BLM Regulation of Class V Geothermal Injection Wells: Seismicity Concerns
The BLM, through an informal agreement with the EPA, regulates the Class V geothermal injection wells in California. Under this arrangement the BLM has recently issued its “Conditions of Approval” for a proposed enhanced geothermal systems project that stipulated the specific procedures to be followed in the event that induced seismicity is observed to be caused by the proposed stimulation (hydraulic fracturing) operation.a As issued by the BLM, the specific procedures include the use of a “traffic light” system that allows hydraulic fracturing to proceed as planned (green light) if it does not result in an intensity of ground motion in excess of Mercalli IV “light” shaking (an acceleration of less than 3.9%g), as recorded by an instrument located at the site of public concern. However, if ground motion accelerations in the range of 3.9%g to 9.2%g are repeatedly recorded, equivalent to Mercalli V “moderate” shaking, then the hydraulic fracturing operation is required to be scaled back (yellow light) to reduce the potential for a further occurrence of such events. Finally, if the operation results in producing a recorded acceleration of greater than 9.2%g, resulting in “strong” Mercalli VI or greater shaking, then the active hydraulic fracturing operation is to immediately cease (red light).
aR.M. Estabrook, BLM, Conditions of Approval for GSN-340-09-06, Work Authorized: Hydroshear, The Geysers, January 31, 2012.
U.S. Geological Survey
The USGS provides scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect quality of life in the United States.9 It is the only federal agency with responsibility for recording and reporting earthquake activity worldwide, and it is often asked to aid state agencies in the investigation of possible induced seismicity. Its Earthquake Hazards Program serves as the USGS component of the multiagency National Earthquake Hazards Reduction Program, which develops, disseminates, and promotes knowledge, tools, and practices for earthquake risk reduction that improve national earthquake resilience. The Earthquake Hazards Program also houses the National Earthquake Information Center (NEIC), which aims to determine the location and size of all destructive earthquakes worldwide and to disseminate this information to concerned agencies, scientists, and the general public.
The USGS is continuing to enhance its earthquake monitoring and reporting capabilities through the Advanced National Seismic System (ANSS). Since 2008 the USGS has