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k The United States Department of Agriculture - Soil Conservation Service (USDA-SCS) indicates the on-site soils to consist of a Madera sandy loam(#193), and references this soil to have very slow permeability. Percolation test results for the shallow 42-inch deep test indicate a comparatively slow m rate at 41.7 min/' h, as described below. l , SSS§ 5.2`,/5.4. The project site has level terrain; consequently, there will be no need to incorporate design considerations for slopes within the leachfield area. The surface and subsurface soil investigation and testing began with drilling a 42-inch Pere test boring, followed by a 144 inch (12 ft) boring representative of sumps, and then a 300 inch (25 ft)boring representative of seepage pits. From the deeper boring completed, it was observed that the soil becomes somewhat sandier with increasing depth. NLS 1.1, As the noted on the A&L Laboratory Soil Analysis Reports, chemical analyses of the soil es from the 25-foot deep boring quantify several constituents that will influence nitrate loading from this project. The important parameters for nitrate loading assessment are the organic matter, pH, cation exchange capacity(CEC), clay content percentage, along with nitrate-nitrogen content. As noted, the organic matter in the soil is low-to-very low in all of the soil samples. This suggests a low potential for future nitrate-nitrogen loading from indigenous nitrogen soil content. It may also suggest a low denitrification potential since organic matter is needed for promotion of denitrification. The nitrate-nitrogen concentrations at each depth are low, and very consistent at five to six ppm throughout the soil profile to 25 feet. Since septic effluent is composed predominately of ammonium (NH4), the pH, along with the CEC, are significant influences on ammonium molecules. The pH of the soil is alkaline which may inhibit ammonium formation and therefore stability, and may create a propensity for ammonia(NI10 formation. The CEC measures the ability of the soil to theoretically trap and hold ammonium molecules. Cation Exchange Capacities of the soil samples are relatively low due to the low clay and higher sand content. This suggests there is a small potential for the retention of ammonium molecules for microbial uptake, and suppression of nitrification. § 5.3, 5.4. Table 1 below summarizes the subsurface soil characteristics encountered from the 5-foot deep boring, from every five-foot interval depth,'illustrating the soil particle analysis, USDA soil classification, nitrate-nitrogen concentration, and pH and CEC: 3 . Chesney Consulting