2023-02-02_PERMIT FILE - M2022013 (6)

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Page 12 6.4.7 EXHIBIT G - Water Information a) 2Considerable efforts are made to control storm flows, including the use of grassed waterways. Some rilling will occur on cut slopes, but the sediment is inbound. A minor 6-inch furrow above cut slopes will create a 1-foot Swale that could minimize such rilling, especially valuable on reclaimed slopes above the final estimated water level of the basins. The stormwater management plan referenced in Exhibit I & J will address broader water management covering the material processing area and any piles of soil or inert fill constructed external to the excavations. b) Impacts to groundwater and area wells from groundwater discharge during mining was evaluated by AWES, LLC in their 27 July 2020 report, as included in this submittal. The report concludes: 'The results of analytical and numerical solutions indicate that the proposed mine dewatering activities will not adversely affect the regional groundwater hydrology. Based on the location of registered water wells, the saturated aquifer thickness west of the mine is sufficient to provided adequate well yields. The predicted drawdown associated with the mine dewatering represents the worst-case scenario and a substantial amount of time will be required before maximum drawdowns will occur.' 3Additional groundwater evaluation is documented in an August 30, 2022 letter report addressing initial adequacy items and an August 31,2022 revised Dewatering Evaluation from AWES, LLC, both provided as addenda to Exhibit G. The estimated time to reach steady state drawdown due to the mining activity is summarized as follows: Assuming a saturated thickness of 35 feet, a transmissivity of 4375 ft2/day, an effective porosity of 0.27 and a radius of influence of 4000 feet the time to reach steady state is calculated to be 273 days. However dewatering will be progressive during mining and an estimated 1000 days will be required to achieve this radius of influence during early dewatering operations.' c) 4POST RECLAMATION IMPACTS have been minimized: i. The AWES report of 27 July 2020 evidences that there will be no measurable impacts of either shadowing or mounding of the resulting lined basin. The operation therefore includes lining of the basin during reclamation of the resulting basin. Satisfaction of Colorado State Standards as to the integrity and functionality of the resulting lined basin 2 Adequacy Item 43:Prevention of significant runoff 3 Supplemental Groundwater Adequacy Item 13 4 Adequacy Item 28: Various edits in this section clarifying post mining land use as lined reservoir VARRA COMPANIES, INC. TWO RIVERS SAND GRAVEL AND RESERVOIR PROJECT MARCH 2O22 A REGULAR IMPACT[1121 CONSTRUCTION PERMIT APPLICATION-COLORADO DIVISION OF RECLAMATION MINING&SAFETY OFFICE OF MINED LAND RECLAMATION