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19 May 2021 Project No. 21-6435 Page 8 of 14 7.0. CHEMICAL AND PHYSICAL PROPERTIES OF SOIL Soil chemical properties were supplied by regionally sourced material for the surrounding area. 7.1. CHEMICAL AND PHYSICAL PROPERTIES OF SITE SOILS The dominant soil composition in the general area of the property was inferred from information provided by the United States Department of Agriculture’s Soil Geographic Database (USDASGD). The USDASGD soil survey indicates the soil type for the property is predominantly composed of Sailboat silt loam having 0 to 2 percent slopes (#234). The Sailboat silt loam is composed of alluvium derived from mixed rock sources. Soils are described as somewhat poorly drained, with a moderately low permeability, and salinity ranging from 0.0 to 2.0 millimhos per centimeter (mmhos/cm). The Sailboat silt loam typically have similar chemical properties and soil profile between surface grade and 61 inches bsg. 7.2. MASS TRANSPORT PROPERTIES OF UNDERLYING SITE SOILS The percolation test and dominant soil type at the site indicates that the soils are semi- permeable and have high water storage. These soils will allow moderate infiltration of water through the surface soils. The longer the effluent remains near the surface, the more treatment is enhanced due to natural processes within the soil. If the permeable soils exist to the depth of the groundwater table, it is possible that surface contaminants may be transported fairly rapidly. 8.0. GROUNDWATER ANALYSIS The subject property is supplied with potable water by a public water municipality. A groundwater sample was not collected from a well and analyzed for nitrates as part of this study. 8.1. DESCRIPTION OF LOCAL GROUNDWATER According to the DWR SGMA Data Viewer for Spring 2020, depth to groundwater at the site is approximately 15 to 20 feet bsg. Between 2011 and 2019, depth to groundwater at the site has fluctuated between 15 and 30 feet bsg. Groundwater flow direction locally appears to be to the southwest. Groundwater was not encountered in the 42-inch-deep percolation test hole advanced on 13 May 2021.