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February 28,2006 NOA Project Number: E0509 1B Page 2 The presence of nitrates its not uncommon in shallow ground water aquifers in.Sar.Joaquin County and other parts of the Centtal Valley. Nitrate in ground water occurs 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 1.900s,natural levels of nitrate in ground water.were measured in rorty-dltce (43) wells throughout the Sacramento Valley,by Bryan (1923). It was thought that ground wa.tet at that tine was close to"natural" conditions. Based on the work by Bryan.it is estimated that under"natural" conditions,ground water concentration containing nittate is no more then about 13.5 mg/L-NO3 (3 mg/L-N).Areas having 24.75 tng/T�NO} (5.5 mg/L-N) or more axe tbose in which nitrate concentrations may be increasing (Hull, 1984). DBCP was found 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 (J',-PA) set the maximum contaminant limit (MCL) at 0.2 parts per billion (ppb) because the EPA believes that given present technology and resources, this is the lowest level to which water systems can. reasonably be required to remove this contaminant should it occur,in drinking water. 7.0 CONCLUSIONS In summary. satisfactory percolation rates of the soil were achieved in the proposed septi.c disposal areas of the lot. The soils of the proposed lot appear suitable for a standard septic system uti'l;zing leach lines and seepage pits. No ground water was encounteted in any of the bozilogs drilled on the property.The depth to ground water,was found to be approximately 30 to 40 feet below the ground surface for the period of Fall 1998 and Spring 1999 based or the San Joaquin County G.tound Water Maps. The water well on the subject properly was tested for nitrate and DBCP.The rutrztc concentration. in the well aTatet sample was found to be 10.9 mg/L-NO3,wbicb.is well below the maximum contaminant ririnkinu water limit of 45 rng/L-NO3. DBCP was detected in tl,Ze water sample a:0.34 ug/T, above the NICL of 0.2 ug/L.We recommend not drinking the well water until the well is repaired or replaced and water quality is within drinking water standards.You should contact the EHD for mote details regarding health issues and repair./replacement options. Best Regard-,, I\ �EIL 0.A-NDERSO.N&ASSOC.,ENTG N I a4y Rosulck _A- Project Manager