REV102374 - Laserfiche WebLink

Home Browse Search

extent of impacts to ground water for all lined water features. All wells that occur within the upgradient and/or downgradient zone of influence should be inventoried and assessed as discussed above. These wells should also be located on a revised map. (The operator may also delineate on a revised map the location of all wells on or within 600 feet of the disturbed land that are not expected to be affected by dewatering or slurry wall construction). 11. The applicant proposes, via the January 28, 1997 RMC letter to Scott Gudahl, several methods for mitigation of water table impacts relating to mine dewatering and mine reclamation (slurry wall construction). For example, the RMC letter states "Where dewatering impacts wells, wetlands or surface features, the impacts can be mitigated by strategically applying dewatering dischazge water or other available water back to the aquifer (recharge) via unlined ditches or infiltration galleries." And, later ... "The shadow effect will, however, impact wells on the south side of Hygiene Road between Foothills Reservoir and 61st Street. However, impacts to these wells can be mitigated by engineering an infiltration structure on the south side of the pond and applying water from the pond or other sources." The applicant should explicitly state which ground water mitigation methods will be employed for the vazious wells identified in the detailed hydrogeologic evaluation and where and how they will be employed. The applicant should also provide on a revised map the location of all ground water mitigation structures or methods to be employed. Aaaendix D - Drawines l2. The applicant has provided engineering designs for a low water crossing of St. Vrain Creek. The Division has several questions regazding the proposed low water crossing(s). How many crossings will the operator construct? Where will the crossing(s) be located? What time of year will the operator install the crossing(s)? At what phase in the mining & reclamation plan will the crossing(s) be installed? Will the crossing(s) be temporary or permanent structures? Has the operator secured a 404 permit or nationwide permit from the US Army Corps of Engineers for installation of the crossing(s)? What will be the height of the crossing(s) above the stream bed? Will the crossing(s) and wing walls be submerged during peak flows expected throughout the life of the operation? Will the expected peak flows be able to pass over or azound the crossing structure(s) with minimal or no impact to the surrounding stream channel? The applicant should revise one of the maps provided to show the location of the proposed structure(s). Please respond.