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F ELDS/FILTER BEDS Capacity (BTC) +Average Daily Flow(ADF) x Soil Factor(SF)_ TC + 920 gal ADF x .200 SF = 584 lineal feet of leachline 6 - 100 foot sections of leachline pipe= 6,000 square foot leachfield The Environmental Health Department may stipulate the initial installation of sumps. However, in the event of leachline failure, sumps should be installed. Based upon the soil characteristics encountered,the leachlines trenches must extend below the hardpan layer to a depth of 42 inches. Although the leachline trench will not extend into the sand strata found at 5.5 ft below grade, an interesting phenomenon is predicted to occur: Downward water movement encountering a sandy stratum will be impeded until the moisture content in the strata above the sand layer becomes sufficiently saturated. The saturation in the silt stratum above the sand stratum will create anaerobic conditions and theoretically promote denitrification. Several scientific studies have demonstrated that the infiltration capacity of a soil absorption system is dependant primarily by the formation of the biomat and not by the permeability of the soil. The biomat is a biological, slimy substance which forms on the soil-effluent interface over time. Effluent hydraulic loading rates range from a conservative criterion of 0.125 gal/ft2/day to 0.5 gal/ftZ/day. As a safety factor, these loading rates apply to trench side wall areas only. NITROGEN IMPACT MITIGATION Nitrogen mitigation will be primarily accomplished by the use of two septic tanks through the following processes: It has been well-documented that gaseous nitrogen emanates from septic tanks. The gaseous formation is apparently attributable to denitrification which is the biological reduction of nitrate (NO3) and nitrite (NO.)to volatile gases. The biochemical processes which occur in septic tanks are highly complex but can be described simplistically: A microbe digesting a waste organic molecule with an attached nitrogen atom may have the freed nitrogen as a surplus atom. To digest the N atom,the microbe can combine it with dissolved molecular oxygen OZ and release it in solution as a molecule of nitrite and possibly nitrate. This occurs under aerobic conditions and is referred to as nitrification. If a microbe needs oxygen within an anaerobic environment, it can take the oxygen from nitrite or nitrate molecules. Not requiring surplus nitrogen atoms, the microbe can combine pairs of surplus nitrogen atoms to form nitrogen gas (NZ). This is the denitrification process. Therefore, the first septic tank should contain a higher concentration of oxygen from sink faucet aeration and the flushing action of toilets. This aerobic environment should promote nitrification. As the oxygen is consumed in the first tank, effluent flowing into the second tank should be predominately anaerobic. Under these conditions, denitrification should occur in the second tank. The following data was obtained from Winneberger(See References) which substantiates the process of denitrification within septic tanks: Argon is an inert gas found in the atmosphere in proportions of 84 parts of nitrogen to 1 part argon. When each of those gases come to equilibrium in water less than one Latmosphere, they exists in a ratio of approximately 37 parts of nitrogen to one part argon. 7 Na!!ey Ag Researck