Pressure decline within The Geysers geothermal reservoir has resulted in decreased power output from existing power plants. As a means of partially arresting these ,pressure declines, several field operators and the County of Lake propose to add approximately 13,000 lpm of treated municipal waste water from several small communities into 6 injection wells in the southeastern corner of the field. Water will be carried to the geothermal field via a 50- or 6O-cm diameter pipeline from the vicinity of Clear Lake, a distance of about 45 km. The results of this study suggest that the proposed injection of effluent could help reducing the high rate of pressure and production rate declines without inducing significant geochemistry incompatibility or microseismicity.