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6. \/ %ftool KLEINFELDER <br /> Standards, communication with Mr. Mike Huggins with SJCEHD, and information provided in a <br /> report dated March 19, 1997 prepared by the Questa Engineering Corporation and authored by <br /> Mr. Hantzsche for a development in the Stockton area. <br /> r <br /> Ne=AWN,(1-D) + (Nb R <br /> LAW+R <br /> Where: <br /> Ne = Average calculated nitrate-nitrogen in groundwater resulting from domestic sources <br /> and precipitation–mg/1, as N. <br /> A = Number of dwelling units per acre on septic tanks (unit/acre) = 0.15 (estimated <br /> based on 15 gallons per full-time employee (7) and 10 gallons per part-time <br /> Zual <br /> yee imum o 23 divided by 150 gallons per dwelling unit divided by <br /> L —� acres. / st03G = 335 3W = 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 /> L <br /> Nw = Nitrate concentration of nitrified leachfield effluent(mg/1) =70 mg/1 (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 sandy nature of the soil. <br /> R = Annual deep percolation of precipitation (inches) = 9.2 inches (representing 80 <br /> percent of average annual rainfall of approximately 11.5 inches in project area. <br /> LRemaining 20 percent of rainfall is assumed to drain off-site into natural or <br /> manmade drainages.) <br /> LNb = Background nitrate nitrogen concentration of rainfall recharge at the water table – <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 /> k` Our calculation is as follows: <br /> N, = 0.15(2)(70)(1 –0.15)+0.5(9.2) = 17.85 +4.6 = 2.4 mg/l as N <br /> 0.15(2)+9.2 0.30+ 9.2 <br /> L <br /> L31917.GOI/ST03RI695 °j November 11,2003 <br /> ©2003 Kleinfelder,Inc. t Page 5 of 7 <br /> IS� <br /> 6. i)I 0 7L <br />