2019-01-23_REVISION - M2014043 - Laserfiche WebLink

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Albert Frei & Sons, Inc. Page 2 Hatchery Pit Permit # M-2014-043 Revised 1/16/19 The location of the Bull Seep and Thornton' s slurry wall will limit the amount of ground water shadowing along the west side of the mine. The Bill Seep will recharge the groundwater and limit the mounding behind the slurry wall on the Thornton site will keep the groundwater elevations constant on this site. The backfilling along the entire north side may have already limited water flow thru this area and is forcing the water to back up on this site. That may be why there is a constant flow of water thru the lateral drain that runs along the north side and along the base of the hill . This may also explain why the water elevation of the old gravel mine lake appears to be higher the it was prior to that area being filled. On the other hand if it has restricted flow thru that site it has not has a significant impact to the east . Most of the existing lateral ditches and small ponds will be removed as mining progresses. They now serve to direct the seepage water and surface waters around the property and back to the western drainage. The existing ditches will be rerouted to more direct routes and new ones will be installed around the mined areas to preserve the historic flow of the water. On the north they will be directed into the existing lake so the water returns to the system. On the south a lateral ditch was built along the south side of the slurry wall so water can be diverted back to the Bull Seep drainage. This ditch also acts as a surface drain for groundwater that may backup along the slurry wall in that area and will carry the flow from the French drain to Bull Seep. Groundwater Monitoring Data Analysis As the data is collected, it will be recorded in a spread sheet and graphed to establish the baseline data that can be used to determine what if any impacts the slurry wall and compacted liner are having on the groundwater table. The data collected to date has allowed us to determine what the new trigger point elevations are. These elevations determine what actions are needed. Data collection will continue on a monthly basis until 13 consecutive samples have been collected and then go to a quarterly basis until 2 years after the liners are complete. Two years after the clay liner has been installed the Operator will evaluate the data and if the groundwater regime has sufficiently stabilized and will obtain DBMS approval prior to reducing the water monitoring frequency to annually. From then on till reclamation is complete, the monitoring will be done once a year. The data collected in the first 3 samples were used to determine the elevations of the compacted liner and French drain elevation in Stage 2 as discussed above. Future data will be used to determine if a trigger point has been reached and what actions will be needed. Baselines and Trigger Points The baselines for each well have been determined by taking the high and low elevations of each well from the data collected in the first 7 samples. The proposed trigger points have been determined to be elevations that are greater than two (2) foot above the highest elevations and/or less than one (1) foot above bedrock elevation in the monitoring Wells 1, 2, & 3 . Based on the data collected it appears that mounding may not be a problem since there is none apparent from the filling done on the adjoining property. In addition, the natural groundwater, pre dewatering, elevations in Stage 2 averaged 5079 . 8 or approximately 30 feet below the surface .