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A CDPHE discharge permit is in place for the operation. <br /> 1 .1 . Sump Capacity <br /> The runoff from a 100 year 24-hour storm event is calculated in Table G-1. It is not anticipated <br /> that any stormwater will escape the site as the pit has more than enough capacity to contain the <br /> entire storm event. <br /> Table G-1 —Runoff Calculations <br /> Base Products 2 <br /> Exhibit G Mining Conditions <br /> Hydrograph Type = SCS Peak Discharge (cfs) = 67.50 <br /> Storm Frequency(yrs) = 100 Time Interval (min) = 9 <br /> Drainage Area(ac) = 80.44 Curve Number(CN) = 85 <br /> Basin Slope(%) = 3.29% Hydraulic Length (ft) = 2858.3 <br /> Tc method = TR55 Time of conc.(min) = 16.30 <br /> Total Precip. (in) = 7.95 Storm Distribution = Type II <br /> Storm Duration (hrs) = 24.0 IShape Factor = 484 <br /> Hydrograph Volume=1,687,654(cuft)=38.74(acft) <br /> The area of the pit that drains to the west sump is 52.0 acres. With a two-foot stormwater berm, <br /> there is a minimum of 103.9 acre-ft of storage. This more than sufficient to contain the entire <br /> 38.7 acre-ft of runoff that drains to this area. <br /> Base Products Gravel Pit 2 <br /> April 2022 G-2 Lewicki&Associates <br />