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leachfield grade. This will allow some evapotranspiration to take place in the summer since the leachfield will be in the lawn area. The leachfield trenches and sumps consists of the following surface area: Each trench=4 ft2 trench sidewalls+2 ft2 bottom of trench x 100 ft length=600 ft' x 8-100 ft sections=4800 ft. Sumps 4 ft wide x 8 ft deep x 8 ft long= 200 ft2 x 4 sumps= 800 ft2 : 4800 ft2 + 800 ft2 = 5600 ft' surface area for effluent infiltration PHASE H: Base Tank Capacity (BTC)+Average Daily Flow(ADF)x Soil Factor(SF)_ 2,000 gal BTC + 507 gal ADF x .200 SF=500 lineal feet of leachline _ 5 - 100 foot sections of leachline pipe= 6,000 square foot leachfield In addition to the leachline, there should be one sump for every two leachlines for a total of two sumps. The leachlines should be placed at a depth of 15-20 inches below final leachfield grade. _ Trench depth should be 36-42 inches. The leachfield trenches and sumps consists of the following surface area: Each trench=4ft2 ench sidewalls+2 ft2 bottom of trench x 100 ft length= 600 ft2 x 5-100 ft sections=3000 W. Sumps 4 ft wide x 8 ft deep x 10 ft long=200 ft2 x 2 sumps=400 ft2: 3000 ft2 +400 ft2 =3400 ft' surface area for effluent infiltration 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. Hydraulic loading rates range from a conservative criterion of 0.125 gal/ft2/day to 0.5 gal/ft2/day for a percolation rate of approximately 1 min/in. These application rate are based on trench side wall areas only. IMPACT MITIGATION Environmental impact from nitrogen has been mitigated within the septic system design by the following methods: First,by the use of three- 2,000 gallon septic tanks in series, there will be a higher percentage of solid organic material trapped within the tanks. Additionally, a filter should be installed on the last tank(e.g. Zabel® or OSI® Filters)before the effluent flows from this tank to the leachfield. There is evidence that septic tanks have the capability to denitrify nitrate: As influent enters the first tank,the wastewater has been aerated from flushing action, and from the aerator on a faucet, etc. But as the oxygen is consumed by microbiological processes, the tank becomes anaerobic and the microbes begin to use nitrate as an electron acceptor. When the effluent reaches the third and last tank,there should be virtually no oxygen within the tank contents, thus theoretically promoting denitrification. 7 vaffey Ag Research