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D <br />FIGURE 3 <br />t Nitrate Concentration Calculations for <br />Barclay Ridge Section III A-3 Subdivision <br />(Calculations suggested by Loudoi~n County Health Department) <br />CN - ~QE CE + QI C1~ / ~QE + Q1~ <br />where, CN =Predicted Nitrate Concentration (mg/1) <br />' QE =Rate of effluent production (1/day) <br />Qi =Rate of influent (natural) groundwater (1/day) <br />CE =Effluent Concentration (mg/1) <br />C, =Influent Concentration (mg/1; from on-site sampling) <br />ENTER <br />VALUES <br />assumptions, Number of Dwellings on site 47 <br />Total Area of Development = 184 acres <br />CE =Effluent Concentration (LCHD requires 65 mg/1) 65 mg/1 <br />C, =Influent Concentration (average from local rainfall) = 0 mg/1 <br />"~ Groundwater Recharge (10 in/yr normal) 10 in/yr <br />,~ Groundwater Recharge (6 in/yr drought) = 6 ii~/yr <br />Number of Persons per Dwelling (LCHD says 3.8) = 3.8 <br />Effluent Volume (LCHD says 60 gal/day-person) = 60 gal/day <br />therefore, <br />Normal Recharge <br />QE = 40,506 1/day <br />QI = 517,867 1/day <br />Drought Recharge <br />QE = 40,506 1/day <br />Q~ = 310,720 1/day <br />Predicted Nitrate Concentrations' <br />CN = 4.7 mg/1 CN = 7.5 mg/1 <br />'EGGI considers these predicted nitrate levels to be unrealistically high, as it assumes no loss of <br />nitrates over time. <br />' Nitrate Calculations for GAR.xIs Emery & Garrett Groundwater, Inc. <br />