
replaced as follows:

“Loss” or “Losses” means losses, lost Section 45 Credits (but only to the extent
such Section 45 Credits relate to Refined Coal actually produced by the New
Facility and solely as set forth in Section 7.1(c)(i) hereof), liabilities,
causes of action, assessments, cleanup, removal, remediation and restoration
obligations, judgments, awards, damages, natural resource damages, contribution,
cost-recovery and compensation obligations, fines, fees, penalties and costs and
expenses (including litigation costs and reasonable attorneys’ and experts’ fees
and expenses).

 

  c. The following sentence is hereby added to the end of Section 1.2 of the
Exchange Agreement:

“All references to an agreement herein mean such agreement as it may be amended,
restated or modified from time to time.”

Section 2.2 Amendment to Section 7.1(c)(ii). Section 7.1(c)(ii) of the Exchange
Agreement shall be deleted in its entirety and replaced as follows:

Except as otherwise provided in Section 7.1(c)(iv), the CCS Parties shall not
have any liability for Lessee Indemnified Costs for breaches of the
representations and warranties in Sections 3.1(a), (b), (c), (e), (g), (j),
(n) and (o) to the extent the aggregate amount of such Losses exceeds the sum of
three million dollars ($3,000,000) plus the Initial Term Rent Payments, Renewal
Term Rent Payments (as such terms are defined in the A&R Equipment Lease) and
any other rent payments made by Lessee to Lessor under the New Equipment Lease
or the A&R Equipment Lease during the Term as of the relevant time of
determination (the “CCS First Cap Amount”).

Section 2.3 Amendment to Section 9.7.

 

  a. The addresses set forth in Section 9.7 of the Exchange Agreement
immediately following “If to the Lessee, to:” shall be deleted in their entirety
and replaced with the following addresses:

GS RC Investments LLC

c/o Goldman Sachs & Co.

200 West St.

New York, NY 10282

Attention: Pooja Goyal

Fax: (212) 256-5304

Email: pooja.goyal@gs.com

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With a copy (which shall not constitute notice) to:

Vinson & Elkins LLP

1001 Fannin St., Suite 2500

Houston, TX 77002-6760

Attention: Kaam Sahely

Fax: (713) 615-5150

Email: ksahely@velaw.com

 

  a. The addresses set forth in Section 9.7 of the Exchange Agreement
immediately following “If to the CCS Parties, to:” shall be deleted in their
entirety and replaced with the following addresses:

Clean Coal Solutions, LLC

One Denver Tech Center

5251 DTC Parkway, Suite 825

Greenwood Village, CO 80111

Attention: Jim Zerefos

Fax: (303) 751-9210

With a copy (which shall not constitute notice) to:

Hogan Lovells US LLP

One Tabor Center

1200 Seventeenth Street, Suite 1500

Denver, CO 80202

Attention: Tyler Harvey

Fax: (303) 899-7333

E-mail: tyler.harvey@hoganlovells.com

ARTICLE III

GENERAL PROVISIONS

Section 3.1Effectiveness and Ratification. All of the provisions of this
Amendment shall be effective as of the date hereof. Except as specifically
provided for in this Amendment, the terms of the Exchange Agreement shall remain
in full force and effect. In the event of any conflict or inconsistency between
the terms of this Amendment and the Exchange Agreement with respect to a period
of time from and after the date hereof, the terms of this Amendment shall
prevail and govern.

Section 3.2Amendment; Entire Agreement. This document contains the entire
agreement among the Parties with respect to the subject matter hereof. There are
no oral agreements among the Parties with respect to the subject matter hereof.

Section 3.3 Governing Law. This Amendment shall be governed by and construed in
accordance with the law of the State of New York, without regard to the
conflicts of law principles of such state.

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Section 3.4 Counterparts. This Amendment may be signed in two or more
counterparts, each of which taken together shall constitute one instrument, and
each of the Parties may execute this Amendment by signing any such counterpart.
This Amendment shall become effective upon execution by all of the Parties. A
facsimile copy or other electronic transmission of an executed counterpart will
be deemed an original.

[Signature Page Follows]

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IN WITNESS WHEREOF, CCS, Lessor and Lessee have caused this Amendment to be
executed and delivered as of the date first set forth above.

 

CLEAN COAL SOLUTIONS, LLC By:  

 

Name:   Title:   AEC-TH, LLC By:   Clean Coal Solutions, LLC,   its managing
member By:  

 

Name:   Title:   GS RC INVESTMENTS LLC By:   GSFS Investments I Corp.,   its
sole member By:  

 

Name:   Title:  

Signature page to Amendment to Exchange Agreement (Thomas Hill)