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Soil Suitability/Nitrate Loading Study Irerracon <br /> Gribaudo Property ■Acampo, CA <br /> November 12, 2019 ■ Terracon Project No. NA197081 <br /> 1.4 Groundwater Information <br /> 1.4.1 Groundwater Depth and Gradient <br /> Groundwater was not encountered within our geotechnical or percolation test borings which were <br /> drilled between 3.25 and 9.0 feet below grade surface (bgs). <br /> According to the California Department of Water Resources, Groundwater Information Center <br /> Interactive Map, groundwater was reported between approximately 120 and 130 feet bgs in the <br /> Spring 2018 and approximately 130 and 140 feet in the Fall of 2018. The groundwater flow <br /> direction and the depth to shallow, unconfined groundwater, if present, would likely vary <br /> depending upon seasonal variations in rainfall and other hydrogeological features. Without the <br /> benefit of on-site groundwater monitoring wells surveyed to a datum, groundwater depth and flow <br /> direction beneath the site cannot be directly ascertained. <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 the DWR Water Data Library, last modified in July of 2018, no additional <br /> groundwater well information was identified within 1 mile of the site. Based on a review of the <br /> State Water Resources Control Board online map, there were no nitrate impacted wells identified <br /> near the site. <br /> Responsive■ Resourceful ■ Reliable 7 <br />