REV93826 - Laserfiche WebLink

Home Browse Search

Given the existence of water in the present pit and that ongoing pit inflows are anticipated • as pits are advanced to the west, the new sedimentation pond design will facilitate temporary retention and treatment to accommodate periodic pumpage of pit water accumulations on an as-needed basis. Given good water quality, the potential also exists for direct discharge of pit pumpage to the receiving drainage with monitoring at the designated discharge point. The new pond is designed with a riser discharge structure with discharge orifice to provide adequate detention time for settling of suspended solids while minimizing overall storage volume. The riser is sized to safely pass the peak discharge from a 25-year, 24-hour storm event as overflow through the top of the riser. SCC has applied for a water right for the proposed sedimentation pond with the intent of retaining the pond for wildlife use following completion of operations. Existing gravel extraction operations and proposed expansion activities require no beneficial use of water except for minor amounts which may be required for dust suppression in active working areas and on haul roads. Potable and sanitary water requirements are provided by a well located nearby. With very limited beneficial use • requirements, accumulations of ground water or surface runoff in active working areas will be pumped out on an as-needed basis to maintain effective pit operating conditions and minimize any associated safety hazards. Pit pumpage will either be routed through the existing or proposed sedimentation ponds or, if water quality is consistent with applicable effluent discharge limitations, discharged directly to receiving drainages. In order to minimize potential hydrologic impacts, pit pumpage will be routed to the sedimentation pond or receiving drainage corresponding to pit drainage source where operationally feasible. The hydrologic balance of the Permit Area and adjacent lands will be protected during gravel extraction operations by collecting disturbed area drainage and routing it through sedimentation ponds and by pumping pit water accumulations to the corresponding drainage where operationally feasible. Timely backfilling, regrading, drainage reestablishment, soil replacement, and revegetation will effectively control runoff, soil erosion, and resultant sediment discharge to the receiving drainages. It is anticipated that sedimentation ponds will remain in place for wildlife use. The postmining topography has been designed to reestablish drainage patterns similar to the premining configuration. As a result of practical limitations imposed by gravel removal G-11a Revised May 1998