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EXHIBIT 3.1 SELKIRK COGEN PARTNERS, L.P.
AMENDMENT NO. 4 TO THE THIRD
AMENDED AND RESTATED AGREEMENT
OF LIMITED PARTNERSHIP This Amendment No. 4 to the THIRD AMENDED AND RESTATED AGREEMENT OF
LIMITED PARTNERSHIP is made as of July 12, 2004, by and among the undersigned
parties. WITNESSETH: WHEREAS, Selkirk Cogen Partners, L.P. (the Partnership) was established
pursuant to a Certificate of Limited Partnership filed with the Secretary of
State of the State of Delaware following the execution and delivery of an
Agreement of Limited Partnership dated as of December 15, 1989 (the Original
Agreement) by and among JMC Selkirk, Inc., a Delaware corporation, as general
partner (JMC), Old State Management Corp., a Massachusetts corporation, as
both general partner and limited partner (OSM), and Makowski Selkirk, Inc., a
Delaware corporation (MSI), as limited partner; WHEREAS, the Original Agreement was amended and restated on June 15, 1990
(the First Amended Agreement) to admit JMCS I Investors, L.P., a Delaware
limited partnership (JMCSI), as a general partner and Old State Selkirk
Associates L.P., a Delaware limited partnership (OSSA), as a limited partner,
and to reflect the withdrawal of OSM and MSI from the Partnership; WHEREAS, the First Amended Agreement was further amended and restated as
of October 23, 1992 (the Second Amended Agreement) to provide, among other
things, for the merger of Selkirk Cogen partners II, L.P. (SCPII) into the
Partnership, with the Partnership as the surviving entity, pursuant to a Merger
Agreement dated October 23, 1992 by and between the Partnership and SCPII; WHEREAS, the Second Amended Agreement was further amended and restated as
of May 1, 1994 (the Third Amended Agreement) to reflect the withdrawal of
OSSA from the Partnership and to provide, among other things, for the admission
of RCM Selkirk GP, Inc. (formerly Cogen Technologies Selkirk GP, Inc.), a Texas
corporation, as a general partner of the Partnership; for the admission of
Makowski Selkirk Holdings, Inc. (Holdings) and RCM Selkirk, L.P. (formerly
Cogen Technologies Selkirk, L.P.), a Delaware limited partnership, as limited
partners of the Partnership; and for the conversion of a portion of the general
partnership interest of JMCSI in the Partnership to a limited partnership
interest; WHEREAS, the Third Amended Agreement was first amended (Amendment No. 1
to the Third Amended Agreement) (i) to reflect the withdrawal of Holdings as a
Class A Limited Partner of the Partnership; (ii) to admit EI Selkirk, Inc., a
Delaware




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corporation (EII), as a Substituted Class A Limited Partner of the
Partnership; and (iii) to make certain conforming changes to the Third Amended
Agreement; WHEREAS, the Third Amended Agreement was further amended (Amendment No. 2
to the Third Amended Agreement) (i) to convert all of JMCSIs general
partnership interest in the Partnership to the limited partnership interest,
which interest is held by PentaGen Investors, L.P. (formerly JMCS I Investors,
L.P.); (ii) to assign a portion of JMCSIs limited partnership interest in the
Partnership to JMC; and (iii) to consent to the consummation of these
transactions; WHEREAS, the Third Amended Agreement was further amended (Amendment No. 3
to the Third Amended Agreement) (i) to reflect the name change of the Class A.
Limited Partner of the Partnership from EII to Aquila Selkirk, Inc., a Delaware
corporation, and (ii) to make certain conforming changes to the Third Amended
Agreement; WHEREAS, Aquila Selkirk, Inc. converted to a Delaware limited liability
company on February 18, 2004, and subsequently changed its name from Aquila
Selkirk, LLC to Teton Selkirk LLC effective March 18, 2004; WHEREAS, the parties hereto desire to further amend the Third Amended
Agreement (i) to reflect the conversion and name change of the Class A Limited
Partner; and (ii) to make certain conforming changes to the Third Amended
Agreement. NOW THEREFORE, in consideration of the mutual covenants and agreements
made herein, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto, intending to
be legally bound, agree as follows: ARTICLE 1
AMENDMENT NO. 4 TO THE THIRD AMENDED AGREEMENT 1. Section 1(x) of the Third Amended Agreement (as amended by Amendments
No. 1, 2 and 3 to the Third Amended Agreement) is hereby amended by deleting
such subsection in its entirety and inserting the following language: (x) Class A Limited Partner. Teton Selkirk LLC, a Delaware
limited liability company, or any Substituted Limited Partner that
acquires all of the Partnership Interest held by the Class A Limited
Partner(s). If there is more than one Class A Limited Partner, the Class
A Limited Partner shall mean one Class A Limited Partner designated by
Teton Selkirk LLC (or if Teton Selkirk LLC is no longer a Class A Limited
Partner, then designated by the Class A Limited Partner which holds the
largest Partnership Interest). -2-




