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Wastewater Treatment System FALL CREEK Engineering Report ENGINEERING,INC. K,. = K200.1)(7-20) where KZo was assumed to be 1.104 d-1, and the temperature was assumed to be 15°C (59°F). KT was calculated at 0.69 d"1. %W %W If the peak wetland influent BOD is 4000 mg/L (20% of 5000 mg/L BOD removed in the septic tank), t is assumed to be 10 days, and KT is 0.69 d"1. Therefore the effluent BOD concentration is: %W C, = C,e_Kr, =4000e-(0.69'10) =4mg/L . ,` This indicates that a 10-day detention time will theoretically produce a BOD reduction of over 99%. 3.6. Stormwater Storage Capacity The wetland has been designed with a 1-foot berm around the entire perimeter. The inlet will be gravity flow from the septic tank. And the effluent will gravity flow to a pump basin. The %W wetland will also have an overflow on the outlet side to an existing stormwater detention area. ,%W The wetland will have a freeboard volume of approximately 48,000 gallons and the invert of the overflow will be set 8.0" above the top of the wetland. The existing stormwater detention area will be reshaped to provide an additional 71,000 gallons of storage. The system will provide a total stormwater storage volume of 119,000 gallons. To determine whether this storage volume would be adequate to contain rainfall and stormwater runoff from the 100-year, 24-hour storm, a water balance was performed. According to NOAA's Precipitation-Frequency Atlas of California,the depth of water in the 100-Yr 24-hr storm is 3.8 inches. Using this number the stormwater runoff volume at the winery facility, was calculated as follows. The calculation assumes that the wetland is full but there is no water in the freeboard volume (water is at the top of the gravel). V, = A*d*C, = 52,000sf*3.8in*\Izr„)*0.88 = 14,490cf = 108,400gallons _ where VS = Volume of stormwater runoff, cf or gallons A = Area, sf d= rainfall depth, ft _ Ci= runoff coefficient This calculation shows that the 100-year, 24-hour storm (108,400 gallons) would be contained by the stormwater facilities (119,000 gallons). 3.7. Land Application _ The design and analysis of the land disposal system is presented in Section 5. ,IESSIE's GROVE WINERY MAY 2002 15