The Ormat NV Casa Diablo IV Geothermal Development Project has found a challenger in the Mammoth Community Water District.
According to an August 27 News Release from the Water District, the District plans to appeal the Bureau of Land Management (BLM) and U.S. Forest Service (USFS) decision approving the project earlier in August. The Water District expressed concern about the impact of the new geothermal project to the Mammoth community groundwater and surface water supply, and advocated a “robust monitoring and mitigation plan” to ensure the project does not negatively effect that water supply during construction or operation.
The Casa Diablo IV Geothermal 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, located near the existing geothermal facility off Highway 395, will include the construction of a new geothermal power plant, up to 16 new production and injection wells, multiple pipelines, and an electric transmission line. Completed, the project will produce enough energy to power 36,000 homes.
In comment letters submitted during the project’s public comment period earlier this year, most residents expressed concern about the potential impact of as many as 14 geothermal wells in the Basalt Canyon area near Shady Rest. Retired petroleum engineer and geologist Brigitte Berman voiced her concern that the construction of the wells might release toxic gases, particularly hydrogen sulfide (see Aug. 3 story “Casa Diablo IV, says Ormat, will not be a gas, gas, gas”).
BLM Project Manager Collin Reinhardt gave his assurance that the project will have a built-in abatement and monitoring plan, should the level by the wells during construction exceed state and federal standards. Once the wells are operational, he added, “There will be no venting of gases.”
However, the Water District noted that no adequate abatement and monitoring plan exists to mitigate the potential impact of the project to Mammoth’s water resources. According to the Water District News Release, those 14 new geothermal wells will be in close proximity to Water District groundwater supply wells, and may impact the groundwater supply. Casa Diablo IV Project will increase geothermal fluid production from the current 19,000 acre-feet to about 29,000 acre-feet per year, the News Release stated. The Water District currently extracts about 2,000 acre-feet if groundwater per year from the coldwater aquifer above the geothermal aquifer, which is enough to supply over 70% of daily water use in Mammoth.
Water District General Manager Pat Hayes explained the impact the increase in geothermal fluid extraction might have on the Water District. “The hydrology in this region is very complicated,” he said. Snowmelt runoff resides in fractured rock known as an aquifer, from which the Water District extracts water with wells. “Underneath the coldwater [aquifer] area is an area of warm water, and deeper still is the geothermal zone, where water is quite hot,” he said. To give a sense of scale, Water Department wells range between 400-700 feet deep. The Casa Diablo IV geothermal wells will range between 1,500-2,000 feet deep, he said.
“Our concern is that the condition of the rock between the bottom of the coldwater zone and the geothermal zone is not well understood,” he said. If Ormat extracts hot water from below the coldwater aquifer, this may reduce pressure created by the hot water, allowing cold water to migrate down through the fractured, permeable rock into the geothermal zone. “This could be catastrophic for Mammoth’s groundwater supplies,” the News Release stated.
Geothermal well drilling also poses a threat to drinking water quality standards, Hayes said. Sufficient pressure in the geothermal zone, which may be released when Ormat begins drilling, could push the geothermal water upward. Geothermal water has some chemical characteristics that degrade water quality, Hayes explained, and a migration of that water upward into the coldwater supply could decay water quality beyond the Water District’s ability to mitigate.
Other issues raised by the Water Department included a concern about the effect of taking roughly 29,000 acre-feet of water from the Shady Rest area and, after extracting the heat, injecting it not back into the area but at a location near the geothermal plant. “That has the potential to upset the balance [of the water] in the area,” Hayes said.
In addition, if water is lost to Mammoth Creek because of geothermal exports, the Water District will have to reduce its own exports from Lake Mary to mitigate the impact to Mammoth Creek and its fish population.
To protect the Mammoth community’s water resources, the Water District is proposing a monitoring and mitigation plan using shallow and deep monitoring wells and aquifer stress tests to determine whether or when the Casa Diablo IV operations might have to cease. The plan would allow monitoring of pressures, temperatures and chemistry of the water, Hayes said.
BLM Project Manager Collin Reinhardt said that such a monitoring plan is now a condition of approval for the project. “This is something that we expected to see, as far as the expansion of the monitoring in relation to the development of the resource,” he said. He added that the involved parties, including the Water District and Ormat, are currently working on the substance of the monitoring plan. “We [the BLM and USFS] haven’t been working in a vacuum,” he said. “There have been lots of conversations about this. It wasn’t a surprise.”
However, because the BLM already approved the project, signing a Record of Decision for the Final EIS/EIR under the National Environmental Policy Act (NEPA), the BLM’s purported requirement for a monitoring plan is more of “an appendage after the fact,” said Hayes, and therefore not necessarily enforceable.
Hayes expressed the Water District’s hope that the Great Basin Unified Air Pollution Control District (GBUAPCD), which determines the Casa Diablo IV Project approval under the California Environmental Quality Act (CEQA), will not approve the project until such a monitoring plan is firmly in place. Once the CEQA is approved, he said, the Water District would lose much of its power to ensure any kind of a monitoring plan for Casa Diablo IV. GBUAPCD will consider approval of the proposed project on September 16.
“Ormat has said they’ll do a monitoring plan and work with the District on it, but so far we haven’t seen much traction with this,” Hayes concluded. “We remain hopeful, but ‘tie your horse up at night.’”
The Water District Board of Directors will hold a special meeting to discuss their concerns with the public on Tuesday, September 3 at 7 p.m. in the District Board Conference Room at 1315 Meridian Boulevard.