Pacific Gas and Electric Company’s Geysers Unit 17 (Geysers 17)

Docket No. 78-NOI-3, 79-AFC-1

NOI Approval on December 20, 1978

Certification Granted on September 20, 1979

AFC Staff Counsel: Steve Burger

Presiding Member: Commissioner Suzanne Reed


Project Summary

AFC Filing

Pacific Gas and Electric Company (PG&E) filed an AFC for its 110 MW Geysers Unit 17 Geothermal Project on February 26, 1979. Geysers 17 was to be the first AFC ever certified by the Energy Commission.

Geysers Overview and Project Description

Geothermal power became the CEC’s most successful preferred technology during the late 1970s and early 1980s, with a total of twelve powerplants ultimately certified in the Geysers Known Geothermal Resource Area (KGRA) of Lake and Sonoma Counties, making it the world’s largest geothermal field. Geothermal, followed later by natural gas-fired cogeneration, was the Energy Commission’s 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 Commission’s creation. Over a dozen PG&E geothermal plants were already operating or under construction before the CEC started licensing geysers facilities, beginning with the Geysers 17 AFC approval. PG&E produced more geothermal power than any other utility in the geysers (if not the planet).

Before the Geysers boom collapsed in the mid 1980s, PG&E was to certify and build Geysers 16, 17, 18, and 20.

The Geysers 17 powerplant site was located in Sonoma County, at the Lake County border, on top of a ridge in the Mayacamas Mountains. It was a rugged, natural area, approximately 70 miles north of San Francisco. Union Oil (now UNOCAL) was PG&E’s steam supplier.

The Siting Process

Geysers 17 was taken through an expedited schedule, with the case completed over four months ahead of the statutory deadline. Air quality was the major subject of concern, as the CEC and PG&E agreed that the utility should required PG&E to upgrade its standard emission control system for hydrogen sulfide to the more effective Stretford Process. (Appendix A of the CEC Decision, pages 55-59) The Stretford Process was considered to be the best available control technology by ARB, EPA, and the Sonoma County air district.

In August 1979, CEC staff issued a comprehensive Final Environmental Impact Report (EIR), which discussed the project’s impacts and proposed mitigation measures. It concluded that, if PG&E complied with adopted standards and the proposed mitigation measures (later compiled in a compliance plan), there would be no significant, adverse environmental impacts from Geysers 17.

The Commission Decision granting the AFC was issued on September 29, 1979, adopting hundreds of Findings and Conclusions, and the Compliance Plan, all of which were consistent with the Final EIR. (In 1981, the Resources Agency certified the Energy Commission as eligible for the Public Resources Code section 21080.5 exemption from preparing future powerplant EIRs. This CEQA process is known as functional equivalency. There is no EIR, but the Energy Commission's compliance with the Warren-Alquist Act and the CEC regulations provides equivalent environmental review under CEQA.)

Geysers 17 began operations in December 1982.


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