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September 27, 2000 Job Number. LG00-312 Page 7 Two soil borings were drilled by Neil O. Anderson& Associates, Inc. to characterize the subsurface and locate a suitable site for the proposed septic field. Boring B-1 was completed near the existing septic field and B-2 was completed in the parking lot area located on the east half of the property. Borings B-1 and B-2 were both drilled to a depth of 10 feet and composed of a - brown fine to medium sand (Plates 8 and 9). No ground water was encountered. One(1) percolation test was performed within B-1 at a depth of three (3) feet. The percolation test casing was 2-inch diameter PVC pipe with slots and an open end on the bottom. Two inches of"pea gravel" was placed in the bottom of the hole, the casing was installed, and one (1) foot of"pea gravel"was backfilled in the annular space. A one (1) hour percolation test was conducted on September 19, 2000 in accordance with the requirements of San Joaquin County Environmental Health Division near the end of the leach lines of the existing septic system(Plate 1). The last '/2 hour of the percolation test was observed by Larry Godinho of that office. A satisfactory percolation rate of 0.44 min/in was measured for the percolation test (See Appendix). 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 syndrome). Serious and occasionally fatal poisonings of infants have occurred following the ingestion of water containing nitrate concentrations greater than 10 mg/I nitrate as N or 45 mg/l nitrate as NO3. Because of the concern of nitrate leaching into ground water, a nitrate loading analysis is required to estimate the average nitrate concentration of percolating water for the subject parcel. If a site is contributing excess nitrogen to ground water, ground water quality can be impacted. The nitrate sources for this project will include the septic effluent and deep percolation of rain water. The nitrate concentration of the"trea ' ic effluent mixed with the deep percolating rain water is estimated before it mixes with ground water and dilutes. The nitrate balance method assumes 100% mixing with rain water over an average yearly period for the area of the subject parcel. The method is based on a simple mass balance formula which takes into account soil denitrification factor that consumes nitrogen, rain fall amount, rain fall nitrate concentration, the waste effluent quantity, and waste effluent nitrate concentration. The formula, assumptions and calculations for the analysis are shown on Plates 10 and 11. The units of nitrate used in the mass p6RJ 1 w O ` �JJOG� r