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November 19A999 <br /> Job Number:S99303' <br /> Page 6 , <br /> A soil boring was drilled.to a depth of 40 feet to charas_terize the soil profile of the site, <br /> ` No ground-water was encountered to a total depth of 40-feet.. GenerallYa:y -la�ers 'consistingof <br /> sand; silt, arid clay were.encountered in burin <br /> g(Plate 8). A 6 foot thick clay layer was found to <br /> exist between 22-to 28 feet: This layer may'tend to imped'the downward flow of percolating <br /> water. No hardpan was observed during drilling: <br /> .One percolation test was performed,adjacent to the exploratory boring- The percolation '. <br /> test was set at 2:0 feet in.depth within soils consisting of brown sand with At(Plate 8). The. <br /> percolation test casing was a 2 inch PVCpipe with slots cuf on the Bottom Two inches of"pea <br /> gravel"was placed in the bottom of hole, the,casing.was installed, and several feet�of"pea gravel <br /> were backfilled in the annular space. <br /> A one hour.percolation test was conducted.on November 9, 4999'n accordance with the <br /> requirements of San Joaquin County Environmen <br /> i <br /> tal Health Division..-The last.1/ �hour of the test <br /> was observed by Mr._Johnny Yoakum of that office.'The result of the percolation 2 foot deep, : ' <br /> percolation test indicates a satisfactory peculation rate of 26-0min/in(Plateal l).' The results <br /> ,! indicate that'a standard leach field-septic desi could be used on the ' <br /> site. <br /> r VII- NITRATE LOADING STUDY <br /> A build up of nitrates in the upper ground-water zones can cause a temporary blood = <br /> disorder in infants called methemoglobinemia(blue baby): Serious and occasionally fatal <br /> poisonings`of infants haveoccurred followingthe in e-stion of water. g e containing nitrate _ <br /> concentrations greater than 10 mg/l nitrate as.N or-45•mg/l nitrate as NO3. ' <br /> ` The nitrate loading analysis estimates the concentration of <br /> nitrate-N of-the septic effluent <br /> combined with rain water after denitrification (prior to mixing and dilution with existing <br /> -ground <br /> water)- The method is based on a simple mass balance formula which takes into account soil <br /> denitrification rain fall, and the .waste e <br /> proposed ffluent quantity and nitrate level. Assumptions <br /> and calculations for the analysis are shown-on Plates 9:and 10. The units.of nitrate in used ' the <br /> mass balance equation is nitrate-N with a maximum.drinking water contaminate level of 10 mg/1. <br /> Decutri£cation is the biological process in the soil whereby certain bacteria utilize the <br /> oxygen in the nitrate(NO3) and release.nitrogen'gas(Nz).to the atmosphere. tDenitnification is <br /> expressed ass-a percentage, and the normally accepted range is 10%.to 25%.'Soils-with higher <br /> clay content, moist soil conditions;and:organic material denitrify about.25%•or more but sails <br /> with Higher sand content and fast peculation rates are estimated to denitrify about 10%- Due.to . <br />