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• -4- east perimeter ditch (see Area III below), a ditch will be constructed to conduct overflow in case of a greater-than 10- year 24-hour event to the lower portion of the east peri- meter ditch and away from the outslope of the main bench. The fines storage stockpile bench will also be sloped inward to form a retention area for runoff from the lower quarry and to prevent runoff from reaching the outslope of the bench. This area will have dimensions of approximately 170 feet by 65 feet, and at a 10% gradient will have a volume of approximately 0.91 acre-feet. This bench will also have an overflow to conduct excess runoff to the east perimeter ditch system (see map). It should be recognized that both benches are active, and the exact configuration and area of the retention areas will change over time. The benches will be maintained to insure positive drainage as described above. AREA III Like Area II, Area III consists of a short identifiable ephemeral stream channel, with a much larger poorly defined area above it draining into it via overland flow and/or sheet wash. The overall drainage is approximately 3,635 feet in length and contains about 64 acres. It has an average gradient of approximately 43%. Topographic, geologic and vegetation regimes are similar to Area I as described above. Calculations using the OSM Storm program indicate a peak discharge for Area III of 4.6 cfs, with a total 10-year 24- hour storm drainage volume of 0.90 acre feet. Further calculations indicate that a triangular ditch constructed for a flow depth of 0.55 feet, riprapped in sections exceeding 11% with material sized according to the gradient of the section, will be adequate to divert this discharge from the quarry. MCR proposes to intercept this drainage at the east boundary of the permit area (map C-la) with a triangular ditch with a minimum depth of 3 feet. The west side slope will be constructed at a nominal 3:1 ratio. The east side will consist of the existing cut slope, which varies upward from less than 2:1. The proposed configuration is given as cross- section B-B' on Figure 2.