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2.3.2 South Area Drainage <br /> The South Area drains towards the north, into a draw that flows to Ralston Reservoir. To prevent <br /> the discharge of sediment laden waters, a sediment pond will be installed on the north side of the <br /> waste embankment area. This pond will contain the l0-YR storm event runoff. Calculations of <br /> said run off are shown below. Map C-2 shows the pond and waste embankment locations. <br /> Runoff Curve Number and Runoff Wed Sep 05 15:11:21 2018 <br /> Project: Ralston Quarry <br /> Project: South Pond By: B Langenfeld Date: 09/05/18 <br /> Location: Ralston Quarry Checked: Date: <br /> Present <br /> 1. Runoff Curve Number(CN) <br /> Cover description CN Soil Group Area(Acre) <br /> Mined Land, Disturbed (Poor) 87 C 4.899 <br /> CN (weighted): 87.0 <br /> Total Area: 4.899 Acre <br /> 2. Runoff <br /> Return Period: 10 YEAR <br /> Rainfall, P: 2.96 in <br /> Runoff,Q: 1.7042 in <br /> Runoff Volume: 0.68 Acre-Ft <br /> The pond has been designed to handle the 10-YR event runoff. Map C-4 shows a stage-storage <br /> curve for the pond. The pond will be cleaned of sediment following any storm event. The <br /> principal and emergency spillway both discharge into the same draw. An NPDES discharge point <br /> will be permitted at the point of the draw just south of the Ralston Reservoir road, and this point <br /> will be monitored as part of a CDPHE stormwater discharge permit. <br /> Ralston Quarry (:M U. k*i ma Anociaws,PLIA' <br /> January 2019 G-3 <br />