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rFaccording <br /> eductions in the nitrate-nitrogen loading from above (40 lbs N/yr) are anticipated, <br /> scientific literature: <br /> em removes 20%N x 40 lbs= 32 lbs <br /> on removes 10%X 32 lbs=29 lbs <br /> Denitrification in silt/clay soil strata removes 20%X 29 lbs=23 lbs <br /> 23 lbs N/yr=total nitrogen load. <br /> Determination of the theoretical nitrogen contribution to the groundwater: <br /> Assume 50%reduction in N (from above): 70 grams N/day - 50% =35 grams N theoretically <br /> oxidized to nitrate-nitrogen/day. <br /> Dilution water available(avg water use),Q,,= 180 gal/day(12 people x 15 gals=681 L/d)+avg gw flow(Qs,,.) <br /> Groundwater flow perpendicular to 100 linear ft of leachfield area= <br /> k(hydraulic conductivity of sat. zone)x(i =% grade) x 10 ft(top mixing layer) X 100 ft= <br /> QB,,,=2 X 10-3 ft/min(estimated)x(60 min/hr x 24 hrs/day) 0.5 x 10 ft x 100 ft= <br /> 1440 ft'/day or 10,771 gals/day (40,773 L/day) <br /> CALCULATED NITROGEN CONCENTRATION TO GROUNDWATER UNDER LEACHFIELD= <br /> 35 grams/QAyg+QB,, =35 g NO3-N/day_(681 L/day+40,773 L/day)=0.000844 grams NO;N/L x <br /> 1000 =0.84 mg/L (ppm)NO3-N/day <br /> This assumes no nitrate contribution from the underlying groundwater. If the groundwater is <br /> assumed to currently possess a nitrate concentration of 7 ppm NO3(1.6 ppm NO3-N),then the <br /> top mixing layer groundwater under the leachfzeld will not exceed the Maximum Contaminant <br /> Level (MCL) of 10 ppm NO3-N: 0.84 + 1.6 =2.44 ppm NO3-N. <br /> C. SEPTIC SYSTEM DESIGN/IMPACT MITIGATION <br /> The design of a future septic system for the facility is based upon the factors of operation, <br /> longevity, and environmental protection. The San Joaquin County Environmental Health <br /> Department will stipulate design requirements. <br /> SEPTIC TANKS <br /> Septic tank designs which affect the sludge, scute and effluent volumes, affect the treatment of <br /> nitrogen within the tanks. Therefore, one-1,200 gallon septic tank may be specified by the <br /> Environmental Health Department based upon the capacity calculation below. The pump-out <br /> interval should be a specified time interval, or periodic inspection either by the Environmental <br /> Health Department or a sewage contractor. <br /> CAPACITY: <br /> Required septic tank capacity: 2.4(QAvE)x Peaking Factor(PF) =2.4(180 gals/day)x 2.0 = <br /> 864 gal tank capacity required: One-1,200 gallon tank may be used. <br /> 6 <br /> Vaffey Ag Research <br />