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i Interestingly, the soil nitrate-nitrogen content directly under the drain rock is 46 ppm. Multiplying this concentration by the conversion factor of 4.43 to convert nitrate-nitrogen concentrations to nitrate, we arrive at a nitrate concentration of 204 ppm,which is comparable the 177 ppm nitrate concentration measured in the EnviroServer effluent, If the nitrate-nitrogen concentration at 2 feet, below the drain rock is converted to nitrate, we have 11 ppm x 4.43 =48.7 ppm nitrate theoretically entering the water table, This theoretical concentration of 48.7 ppm nitrate is slightly above the MCL of 45 ppm, and may be lower since the effluent must travel through another two-to-three feet of soil before encountering the water table. The soil test results reveal a distinctive decrease in nitrate nitrogen concentration from the sampled depths as illustrated in Table 2. In all probability, this is attributable to denitrification within the clay soil profile. Denitrification is markedly affected by the environment. Primary among the environmental influences are the nature and amount of organic matter, aeration, moisture content,pH and soil temperature. The gross organic matter content of the underlying soils can be considered low, but this.measurement does not analyze different fractions, microscopic portions of organic fractions which may be present. The pH of the soil environment is particularly important to the denitrifying microorganisms. Denitrifying bacteria are sensitive to acidic soils: Test results for pH reveal an alkaline soil at the 1 FT and 2 FT sample depths;which would be beneficial for the denitrifying bacteria. Probably the most important and critical environmental consideration is the oxygen availability within the soil environment. Anaerobic microenvironments exist within the microscopic pores of the clay soil. The oxygen atom from the nitrate molecule becomes preferential electron acceptor for respiration, thus chemically reducing the nitrate concentration. Given that the sampled soils were very moist and tight, the almost.assured anaerobic conditions promoted denitrification to the observed extent. Soil chloride concentration was also measured for comparison purposes to the nitrate concentration. Medium-to-high soil and groundwater chloride concentrations may indicate contamination from septic system effluent, since human wastes are generally high in chloride content. Chlorides travel exceptionally well in the soil environment, even better than nitrate, and can be an excellent indicator of septic effluent pollution. The chloride test results on the underlying soil in Table 2 reveal that there has been percolation of effluent through the.soil profile. The alkalinity concentration determined in the-domestic well water(157 ppm) is 36% lower than the alkalinity observed in the conventional septic tank (245 ppm). Therefore, the wastewater must be contributing alkalinity, which is then being utilized by the EnviroServer to nitrify the ammonia nitrogen concentrations. The calculated Average Daily Flow (ADF) from the actual effluent flow meter over a period of 68 months, plus the projected ADF from the new development indicate that the total effluent flow volumes will be slightly below the 1,200 gallons per.day maximum for the EnviroServer at 1,162 gallons per work day. This ADF figure incorporates a significant safety factor. The water table (groundwater) under the filter bed was not sampled since this would not have been a representative analysis of any potential impact to the underlying groundwater from the percolating effluent. Page "7- Chesney Consulting