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Sunrise Trucking— Soil Suitability Section Page 5 of 16 <br /> Our Project Number: NA157003G <br /> 1 October 23, 2015 <br /> 1.3.7 Expected On-Site Maximum Septic Tank Usage <br /> ' The guard shack will be open five days a week; Monday through Friday from 7:00 am to 7:00 pm. <br /> There will be up to two permanent employees operating the guard shack during business hours; <br /> no visitors will be permitted to use the restroom facilities of the guard shack. One restroom will <br /> be located in the proposed guard shack, with a total of one toilet and one sink. Septic system <br /> design should be based on the San Joaquin County On-Site Wastewater Disposal Standards or <br /> other engineering recommendations. <br /> 1.4 Groundwater Information <br /> 1.4.1 Groundwater Depth and Gradient <br /> Groundwater was not encountered in our percolation test hole excavated to depth of 42 inches <br /> on September 28, 2015. <br /> The San Joaquin County Flood Control and Water Conservation District groundwater depth maps <br /> were reviewed to determine the groundwater levels near the Site. The Spring 2014 and Spring <br /> 2015 depth to groundwater maps are the most current official maps available from the County <br /> Groundwater Report. According to these maps (Plates 3 and 4) groundwater lies approximately <br /> 25 feet bgs. Per the Department of Water Resources (DWR) Water Data Library an irrigation <br /> ' well', approximately 950 feet west of the site, had a depth to groundwater of 26.7 feet on March <br /> 3, 2015. The approximate site elevation is 22 - 28 feet above mean sea level. The groundwater <br /> flow gradient is approximately 3.33 feet per mile to the north-northeast. <br /> 1.4.2 Potential Groundwater Contamination Issues <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 /> 1 htto://www.water.ca.sov/waterdatatibrary/Groundwater level station site code: 378562N1212685W001 <br /> 02015 Neil O.Anderson&Associates,Inc. <br /> A Terracon Company <br />