2019-09-19_REVISION - M2002120 (17)

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Page 2 Mr. Eric Scott September 18, 2019 Please verify Exhibit F-Reclamation Plan Map to depict the proposed final shoreline configurations and setbacks for the reservoirs in Cells 2 and 3 with respect to the existing utilities (electric,gas, etc). The maps have been updated to depict the most recent configurations. Should a change in configuration occur a technical revision will be submitted to the DRMS. Please verify the proposed locations of all spillway inledoutlet structures on the Exhibit Reclamation Plan Map. Some justification should be pro vided as to why only one inlet/outlet structure is believed to be sufficient for Cell 5. Given the configuration of the cell and proximity to the river DRMS feels a reinforced outlet structure located near the southeast corner of the cell may also be required to prevent stream capture during a flood event. A spillway design memo has been attached discussing the spillways in more detail. Please provide additional rationale for the statement made in the adequacy response for Exhibit G that ".. the mining and reclamation are not expected to directly affect the surface or groundwater systems." Factors affecting surrounding groundwater due to slurry lining a mine are from shadow(decrease in water surface elevation)and mounding (increase in water surface elevation). The Bernhard Gravel Mine has been in operation since approximately 2004 and slurry lining of the cells began shortly thereafter. To date all mining takes place within lined cells and the northwest area has been a silt pond and fresh water pond since commencing mining around 200412005. As a result the dewatering effects and drawdown due to mine activity mine are very small if not insignificant since the slurry walls are working properly. Shadow and Mounding: The mining and slurry lining of the site started approximately 15 years ago. Cell 2 and 3 have are approved liners and Cells 4 and 5 are conditionally approved liners. There are two houses approximately 260 feet to the west of Cell 2. The average groundwater depth across the site is 8.5 feet below ground surface and the groundwater depth nearest the house was just reported as 13.5 feet below ground. The Cell 2 slurry wall was the first slurry wall to be installed and was approved in 2009. The homes to the west were constructed prior to the installation of the slurry wall. To date there have been no complaints or discussions with the miner, DRMS or the Division of Water Resources concerning a mounding effect west of Cell 2.This could be due to the depth to groundwater,the proximity of the mine to the river and the river acting as a natural groundwater relief but as stated earlier there have been no reports of mounding on the upstream or west side of the mine that have negatively affected adjacent structures. The downstream or shadow side of the mine does not contain many groundwater wells, irrigation ponds or areas that rely on groundwater. The area to the east is mainly agricultural (which is owned by the mining area land holder Bernhardt)with some industrial development to the southeast. The river might act as a groundwater control as it bisects the site and is within close proximity to the mining area. To date there have been no complaints or discussions with the miner, DRMS or Division of Water Resources concerning a shadow effect east of Cell 2. The miner continues to monitor groundwater wells onsite. Data is attached showing the location of the groundwater monitoring wells along with recent groundwater depths. Exhibit L -Reclamation Cost Estimate will need to include detailed information for the line item(s) for spillway construction. Reclamation costs provided will be reviewed by DRMS when all