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Soil Suitability/ Nitrate Loading Study Irerracon <br /> Buddhist Temple Proposed Dormitory ■ Stockton, California <br /> July 11, 2019 ■ Terracon Project No. NA177056 <br /> Refer to Section 2.3.4.1 for further discussion. <br /> 1.4 Groundwater Information <br /> 1.4.1 Groundwater Depth and Gradient <br /> Groundwater was not encountered in our percolation test borings (61 and 132) excavated to a <br /> depth of 3.5 feet below grade surface (bgs). According to the California Department of Water <br /> Resources, Groundwater Information Center Interactive Map, depth to groundwater lies between <br /> approximately 20 and 40 feet bgs. The groundwater flow direction and the depth to shallow, <br /> unconfined groundwater, if present, would likely vary depending upon seasonal variations in <br /> rainfall and other hydrogeological features. <br /> 1.4.2 Potential Groundwater Contamination Issues <br /> Potential groundwater contamination can occur from a number of sources including historical <br /> petroleum hydrocarbon use, agricultural activities, dairies, septic systems, and storm water <br /> infiltration. As per EHD requirements nitrate as N and 1,2-dibromo-3-chloropropane (DBCP) have <br /> been included as part of the SSS discussion. Identifying potential groundwater contamination <br /> other than nitrates and DBCP is beyond the scope of work for this report. <br /> The presence of nitrates is not uncommon in shallow groundwater aquifers in San Joaquin County <br /> and other parts of the Central Valley. Nitrate in groundwater occurs as a result of the application <br /> of fertilizers, livestock waste, and untreated septic tank waste. Nitrate is mobile and often <br /> accumulates in the shallow groundwater zones. <br /> In the early 1900s, natural levels of nitrate in groundwater were measured in forty-three (43)wells <br /> throughout the Sacramento Valley by Kirk Bryan (1923). It was thought that groundwater at that <br /> time was close to "natural" conditions. Based on the work by Bryan, it is estimated that under <br /> "natural" conditions, groundwater concentration containing nitrate is no more than about 13.5 <br /> milligrams per liter (mg/L) nitrate (NO3) or (3 mg/L-N). Areas having 24.75 mg/L-NO3 (5.5 mg/L- <br /> N) or more are those in which nitrate concentrations may be increasing (Hull, 1984). <br /> DBCP (dibromochloropropane) is a nematocide and soil fumigant for vegetables and grapes. It <br /> is thought to cause health problems consisting of kidney damage, liver damage, and cancer. The <br /> use of DBCP was discontinued in 1979. <br /> Based on a review of 2006 NOA SSNLS report, the site has a history of elevated nitrate levels in <br /> groundwater. Refer to Section 1.1 for further discussion. <br /> Responsive ■ Resourceful ■Reliable 9 <br />