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k'g KLEINFELDER <br /> have used the Hantzsche mass balance equation (source: Predicting Groundwater Nitrate- <br /> Nitrogen Impacts, Hantzsche and Finnemore (1992)), which is presented below. <br /> Ll Nc=AWN,, 1-D + R <br /> AW+R <br /> lection of arameters used in the equation- was based on previous studies and <br /> The se p <br /> investigations performed by our firm and others, San' Joaquin County Sewage Standards, <br /> previous 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 fora development in the Stockton area. <br /> Residential Parcels <br /> L Current-laws allow a maximum of two single-family residences-on each parcel in San Joaquin <br /> County. To calculate the highest expected nitrate loading for the residential :parcels, the <br /> following calculations assume-two residences constructed on the smallest parcel (2 acres). <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) = 1.0 (based on 2 <br /> ----------------------- <br /> homes divided by 2 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/Lay unit.) <br /> NW = Nitrate concentration 'of nitrified leachfield effluent (mg/1) = 40 mg/l ((Hantzsche <br /> and Finnemore(1992)based on residential uses.) <br /> D = Percent dentrification of leachfield effluent=0.3 percent (0.1 to 0.35 percent typical <br /> per Hantzsche and Finnemore (1992)). '0.3 selected given depth to groundwater. <br /> R — Annual deep percolation of precipitation (inches) = 11.9 inches (representing 70 <br /> percent of the average annual rainfall of approximately 17 inches. The remaining 30 i <br /> percent of rainfall is assumed to drain off-site into natural or manmade drainages or <br /> be lost to evapotranspiration.) <br /> Ne = Background nitrate nitrogen concentration of rainfall recharge at the water table =. <br /> 0.5 m /l (perTechnical .Memorandum, Hydrologic and Soil Investigation for the <br /> �l Chico Urban Area, page 6, Dames and-Moore, Apnl 1996) <br /> Our calculation is as follows:. <br /> 55208.GO1/ST05R644 June 1,2005 <br /> @11005 Kleinfelder,Inc: Page 6 of 9 <br />