Exhibit 10.13.2

EXECUTION COPY

FIRST SUPPLEMENTAL INDENTURE

FIRST SUPPLEMENTAL INDENTURE (this ‘‘Supplemental Indenture’’) dated as of June
14, 2006, among Orcal Geothermal Inc., a Delaware corporation (the ‘‘Issuer’’),
and Union Bank of California, N.A., as trustee (the ‘‘Trustee’’) and as
collateral agent (the ‘‘Collateral Agent’’), in each case, under the lndenture
referred to below.

W I T N E S S E T H

WHEREAS, the Issuer and the guarantors named therein have heretofore executed
and delivered to the Trustee an indenture (the ‘‘Indenture’’) and a First Series
Supplemental Indenture (the ‘‘First Series Supplemental Indenture’’), each dated
as of December 8, 2005, and together providing for the issuance of $165,000,000
in aggregate principal amount of 6.21% Senior Secured Notes due 2020 (the
‘‘Initial Notes’’);

WHEREAS, the Indenture provides that under certain circumstances the Indenture
may be supplemented or amended by the Issuer, the Trustee and the Collateral
Agent; and

WHEREAS, pursuant to Article VllI of the Indenture, the Trustee is authorized to
execute and deliver this Supplemental Indenture.

NOW, THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the parties
hereto mutually covenant and agree for the equal and ratable benefit of the
Holders of the Initial Notes as follows:

1.    CAPITALIZED TERMS.    Capitalized terms used herein without definition
shall have the meaning assigned to them in the Indenture.

2.    AMENDMENT.    The parties hereby agree to amend Section 2.04 of the
Indenture by deleting Section 2.O4 and replacing it in its entirety with the
following new provision:

‘‘Section 2.04 Denominations.    The Senior Secured Notes shall be issuable only
in registered form without coupons and in denominations of $1,000 and any
integral multiple of $1,000 in excess thereof. Any repayments (either scheduled
or pursuant to any redemption) of any Senior Secured Note shall be made only in
the denomination or integral multiple thereof set forth above. Notwithstanding
the foregoing, any repayments (either scheduled or pursuant to any redemption)
and any transfers or exchanges of any Initial Note shall be made in a
denomination rounded to the nearest $0.01.’’

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3.    REFERENCES TO AND EFFECT ON INDENTURE.    (a) On and after the execution
of this Supplemental Indenture, each reference in the Indenture to ‘‘this
Indenture,’’ ‘‘hereunder,’’ ‘‘hereof’’ or words of like import referring to the
Indenture, shall mean and be a reference to the Indenture, as amended by this
Supplemental Indenture.

(b)    The Indenture, as specifically amended by this Supplemental Indenture, is
and shall continue to be in full force and effect and is hereby in all respects
ratified and confirmed.

4.    EFFECTIVENESS.    This Supplemental Indenture shall be effective upon
execution hereof by the Issuer, the Trustee and the Collateral Agent.

5.    BENEFITS OF THIS SUPPLEMENTAL INDENTURE.    Nothing in this Supplemental
Indenture, express or implied, shall give to any person, other than the parties
to the Indenture and their respective successors thereunder and the Holders of
the Notes, any benefit or any legal or equitable right, remedy or claim under
this Supplemental Indenture.

6.    GOVERNING LAW.    THE INTERNAL LAW OF THE STATE OF NEW YORK SHALL GOVERN
AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE WITHOUT GIVING EFFECT TO
APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF
THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

7.    COUNTERPARTS.    The parties may sign any number of copies of this
Supplemental Indenture. Each signed copy shall be an original, but all of them
together represent the same agreement.

8.    EFFECT OF HEADINGS.    The Section headings herein are for convenience
only and shall not affect the construction hereof.

9.    THE TRUSTEE.    The Trustee shall not be responsible in any manner
whatsoever for or in respect of the validity or sufficiency of this Supplemental
Indenture or for or in respect of the recitals contained herein, all of which
recitals are made solely by the Issuer.

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IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture
to be duly executed and attested, all as of the date first above written.

Dated: June 14, 2006

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[spacer.gif] [spacer.gif] [spacer.gif] [spacer.gif] [spacer.gif] [spacer.gif]
[spacer.gif]   [spacer.gif] [spacer.gif] ORCAL GEOTHERMAL INC.   [spacer.gif]
[spacer.gif]   [spacer.gif] [spacer.gif]     [spacer.gif] [spacer.gif] By:
[spacer.gif] [spacer.gif] /s/ Yehudit Bronicki      [spacer.gif] [spacer.gif]  
[spacer.gif] [spacer.gif] Name:   [spacer.gif] [spacer.gif]   [spacer.gif]
[spacer.gif] Title:   [spacer.gif] [spacer.gif] UNION BANK OF CALIFORNIA, N.A.,
as Trustee   [spacer.gif] [spacer.gif]   [spacer.gif] [spacer.gif]    
[spacer.gif] [spacer.gif] By: [spacer.gif] [spacer.gif]  /s/ JAMES MYERS  
[spacer.gif] [spacer.gif]   [spacer.gif] [spacer.gif] Name:   JAMES MYERS  
[spacer.gif] [spacer.gif]   [spacer.gif] [spacer.gif] Title:     VICE PRESIDENT
  [spacer.gif] [spacer.gif] UNION BANK OF CALIFORNIA, N.A., as Collateral Agent
  [spacer.gif] [spacer.gif]   [spacer.gif] [spacer.gif]     [spacer.gif]
[spacer.gif] By: [spacer.gif] [spacer.gif]  /s/ JAMES MYERS   [spacer.gif]
[spacer.gif]   [spacer.gif] [spacer.gif] Name:   JAMES MYERS   [spacer.gif]
[spacer.gif]   [spacer.gif] [spacer.gif] Title:     VICE PRESIDENT [spacer.gif]

[Signature Page to First Supplemental Indenture]

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