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rN August 1,2002 I L Job Number: G 02483 ' Page 4' Table 2: : - Summary of Available Ground Water Information. ; Date;Description,Source Groundwater Depth Nates: June 11,,2602;ground water sample Ground water'depth not obtained Nitrate:']3.4 mg/1-NO, obtained from the'existing domestic well, from well.. DBCP:Not Detected Far West Laboratories,.Inc. Fall 1998, San Joaquin County Ground. About 130 feet in depth. Gradient about 7.1.ft/mi, Water Map,Plates 2 and.4 flowing approx.north. Spring 1990,-.San Joaquin County Ground About 120 feet in depth. Gradient about 3..8 ft/mi, �. Water Map,Plates 3 and 5 Mng northeast. The existing on-site'domest_ic water well is located on proposed Parcel 2 ju' :north of the . ' house and garage. Julia Shoneff, contracted with.FarWesi Laboratories, Inc. to collect aground- water sample from.the on site well. The sample was collected on June 12, 2002 by P..Delano, an employee of FarWest Laboratories„Inc. for testing to detect the presence of' dibromochloropropane(DBCP] and Nitrate(NO3) per County requirements:'The test results indicated that DBCP was found to be non-detectable andnitrate as NO3 found to be 13.4 mg/L. Both tests indicated the ground water sample was below the maximum contaminate level set by 4 the United States Environmental Protection Agency of 0.21tig/l for DBCP and 45 mg/L as NO3. . ' The presents.of nitrates and DBCP are not:uncommon.in'shallow ground-water aquifers in San.Joaquin County and other parts of the Central'Valley. Nitrate in ground water originates E from agricultural 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 grround.water were Measured in 43 wells throughout the SacramentoValley by Bryan.' It-was'thought that groundwater at that time was close to "natural"conditions. Based on the work by Bryan it is estimated that under natural conditions, groundwater concentration of nitrate is no more then about 3 mg/L-NO3. Areas having 5'.5 mg/L-NO3 or more are those in which k nitrate concentrations may be increasing.3 _ 2 B an K. 1923 Geology and round-water resources of Sacramento Valle ry , gy . g, y of California: U.S. Geological Survey'Water-Supply Paper 495,285p.: 3 Hull, L.C., 1984,.Geocherriistry of Ground Water in the Sacramerito Valley,California: U.S. Geological Survey Professional Paper 1401-13. x � r .