Santa Rosa Injection and Seismicity Update

The Santa Rosa - Geysers Recharge Project (SRGRP) began piping tertiary-treated reclaimed water up to Calpine's Geysers steamfields in significant quantities in November 2003. So far the project looks like a success. The system has been operating reliably and we're already seeing evidence of some benefits in certain areas. As of the end of August, 2004, the system had delivered over 3 billion gallons of SRGRP reclaimed water, all of it distributed via Calpine's new pipeline system into 11 injection wells. Compared to the average injected for the same period (November through August) during the previous six seasons, injection is up by about 36% (see table). On the other hand, total injection with SRGRP on line was not much higher than previously achieved during the winter of 1997 - 98, when unusually wet weather provided an abundance of freshwater and plant condensate for injection.

Fieldwide seismic activity has also been similar to that of the 1997 - 98 season. In general, the seismic response to the SRGRP injection has been much as predicted in the Environmental Impact Report: more microearthquakes, but little change in the number of larger quakes. The table below shows that seismic activity of magnitudes 1.5 and above has increased by 34% since SRGRP has been operating, compared to the average for the same period during the previous six years. The vast majority of these microearthquakes are too small and/or distant to be felt by people. On the other hand, earthquakes of magnitudes 3.0 and greater have been virtually unchanged since SRGRP started up, compared with the previous six-season average. The 2003 - 04 total of 13 earthquakes in this magnitude range was equaled or exceeded in three of the six pre-SRGRP seasons.

Overall, in terms of both injection and seismicity, the SRGRP is performing as expected, and Calpine looks forward to many years of future success in this partnership with the City of Santa Rosa. - Mitch Stark, Calpine Corporation

* Data Source: USGS Northern California Seismic Network

Recent Earthquakes of the S.F. Bay Region