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Soil Suitability / Nitrate Loading Study Ernst Property ■ Tracy, CA Irerracon February 21, 2019 revised April 9, 2019 ■ Terracon Project No. NA197000 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. 1.4.2 Potential Groundwater Contamination Issues Potential groundwater contamination can occur from a number of sources including historical petroleum hydrocarbon use, agricultural activities, dairies, septic systems, and storm water infiltration. As per EHD requirements nitrate as N and 1,2-dibromo-3-chloropropane (DBCP) have been included as part of the SSS discussion. Identifying potential groundwater contamination other than nitrates and DBCP is beyond the scope of work for this report. 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 milligrams per liter(mg/L) nitrate (NO3) or (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. Based on the historical information, the past agricultural land use and septic systems in the area should be considered potential groundwater contamination sources. 1 .4.3 Water Sample Location According to Mr. Ernst the site is connected to a municipal water supply and there are no functioning groundwater wells on the site; therefore, a groundwater sample was not collected. According to Mr. Chang Cao, of the San Joaquin County Public Works Department, the site receives water from the County Service Area 35 primarily by Well#1. Mr. Cao indicated the well is located on Currier Drive which is approximately 1,600 feet east of the site. Mr. Cao was not aware of elevated nitrate levels or DBCP in the municipal supply well for the area. 1 .4.4 Groundwater Sample Analysis Not applicable. Refer to Section 1.4.3. Responsive■ Resourceful ■ Reliable 7