The United States Geological Survey recently released a report entitled “Hydraulic, Geochemical and Thermal Monitoring of an Aquifer System in the Vicinity of Mammoth Lakes” which could have broad implications for local citizens.
On July 10, Wildermuth Environmental, sent a nine-page letter to Mammoth Community Water District’s Interim General Manager Mark Busby in analysis of the latest USGS report.
Wildermuth concludes that the potential Casa Diablo IV project “would place new stresses on the region’s complex hydrologic system” and “may reduce the supply of groundwater necessary for public water system use available to the MCWD from the Mammoth Groundwater Basin and may degrade the water quality of waters in the shallow groundwater aquifer used by the MCWD. These deleterious changes … may not become apparent immediately after the start of the CD-IV Project operations and couild take several years to manifest themselves in groundwater monitoring data … The seepage volume could be comparatively small and unnoticeable to the project develooper but could be significantly large to MCWD and the Town of Mammoth Lakes.”
Further, the new USGS data, according to Wildermuth, debunks the EIS/EIR environmental documents upon which the CD-IV permit was issued.
From the published USGS abstract:
“The digitally filtered water-level data indicated that some hydraulic communication exists between the deep geothermal aquifer and the shallow groundwater aquifer at the location of the flow test, northeast of Mammoth Lakes. Groundwater-chemistry data from three wells indicated that shallow groundwater naturally mixes with a small component of geothermal water along the northern periphery of the shallow aquifer system.”
The new data also confirm what Wildermuth has contended since March, 2018 regarding connectivity.
Discussion of this USGS Report was scheduled for the Thursday, July 18 MCWD Board meeting.
In his staff report, District Engineer John Pedersen suggested the new evidence supports the District’s request to have the BLM (Bureau of Land Management) update the current Groundwater Monitoring and Response Plan to include:
1. Requirement of a second deep monitoring well with a shallow nested pair monitroing well.
2. Require 18 months of baseline monitoring for these new wells prior to start of operations.
3. Establish thresholds that define when BLM must impose modifications on CD-IV production operations.
The District has spent millions of dollars fighting Great Basin Unified Air Pollution Control District’s approval of the CD-IV project back in 2013 and lost a 2015 Superior Court case it pursued against Great Basin Unified claiming it had violated CEQA (California Environmental Quality Act).
Recently, MCWD has adopted a more collaborative tone in trying to get its concerns addressed.