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L \,/ KLEINFELDER <br /> L <br /> Current laws allow a maximum of two single-family residences on each parcel in San Joaquin <br /> L County. To account for the nitrate loading from the proposed office and the potential of two <br /> on-site residences, the calculations have been performed for both the commercial and <br /> residential uses. The sum of nitrate loading due to commercial and residential uses would be <br /> the calculated total nitrate loading at the site. <br /> L <br /> Nitrate Loading Due to the Proposed Commercial Office <br /> N, = Average calculated nitrate-nitrogen in groundwater resulting from domestic sources <br /> and precipitation-mg/l, as N. V,7 <br /> ` A = Number of dwelling units per acre on septic tanks (unit/acre) = O-.Y (Based on 5 <br /> employees using 30 gal/day each, divided by 150 gaUday/dwellingunit, divided by <br /> L3.1 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 gaUday/dwehingmat-)-, <br /> ` �pMM4tPC�yam,. 1a/ol1 <br /> Nw = Nitrate concentration of nitrified leach-field effluent (mg/1) = 70 mg/1 ((Hantzsche <br /> _ and Finnemore (1992) This value selected for commercial uses based on past <br /> discussions with Mr. Mike Huggins of SJCEHD.) <br /> ` D = Percent dentrification of leachfield effluent=0.1 percent (0.1 to 0.35 percent typical <br /> per Hantzsche and Finnemore (1992)). 0.1 selected given the sand soil and the <br /> depth to groundwater. <br /> L <br /> R = Annual deep percolation of precipitation (inches) = 9.0 inches (representing 75 <br /> percent of the average annual rainfall of approximately 12 inches. The remaining 25 <br /> L percent of rainfall is assumed to drain off-site into natural or manmade drainages or <br /> be lost to evapotranspiration.) <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 fows: <br /> 8 <br /> L Ne = 01�(2)(70N1 -0.1)+ 0.5(8.4) = 37.8 +4.2 = 4.7mg/lasN <br /> CO(2)+ 8.4 0.6+ 8.4 cu(� <br /> L <br /> L 52251.001/STOSR192 February 17,2005 <br /> I ©2005 Kleinfelder,Inc. Page 5 of 8 <br /> L <br />