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12 October 2020 AdvancedGeo <br /> An Employee-Owned Company <br /> Project No. 20-6164 ; <br /> Page 9 of 15 <br /> hour percolation test; the smallest reading over the 4-hour period was used to calculate <br /> the percolation rate. The use of the existing and proposed septic systems should follow <br /> the San Joaquin County On-site Wastewater Treatment Standards. <br /> 7.0. CHEMICAL AND PHYSICAL PROPERTIES OF SOIL <br /> Soil chemical properties were supplied by regionally sourced material for the surrounding <br /> area. <br /> 7.1. CHEMICAL AND PHYSICAL PROPERTIES OF SITE SOILS <br /> The dominant soil composition in the general area of the property was inferred from <br /> information provided by the United States Department of Agriculture's Soil Geographic <br /> Database (USDASGD). The USDASGD soil survey indicates the soil type for the <br /> property, and the area of the proposed septic disposal field, is predominantly composed <br /> of San Joaquin sandy loam having 0 to 2 percent slopes (#236). The San Joaquin sandy <br /> loam is composed of alluvium derived from granitic rock sources. Soils are described as <br /> moderately well drained; with low permeability; and salinity of less than 2.0 millimhos per <br /> centimeter (mmhos/cm). Soil in the San Joaquin sandy loam complex typically have a <br /> profile of sandy loam to 13 inches, clay to 20 inches, and indurated loam from 20 to 60 <br /> inches bsg. <br /> 7.2. MASS TRANSPORT PROPERTIES OF UNDERLYING SITE SOILS <br /> The percolation test and dominant soil type at the site indicates that the soils are semi- <br /> permeable and have low water storage. These soils will allow slow to moderate infiltration <br /> of water through the surface soils. The longer the effluent remains near the surface, the <br /> more treatment is enhanced due to natural processes within the soil. If the permeable <br /> soils exist to the depth of the groundwater table, it is possible that surface contaminants <br /> may be transported fairly rapidly. <br /> 8.0. GROUNDWATER ANALYSIS <br /> The subject property is supplied with potable water by the onsite domestic water well <br /> located to the west of the existing residence (Figure 2). A groundwater sample was <br /> collected from the well and analyzed for nitrates as part of this study. <br /> 8.1. DESCRIPTION OF LOCAL GROUNDWATER <br /> According to the San Joaquin County Flood Control and Water Conservation District's <br /> Lines of Equal Depth to Groundwater Fall 2018 and the DWR SGMA Data Viewer, depth <br />