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V kq KLEINFELDER <br /> Ne=AWNw (1-D1 + (N R <br /> 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 units per acre on septic tanks (unit/acre) = 1.05 (estimated <br /> based on 1 residence (trailer) plus 15 gallons per full-time employee (1 part-time <br /> employee worst case) divided by 150 gallons per dwelling unit divided by 1.05 <br /> 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) = 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 = 0.25 percent (0.1 to 0.35 percent <br /> typical per Hantzsche and Finnemore (1992). 0.25 selected given the depth to <br /> groundwater and strata of low-permeable soil. <br /> R = Annual deep percolation of precipitation (inches) = 11.6 inches (representing 80 <br /> percent of average annual rainfall of approximately 14.5 inches in project area. <br /> Remaining 20 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 = 1.05(2)(70)(1 —0.25)+ 0.5(11.6) = 110.3 + 5.8 = 8.5 mg/1 as N <br /> 1.05(2) + 11.6 2.1 + 11.6 <br /> CONCLUSIONS <br /> As shown above, we calculate 8.5 mg/l of nitrate-nitrogen (l) in groundwater resulting from the <br /> proposed leach fields, a result that is below the state standard of 10 mg/l. Based on this <br /> relatively low level of nitrate-nitrogen, we anticipate that the impact on surrounding wells will be <br /> minimal and no remediation will be necessary. Duck Creek and a small tributary are the nearest <br /> natural water bodies to the site and are located approximately 1,200 and 300 feet from the site, <br /> respectively, but are generally not down gradient and are shallow bodies of water. Based on the <br /> 35228.G0I/STO3R1508 October 14,2003 <br /> © 2003 Kleinfelder, Inc. Page 5 of 6 <br />