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Sump Sizing Calculations <br />Western Gravel E P Waste Disposal Facility <br />NWCC INC. <br />JANUARY, 2011 <br />Objective: Determine size of sump required to contain 2 year 24 hour storm <br />event. One leachate sump will be constructed for each Cell. <br />The sump and leachate and removal appurtenances will be similar <br />for each cell. <br />Assumptions: <br />1) From NOAA Precipitation- Frequency Atlas Volume III <br />2 yr 24 hour Storm Event is 1.0 inches. <br />2) Effective porosity of leachate gravel in sump is 32 %. <br />3) Newly completed Cell Footprint is approximately 4 acres. <br />4) A portion of the rainfall is stored in operations layer and leachate <br />gravel layer outside of sump area. <br />Calculations: <br />Volume of water to be collected by Cell if totally open is: <br />1.0 inch x 1 foot x 4 acres x 43,560 ft2 = 14,520 ft3 <br />12 inch Acre <br />Volume of water to be absorbed /stored by Operations Layer (10 %) is: <br />(0.10)14,520 ft3 =1,452 ft3 <br />Volume of water to be held in 3 inches of 12 -inch thick leachate gravels <br />outside of sump is: <br />3" x 12t x 91,000 ft3 x 0.32 = 7,280 ft3 <br />Volume of water required to be held by sump is: <br />14520 ft3 - 1,452 ft3 - 7280 ft3 = 5,788 ft3 <br />Volume of Sump required to hold 5,788 ft3 of water is: <br />5,788 ft3 = 18,088 ft3 <br />0.32 <br />Volume of Designed triangular sump area (100x200x2.5) <br />with bottom slope of 2 -3% is: = 19,604 ft3 <br />Conclusions: Designed sump as shown above is acceptable. <br />References: <br />1) National Oceanic and Atmospheric Administration Atlas 2. "Precipitation - <br />Frequency Atlas of Western United States, Volume III - Colorado ". <br />F \Jobs \10 -8718 Western Gravel E &P Disposal Facility\Engineenng\Design Phase I \Design Calculations \Sump Sizing Calculations <br />