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Predominate land use south of Linne Road has been gravel pits and agricultural production land for many decades. Both land uses are evidenced by the United States Department of Agriculture (USDA) Soil Maps for San Joaquin County for this area in the 1970s. It appears the subject property may have been in orchard trees during the 1970s. Applications on file with the Environmental Health Department reveal that there have been four permits issued for additions to existing systems within a one mile study area,with particular emphasis to structures on Linne Road. B. SOIL PHYSICAL CHARACTERISTICS The project site does not have sloping terrain in the proposed leachfield area severe enough to warrant terracing or other types of unique effluent management techniques. The soil profile as determined during the drilling of the deep, 25-foot perc test boring with a truck mounted drill rig is illustrated on the FIELD PERCOLATION TESTING REPORT and is described as follows: From 0 to 10 feet in depth, the soil structure consists of brown clayey, fine sandy silt, with intermittent thin gravel strata(CL/SM/GC). From 13 to 18 feet, there is a well- defined gravel stratum consisting of well-graded gravel (GV). From 18 to 23 feet is a clayey fine sand stratum (SC) and from 23 to 25 feet exists a clayey gravel (GC) stratum. The United States Department of Agriculture -Natural Resources Conservation Service (USDA- NRCS) indicate the on-site surface soils consist of a Stomar Clay Loam (#252) soil type. The top 60 inches consist of a grayish brown clay and clay loam. The Unified Soil Classification System(USCS) has been used above in parentheses to identify the strata encountered during drilling. According to the USDA Handbook, the surface soils to 60 inches is poor for septic tank absorption fields due to slow percolation. However, numerous percolation tests have been conducted within Stomaz Clay Loam soil with excellent percolation rates, as evidenced by the perc rates obtained for this study. Large particle sized material allows for increased percolation rates; however, there is also adequate fine material (clay and silt sized particles)to ensure biological treatment of the effluent before reaching the water table, -75 ft below grade. Biological treatment includes the destruction of bacteria and viruses. If there were no strata of fine-grained soils below the standard leachline trench depth of 42 inches and it was composed mostly of gravel, this would theoretically allow for saturated flow conditions and allow bacteria, viruses and nitrate to readily enter the water table. The important soil parameters for nitrate loading assessment are the organic matter, pH, cation exchange capacity (CEC), soluble salts, along with nitrate-nitrogen content. Organic matter in the indigenous soils is low. The estimated nitrogen release (ENR) is 45 lbs N/Ac which is very typical of virgin soils. Low organic matter and low ENR indicates a small potential for future nitrate-nitrogen loading from the indigenous soils. Page -2- CFiesney Consulting