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Sam <br /> Kl£IN ££ LD£ R <br /> • <br /> NITRATE LOADING CALCULATIONS <br /> Per SJCPHS/EHD requirements, the following summarizes our nitrate loading calculations for <br /> the proposed leach field for the new residence. The State drinking water standard for nitrate is <br /> 45 milligrams per liter (NO3) and 10 mg/1 as Nitrogen (N) in groundwater. In our evaluation of <br /> nitrate loading, we have used the Hantzsche mass balance equation (source: Predicting Ground- <br /> Water Nitrate-Nitrogen Impacts, Hantzsche and Finnemore (1992)), which is presented below <br /> with an explanation for each factor and the value used in our study. The selection of parameters <br /> was based on previous studies and investigations performed by our firm and others, San Joaquin <br /> County Sewage Standards, communications with Mr. Mike Huggins with the SJCPHS/EHD, and <br /> information provided in a report dated March 19, 1997 prepared by the Questa Engineering <br /> Corporation and authored by Mr. Hantzsche for a development in the Stockton area. <br /> Ne =AYT tilYw�1-D)+(NniR <br /> AW+R <br /> Where: <br /> Ne — 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) = 0.026 (estimated <br /> based on an estimated water usage of 150 gal./day, a typical water usage for a single <br /> family residence per the SJCPHS/EHD Sewage Standards divided by I50 gal./day to <br /> obtain an equivalent number of homes, divided by 39.09 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/1 typical <br /> (communication with Mr. Mike Huggins with SHCPHS/EHD) <br /> D = Percent dentrification of leachfield effluent = 0.25 percent (0.1 to 0.35 percent <br /> typical per Hantzsche and Finnemore([1992]). <br /> R — Annual deep percolation of precipitation (inches) = 7.6 inches (representing 80 <br /> percent of average annual rainfall of 9.5 inches in project area. Remaining 20 <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/l (per Technical Memorandum, Hydrologic and Soil Investigation for the <br /> Chico Urban Area, page 6,Dames and Moore,April 1996) <br /> 16796.GOJ/ST02R278 July 25,2002 <br /> ®2002 Kleinfelder,tnc. Page 3 of 5 <br />