2023-05-25_PERMIT FILE - M2022048 (9)

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ENVIRONMENT, INC. PAGE 12 L.G. EVERIST, INC. -WEST FARM RESERVOIR ADEQUACY RESPONSE 01 MAY 23, 2023 Any letters from other commenting agencies/entities received by the Division for this permit to date are available for review through the imaged document data link provided below, or through the DRMS website. http✓/www.colorado.gov/pacific/drms/data-search OFFICE OF THE STATE ENGINEER L.G. Everist, Inc. understands the requirement for obtaining a well permit and preparing a Substitute Water Supply Plan for this mine. This will be done prior to exposing ground water. A copy of the permit and SWSP will be provided to the Division for the File. The SWSP will remain in effect until the proposed reservoir liners are approved and all lagged depletions have been met. L.G. Everist, Inc. will follow all plugging and abandonment requirements for any wells removed during mining. An abandonment report will be filed for each well as needed. L.G. Everist, Inc. understands the issue with groundwater mounding, shadowing and return flows associated with liners around reservoirs. The attached groundwater impact report addresses how the company plans to mitigate these concerns by installing a french drain or ground water trench along the up gradient (south) side to regulate the ground water elevation to historic maximums and divert the water back to the river system. In addition, the 4 reservoirs are not linked as one big liner but rather have a 200+ foot wide east to west corridor and a north to south corridor that varies from 85 to 245 feet wide where water that backs up along the west and south sides will return to the river across the mine site. There are no adjoining reservoirs and the site is flanked on the east and north side by the South Platte River. The river acts as a water barrier so any adjoining properties will not be impacted by draw down (shadowing). We believe the temporary impacts that may slow the groundwater flow around the liners will have little impact on the system and will be resolved once the ground water levels stabilize. L.G. Everist, Inc. will comply with the requirement to release any out of priority stormwater that collects in the mine within 72 hours or provided for the evaporative loss in the SW5P if not released. Dewatering will be taking place during mining, so any stormwater will be discharged under the COPS Permit to be obtained from Colorado Department of Health and Environment - Water Quality Control Division. COLORADO PARKS AND WILDLIFE L.G. Everist, Inc. wishes to thank Mr. Brandon Marette for taking time to review the permit and provided the information in his 12/28/2022 comment e-mail.