FORTY-EIGHTH SUPPLEMENTAL INDENTURE

THIS FORTY-EIGHTH SUPPLEMENTAL INDENTURE , dated as of August 1, 2009, is between OGLETHORPE POWER CORPORATION (AN ELECTRIC MEMBERSHIP CORPORATION) , formerly known as Oglethorpe Power Corporation (An Electric Membership Generation & Transmission Corporation), an electric membership corporation organized and existing under the laws of the State of Georgia, as grantor (the “Company”), and U.S. BANK NATIONAL ASSOCIATION , a national banking association, as successor to SunTrust Bank, formerly known as SunTrust Bank, Atlanta, as trustee (in such capacity, the “Trustee”).

WHEREAS, the Company has heretofore executed and delivered to the Trustee an Indenture, dated as of March 1, 1997 (the “Original Indenture”), a conformed copy of which is attached hereto as Exhibit A to the counterpart of this Forty-Eighth Supplemental Indenture that will be recorded in Warren County, Georgia, and such Original Indenture is incorporated herein by reference, for the purpose of securing its Existing Obligations and providing for the authentication and delivery of Additional Obligations by the Trustee from time to time under the Original Indenture (capitalized terms used herein and not otherwise defined shall have the meanings assigned to them in the Original Indenture);

WHEREAS, (i) the Company has heretofore executed and delivered to the Trustee forty-seven Supplemental Indentures (the Original Indenture, as heretofore, hereby and hereafter supplemented and modified, the “Indenture”), (ii) the Original Indenture and the forty-seven Supplemental Indentures have been recorded as set forth on Schedule 1 , (iii) conformed copies of the prior forty-seven Supplemental Indentures are attached hereto as Exhibit B to the counterpart of this Forty-Eighth Supplemental Indenture that will be recorded in Warren County, Georgia, and (iv) such Supplemental Indentures are incorporated herein by reference;

WHEREAS, the Company is entering into that that certain Committed, Revolving Credit Facility Agreement, dated as of August 1, 2009 (as it may be amended, modified, supplemented or extended from time to time, the “Credit Facility Agreement”), with CFC pursuant to which CFC has agreed to advance funds to the Company from time to time in an aggregate principal amount not to exceed $250,000,000 at any one time outstanding, to be used by the Company for general corporate purposes;

WHEREAS, the Company’s obligation to repay amounts advanced under the Credit Facility Agreement is evidenced by that certain First Mortgage Note, Series 2009B CFC Note, dated the date of its authentication (the “Series 2009B CFC Note”), from the Company to CFC;

WHEREAS, the Company is also entering into that certain Term Loan Agreement, dated as of August 1, 2009 (as it may be amended, modified, supplemented or extended from time to time, the “Term Loan Agreement”), with CFC which, among other things, provides the terms and conditions of a non-revolving, secured term loan from CFC in an aggregate principal amount not to exceed $250,000,000, to be used by the Company for general corporate purposes;

WHEREAS , the Company’s obligation to repay amounts advanced under the Term Loan Agreement is evidenced by that certain First Mortgage Note, Series 2009C CFC Note, dated the date of its authentication (the “Series 2009C CFC Note,” and together with the Series 2009B CFC Note, the “Series 2009 CFC Notes”), from the Company to CFC;

WHEREAS, the National Rural Utilities Cooperative Finance Corporation (“CFC”) will be issuing a series of its Clean Renewable Energy Bonds (Cooperative Renewable Energy Projects) later in 2009 (the “CREBs”), pursuant to Section 54 of the Internal Revenue Code of 1986, as amended (the “Code”);

WHEREAS, CFC has agreed to loan up to $23,864,000 in aggregate principal amount of the proceeds from the sale of the CREBs (the “Loan Amount”) to the Company pursuant to that certain Loan Agreement, to be dated later in 2009, between CFC and the Company (as it may be amended, modified, supplemented or extended from time to time, the “CREBs Loan Agreement”);

