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'September 24, 1999 .Tab Nam-iber. 5992.44 Page 6 identified between 7 47-fet-i&de*. After evaluation, the exploratory baring was backfilled to the surface. A.percolation test was locatedabout 5 feet south of the explorato y b'-ring and drilled to a . depth of 10"5 feet in'a fine to medium sand" A 2 inch PVC.pipe with slots.on the bottom was installed in the boringfor the percolation test.-Several-inches of"pea gravel"was placed in the bottom of the hole;the casing was installed, and'several feet of"pea gravel"was backfilled in the 'E annular-.space. The percolation test was conducted on September 14, 1999 in accordance with the requirements of San Joaquin County Environmental Health'Division and was observed by Mr. Johnny Yoakum of that office. The result of the percolation test indicates a satisfactory peculation 'rate of for the sandy soils located at about 10.5 feet in'depth(Plate-6 and Plate'7). VII. NITRATE LOADING STUDY A build up of nitrates in the upper ground-water zones can cause.a temporary blood disorder in infants called.methemoglobinemia(blue baby). Serious and occasionally fatal poisonings.in infants have occurred'following the ingestion of water containing nitrate a concentrations greater than 10 mg/1 nitrate as N or 45 mg/l nitrate as NO3. .The nitrate loading analysis estimates the concentration of.nitrate-N of the septic effluent combined with -rain water after denitrification before rriixing with ground water.. The method is ' based on a simple mass balance formula which takes into accountsoil.denitrification,rain fall, and the proposed waste effluent quantity and nitrate level: Assumptions and calculations for the analysis are.contained on Worksheets No. 1 and 2 (Plate 9 and Plate 14)..The units of nitrate in used in the mass balance equation is nitrate-N with a maximum drinking water contaminate level. of 10 mg/i. . . Denitrification is the biological process in the soil whereby certain bacteria utilize the' 1 oxygen in the nitrate'(NO3) and release nitrogen gas("2)to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range Js 10%to 25% . Soils with higher clay content moist soil conditions and organic material denitrify' Y ,. g about 25% or more but sails with higher sand content and fast peculation rates are estimated to denitrify about 10%" Due to the presence of dark gray clay material located in the first three (3) feet, we estimate the denitrification factor be about 25 %" 'In our approach to.estimate the nitrate concentration, we used the following information for our calculation.