2013-07-03_REVISION - M1985112 (3)

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M- 1985 -112 — Loloff Construction, Inc. — Loloff Pit — Technical Revision Request No. 1 July 3, 2013 -3- 2. Full depth dewatering of the pit with an aquifer recharge of 1000 gpm and the following assumptions: • A constant dewatering pumping rate = 3,000 gpm • A constant recharge rate = 1000 gpm through recharge ditches /ponds placed around the perimeter of the pit • Dewatering depth = 37 ft • Radius of the pit = 600 ft • A hydraulic conductivity value of 1000 gpd /sq -ft was assumed for the soil types found on this site. The inflow to the pit through the mining slopes was assumed to be supplied by both the groundwater present in the aquifer and by the recharge water being added to the aquifer. The net effect is that the groundwater being supplied by the aquifer (removed from the aquifer by the dewatering activities) would be reduced by 1000 gpm or 33% of the total dewatering pumping rate. This factor was applied to the hydraulic conductivity value, which was reduced to 667 gpd /sq -ft for this condition, to compensate for a lesser overall amount of groundwater being removed from the aquifer. The result for condition 1 was the cone of depression /radius of influence extended beyond the mining limit/pit wall approximately 1,024 feet with a total dewatering depth at the pit of 37 feet. The result for condition 2 was the cone of depression /radius of influence extended beyond the mining limit/pit wall approximately 566 feet with a total dewatering depth at the pit of 37 feet. These results should be an accurate estimation of what the cone of depression /radius of influence will be at any time during the mining activities. The detailed calculations have been attached for your reference. Loloff Construction, Inc.'s dewatering pumping rate data has been also been included in the calculations. Currently the dewatering pumping is occurring in the southwest corner of the pit and then discharged into Mr. and Mrs. Monroe's wetland pond as shown on the attached Loloff Pit Site Map that includes the location of the dewatering point, discharge point, and locations of wells where Loloff Construction, Inc. will monitor the groundwater levels. As part of the mitigation plan for recharge Loloff Construction, Inc. is pumping into the Monroe Wetland Pond to recharge the aquifer to mitigate the effects of the dewatering of the pit. Loloff Construction proposes to install a recharge ditch along the west side of the pit to mitigate impacts if there are impacts from the dewatering to the other wells adjacent to the pit that are within 600 feet of the mining limit. Mr. Don Loloff is currently pursuing agreements with the existing well owners that are within 600 feet of the mining limit of the pit. Mr. Loloff is also pursuing agreements to use the existing wells from Mr. Brian Harrell, Mr. and Mrs. Larry Monroe, and Mr. Robert "Rocky" Francis to take groundwater level measurements to monitor the depth of the ground water adjacent to the existing pit. Loloff Construction, Inc. will note what the groundwater depths are in the Derr Pit monitoring wells (MW -7, MW -8, and MW- 1 as Mr. Derr is sharing this data), Mr. Harrell's existing well, Mr. and Mrs. Monroe's existing well, and Mr. Francis's existing well to monitor those levels throughout the course of the mining. Measurements will be taken once a month and recorded. Should the levels in the existing wells change by 2 -4 feet then Loloff Construction, Inc. will mitigate by recharging at locations along the pit to increase the levels of the groundwater so that the impact from dewatering is minimized. v 305 Denver Avenue — Suite D • Fort Lupton CO 80621 • Ph: 303 - 857 -6222 • Fax: 303 - 857 -6224