News and analysis about energy in California with an eye toward renewables.

Mammoth Geothermal Project Dragged Into Court

Mammoth Lakes residents fear a new geothermal plant may impair its drinking water. | Photo: Madhan Kumar/Flickr/Creative Commons License

An Eastern Sierra water agency will be filing suit over the approval of a geothermal power plant expansion, saying the project poses a threat to the local water supply.

The Mammoth Community Water District (MCWD), which provides water to Mammoth Lakes and nearby communities in Mono County, announced Friday that it will be suing the Great Basin Unified Air Pollution Control District for signing off on the 33-megawatt Casa Diablo IV geothermal plant east of town.

MCWD charges that the air district illegally approved Casa Diablo's state and federal Environmental Impact assessments despite what it calls a flawed analysis of the project's likely effect on Mammoth's potable groundwater.

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As we reported in June, the geothermal aquifer that Casa Diablo IV's owner Ormat Technologies would tap to generate power lies below the aquifer of potable water that MCWD relies on, especially during drought years when the town's surface water is scarce. Locals have long expressed concern that reinjecting cooled geothermal fluids into the deeper hot water aquifer could reduce that aquifer's pressure, causing the potable aquifer above to withdraw deeper into the earth.

As the project's Final Joint Environmental Impact Statement/ Environmental Impact Report doesn't adequately address that potential impact, says MCWD, or the possible connections between the two aquifers, it thus violates the California Environmental Quality Act.

Ormat will also be named as a party in the lawsuit, said MCWD representatives.

"Our Board's decision to pursue a lawsuit against Great Basin and Ormat is in line with our top priority: the protection of our local water supply," said Patrick Hayes, MCWD's general manager. "Unfortunately, the environmental document certified by Great Basin for Casa Diablo IV was blatantly inadequate in its consideration of the project's potential negative impacts on our water supply, an error that we cannot overlook, particularly during a record statewide drought."

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About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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