2020-02-05_REVISION - M1998013 (27)

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Page 4 Mr.Mark Johnson January 31,2020 Mitigation Plan Dewatering during mining of Cell 1 may affect four wells as addressed above. After reclamation,the wells should perform in a manner that approximately matches premining uses. However, if the miner receives a complaint,the following mitigation plan will be implemented. The site monitoring wells will be measured monthly to identify potential changes in alluvial groundwater flow or elevation associated with mining and reclamation activities. Baseline data collected from the monitoring program will provide a range of relative water levels associated with premining groundwater conditions. Experience at other mines in similar geologic settings has found that groundwater levels tend to fluctuate being highest in the summer irrigation season and lowest in the winter and early spring. If,during mining or reclamation,the relative seasonal groundwater elevation at any monitoring wells differs from baseline conditions by more than 2 feet, and the condition was not observed during baseline monitoring,or if the miner receives a complaint from any well owner within 600 feet of the site boundary, then the miner will evaluate the cause and take action within 30 days and notify the DRMS. After the DRMS has been notified,the miner will review the data and available information and submit a report to the DRMS within 30 days. The evaluation will include discussions with the well owner who has contacted the miner regarding a concern and review of baseline data from the well and vicinity to evaluate whether changes may be due to seasonal variations,climate, mining,slurry wall lining or other factors. The report will identify the extent of potential or actual impacts associated with the changes. If the extent of groundwater changes due to mining or reclamation activities is determined to be a significant contributing factor that has or may create adverse impacts,the mining associated impacts will be addressed to the satisfaction of the DRMS. Miner will begin implementing one or more mitigation measures if mining and reclamation activity is determined to be a significant factor to groundwater changes requiring mitigation. Mitigation measures may include, but are not limited to: Placing water in a recharge pond to raise groundwater levels around the well. Constructing a local clay liner at the edge of the mine Cell(i.e. between the dewatering point and the well) in order to raise water levels on the well side of the liner and mitigate dewatering effects. Cleaning the well to improve efficiency. Providing an alternative source of water or purchasing additional water to support historic well use in terms of water quantity and quality. If needed,water quality parameters will be checked in affected wells to ensure alternative sources support historic use. Modifying a well to operate under lower groundwater conditions. This could include deepening the well or lowering pumps. All work would be done at the miner's expense with the exception of replacing equipment that was non-functional prior to mining.