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Nitrate Loading Study Irerracon Morris Property w Ripon, California September 12, 2018 a Terracon Project No. NA187039 inches per hour. For homesite development with septic tank absorption fields, the main limitations are rapid permeability and poor filtration. A tillage pan may form if soil is tilled when wet; however, the pan may be broken up by chiseling or ripping. Timor loamy sandy soils comprise approximately 55% of soils near the northeastern portion of the site and consist of moderately well drained soils. Timor loamy sandy soils have rapid permeability and slow runoff. The rate of water in-take in irrigated areas is anticipated at 3.0 inches per hour. For homesite development with septic tank absorption fields,the main limitations are depth to hardpan, approximately 4 feet below grade surface (bgs), and rapid permeability. Hardpan can be broken up by chiseling or ripping which may improve leach field absorption. The longer effluent remains near the surface, the more treatment is enhanced due to natural processes within the soil. Based on the loamy sandy soils and rapid permeability anticipated for the majority of the surface soils on the site, the potential for effluent to remain near the surface is low; therefore, there is a potential leaching from sewage effluent or other surface contaminants may affect groundwater. 2.0 GROUNDWATER ANALYSIS 2.1 Regional Groundwater Based on a review of the San Joaquin County Flood Control and Water Conservation District Groundwater Report, from 2015 to 2016, Spring & Fall depth to groundwater near the site was between approximately 50 and 60 feet bgs. Based on a review of groundwater data available on the California Department of Water Resources (DWR) Water Data Library, between the years 2015 and 2018, depth to groundwater measured between approximately 45 to 58 feet bgs at groundwater wells located approximately one mile north and east of the site.The groundwater flow direction and the depth to shallow, unconfined groundwater, if present, would likely vary depending upon seasonal variations in rainfall and other hydrogeological features. Without the benefit of on-site groundwater monitoring wells surveyed to a datum, groundwater depth and flow direction beneath the site cannot be directly ascertained. 2.2 Potential Ground Water Contamination Issues The presence of nitrates is not uncommon in shallow groundwater aquifers in San Joaquin County and other parts of the Central Valley. Nitrate in groundwater occurs as a result of the application of fertilizers, livestock waste, and untreated septic tank waste. Nitrate is mobile and often accumulates in the shallow groundwater zones. In the early 1900s, natural levels of nitrate in groundwater were measured in forty-three (43)wells throughout the Sacramento Valley by Kirk Bryan (1923). It was thought that groundwater at that time was close to "natural' conditions. Based on the work by Bryan, it is estimated that under "natural' conditions, groundwater concentration containing nitrate is no more than about 13.5 Responsive ■ Resourceful ■ Reliable 4