Exhibit 10.66 Acknowledgment and Agreement -- Release --------------------------------------- The undersigned hereby acknowledge and agree to be bound by the terms of Sections 6.4 and 11.13 of the Purchase Agreement, dated January 16, 1999 by and among Caithness Energy, L.L.C., Caithness Acquisition Company, LLC, and CalEnergy Company, Inc., to the same extent as the Buyer named therein including, without limitation, (i) the general release, (ii) the waiver of Section 1542 of the Civil Code of California and hereby covenant to take any and all actions and execute any further documents reasonably requested by Seller named therein to implement and enforce such Sections. Dated May 28, 1999 COSO FINANCE PARTNERS, a California general partnership By: New CLOC Company, LLC, a Delaware limited liability company, its Managing General Partner By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President By: ESCA, LLC, a Delaware limited liability company, its General Partner By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President New CLOC Company, LLC, a Delaware limited liability company By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President ESCA, LLC, a Delaware limited liability company By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President COSO ENERGY DEVELOPERS, a California general partnership By: New CHIP Company, LLC, a Delaware limited liability company, its Managing General Partner By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President By: Caithness Coso Holdings, LLC, a Delaware limited liability company, its General Partner By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President New CHIP Company, LLC, A Delaware limited liability company By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President Caithness Coso Holdings, LLC, a Delaware limited liability company By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President 2 COSO POWER DEVELOPERS, a California general partnership By: New CTC Company, LLC, a Delaware limited liability company, its Managing General Partner By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President By: Caithness Navy II Group, LLC, a Delaware limited liability company, its General Partner By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President New CTC Company, LLC, a Delaware limited liability company By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President Caithness Navy II Group, LLC, a Delaware limited liability company By: /s/ Christopher T. McCallion ---------------------------- Christopher T. McCallion Executive Vice President 3