Federal: Guidelines regulating land use, soil erosion, pipeline integrity testing, seismic design standards, and earthquake hazards have been outlined at the federal level in documents such as the Bureau of Land Management (BLM) Geothermal Resources Operational Orders and the Watershed and Air Management Manual.
State: The Alquist-Priolo Earthquake Fault Zoning Act and the Seismic Hazards Mapping Act.
Local: The agencies of Mono County and the Town of Mammoth Lakes.
The project is built to avoid or reduce any potential risks to facilities, worker safety, and the surrounding environment. Such risks include faulting, seismic hazards, landslides, subsidence, liquefaction, collapse, and expansive soil. The project should be performed in a way that reduces or avoids significant impacts to topsoil and erosion. The impact on geologic, soil, and mineral resources for both the proposed action and Alternative 2, is considered negligible after considering mitigation measures. However, Alternative 3 is considered to be the best option for these resources because the pipeline installation has less dispersed impacts on the geologic and soil resources.
Cumulative Effects
None mentioned.
Mitigation
The proponent will:
Develop a Soil Erosion Control Plan that must be reviewed and approved by the appropriate authorities;
Prepare a final geotechnical investigation that provides recommendations to address seismic safety;
Review the subsidence monitoring program and install additional monitoring equipment; and
Provide the results of the surface fault rupture hazard investigation to the USFS and demonstrate that these findings have been considered in the project design.
Residual Impacts
None mentioned.
The report properly addresses the main public concerns for these resources, namely the potential for geothermal wells to induce seismicity and the potential for fault ruptures and subsidence. The sources of concern and the project’s impact were well defined.
An issue with this EIA is that it brushes over the fact “soils within the project area could experience long term adverse impacts in specific areas through degradation of soil function and increased susceptibility to erosion” (EIA Report p.508). However, this important impact is disregarded as the soil is not prime farmland or considered to be valuable.