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• Soil Suitability/ Nitrate Loading Study 1 ferracon Sun Valley Express Truck Center■ Acampo, California August 14, 2017 ■ Terracon Project No. NA177026 visitors/truckers at 5 gallons per day per person, 7 days per week for 152 days per year). The maximum daily usage should not be reduced for the purpose of design of the septic system since it is only in use for 152 days a year given the usage is continuous during this time. For the purpose of nitrate loading and septic suitability purposes an average daily usage may be reduced to 214.5 gallons per day given the 152 day season. 1.4 Groundwater Information 1.4.1 Groundwater Depth and Gradient Groundwater was not encountered in our percolation test borings excavated to a depth of 25 feet • bgs on June 20, 2017. According to the California Department of Water Resources Groundwater Information Center Interactive Map, Spring 2017 to Spring 2016 groundwater depth and elevation maps, groundwater depth lies between approximately 90 and 100 feet bgs with an anticipated easterly 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 as pr1 fined. 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 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 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 (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, 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 low to moderate due to the depth to groundwater of 90 to 100 feet bgs. • Responsive ;- Resourceful Reliable 7