Feinstein expresses doubts about Casa Diablo IV

U.S. Senator Dianne Feinstein recently echoed the Mammoth Community Water District’s (MCWD) questions and concerns about the proposed Casa Diablo IV Geothermal Power Plant off Route 395 near Mammoth Lakes, according to an MCWD press release.

The Casa Diablo IV project has been in the works since 2010. According to the project’s Final Environmental Impact Statement (EIS) and Environmental Impact Report (EIR), the 40-megawatt geothermal project will include the construction of a new geothermal power plant near the existing geothermal facility, up to 16 new production and injection wells, multiple pipelines, and an electric transmission line.

Completed, the project would produce enough energy to power 36,000 homes.

MCWD alleges that the project, owned by Ormat Technologies, Inc., would pump about 29,000 acre-feet of hot water from below the cold groundwater zone. For comparison, MCWD General Manager Pat Hayes told the Mammoth Lakes Contractors Association in a presentation on July 10 that MCWD pumps 2,000 acre-feet of water per year to provide 70 percent of Mammoth’s daily water use.

Hayes noted that surface water usually supplements Mammoth’s water supply, but three years of drought have finally taken their toll.

“Normally, we’re getting 220-240 cubic feet per second runoff into Lake Mary,” the District’s source for surface water, Hayes said. “This year, in June, we never got over 30 cubic feet per second. By August, we will rely almost exclusively on groundwater.”

Since last year, MCWD has expressed concern that the amount of pumping proposed by Ormat could negatively affect Mammoth’s precious groundwater supply. Hayes said the District is concerned that geothermal pumping could increase the temperature of the groundwater; pollute groundwater with arsenic and manganese; or pull water down deeper into the aquifer, below the District’s ability to pump.

Hayes argued that current geothermal pumping already appears to have impacted MCWD wells, citing the example of two District wells closest to Ormat’s existing geothermal wells. The first MCWD well, at Sam’s Wood Site, has a water temperature of 70 degrees. A second well near MCWD headquarters is now up to 99 degrees.

In a statement released in late June of this year, Ormat maintained that, “In 30-years of operation and eight years of production, there has never been any identified effect on the MCWD’s water supply.”

MCWD has argued that Ormat must have a monitoring and mitigation plan in place before breaking ground on the geothermal plant. Yet the Bureau of Land Management (BLM) and U.S. Forest Service already approved the project’s Final EIS/EIR without such plans in place.

“Given the scarcity of other available water supplies in the area, it is important that the United States Bureau of Land Management and United States Forest Service ensure that this project does not affect critically important groundwater supplies,” said Senator Feinstein.

“Consequently, I request that the BLM and Forest Service provide information summarizing the basis upon which they conclude in the EIS/EIR that the project is unlikely to affect the quality and availability of shallow groundwater resources.”

Senator Feinstein asked that the U.S. Geological Survey assess the project’s proposed monitoring and mitigation plan “to ensure Mammoth’s water resources remain accessible and safe.”

Senator Feinstein’s request comes several weeks after similar statements released by California Congressional Representatives Paul Cook and John Garamendi.

Ormat said it has been working with the BLM, USFS, Great Basin Unified Air Pollution Control District, and MCWD, to address the District’s concerns.

“We’re not trying to scare people,” Hayes concluded at Thursday’s Contractors Association meeting. “We think there’s a way to mitigate this.” But, he added, Ormat has thus far only proposed one or two shallow monitoring wells, which the District believes is not enough to monitor changes to groundwater.

“We’re really taking baby steps at this point,” he said.

Because MCWD has appealed the BLM’s decision regarding the Casa Diablo EIS/EIR, Hayes said, “We could sue … but we don’t want to get to that point.

Nevertheless, he said, “We have an ethical, moral obligation to say, ‘Wait a minute, you need to protect this resource.’”