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Nitrate Loading Study 1�err�con Rowe Propertyy a Lodi, CA November 6, 2017 ■ Terracon Project No. NA177059 an anticipated southerly flow direction. 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. Itis 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 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 surface permeable soils, depth to groundwater of 90 and 110 feet bgs, and the potential for interstratified finer grained soils between the upper near surface soils and groundwater. 2.3 Current and Future On-Site Ground Water Uses According to a site diagram provided by Ms. Rowe, the site is equipped with a domestic groundwater well located approximately 30 feet southeast of the existing residence. Ms. Rowe indicated the groundwater well is currently being used for the existing residence and will continue to be used for the existing residence and the proposed new construction. Terracon requested a copy of the groundwater well permit on file with the EHD. Copies of the permits are included in Appendix C. Responsive ■ Resourceful ■ Reliable 4