2016-07-14_PERMIT FILE - M2016010

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Jerry Schnabel, Bob Stabo July 11, 2016 Page 7 Potential Impacts to Surface Water Comment: A few of the public comments questioned whether the proposed mining would induce flash flooding or increase the likelihood offlash flooding in the areas adjacent to the mining. The CDRMS raised several questions requesting additional information regarding potential impacts to surface water associated with the proposed mining. The CDRMS has requested an explanation of potential impacts to Deadman's Creek as the mining extends below the elevation of the creek bed, additional information regarding potential surface water diversions and impoundments within the mining area, discussion regarding the maintenance of existing drainages, details regarding the seeps that will be.intercepted by the mining and an explanation of how mining will proceed if ground water is encountered. Response: During mining, benches created by the mining operations will be reclaimed with trees and grasses. This revegetation will minimize any runoff from the mined areas and maintain current runoff patterns. Accordingly,there should not be any significant runoff from the mine areas during mining. Berms will be installed at the quarry floor to facilitate the settling of sediment before any limited runoff from the mine floor enters either Little Turkey Creek or Deadman's Creek. For these reasons, increased runoff, heightened stream flow and more frequent flash flooding is unlikely. As mentioned in the February 18, 2016 summary, Deadman's Creek rarely flows based on field observations made by Transit Mix. Accordingly, the surface drainage is not in connection with the ground water system within the mine boundary. When the creek does flow, seepage from the creek will infiltrate the fractures that control the creek and recharge the ground water system. To the extent that flow into the North Pit extension is observed during any flow events during mining, the inflow will be pumped back to the creek to minimize any impact to the hydrologic balance of the system. Although the ground water in the Deadman's Creek drainage has not been specifically investigated as part of this effort,the exploratory drilling in the area did not identify any ground water near the creek and it is clear from visual observation that there is not a shallow aquifer system connected to the creek,providing for hydraulic separation. If there was a shallow ground water connection, there would be flow in the creek. Depending on the depth to the water table beneath the creek and the proposed mining areas that extend below the elevation of Deadman's Creek, the mining may not encounter any ground water and may only experience small amounts of inflow during runoff events as mentioned above. If shallow ground water is encountered during the excavation of the North Pit areas, Transit Mix would either terminate mining at the ground water table surface or install a drain system discharging back to Deadman's Creek to allow for mining below that depth. There are no existing surface water diversions or impoundments within the proposed mining area and Transit Mix does not propose any new surface water diversions or impoundment on the existing drainages. The only impoundments contemplated by Transit Mix will be in the floors of the mining areas to control runoff through the mined areas to allow for settling of any fine grained material.