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2. All references in the Third Amended Agreement and in Amendments No. 1,
2 and 3 to the Third Amended Agreement to the Class A Limited Partner (EII)
and the Class A Limited Partner shall refer to the Class A Limited Partner as
defined in Paragraph 1 above. 3. Section 2(d) of the Third Amended Agreement (as amended by Amendments
No. 1, 2 and 3 to the Third Amended Agreement) is hereby amended by deleting
such subsection in its entirety and inserting the following language: (d)
Registered Office and Registered Agent. The registered office of the
Partnership in the State of Delaware and the registered agent of the
Partnership in the State of Delaware for service of process shall be
Corporation Service Company, 2711 Centerville Road, Suite 400, Wilmington,
Delaware 19808. 4. Schedule VIII of the Third Amended Agreement (as amended by Amendments
No. 1, 2 and 3 to the Third Amended Agreement) is hereby amended by deleting
the address for Aquila Selkirk, Inc. and replacing it with:  Teton Selkirk LLC
c/o ArcLight Capital Holdings, LLC
200 Clarendon Street
55th floor
Boston, MA 02117
Attn: PresidentWith a copy to:Caithness Teton Operating Services, LLC
565 Fifth Avenue, 29th floor
New York, New York 10017
Attn: Business Manager, Selkirk 5. Schedule VIII of the Third Amended Agreement (as amended by Amendments
No. 1, 2 and 3 to the Third Amended Agreement) is hereby further amended by
deleting the addresses for JMC Selkirk, Inc. and PentaGen Investors, L.P. and
replacing them with:  JMC Selkirk, Inc.
7600 Wisconsin Avenue
Bethesda, Maryland 20814
Attn: General CounselPentaGen Investors, L.P.
7600 Wisconsin Avenue
Bethesda, Maryland 20814
Attn: General Counsel -3-




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6. Schedule VIII of the Third Amended Agreement (as amended by Amendments
No. 1, 2 and 3 to the Third Amended Agreement) is hereby further amended by
deleting the addresses for RCM Selkirk GP, Inc. and RCM Selkirk L.P. and
replacing them with:  RCM Selkirk GP, Inc.
RCM Selkirk L.P.
c/o The McNair Group
Five Post Oak Park
4400 Post Oak Parkway, Suite 1400
Houston, Texas 77027-3440
Attn: Scott E. Schwinger 7. All capitalized terms used in the Amendment shall have the meanings
ascribed to them in the Third Amended Agreement as in effect on the day
immediately preceding the day and year as first above written. 8. Except as amended by this Amendment all other terms and provisions of
the Third Amended Agreement as in effect on the day immediately preceding the
day and year first written above shall continue in force and effect and
unchanged and are hereby confirmed in all respects. IN WITNESSETH WHEREOF, the parties hereto have caused this Amendment to be
duly executed by their authorized representatives on the day and year first
written above. JMC SELKIRK, INC.,as Managing General Partner, pursuantto Section 16(a)(i) of theThird Amended AgreementBy:
    
    /s/ F. JOSEPH FEYDERName: F. Joseph FeyderTitle: Vice President
 -4-