Ambient Air Monitoring at The Geysers: A Historical Perspective and Current Status

Abstract

The results of three ambient air monitoring programs performed downwind of the Geysers, California are described., These studies, conducted since 1976 have monitored the declining ambient air concentration of hydrogen sulfide (H2S) in Lake County. During the 13 years of monitoring, geothermal power production has increased form approximately 500 to 2000 megawatts, H2S emissions from power plants have declined from 1900 to less than 200 lb/hr, and ambient H2S concentration have significantly declined. Annual average concentrations of H2S at four long term sites have declined by a factor of 2.8, maximum H2S concentrations have declined by a factor of 3.4 and the frequency of exceedance of the California Air Quality Standard (0.03 ppm) averaged over 1 hour has declined from an average frequency of 52 times per year to less than 1.