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lierracon Nitrate Loading Study Nielsen Property Ripon, California January 15, 2019 Terracon Project No. NA187066 the majority of the surface soils on the site, the potential for effluent to remain near the surface is low; therefore, there is a potential leaching from sewage effluent or other surface contaminants may affect groundwater. 2.0 GROUNDWATER ANALYSIS 2.1 Regional Groundwater Based on a review of the San Joaquin County Flood Control and Water Conservation District Groundwater Report, from 2015 to 2016, Spring & Fall depth to groundwater near the site was between approximately 50 and 60 feet bgs. Based on a review of groundwater data available on the California Department of Water Resources (DWR) Water Data Library, between the years 2015 and 2018, depth to groundwater measured between approximately 45 to 58 feet bgs at groundwater wells located approximately one mile north and east of the site. The groundwater flow direction and the depth to shallow, unconfined groundwater, if present, would likely vary depending upon seasonal variations in rainfall and other hydrogeological features. Without the benefit of on-site groundwater monitoring wells surveyed to a datum, groundwater depth and flow direction beneath the site cannot be directly ascertained. 2.2 Potential Ground Water 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 the 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). DBCP (dibromochloropropane) is a nematicide 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 (ethylene dibromide) was used in gasoline to prevent lead deposits and build up. It was also used in pesticides and fumigants. Exposure to EDB is linked to many adverse health effects stemming from organ damage to cancer. Agricultural land use and septic systems in the area should be considered potential groundwater contamination sources. The concerns for groundwater contamination in this area are deemed moderate to high based on the agricultural land use and anticipated depth to groundwater between 45 to 60 feet bgs. Responsive • Resourceful • Reliable 4