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f <br /> 1H KLEINFELDER <br /> f <br /> N � <br /> information provided in a report dated March 19, 1997 prepared by the Questa Engineering <br /> Corporation and authored by Mr. Hantzsche for a development in the Stockton area. <br /> N, =AWNW 1-D + R <br /> t AW+R <br />€ � Where: <br /> Nc Average calculated nitrate-nitrogen in groundwater resulting from domestic sources <br /> and precipitation—mg/l, as N. <br /> A — Number of dwelling = <br /> units per acre on septic tanks (unit/acre) 1.54 {The previously <br /> described total daily.flt of 250 gal/clava divided by 150 gal/dwelling unit, divided <br /> by 1.08 acres.) <br /> i <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 /> f <br /> NW = Nitrate concentration of nitrified leachfield effluent (mg/l) =70 mg/l (Hantzsche and <br /> Finnemore (1992)). Percent denitrification selected based on past discussions with <br /> Mr. Mike Huggins of SJCEHD. <br /> D = Percent dentrification of leachfield effluent = 0.15 percent (0.1 to 0.35 percent <br /> typical per Hantzsche and Finnemore (1992)). 0.15 selected given the shallow depth <br /> to groundwater and clayey soil. <br /> it <br /> R = Annual deep percolation of precipitation (inches) = 6.7 inches (representing 70 <br /> percent of the average annual rainfall of approximately 9.5 inches being collected <br /> into the on-site drainage basin and percolating into the soil. The remaining 30 <br /> percent of rainfall is assumed to evapotranspirate or drain off-site into natural or <br /> manmade drainages.) <br /> Nb = Background nitrate nitrogen concentration of rainfall recharge at the water table = F <br /> 0.5 mg/l (per Technical Memorandum, Hydrologic and Soil Investigation for the <br /> Chico Urban Area, page 6, Dames and Moore, April 1996) <br /> V <br /> Our calculation is as follows: <br /> ei;,d R/ <br /> k N, = 1.54(2)(70)(1 —0.15) + 0.5(6.7) = 183.3 + 3.4 = 19.1 m l as N <br /> 1.54(2) + 6.7 3.1 + 6.7 <br /> h � <br /> Based on ,SJCEHD requirements, due to the high level of nitrates detected in groundwater in the <br /> I project area and the calculated nitrate loading that is above the state drinking water standard, <br /> k engineered or alternative sewage dis osal system will be required to reduce the loading of <br /> r <br /> + 38058.G0 i/ST04L442 September 20,2004 <br /> ©2004 Kleinfelder,Inc. Page 2 of 3 <br /> I j <br /> �� f <br />