WHEREAS, the Company’s obligation to repay the Loan Amount will be evidenced by that certain First Mortgage Note, Series 2009D CFC Project Note, dated the date of its authentication, in the face principal amount of up to $23,864,000 (the “Project Note”), from the Company to CFC;

WHEREAS , the Company will use advances of the Loan Amount to finance (i) the reimbursement of the cost of certain improvements to Unit 3 at the Rocky Mountain Pumped Storage Hydroelectric Facility (the “Project”) and (ii) a portion of CFC’s costs in issuing the amount of CREBs that are loaned to the Company for the Project;

WHEREAS, the Company has complied or will comply with all provisions required to issue Additional Obligations provided for in the Original Indenture;

WHEREAS, the Company has acquired certain real property located in Warren County, Georgia, more particularly described on Exhibit C attached hereto (the “Warren County Property”);

WHEREAS, at the time the Company executed and delivered the Original Indenture, the Company did not have a property interest in any real property located in Warren County, Georgia;

WHEREAS, the Company desires to execute and deliver this Forty-Eighth Supplemental Indenture, in accordance with the provisions of the Original Indenture, for the purpose of (i) subjecting, conveying and confirming unto the Trustee the lien of the Indenture with respect to the Warren County Property and the property more particularly described on Exhibit D attached hereto, and (ii) providing for the creation and designation of the Series 2009 CFC Notes and the Project Note as Additional Obligations and specifying the form and provisions thereof;

WHEREAS, Section 12.1 of the Original Indenture provides that, without the consent of the Holders of any of the Obligations, the Company, when authorized by a Board Resolution, and the Trustee may enter into Supplemental Indentures for the purposes and subject to the conditions set forth in said Section 12.1, including (i) to subject, convey and confirm property under the lien of the Indenture, and (ii) to create additional series of Obligations under the Indenture and to make provisions for such additional series of Obligations; and

WHEREAS, all acts and proceedings required by law and by the Articles of Incorporation and Bylaws of the Company necessary to secure under the Indenture the payment

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of the principal of (and premium, if any) and interest on the Series 2009 CFC Notes and the Project Note, to make the Series 2009 CFC Notes and the Project Note to be issued hereunder, when executed by the Company, authenticated and delivered by the Trustee and duly issued, the valid, binding and legal obligations of the Company, and to constitute the Indenture a valid and binding lien for the security of the Series 2009 CFC Notes and the Project Note, in accordance with its terms, have been done and taken; and the execution and delivery of this Forty-Eighth Supplemental Indenture has been in all respects duly authorized by the Company;

NOW, THEREFORE, THIS FORTY-EIGHTH SUPPLEMENTAL INDENTURE WITNESSES , that, to secure the payment of the principal of (and premium, if any) and interest on the Outstanding Secured Obligations, including, when authenticated and delivered, the Series 2009 CFC Notes and the Project Note, to confirm the lien of the Indenture upon the Trust Estate, including property purchased, constructed or otherwise acquired by the Company since the date of execution of the Original Indenture and including the Warren County Property, to secure performance of the covenants therein and herein contained, to declare the terms and conditions on which the Series 2009 CFC Notes and the Project Note are secured, and in consideration of the premises thereof and hereof, the Company by these presents does grant, bargain, sell, alienate, remise, release, convey, assign, transfer, mortgage, hypothecate, pledge, set over and confirm to the Trustee, and its successors and assigns in the trust created thereby and hereby, in trust, all property, rights, privileges and franchises (other than Excepted Property or Excludable Property) of the Company, whether now owned or hereafter acquired, of the character described in the Granting Clauses of the Original Indenture, wherever located, including all such property, rights, privileges and franchises acquired since the date of execution of the Original Indenture, including, without limitation, all property described on Exhibit C and Exhibit D attached hereto, subject to all exceptions, reservations and matters of the character referred to in the Indenture, and does grant a security interest therein for the purposes expressed herein and in the Original Indenture subject in all cases to Sections 5.2 and 11.2 B of the Original Indenture and to the rights of the Company under the Original Indenture, including the rights set forth in Article V thereof; but expressly excepting and excluding from the lien and operation of the Indenture all properties of the character specifically excepted as “Excepted Property” or “Excludable Property” in the Original Indenture to the extent contemplated thereby.

