2007-01-08_REVISION - M1983102 - Laserfiche WebLink

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ENVIRONMENTS INC. THOMPSON PROPERTIES ~ THOMPSON RESOURCE PIT PERMIT ~}` M-i 983-7 02 ADE4UACY RESPONSE JANUARY 8, 2007 PAGE 4 Groundwater Monitoring Plan. Thompson properties proposed to monitor the ground water table for this mining operations by using their well located near the house in the expansion area, See map Exhibit C. In the water reports submitted, the well is identified as the Hahn well but it is owned by Thompson Properties. This well is located in a central portion of the mined area and would be the first well to be impacted by mining. Our studies show that the floor of the mine will be approximately 20 feet above the groundwater table at this point. During the first few years mining will progress toward this well and if there are any impacts due to mining they will be noted in it first before the impacts could leave the mine site. On a quarterly basis the operator will record the static ground- water elevation in this well. Approximately 12 to 18 months of gravel is left in the existing mine so the only activity that will take place in the new area will be to start stripping the topsoil on the west side and building topsoil berms on the north and east permit lines. During this time period, once a quarter for 5 consecutive quarters, the groundwater level in the Thompson well will be logged and recorded to establish the baseline groundwater level. This report will be submitted to the Division once completed. As mining progresses into the new area monitoring will continue on this well and the results will be recorded. This information can be used to confirm that the mine floor is at least 2 feet above the groundwater table. All of the groundwater information we have shows that the depth to the water table will be much greater than 2 feet. This based on the operators commitment to leaving a gentle east to west sloping floor approximately 40 feet below the existing ground surface. That is 40 feet below the existing ground surface or 20 plus feet above the groundwater table. Mitigation Plan It is not Thompson's intent to expose groundwater at this mine. As noted in Exhibit G and the Report prepared by ERO Resources, the groundwater depth is estimated to be nearly 20 feet below the proposed floor of the mine. The monitoring plan above will allow us to track the natural fluctuations in the groundwater table. Our best guess in that there will be seasonal changes but none so great as to come within 2 feet of the mine floor. We expect to have some surface runoff associated with storm events and spring time seepage as the snow pack melts and the gravel travels thru the gravel strata entering the mine. This is not part of the groundwater table so it will be channeled around the mine area and allowed to enter a natural drainage off the mine site to protect its historic flow pattern and not impound it. In the remote chance that mining encounters the ground water table, mining would stop and the exposed water would be covered with 2 feet of cover. The operator would then evaluate the source of the water and the groundwater table elevation and change the mine floor elevation, if needed, so it is at least 2 feet above the groundwater table.