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• 0.0% Ponding <br />• Runoff Q: 2.19 inches <br />3. Existing Hydrology and Sediment Control (Map C-1) <br />3.1 Lincoln Gallery and Most of Washington WRL <br />Most affected area and undisturbed areas drained by the site infrastructure is routed into the <br />Washington Gallery. Designs for the inside ditch of the mine roads have been designed for the <br />maximum disturbance drainage basin during the mines life. Please see Mine Development <br />Hydrology and Sediment Control (Map C-2) for ditch design and calculations. <br />3.2 Remaining Washington WRL <br />Smaller sediment basins have been designed to capture runoff from areas which cannot be collected <br />by the Washington Gallery. Until the first bench of block walls has been built in the Washington <br />WRL, the existing ponds shown on Map C-1 will continue to be utilized. These ponds were designed <br />to handle a much larger area prior to routing most water into the Washington Gallery under AM -01 <br />of this permit. The calculations are shown below for the basins and ditches. <br />These 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 <br />at the mine. The sumps and ditches will be allowed to silt in after mining is completed, therefore, all <br />designs are considered temporary, thus the 10 year event is used in sizing, with the exception of the <br />emergency spillways, which are designed to pass the 100 year 6 hour event. For this reason, the <br />sumps, principal spillway pipe and an emergency spillway of 3 feet width and 1 feet depth with <br />2H:1V sideslopes. The emergency spillways will be lined with 6" size durable rock over a 12" <br />thickness and will be designed to pass the 100 year 6 hour event. The design specifics are shown <br />further on in this exhibit. <br />A metal or plastic pipe of 2-6" diameter with an accessible gate valve will be placed within 1 foot of <br />the low point of the sumps so that water can be discharged after it is settled and to allow the storage <br />volume to recover to handle subsequent storm events. When enough settling has occurred in the pond, <br />The Pride of America DRMS 112c <br />Exhibit G - 3 12/23/15 <br />