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Design Volume Calculations Sed Pond Fetcher Vale Pit Area (acres) 17.57 Design Event 100 yr. storm Design Precipitation 3.4 Calculated S 2.34567901235 Average CN 81 Description Exposed Porous Gravel and Part Undisturbed grass Calculated Runoff Volume (Q) 1.62795311299 Calculated Runoff Volume (acre-ft.) 2.38359468294 Ponding Percentage 5 Actual Runoff Volume (acre/ft.) 2.26 The pond will be designed to contain the 100 year runoff of 2.26 acre-feet and 0.2 ac-ft for sediment buildup. This totals 2.46 acre-feet. The pond will be only incised to a depth of 0.5 feet and the dam will be approximately 3.5 feet high and will have 2.OH:1V sideslopes. The pond area as shown on the Mine Plan Map is 0.8 acres, therefore the average depth needed is approximately 3.0 feet. The dam will provide 3.5 feet height and the 0.5 feet below ground level will be used to store sediment that enters the pond. Since the sump will only excavate a depth of 0.5 feet, there is no chance that groundwater will be exposed. The pond will detain the water for 24 hours but will allow it to seep into the ground so that the water is returned to the natural drainage. In order that the seepage occurs with detention, the material used to construct the embankment will meet the following size specifications: <5% minus 200 mesh, <20% minus 25 mesh, <50% minus'/<", <100% minus 4 inches. As shown on Exhibit C-2, a collection ditch along the dirt road on the southwest part of the permit area will be used to direct water to the sump. This ditch will be 1.5 feet deep and 2:1 sideslopes. Once mining extends to this southwest corner, a lower collection ditch will be installed to ensure that all disturbed water will flow to the sediment sump. This ditch will have the same dimensions as the first ditch. In order to provide vehicle access to the site and direct all flows from the east into the sump, a mild berm of 1.5 feet height and 6H:1V sideslopes will be used. See Exhibit C- 2.