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Performa Inc. May 7,2003 Page 7 Engineering Department, was contacted regarding his knowledge of nitrogen impacts of the ' aquifer in this area. Dr. Litton indicated he has not worked in this local area. He indicated he is not aware of any nitrate plumes in this area. It has been recognized historically when dairies, agriculture, or septic systems are sited on sandy surface soils and shallow ground water, nitrate contamination of the aquifer is an elevated risk. t5.2 Gradient and Flow Direction,Historic Levels Neil O. Anderson and Associates researched the ground water levels in the area of the subject property. In 1983, a near one hundred year event took place in respect to precipitation. The groundwater depth in the County was historically shallow for that period. Historic data from ' the San Joaquin County Flood Control and Water Conservation District's Ground Water Report, Spring 1983 was reviewed. The ground-water depth below the subject property was near the ten foot contour,between ten and twenty feet below ground surface. There was no data to the west of ' the subject property in this year. The ground-water flow direction has been determined to be either to the west or north. An exact estimation cannot be determined because of the absence of data to the west of the subject property. More recent ground-water information was gleaned from the same report produced in the fall of 1998 and the spring of 1999. According to the Fall 1998 edition, ground water in the area of the subject property can be found between twenty and thirty feet,nearer to the twenty foot contour, below ground surface. The flow direction in the area was estimated to be to the north taking 2.1 miles to drop ten feet. According to the Spring 1999 edition, ground water in the area of the subject property can be found at a depth of twenty feet below ground surface level. The flow direction is estimated to be to the north-northeast taking 1.5 miles to drop ten feet in elevation. ' 5.3 Ground-Water Quality Sampling ' On March 24,2003,physical samples of first ground water collected from B-1, the 20 foot soil profile boring and were remanded through due chain of custody to Precision Enviro-Tech Analytical laboratory of Stockton where they were tested for nitrate as N031 dibromochloropropane(DBCP), and ethylene dibromide (EDB). The samples tested non-detect for DBCP/EDB, but nitrate was detected at a concentration of 163 mg/L as NOS. This nitrate level, well over the Maximum Contaminant Level of 45 mgtL as N031 indicates that shallow ' ground-water aquifer at the site has been impacted by nitrates. The laboratory results and chain of custody are attached in Appendix D. ?OE f0 O� O'Is0