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I September 27,2000 Job Number. LG00-312 Page 5 The South San Joaquin Irrigation District( 1011 E. Hwy 120)building is located several thousand fd±scut-a the subject site and has a perienced similar levels of nitrate in their water well in the pas The South San Joaquin Imga f District posted a notice over a drinking water fountain inside their building that indicated three(3)water samples were collected and analyzed for nitrates between January and April 1999 which ranged between 45 and 48 mg/L as NO3 (about 10.0 to 10.7 mg/LN). Because of the nitrate problem,the South San Joaquin Irrigation District is currently using bottled water for drinking. Mr. Frank Mello,Director of Maintenance Manteca School District, indicated that Calla High School, located just south of the site, does not experience the nitrate problem. The well is tested several times a year. A new well was installed in 1986 because of diminished capacity of the old well. The Calla lEgh School water well did recently experience some bacteria contamination that was caused by a missing inspection plug located on the well. Mr. Mello indicated that the problem was fixed and the well.is presently experiencing no water quality problems. The presence of nitrates and DBCP are not uncommon in shallow ground-water aquifers in San Joaquin County and other parts of the Central Valley. Nitrate sources in ground water occur as a result of the application of fertilizers, livestock waste, and untreated septic tank waste. Nitrate is mobile and often accumulates in the shallow ground-water zones. In the early 1900's, natural levels of nitrate in ground water were measured in 43 wells throughout the Sacramento Valley by Bryan.2 It was thought that ground water at that time was close to "natural" �- conditions. Based on the work by Bryan,it is estimated that under"natural" conditions,ground water concentration of nitrate is no more then about 3 mg/L-N. Areas having 5.5 mg/L-N or more are those in which nitrate concentrations may be increasing.3 DBCP was not detected in the water sample. DBCP is a nematocide and soil fumigant for vegetables, and grapes. It is thought to cause health problems consisting of kidney damage, liver damage, and cancer. The use of DBCP was discontinued in 1979. The Environmental Protection Agency(EPA) set the maximum contaminate limit(MCL) at 0.2 parts per billion(ppb)because 2 Bryan,K., 1923,Geology and ground-water resources of Sacramento Valley of California:U.S. Geological Survey Water-Supply Paper 495,285p. 3 Hull,L.C., 1984,Geochemistry of Ground Water in the Sacramento Valley,California:U.S.Geological Survey Professional Paper 1401 B. �pE l,f Oy = A Q {rso