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Albert Frei and Sons, Inc. Page 3 <br /> Hatchery Pit - M-2014-043 <br /> January 7, 2019 <br /> The installation of the clay liner and the french drain in Stage 2 will regulate the ground <br /> water levels close to historic levels up on gradient areas. Please review the Hatchery Pit <br /> Phase 2 Slope Liner design prepared by Deere & Ault for additional information. <br /> c. Update the trigger levels identified for mitigation. Given the already lowered <br /> groundwater levels in the Stage 2 area, the two foot trigger has already been hit. The <br /> trigger for mitigation measures needed as a result of groundwater drawdown will now <br /> be trigger by a complaint. There are several commercial, domestic and irrigation wells <br /> located outside of the 600 foot radius of the site but within about 800 feet of the <br /> operation that could potentially be impacted by dewatering. <br /> The table in the revised Ground Water Monitoring and Mitigation Plan show the baseline <br /> elevations we propose using from this time forward. There are 6 well within 800 feet of <br /> the permit area on the up gradient side of the mine. They are along the east side from <br /> near the northeast corner to about two-thirds of the way along the south side. Five are <br /> listed as residential, 1 commercial and one general purpose. Five of the 6 wells vary from <br /> 276 to 700 feet deep and will not be affected by surface dewatering. The last is a <br /> residential well located 833 feet east of the mine and in the middle of the paved parking <br /> lot on the Mile High Flea Market east of I-76. It was drilled in 1959 and there are no <br /> records of it being moved or used since the Flea Market was built in 1986. This well was <br /> most likely abandoned but not reported as such. <br /> Any wells located along the west and north sides will not be impacted by draw down or the <br /> shadowing once the liner is installed, because on the north another property owner filled <br /> the area immediately north of the Hatchery Pit. Along the west side is a developed Water <br /> Storage reservoir where the slurry wall liner parallels the west side of Bull Seep. Bull <br /> Seep acts as a recharge facility and has water in it year around. The shadowing along this <br /> side will be limited to just the area immediately adjacent to the Stage 1 slurry wall and Bull <br /> Seep. The ground water elevations in monitoring wells # 6 and #7 show no signs of <br /> shadowing at this time. <br /> Clay liner and French Drain: <br /> The top of the clay liner and the current design for the top of the slurry wall for Stage 2 is <br /> set at 5,072 feet. Based on the pre-mining water levels on the east side of the site being recorded <br /> at 5,083+/- feet, it does not appear the top elevation of the clay liner and the slurry wall will <br /> effectively block the groundwater flow to the site. Also, by placing a French drain at the top of the <br /> clay liner this could effectively dewater the groundwater levels to this elevation continually. <br /> Given these issues, please address the following: <br />