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KLEINFELDER <br /> Nitrate Loading Due to Two Residences <br /> N, = Average calculated nitrate-nitrogen in groundwater resulting from domestic sources <br /> and precipitation—mg/l, as N. <br /> A = Number of dwelling units per acre on septic tanks (unit/acre) = 0.65 (Based on the <br /> potential for 2 residences divided by 3.1 acres. Current laws allow for two <br /> residences on each parcel in San Joaquin County). <br /> W = Annual wastewater loading per dwelling unit per acre (inches) 2.0 inches (Per year <br /> per dwelling unit assuming a flow of 150 gal/day/dwelling unit.) <br /> 6. Nw = Nitrate concentration of nitrified leach-field effluent (mg/1) = 35 mg/I ((Hantzsche <br /> and Finnemore (1992) Based on residential uses.) <br /> L D = Percent dentrification of leachfield effluent= 0.1 percent (0.1 to 0.35 percent typical <br /> per Hantzsche and Finnemore (1992)). 0.1 selected given the sand soil and the <br /> depth to groundwater. <br /> R = Annual deep percolation of precipitation (inches) = 9.0 inches (representing 75 <br /> i percent of the average annual rainfall of approximately 12 inches. The remaining 25 <br /> percent of rainfall is assumed to drain off-site into natural or manmade drainages or <br /> be lost to evapotranspiration.) <br /> Nb = Background nitrate nitrogen concentration of rainfall recharge at the water table = <br /> 0.5 mg/1 (per Technical Memorandum, Hydrologic and Soil Investigation for the <br /> r, Chico Urban Area,page 6, Dames and Moore, April 1996) <br /> Our calculation is as follows: <br /> NC = 0.65(2)(35)(1 —0.1) + 0.5(9.0) = 41.0 + 4.5 = 4.4 mg/1 as N <br /> 0.65(2) + 9.0 1.3 + 9.0 <br /> Total Nitrate Loading <br /> Nc(commercial) +Nc(residential) = Nc(total) <br /> L 4.7 + 4.4 = 9.1 mg/I as N <br /> L <br /> L <br /> L52251.GOI/ST05RI92 February 17,2005 <br /> ©2005 Kleinfelder,Inc. Page 6 of 8 <br /> L <br />