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Nitrate Loading Study 1 Terracon Landavazo Property Tracy, CA December 15, 2017 Terracon Project No. NA177067 ranged between approximately 110 feet and 120 feet bgs and between 90 feet and 100 feet bgs in Fall 2015. Based on a review of the above mentioned sources, depth to groundwater has historically been shallow; however, depth to groundwater has increased to greater than 100 feet bgs in recent years. 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. Septic systems in the area should be considered potential groundwater contamination sources. The concerns for groundwater contamination in this area are deemed low due to slow permeable soils and anticipated depth to groundwater of 90 and 140 feet bgs. 2.3 Current and Future On-Site Ground Water Uses According to Mr.Landavazo, there are no groundwater wells located on the site. Mr. Landavazo indicated an off-site municipal groundwater supply well, located approximately 1,500 feet from the site, will provide water to the site. Based on the absence of an onsite groundwater well, a groundwater sample was not collected. Terracon requested nitrate and DBCP information which may be on file with the EHD for the surrounding properties. According to Mr. Dom Martorella of the EHD, groundwater results for the constituents were not available. Responsive■ Resourceful ■ ReliaWb 4