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KLEINFELDER <br /> Ne =AWNw(1-D)+ R <br /> AW+R <br /> Where: <br /> Nr = 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) = 0.37 (estimated <br /> based on two homes on each of the ten lots divided by 54.7 acres.) <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 /> Nw = Nitrate concentration of nitrified leachfield effluent (mg/1) = 35 mg/I (Hantzsche and <br /> Finnemore (1992)). Percent denitrification selected based on depth to groundwater <br /> and presence of interbedded low-percable soil strata. <br /> D = Percent dentriffcation of leachfield effluent = 0.35 percent (0.1 to 0.35 percent <br /> typical per Hantzsche and Finnemore (1992). 0.35 selected given the large depth to <br /> groundwater(90+feet). <br /> R = Annual deep percolation of precipitation (inches) = 8.4 inches (representing 70 <br /> percent of average annual rainfall of approximately 12 inches in project area. <br /> Remaining 30 percent of rainfall is assumed to drain off-site into natural or <br /> manmade drainages.) <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 /> Chico Urban Area,page 6, Dames and Moore, April 1996) <br /> Our calculation is as follows: <br /> Ne = 0.37(2)(35)(1 —0.35) +0.5(8.4) = 16.84 +4.2 = 2.3 mg/l as N <br /> 0.37(2)+8.4 0.74 +8.4 <br /> CONCLUSIONS <br /> As shown above, we calculate 2.3 mg/l of nitrate-nitrogen (N) in groundwater resulting from the <br /> proposed leach fields, a result that is below the state standard of 10 mg/1. Based on this <br /> relatively low level of nitrate-nitrogen, we anticipate that the impact from the proposed <br /> construction on surrounding wells will be minimal. Little Johns Creek is the nearest natural <br /> water body to the site and is located approximately 0.7 miles down gradient from the site. Based <br /> 32585.G01/ST03RI168 August 13,2003 <br /> ©2003 Kleinfelder,Inc. Page 5 of 6 <br />