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Drainage Basin Run-off Calculations and Sump Designs <br />All ditch and sump designs are based on the 10 year 6 hour storm event of 1.6 inches, as determined <br />from the NOAA Atlas 2 Volume III Isopluvial Map.The granular nature of the sump materials will <br />allow infiltration of the water in the ground within 48 hours. This is based on existing site experience at <br />the mine. <br />For this reason, the sumps have no principal spillway but have an emergency spillway of 3 feet width <br />and 1 feet depth with 2H:1 V sideslopes. The emergency spillways will be lined with 6" size durable <br />rock. <br />Any berms needed for the sumps will be no greater than 2 feet high and will be constructed of earth fill <br />that will prevent water seepage when compacted to 90% maximum dry density, which will be achieved <br />with these berms. <br />The NPDES discharge permit is being modified to contain the discharge points for all 5 basins as well as <br />the water pumping from the South Portal, as shown on Map C-2. <br />All watershed basin areas have been calculated in CAD and are shown on Map C-2. <br />All of the following calculations were performed in the hydrology module in Carlson engineering <br />software working in Autocad. <br />Yule Quarry April 10 19