- Docket Number
- 41 MW
- Sonoma County
- Steam Turbine
- Project Status
- Operational (Geothermal)
- Project Type
- Application for Certification
The Grant Geothermal Project (Unit 20) is in an unincorporated area of Sonoma County in the Geysers Known Geothermal Resource Area along the ridgeline of the Mayacamas Mountains with moderately steep terrain near the Lake County line, approximately 15 miles west of the town of Cobb. Unit 20, originally known as Pacific Gas & Electric Company’s (PG&E) Geysers Unit 20 Geothermal Project was certified by the California Energy Commission (CEC) in February 1983. Commercial operation began in October 1985.
Unit 20 was designed to provide 110-megawatts; however, due to reduced steam pressures, the plant currently (as of January 2021) supplies approximately 41-megawatts of baseload electricity to northern California's power grid. Unit 20’s major structures on the plant site are enclosed with a seven-foot security fence. These structures include a power cycle consisting of a turbine-generator and condensate and circulating water systems; a multiple cell mechanically induced crossflow cooling tower; a transmission switchyard, adjacent to the turbine generator building; and, a hydrogen sulfide (H2S) abatement system. Primary treatment will be through a Stretford system, in which H2S is scrubbed from the vent gas stream and catalytically oxidized to elemental sulfur.
In April 1999, the CEC granted a transfer of ownership of Grant Geothermal (Unit 20), the former PG&E Geysers Unit 20 Geothermal Project to Geysers Power Company, LLC, a wholly owned subsidiary of the Calpine Corporation.
Project Amendment List
Order Approving Change on Tapline Termination and Amending Certification Decision, Not in Docket, Order No. 85-0501-01, Commission approval of change on tapline termination; constructing 100 feet of conductor to the existing occupied Unit 13 circuit, as the new termination point.
Order Approving Modifications to Biology, Waste Management, and Power Plant Efficiency and Reliability Conditions of Certification, TN 8882, 05/25/1995, Order No. 95-0315-09, Commission approval of modifications to Biology Condition of Certification 5-5, Waste Management Condition of Certification 11-7, and deletion of Power Plant Efficiency and Reliability Condition of Certification 17-9.
Approval of Requested Changes to Verifications for Air Quality and Public Health Conditions of Certification, Not in Docket, 03/23/1995, Staff approval of verification changes for Conditions of Certification Air Quality 1-2 subparts 4 and 7, and Public Health 2-1.
Commission Order Approving Ownership Transfer, TN 11769, 04/22/1999, Order No. 99-0414-01b, Commission approval of ownership transfer from PG&E to Geysers Power Company.
Approval of Petition to Use Reclaimed Wastewater and Approval of Verification Changes, TN 31101, 03/12/2004, Staff approval of the use of reclaimed municipal wastewater at the six Calpine Geysers geothermal power plants as well as revision of the reporting requirements in the condition of certification verifications.
Authorization for Calpine to Obtain Demolition Permits from Sonoma and Lake Counties for Demolition, TN 206701, 11/19/2015, Staff approval for Calpine to obtain and implement county-issued demolition permits to abate fire damage to structures at Geysers 16, 18, and 20.
Authorization of the Revised ATC Incorporated into the project Final Decision, TN 210233, 02/08/2016, Final permission for Executive Order B-36-16 expedited processing and N. Sonoma Air Pollution Control District Authority to Construct necessary for wildfire remediation and to restore power plant operations.
Order Approving to Replace Temporary Portable Emergency Diesel Engines with Stationary Permanent Emergency Diesel Engines, TN 226129, 12/17/2018, Order No. 18-1210-02, Commission approval to replace temporary portable emergency diesel engines with stationary permanent emergency diesel engines for the cooling tower wet-down systems to aid in fire prevention at the Quicksilver, Socrates, and Grant geothermal power plants.
Resolution Approving (DCBO) Services for Fire System Recommissioning Activities at the Geysers Facilities, TN 230281, 10/18/2019, Resolution No. 19-1014-04, Approval of Agreement 700-19-003 with NV5, Inc. for a $0 contract to provide delegate chief building official (DCBO) services for fire system recommissioning activities at the Geysers facilities.
Order Approving Settlement for Fire Protection System, TN 235698, 11/19/2020, Order No. 20-1116-02, Commission approval of the Settlement Agreement and changes to the conditions of certification and direct the Executive Director to execute the Settlement Agreement on behalf of the CEC.
Attention: Non-hypertext items above will need to be requested from the Compliance Project Manager, along with the document TN number, if provided above.
Power Plant Certification and Exemption Processes
As required by the Warren-Alquist Act, the Energy Commission monitors Commission-certified energy projects throughout construction, operation, and closure to ensure compliance with the conditions of certification imposed by the Commission’s Final Decision for approving the projects.