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d = Fraction(%)of nitrate-nitrogen combined loss in the very high clay content soil due to: 1.) Prevention of nitrification and 2.)The denitrification of nitrate molecules that may form. R = Average recharge rate of rainfall - inches per yr NLS§3.2 Nb = Background nitrate-nitrogen concentratio of rainfa charge,exclusive of wastewater influences (ppm NO3-N). Values and Assumptions: I= 109,500 izals=total W W/yr=14,600 cu ft =3.7 in/yr 1.1 Ac x 43,560 sq ft/Ac x (1 ft/12 in) Nw= 60 mg N/L d = Assume 50%due to the very high percentage of clay soil(43%)throughout the upper soil profile that not only mitigates nitrification,but also promotes denitrification of nitrate molecules that may form. R = 8.5 in/yr. Nb= Assumed to be 0.1 ppm NO3-N 3.7 in/yr(60 mg N/L) (1 -0.5)+(8.5 in/yr x 0.1 m L) Nr _ _ �(3.7 in/yr+ 8.5 in/yr) Nr = 9.2 ppm as nitrate-nitrogen (NO3-N)or 41 ppm as nitrate(NO3) C. DISCUSSION OF THE EXISTING SEPTIC SYSTEMS In accordance with the request by EHD, the following information describes the apparent operations of the existing on-site septic systems: Beginning with the small apartment nearest Durham Ferry Road, this structure has a small,round approximate 250 gallon septic tank. Effluent from this tank is apparently disposed of through a small filter bed of unknown construction details and is within the 50 ft radius from the domestic well. The structure closest to the intersection of Hwy 33 and Durham Ferry Road is served by an unknown sized tank and unknown sized filter bed. To the north, the largest structure is served by an approx. 1,200 gallon tank and at least 90 ft leachline. This septic tank and leachline also serve the garage structure to the north, which has a bathroom. All of these existing septic system structures will be closed-in under EHD permit. IV. SEPTIC SYSTEM OPERATIONAL PARAMETERS AND COMPONENTS A. PROPOSED SEPTIC SYSTEM COMPONENTS AND OPERATIONAL PARAMETERS TO SERVE THE ENTIRE PROPERTY/FACILITY SSyS0.1 The design of the future pressurized filter bed disposal system for the facility is based u -the factors of efficient operation, disposal field longevity, and environmental protection. An overview of the system operation is as follows for the entire property: Beginning with southernmost residential unit, influent from this structure will flow into a new two-compartment 1,200 gal septic tank directly north of this structure. A new tank will be installed because the existing tank is structurally unsound and the distance to move solids to a new two compartment 2,000 gal tank is Page-8-