Hazardous waste from geothermal energy: a case study

Hazardous wastes at The Geysers in northern California come partly from normal drilling activities but mostly from power generation. Wastes created during drilling include drilling mud, rock cuttings, drilling-mud additives, lost circulation materials, cement, hydrogen-sulfide abatement chemicals, and miscellaneous oily residues from machinery discharges and/or minor spills on drill pads. During well flow testing it is frequently necessary to oxidize the hydrogen sulfide with two hazardous materials, sodium hydroxide and hydrogen peroxide. Drill cutting may contain constituents such as arsenic, boron, cadmium, chromium, nickel, mercury, and zinc. Fine Colloidal clay particles are particularly toxic to fish if the drilling mud enters streams. Some accidents and spills of materials during transport that occurred at the Geysers are recalled and the way the problems were resolved is described. This experience may be useful for other geothermal energy developments.