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09/07/2001 10:36 6842627 013RIENICLAVBAR PAGE 05 <br /> Ne -A,-W—N. 1-D + NpII <br /> - AW+r <br /> 'When: <br /> N, = Avcrage calculated nitrate-nitrogen irk groundwater resulting from domestic sources and <br /> - precipitation-mg/l, as N <br /> eptic tartkS(unit/acro} <br /> A, Number of dwelling units per acres on s = .44 <br /> W - Anmsal wastewater loading per dwelling unit per acre (inches) _ .� inches (wed on 150 <br /> y gpolresidence) <br /> NW Nitrate concentration of nitrified leachfield effluent(m9A)= 35 to 45 mg/l typicalHantzsche <br /> and Finnemore(1992)) <br /> l7 percent derttrification of leachfield effluent = (t.25 percent (0.1 to 0.25 percent <br /> TYPit cal Per <br /> b <br /> 14ansche and pimemore (1992). 0.25 selected given, the large depth to groundwater <br /> 120 <br /> feet-) and a majority of the soil$ Mcount,ered oonsist of fire clays and silts that tend to <br /> - increase denitrification) <br /> X Annual deep percolation of precipitation (inches) = 4.0 inches (increase over the 3 inches <br /> used by Mr.Hantzsche in the Stockton area to reflect the sandy soil conditions anticipated at <br /> - the percolation depth$for the leach tranches) <br /> Nb Background nitrate concentration of the deep percolating precipitation-moll=2.2 rrxgll as N <br /> Our calculation is as follows: <br /> I <br /> Low Estimate <br /> f <br /> l N, = 44 2 3 l -0.25 +2.2 4 23 + = 6.5 xztg/1 as N <br /> .44(2)+4 0.89+4 <br /> High Estimate <br /> k <br /> Ne _= 4 45 1 _25 +2 4) 29.7 +8.8 7.9 mg/t as N <br /> .4.4(2)+4 0.88+4 <br />' Average N,=7.2 mgll as N <br /> One of the factors that may be re�quimd by the SJCPHS is to determine the existing value Of <br /> nitrata in e site. Based on our previous discissions with NU. Huggius <br />� <br /> of SJCPHS, we have been advised to use a background nitrate (NO3) conce-ntration of IU mg,/1 to <br /> f the groundwater. While Mr. Hugging has not provided a background level of nitrate as N in the <br /> I groundwater, based an previous testing by our firm the value of nitrate as N cornparcd to NO3 is <br /> usually about 25 percent or less. tri other words, if 10 mg/l is expected for NO3, the initial or <br /> C background level of rxitrate as N might be expected to be ou the order of 2.5 me or less. <br /> I Accordingly, the total nitrate concentration determined in growodwater from the leach fields <br /> I ranges from 9 to 10.4 mgl1, with an average of 9.7 mg/l. <br /> M <br /> i <br /> 20-447645 t.GUW_000R823 <br /> 5epre�her LM1,zDQO <br /> 2ow,Clainfelder,Inc. Page 4 of S <br /> I <br />