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B. SOIL PHYSICAL CHARACTERISTICS AND ANALYTICAL TEST RESULTS The project site has level terrain; consequently,there will be no need to incorporate design considerations for slopes. The United States Department of Agriculture (USDA) soil map indicates the on-site soils to consist of a Stockton clay (250). The leachlines for the facility will be installed in, or immediately below this material. However, the seepage pits will be excavated down to a very fine sandy, clayey silt,which was encountered during percolation testing procedures. A comparatively slow perc rate was obtained in this soil type. The log of boring for the test pit is found on the FIELD PERCOLATION TESTING REPORT illustrates the variability of the subsurface soil characteristics encountered. Photographs of the subsurface soil material are also included with this study. As referenced on the USDA soil maps,the surface soils to three feet consist of a black clay soil, indicative of an organic clay. Below three feet and extending to six feet exists a compacted clayey silt. From six to 14 feet there is a severe cemented silts/fine sands hardpan, which was classified as a sandy loam on the Soil Analysis Report. From 14 to 22 feet exists a clayey, silty, very fine sand. A feature observed in the perc test pit soil was rust mottling, as evidenced by the photographs. This can be attributed to seasonal soil saturation. As the water encounters a strata of slower permeability, which would be the hardpan layer,the percolating water "pools" on top of the slower permeability layer. This creates an anaerobic zone. Rust mottling occurs when anaerobic bacteria decompose organic matter and create oxidized iron(rust) in their metabolic processes. Indication that these two conditions are present- organic matter from the black clay above and an anaerobic environment signify that denitrification may be supported. Two soil samples were obtained from the proposed leachfield area. The first sample was retrieved from the anticipated leachline depth of 3 ft(Sample Number LF 3). The second sample was taken from 12 ft below grade (Sample Number LF 12). As the noted on the SOIL ANALYSIS REPORTS,the nitrate-nitrogen (NO3-N) concentration is very low at both depths and relatively equal at 3 ppm and 4 ppm,respectively. Therefore,there should not be further nitrate impact(i.e., loading) from indigenous nitrate within the soil profile. Additional chemical analyses on the soil samples from the two depths referenced above was also done to quantify other important constituents. These parameters for nitrate loading assessment include the organic matter, pH, cation exchange capacity (CEC), along with nitrate-nitrogen content. As noted, the organic matter in the soil is considered low for agronomic purposes, although for general purposes, the organic matter percentages are medium. In a lighter, sandier soil, this would indicate a slight potential for additional nitrate-nitrogen loading in the future. 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 at the deeper depths which may slightly inhibit ammonium formation and stability. The CEC measures the ability of the soil to theoretically trap and hold ammonium molecules. A CEC of 41.9 and 26.0 from the respective depths indicates there is considerable potential for the retention of ammonium molecules for microbial uptake, and suppression of nitrification, particularly at the Lleachlinepth. 2 Va(ky Ag Research