Sonoma Geothermal Project - Unit 3

The Sonoma Geothermal project (Unit 03) is in Sonoma County near the Sonoma/Lake County line, in the Geysers Known Geothermal Resource Area along the ridgeline of the Mayacamas Mountains with moderately steep terrain, approximately 15 miles west of the town of Cobb. Unit 03, originally known as Sacramento Municipal Utility District (SMUD) SMUDGEO No. 1 Geothermal Project (SMUDGEO1), was certified by the California Energy Commission (CEC) in March 1981 and began commercial operation in December 1983.

Unit 03 is a dry steam geothermal power plant and was designed to provide 78 MW of electricity; however, due to reduced steam pressures, Unit 03 currently provides 35 MW of baseload power to northern California’s power grid.

Prior to the project being licensed, a Memorandum of Understanding dated February 27, 1980, between the CEC, United States Geological Survey (USGS), and the Bureau of Land Management, was prepared to create a cooperative effort to comply with National Environmental Policy Act and California Environmental Quality Act and to issue the necessary permits and licenses for the project.

On February 3, 1981, a Letter of Understanding (LOU) was signed by the CEC and USGS to further clarify duties and responsibilities of the agencies following the issuance of the licenses and approvals for the project. The LOU stated that the ultimate decision-making authority over the operation of the facility resided with the USGS and the BLM. The LOU required Plans of Operation, Applications for Permits, reports, designs, and similar documents to be submitted to the USGS and reviewed by the CEC. All annual reports of compliance were to be submitted to the USGS.

The 1981 Final CEC Decision stated that state and federal agencies participated in a joint environmental statement since the project is on federal lands. The conditions set forth in the Final Decision were consistent with the MOU and the LOU and required the project owner to file various report and other ongoing compliance documents with the USGS.

In April 1999, the CEC granted a transfer of ownership of the Sonoma Geothermal (Unit 03), the former Sonoma Geothermal Power Project (formerly SMUDGEO) from Calpine Geysers Company, L.P. to Geysers Power Company, LLC, a wholly owned subsidiary of Calpine Corporation. In August 2010, the CEC approved a USGS letter requesting that they be terminated as the primary compliance monitoring agency.