Pacific Gas and Electric Companyís Geysers Unit 20 (Geysers 20)

Docket No. 82-AFC-1

Certification Granted on February 9, 1983

Staff Counsel: Gary Fay

Presiding Member: Commissioner Karen Edson


Project Summary

AFC Filing and Data Adequacy

Pacific Gas and Electric Company (PG&E) filed an AFC for its 110 MW Geysers Unit 20 Geothermal Project on March 29, 1982. Under the regulations then in effect, the Executive Director accepted the AFC conditionally, effective March 29, 1982, based upon PG&Eís commitment to provide a worst case air quality analysis and a plan for mitigating biological impacts. PG&E submitted this data, satisfying the conditions of acceptance.

Geysers Overview and Project Description

Geothermal power was the CECís most successful preferred technology during the late 1970s and early 1980s, with a total of twelve powerplants certified in the Geysers Known Geothermal Resource Area (KGRA) of Lake and Sonoma Counties, making it the worldís largest geothermal field. Geothermal, followed later by cogeneration, was the Energy Commissionís chosen alternative to the large coal and nuclear plants long favored by utilities.

PG&E had pioneered in the geysers many years earlier, prior to the Energy Commissionís creation. Over a dozen PG&E geothermal plants were already operating before the CEC started licensing geysers facilities, beginning with AFCs for PG&E Units 16, 17, and 18. PG&E produced more geothermal power than any other utility in the geysers (if not the planet).

Projections had indicated that a vast potential existed for additional geothermal plants, with virtually no end in sight. Municipal utilities and even qualifying facilities (QFs) wanted their share of the geothermal bonanza. PG&E itself had identified sites for Units 21-24.

But by the mid 1980s, the geysers boom would come to an end. The PG&E service area developed a surplus of electricity, in large part due to an influx of QF projects with a capacity below 50 MW, and thus not subject to CEC jurisdiction. PG&E then stopped building powerplants altogether, as other, more reliable/cheaper options, became available, such as the purchase of energy from outside California.

Meanwhile, the geysers steam supply unexpectedly started to decline, reducing the output of many existing powerplants, while dooming future projects. PG&E began to close its older, less efficient Geysers units in order to conserve steam. Geysers 20 thus became the last PG&E geothermal unit actually constructed. (Geysers Unit 21 would later be certified, but not built, Docket No. 84-AFC-1.)

The Geysers 20 site was located in eastern Sonoma County, near the Lake County border, on a spur west of the main ridge of the Mayacamas Mountains. Lake County communities such as Anderson Springs and Whispering Pines were the closest residential areas to the site. Approximately 510,000 cubic yards of soil and rock material would have to be cleared from the site and disposed of to establish 7 acres of flat, graded surface for the powerplant. As usual, Union Oil (now UNOCAL, was PG&Eís steam supplier, on land leased from the Federal government.

Steam Sufficiency Hearing

Under Public Resources Code section 25540.2(a), a 12-month geothermal AFC, without an NOI, can be reviewed by the Energy Commission only if, at the outset of the proceeding, the applicant can reasonably demonstrate that the site is capable of providing geothermal resources in commercial quantities.

The Committee conducted an uncontested steam sufficiency hearing for Geysers 20 on April 28, 1982, followed by a ruling that the leasehold had adequate steam resources for the life of the project, in accordance with Public Resources Code section 25540.2(a). (Pages 6-7 of the CEC Decision.)


There were no major disputed issues among the parties in the Geysers 20 case. Demand Conformance was uncontested. PG&E and CEC staff supported the Northern Sonoma County Air Districtís Determination of Compliance (DOC), which found that the project satisfied all applicable air quality laws.

Commenting as a member of the public, the Lake County Air Pollution Control Officer disagreed with his Sonoma County counterpart. He called for changes to the DOC which would have further limited emissions. However, the Committee accepted the Sonoma County DOC as sufficient.

In the area of Socioeconomics, PG&E reached mitigation agreements with the Sonoma and Lake County School Districts, so the schools would be compensated for new students attributable to Unit 20. (Appendix D to the CEC Decision.) PG&E also entered into an October 1, 1982 agreement with Sonoma County, under which the parties pledged to later negotiate specific mitigation for Unit 20ís impacts upon county roads and housing. (Appendix C to the CEC Decision.) (A similar agreement with Lake County was later required by the Commission at page 69 of the CEC Decision, socioeconomics Condition of Certification 3-7.) The parties subsequently disagreed regarding the scope of their intended settlement and questioned the Commissionís role in ratifying the products of negotiation.

The Committee and the Commission maintained their rights to ratify any mitigation agreements as necessary in the due exercise of CEC licensing responsibilities. The Commission further directed PG&E to negotiate the mitigation agreements, covering both transportation and housing, precluding construction until the agreements had been reached and ratified as sufficient mitigation. (Page 70 of the Commission Decision.)


The Energy Commission certified PG&E Geysers Unit 20 at its February 9, 1983 Business Meeting. It was constructed and began operation in December 1985.


As part of electric industry de-regulation, PG&E divested itself of most powerplants that it owned. This sale covered all the operational Geysers plants, including the four with CEC licenses: Geysers 16, Geysers 17, Geysers 18, and Geysers 20. The PG&E Geysers plants were purchased by Calpine in 1999. (See PUC Application 98-01-008, Decision 99-04-026, April 1, 1999.)