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The nitrate-nitrogen concentrations are also very high. At 24 inches, the concentration is extremely high, but dramatically decreases by a factor of 3.3 at the 40-inch depth. This may suggest a high denitrification potential between the 24 and 40 inch depths. Organic matter is needed for promotion of denitrification and since the TKN is high, denitrification potential may also be high. Because 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 slightly alkaline which may have little 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 are comparatively high due to the high clay content. This means there is a high potential for the retention of ammonium molecules for microbial uptake, and denitrification potential. This is what may be occurring at the 24 to 40 inch depths, as was noted by the decrease in nitrate-nitrogen co en on. NL S§3. , S § 5Table 1 below summarizes the surface and subsurface soil characteristics cou red om a three soil samples, illustrating the particularly high clay content percentages from each sample: TABLE 1 SOIL PROFILE CHARACTERISTICS AND ANALYTICAL TEST RESULTS SAMPLE LOCATION, SAND,Sn.T AND SOIL SOIL NITROGEN PH AND SAMPLE DEPTH AND CLAY CLASSIFICATION CONTENT CATION EXCHANGE (SAMPLE NUMBER) PERCENTAGES TKR CONTENT CAPACITY DISPOSAL FIELD AREA 39%,30%,30% Clay Loam 51 ppm NO,-N (7.321.3 meq 100e SURFACE (SURF.) 1698 mg/kg DISPOSAL FIELD AREA 31%,32%,36% Clay Loam/ 285 ppm NO,-N 8.0 25.9 meq/100g 24 IN DEPTH (241N) 1435 mg/kg DISPOSAL FIELD AREA 31%,32%, 36% Clay Loam 87 ppm NO,--N 7,9 30.6 meq/1008 40 IN DEPTH (40 IN) 1315 mg/kg C. PERCOLATION AND INFILTRATION TEST RESULTS SSS§ 6.2. To assess the permeability and the infiltration capabilities of the proposed mound system a, two percolation tests were completed in the locations depicted in the Site Plan found in Appendix C. The test depths were 24 and 40 inches below existing grade, giving a comparatively detailed observation of subsurface permeability at these two strata. Only the 40-inch test depth is recognized as`official'by EHD. The test depths can be considered to represent the average permeability throughout the effluent receiving soil profile. LL 4 Chesney Consulting