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KLEINFELDER <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/1 typical <br /> (Hantzsche and Finnemore (1992)) <br /> D = Percent dentrification 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(60+ feet)) <br /> r = Annual deep percolation of precipitation (inches) = 10.2 inches (representing 85 <br /> percent of average annual rainfall of 12 inches in project area. Remaining 15 <br /> percent of rainfall is assumed to drain off-site into natural or 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: ��,�.�Qf <br /> N< 1.""x(35)(1 —0.35) +0.5(10.Z = 87.8 + 5.1 = 6.6 mg/l as N � <br /> 3.8 +10.2 <br /> CONCLUSIONS �'" joeo <br /> U1104 I <br /> Based on the above evaluation, we conclude that wastewater produced by the proposed leach QyV <br /> fields should not have a nitrate as nitrogen (I) concentration at the groundwater level greater f <br /> than 10 mg/l. <br /> The results of our percolation tests indicate that the upper clays, silts and clayey sands will not <br /> meet SJCPHS/EHD percolation criteria (minimum 60 minutes/inch or faster) for on-site sewage <br /> disposal. The underlying silty and "clean" sand, however, clearly satisfies SJCPHS/EHD <br /> criteria. Accordingly, conventional septic tank/leach trench sewage disposal systems with <br /> seepage pits that extend into the silty and "clean" sands should adequately serve the proposed <br /> development. <br /> LIMITATIONS <br /> The conclusions of this report are based on the information provided regarding the proposed <br /> development and on the site conditions. It was assumed that the percolation test results are <br /> representative of the subsurface conditions in the general area. <br /> 204685-01.601/20028367 April 18,2002 <br /> ©2002 Kleinfelder,Inc. Page 4 of 5 <br />