PROVIDED, HOWEVER , that if, upon the occurrence of an Event of Default, the Trustee, or any separate trustee or co-trustee appointed under Section 9.14 of the Original Indenture or any receiver appointed pursuant to statutory provision or order of court, shall have entered into possession of all or substantially all of the Trust Estate, all the Excepted Property described or referred to in Paragraphs A through H, inclusive, of “Excepted Property” in the Original Indenture then owned or thereafter acquired by the Company, shall immediately, and, in the case of any Excepted Property described or referred to in Paragraphs I, J, L, N and P of “Excepted Property” in the Original Indenture (excluding the property described in Section 2 of Exhibit B in the Original Indenture), upon demand of the Trustee or such other trustee or receiver, become subject to the lien of the Indenture to the extent permitted by law, and the Trustee or such other trustee or receiver may, to the extent permitted by law, at the same time likewise take possession thereof, and whenever all Events of Default shall have been cured and the possession of all or substantially all of the Trust Estate shall have been restored to the Company, such Excepted Property shall again be excepted and excluded from the lien of the Indenture to the extent and otherwise as hereinabove set forth and as set forth in the Indenture.

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The Company may, however, pursuant to the Granting Clause Third of the Original Indenture, subject to the lien of the Indenture any Excepted Property or Excludable Property, whereupon the same shall cease to be Excepted Property or Excludable Property.

TO HAVE AND TO HOLD all such property, rights, privileges and franchises hereby and hereafter (by a Supplemental Indenture or otherwise) granted, bargained, sold, alienated, remised, released, conveyed, assigned, transferred, mortgaged, hypothecated, pledged, set over or confirmed as aforesaid, or intended, agreed or covenanted so to be, together with all the tenements, hereditaments and appurtenances thereto appertaining (said properties, rights, privileges and franchises, including any cash and securities hereafter deposited or required to be deposited with the Trustee (other than any such cash which is specifically stated in the Indenture not to be deemed part of the Trust Estate) being part of the Trust Estate), unto the Trustee, and its successors and assigns in the trust herein created by the Indenture, forever.

SUBJECT, HOWEVER , to (i) Permitted Exceptions and (ii) to the extent permitted by Section 13.6 of the Original Indenture as to property hereafter acquired (a) any duly recorded or perfected prior mortgage or other lien that may exist thereon at the date of the acquisition thereof by the Company and (b) purchase money mortgages, other purchase money liens, chattel mortgages, conditional sales agreements or other title retention agreements created by the Company at the time of acquisition thereof.

BUT IN TRUST, NEVERTHELESS , with power of sale, for the equal and proportionate benefit and security of the Holders from time to time of all the Outstanding Secured Obligations without any priority of any such Obligation over any other such Obligation and for the enforcement of the payment of such Obligations in accordance with their terms.

UPON CONDITION that, until the happening of an Event of  Default and subject to the provisions of Article V of the Original Indenture, and not in limitation of the rights elsewhere provided in the Original Indenture, including the rights set forth in Article V of the Original Indenture, the Company shall be permitted to (i) possess and use the Trust Estate, except cash, securities, Designated Qualifying Securities and other personal property deposited, or required to be deposited, with the Trustee, (ii) explore for, mine, extract, separate and dispose of coal, ore, gas, oil and other minerals, and harvest standing timber, and (iii) receive and use the rents, issues, profits, revenues and other income, products and proceeds of the Trust Estate.

THE INDENTURE, INCLUDING THIS FORTY-EIGHTH SUPPLEMENTAL INDENTURE, is intended to operate and is to be construed as a deed passing title to the Trust Estate and is made under the provisions of the laws of the State of Georgia relating to deeds to secure debt, and not as a mortgage or deed of trust, and is given to secure the Outstanding Secured Obligations.  Should the indebtedness secured by the Indenture be paid according to the tenor and effect thereof when the same shall become due and payable and should the Company perform all covenants contained in the Indenture in a timely manner, then the In