Casa Diablo IV Geothermal Development Project Technical Assessment - PowerPoint PPT Presentation

Casa Diablo IV Geothermal Development Project Technical Assessment of the NEPA/CEQA Documentation, the Potential Impacts to MCWD, and Next Steps September 16, 2013

CD IV Expansion  16 New geothermal well sites with 14 in Basalt Canyon  Geothermal production will be increased from:  12,000 gpm to 18,000 gpm or  19,000 acre-ft/yr to 29,000 acre-ft/yr  Injection wells will be located in the Casa Diablo area

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MCWD Review  WEI reviewed portions of administrative copy of Joint NEPA/CEQA Document in July 2012 and provided comments  WEI and Schmidt reviewed the draft Joint NEPA/CEQA Document and prepared comments in January and February 2013 MCWD submitted these to the lead agencies  WEI provided a comment letter in July 2013 responding to the final Joint NEPA/CEQA Document’s response to the MCWD’s comments on the draft Joint NEPA/CEQA Document  Finally, WEI provided a letter report in August 2013 outlining a recommended monitoring and mitigation plan

Joint NEPA/CEQA Conclusions Regarding the Degree of Hydraulic Connection  Joint NEPA/CEQA Document concludes:  Shallow cold-groundwater system is hydraulically isolated from the geothermal system  Ormat assumed no impact to the shallow cold-groundwater system – no definitive analysis to confirm assumption  Therefore no impacts were projected to the cold groundwater system and MCWD  Computer simulations of the geothermal reservoir described in the Joint NEPA/CEQA Document did not include simulation of the cold groundwater and geothermal systems together  No mitigation of impacts to the cold groundwater were required because no impacts were assumed

WEI/Schmidt Conclusions  Inadequate hydrogeologic characterization  There is a two to three square-mile area between the proposed and existing geothermal wells in the Basalt Canyon and the District’s well field for which no boreholes have been drilled or wells constructed.  This means that the hydrogeology in this area has not been characterized  No analysis of hydraulic connectivity has ever been done  There is no technical basis for the certainty of no impacts to the cold groundwater system and to MCWD as expressed in the Joint NEPA/CEQA Document

WEI/Schmidt Conclusions  MCWD concerns:  The expansion of geothermal production nearer the MCWD wells will induce downward flow of groundwater and reduce the groundwater resource available to the MCWD  There is some evidence of connectivity at MCWD well 17  The impact could take years to manifest itself and reduce the availability of groundwater during dry-years  May reduce the surface water discharge in Mammoth Creek and impair beneficial uses of that supply

The Way Forward  The BLM and FS have entered a Record of Decision (ROD) on the NEPA document  The Great Basin Unified APCD has stated it would defer certification of the CEQA document pending the development of a monitoring and mitigation plan acceptable the MCWD  MCWD and Ormat have verbally agreed to attempt to develop a monitoring and mitigation plan – we start this process later this month

Mitigation Plan  The MCWD requires that the monitoring and mitigation plan be defined prior to project approval  Metrics need to be developed with thresholds or “bright - lines” that trigger mitigation of known capacity

Two-Part Monitoring Plan  Part 1 – Conduct aquifer stress tests to determine hydraulic connectivity before the CD-IV wells are constructed  Ormat should construct at least four new monitoring well pairs with each pair consisting of a new geothermal well and an existing or new cold groundwater well  Ormat will stress either the cold or geothermal system in each well pair and measure response to determine hydraulic isolation

Two-Part Monitoring Plan  Part 2 – Conduct new and continuous monitoring to determine if the CD-IV project is impacting the cold- groundwater system – needs to be implemented before the CD-IV wells are operational  Piezometric measurements in select wells including the new cold and geothermal well pairs  Chemistry and physical property measurements in select wells including the cold and geothermal well pairs

Next Steps  Develop monitoring and mitigation plan with Ormat;  Develop and execute the monitoring plan  Develop a mitigation plan  Develop metrics & triggers, and the monitoring required to evaluate metrics and assess if a “triggering” event has occurred

Questions?

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