Laserfiche WebLink
B. DRMS Response: The Division's geotechnical stability staff is currently <br /> reviewing the Earth Engineering Consultants analysis. If any additional <br /> information or questions arise we will forward them to you as soon as possible <br /> C. TCVMD 2"d Response: We received an email dated June 22, 2018 from <br /> Jared Ebert stating that the Division has completed the review of the <br /> geotechnical engineering analysis and found the analysis adequate to address <br /> the original adequacy review issue <br /> Additional comments <br /> I Per the DWR comment letter, the proposed reservoir expansion operation <br /> will not qualify the reservoir for storage if the expansion occurs below the <br /> groundwater level. Therefore in order for the reservoir to be approved for <br /> water storage the operator must line the reservoir and perform a liner leak <br /> test in accordance with the August 1999 State Engineer Guidelines for <br /> Lining Criteria for Gravel Pit (1999 SEO Guidelines) once mining is <br /> complete and the site is at final grade. Does TCVMD anticipate needing <br /> to line the reservoir to prevent the inflow of groundwater? if so, please <br /> provide a plan for lining the reservoir and provide a cost estimate for the <br /> installation of the liner. <br /> a. TCVMD Response: TCVMD does not anticipate needing to line the <br /> reservoir to prevent the inflow of groundwater. We have attached a <br /> subsurface exploration report for Signal 1 Reservoir modifications/ <br /> improvements prepared by Earth Engineering Consultants. The <br /> purposed of this study was to investigate if material located in the <br /> reservoir area was suitable for use in the core of the high hazard <br /> Signal No. 1 Dam Rehabilitation project. Please see the bore logs <br /> included in this report which indicate that the subsurface materials <br /> consist mostly of lean clay with sand, clayey sand, sandy fat clay, <br /> siltstone/Claystone bedrock. It was determined that these materials <br /> are suitable for use in the impermeable core for the high hazard <br /> Signal No. 1 dam rehab project. Due to the lack of pervious materials <br /> (sands and gravels), TCVMD does anticipate need to line the bottom <br /> once excavation is completed. The material being excavated in <br /> considered liner grade material. It should also be noted that water <br /> was only encountered in 5 of 17 bore holes at depths ranging from 25 <br /> to 38 feet below existing site grade. It is our opinion that this water is <br /> likely zones of perched and or trapped water present in the relatively <br /> impervious bedrock and or fractures/fissures within the bedrock <br /> formations as noted in the EEC report. TCVMD is anticipating that the <br /> vast majority of any water that may be encountered during excavation <br /> will have originated from the very slow seep of water from Signal 2 <br /> Reservoir located immediately east of the permit area. The Signal 2 <br /> Reservoir is the only regular source of wafer located within 1000 feet <br /> of the permit area. TCVMD is aware and will comply with the State <br /> Engineer Guidelines for Lining Criteria for Gravel Pits. If water is <br /> encountered during excavation, the water will be metered and <br /> measured to compare the amount of water observed to the August <br /> 1999 State Engineer Guidelines for Lining Criteria for Gravel Pits. <br />