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September 20,2001 Job Number: LGOi-098 Page 5 _ Date,Source Groundwater Depth Notes Fall 1998, San Joaquin County Flood 26 feet. Gradient: 5.6 feet/mile flowing Control and Water Conservation District north-northwest. map.' Plates 2 and 4. Spring 1999, San Joaquin County Flood 20 feet. Gradient: 6.3 feet/mile flowing north Control and Water Conservation District_ Plates 3 and 5. Note: ND=Non-Detectable(or not found at detectable limits). The depth to ground water at the site, measured in east well, was found to be 34 feet below the ground surface on August 17, 2001. A water sample was obtained from east well to -- detect the presence of dibromochloropropane (DBCP) and Nitrate (NO3) per County requirements. The access to the well was difficult and the water sample that was finally pulled from the well was brown to creamy tan colored. The sample was sent to Precision — Environmental Laboratory for testing on the same day. The test results indicates that DBCP was non-detectable(ND) and nitrate as NO3 was found at 100,000 ug/1-N. The result of the nitrate test indicates the ground water is above the maximum contaminate level (MCL) set by the United States Environmental Protection Agency of 10 mg/L as nitrate N or 1,000 ug/L as nitrate N. This is equivalent to 10 times the MCL for nitrate of 1000 ug/L as N. The extremely high result may be due to a contaminated well sample not reflective of the condition of the aquifer_ The well has sat idle for many years. Due to the questionable nitrate result, a second sample was collected from the fire station ell located north and across the street from the site. The fire station keeper said the well was probably shallow and they have water quality problems which require monitoring and the use of a membrane filter. The water sample was collected at the spigot at the well head before the filter. The result�f thicte,t is 0.71 mg/L as Nitrate N or 71.0 ug/L as Nitrate N. The result of the second nitrate test indicates the ground water sample was well below the maximum contaminate level set by the United States Environmental Protection Agency of 10 mg/L as Nitrate N or 1,000 ug/L as Nitrate N. 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 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. ' ?VERSO 1 ► n Z � O � ,SSOG\