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Nr = Resultant average concentration of nitrate-nitrogen in recharge water - (ppm NO,-N) I = Volume rate of wastewater entering the soil averaged over the gross developed area in in/yr Nw = Total nitrogen concentration of wastewater in mg NIL d = Fraction (%) of nitrate-nitrogen combined loss in the soil due to denitrification. R = Estimated Annual Rainfall Recharge. Nb = Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater influences Values and Assumptions: I = 200 and x 365 d/yr = 73,000 gals/yr = total WW/yr = 9,759 Cu ft = 5.85 in/yr 0.46 Ac x 43,560 sq ft/Ac x (1 ft/12 in) Nw = 34.43 mg N/L (Original concentration used in the Advanced Geo Report) d = 30% (Original percentage used in the Advanced Geo Report) R = 8.82 in/yr. (2.99 in/yr used in the Advanced Geo Report) Nb = Assumed to be 0.1 ppm NO3-N 5.85 in/yr (34.43 mg NIL) (1 - 0.30) + (8.82 in/yr x 0.1 mg/L) Nr = (5.85 in/yr + 8.82 in/yr) Nr = 9.7 ppm as nitrate-nitrogen (NO3-N) or 43.2 ppm as nitrate (NO3) The following calculation demonstrates nitrate loading potential if the parameters of total nitrogen concentration of wastewater is reduced to 25.7 mg NIL as calculated, and the denitrification potential is increased 1.5x from the original 30% = 45% (Page 3). 5.85 in/yr (25.7 mg N/L) (1 - 0.45) + (8.82 in/yr x 0.1 mg/L) Nr = (5.85 in/yr + 8.82 in/yr) Nr = 5.7 ppm as nitrate-nitrogen (NO3-N) or 25.4 ppm as nitrate (NO3) It was originally anticipated to pump the effluent throughout the filter bed to alleviate nitrate loading potential through precise equal effluent distribution. However, the nitrate potential has been reduced by: 1). Soil test data obtained illustrating a significant denitrification potential, 2.) A decrease in the calculated wastewater nitrogen concentration by increasing tank volume, and 3.) The use of a different numerical NRR in the nitrate loading calculations. Using the NRR exclusively has lowered the nitrate loading to below the MCL. Therefore, pumping is no longer necessary since comparatively equal distribution of effluent can be achieved under gravity. The application rate was determined from the perc rate to be 0.757 gallons/ft2 /day. The total filter bed area is 1,250 ft2 of floor area exclusively. Therefore, the filter bed can theoretically manage: 0.757 gallons/ft2/day x 1,250 ft2 = 946 gpd. The filer bed infiltrative area including one foot of the sidewalls = 2,500 ft2 + 1,250 ft2 = 3,750 ft2 . Factoring a long term acceptance rate (LTAR) after biomat formation of 0.2 gals/ft2 /day, an acceptance rate is now calculated to be: 0.2 gallons/ft2/day x 3,750 ft2 = 750 gpd. Given a reasonable wastewater ADF generation of 70 gals/bedroom = 3 bedrooms x 70 gpd/bedroom = 210 gpd x 2 = 420 gpd, sufficient infiltrative area exists to manage the LTAR. Eage_A- Chesney Consulting