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Odyssey Landscape—Soil Suitability Section Page 5 of 13 Our Project Number: NA157000 March 17, 2015 elevation is 15 feet above mean sea level. The groundwater flow gradient is approximately 5.85 feet per mile to the east. 1.4.2 Potential Groundwater Contamination Issues The presence of nitrates is not uncommon in shallow groundwater aquifers in San Joaquin County and other parts of the Central Valley. Nitrate in groundwater occurs as a result of theZJ application of fertilizers, livestock waste, and untreated septic tank waste. Nitrate is mobile and often accumulates in the shallow groundwater zones. In the early 1900s, natural levels of nitrate in groundwater were measured in forty-three (43) wells throughout the Sacramento Valley by Kirk Bryan (1923). 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 containing nitrate is no more than about 13.5 mg/L-NO3 (3 mg/L-N). Areas having 24.75 mg/L-NO3 (5.5 mg/L-N) or more are those in which nitrate concentrations may be increasing (Hull, 1984). As indicated, DBCP (dibromochloropropane) and EDB (ethylene dibromide) were not detected in the well 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. EDB was used in gasoline to present lead deposits and build up. It was also used in pesticides and fumigant. Exposure to EDB is linked to many adverse health effects stemming from organ damage to cancer. The Environmental Protection Agency (EPA) set the maximum contaminant limits (MCL) at 0.2 parts per billion (ppb) for DBCP and 0.05 ppb for EDB 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. Agricultural activities, industrial activities, and the use of septic systems in the area should be considered potential groundwater contamination sources. The concerns for groundwater contamination in this area are deemed moderate due to the depths involved. 1.4.3 Water Sample Location One water well exists on the site. There were no permits found during a recent file review at / EHD for the address of 5400 West Highway 12. Groundwater is a source of drinking water for the site; therefore, two samples were collected from a spigot in the vicinity of the water well for testing of DCBP, EDB and Nitrate. 1.4.4 Ground Water Sample Analysis Two ground water samples were taken from an existing well on the site. The sample for nitrate was collected in a sterile plastic container; the sample for DBCP/EDB was collected in two sterile glass vials. Samples were transported on ice and remanded under chain of custody to McCampbell Analytical, Pittsburg. A copy of the chain of custody and lab report from McCampbell Analytical has been included in Appendix E. "44 ©2015 Neil O.Anderson&Associates,Inc. A Terracon Company