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The project site has level terrain; consequently, there will be no need to incorporate design considerations for slopes for the future disposal area. Under EHD requirements and regulations, a ✓�� mound system for effluent disposal would not be allowed for this future project even though tight clayey surface soils exist. B. SOIL PHYSICAL CHARACTERISTICS AND ANALYTICAL TEST RESULTS The United States Department of Agriculture - Soil Conservation Service (USDA-SCS) indicates the property soils are Jacktone clay (4180). The Soil Survey of San Joaquin County states that permeability is slow in these soils, which was observed in the percolation testing conducted. SSS§5.2. The surface and subsurface soil investigation began on May 14, 2011 with the drilling of a 25 feet deep exploratory boring, which was converted to a deep pert test boring, and three percolation test borings with a truck mounted drill rig and solid stem auger. Three of the test borings were drilled in the extreme northeast corner of the property as illustrated on the Site Plan, near where the disposal area is to be installed. The last pert test boring was a shallow 40 inch deep drilling to test the permeability of the soil under the existing leachlines. This test is discussed in Section Ill D of this Study. ; NLS§ 1.1, 1.2. Soil cutting samples from the 25-ft exploratory test boring were retrieved at 40 inches (3.3 ft), 102 inches (8.5 ft) and 294 inches (24.5 ft) for chemical analysis. No standing water, or saturated soil was observed at the bottom of this exploratory boring. As the noted on the A&L Laboratory Soil Analysis Reports in Appendix B, chemical analyses of the three soil samples quantify several constituents that influence nitrate loading for this project. The important �'r� parameters for nitrate loading assessment are the organic matter,pH,'cation exchange capacity (CEC), and the nitrate-nitrogen content of the soil. y� As noted, the organic matter in the surface soils is higher than the subsoils, which is to be expected given the property was once farmed. The nitrate-nitrogen concentration is low in the surface soils at 5 ppm, increases dramatically at the 102 inch depth tp 20 ppm, and then decreases to a very low concentration at the 294 inch at 3 ppm. These concentrations suggest that significant denitrification is occurring in the upper surface soils. However, as the nitrate that does form percolates downward, it encounters a higher porosity soil around seven feet. From soil physics, it is known that water migration does not readily enter a higher porosity soil from a lower porosity soil until the lower porosity soil becomes saturated. It is theorized that this is what is occurring when the percolating water"pools"on top of this higher porosity soil,thus creating a higher soil nitrate-nitrogen content at this depth. Additionally,this stratum is most likely anaerobic when seasonally saturated, further creating a favorable denitrifying environment and this is a reason why we see low soil nitrate-nitrogen concentrations at the deeper depths. .Because septic effluent is composed predominately of ammonium(NH,),the pH,along with the CEC, are significant influences on ammonium molecules. The pH of the soil is somewhat alkaline throughout the soil profile which may have an effect on ammonium formation and stability. The CEC measures the ability of the soil to theoretically trap and hold ammonium molecules. Cation Exchange Capacities of the soil samples illustrate increasing CEC with increasing depth. This suggests a high potential for the retention of ammonium molecules for microbial uptake, and may also be a reason why there is low soil nitrogen at the 0,_0 deeper depths. } 3 j Chesney Consulting