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20 January 2021 <br />Project No. 20-6284 <br />Page 9 of 14 <br />percolation rate. The use of the proposed septic system should follow the San Joaquin <br />County On-site Wastewater Treatment Standards. <br /> <br /> <br />7.0. CHEMICAL AND PHYSICAL PROPERTIES OF SOIL <br /> <br />Soil chemical properties were supplied by regionally sourced material for the surrounding <br />area. <br /> <br /> <br />7.1. CHEMICAL AND PHYSICAL PROPERTIES OF SITE SOILS <br /> <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 Hollenbeck silty clay having 0 to 2 percent slopes (#173). The Hollenbeck silty clay is <br />composed of alluvium derived from mixed rock sources. Soils are described as <br />moderately well drained; with very low permeability; and salinity of less than 2.0 millimhos <br />per centimeter (mmhos/cm). Soil in the Hollenbeck silty clay complex typically have a <br />profile of silty clay to 10 inches, clay to 37 inches, silty clay loam to 42 inches, and <br />cemented loam from 42 to 60 inches bsg. <br /> <br /> <br />7.2. MASS TRANSPORT PROPERTIES OF UNDERLYING SITE SOILS <br /> <br />The percolation test and dominant soil type at the site indicates that the soils are semi- <br />permeable and have moderate water storage. These soils will allow slow for moderate <br />infiltration of water through the surface soils. The longer the effluent remains near the <br />surface, the more treatment is enhanced due to natural processes within the soil. If the <br />permeable soils exist to the depth of the groundwater table, it is possible that surface <br />contaminants may be transported fairly rapidly. <br /> <br /> <br />8.0. GROUNDWATER ANALYSIS <br /> <br />The subject property will be supplied with potable water by the onsite domestic water well <br />(Figure 2). A groundwater sample was not collected from the well as part of this study <br />because there is no electrical power to the site. <br /> <br /> <br />8.1. DESCRIPTION OF LOCAL GROUNDWATER <br /> <br />As described in section 4.1, depth to groundwater at the site is approximately 90 to <br />100 feet bsg. Between 2011 and 2018, depth to groundwater at the site has fluctuated