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• TABLE H-1 <br />SUMMARY OF PEAK FLOW DETERMINATION <br />EAST ROATCAP CREEK <br />COLORADO WESTMORELAND, INC. <br />RECURRENCE METHOD 1 METHOD 2 <br />INTERVAL USGS, 1985 TM-1, 1976 <br />SW-6A PORTAL SW-6A PORTAL <br />BENCH BENCH <br />Q2 27.7 27.9 23.3 23.5 <br />QS 44.3 44.6 36.4 36.7 <br />Q10 56.0 56.4 * 47.9 98.3 <br />Q25 71.3 71.8 66.0 66.6 <br />Q50 82.7 83.3 79.8 80.4 <br />• * <br />Q100 94.3 95.0 94.1 94.8 <br />Q500 122.0 122.9* 134.1 135.2 <br />* Used for design <br />NOTE: Mountain Region used in both Methods. Parameters for <br />calculation included Area, Mean annual precipitation and Mean <br />basin slope. Area for SW-6A is 3.71 mi Area for the portal <br />bench is 3.75 mil. Mean annual precipitation was estimated as 22 <br />in. Mean basin slope was 128 for both watersheds. <br />• <br />