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P Tor) (0*-) { August 31, 2006 NOA Project Number: E06091A residential concentrations. Please see the following equation for further detail: Weighted Average Calculation for Total Nitrogen Concentration in Residential and Commercial Flow On-Site Religious assembly flow Co mercaal concentration Flow concentration F1240 gallons_per day average * 80 L-N = 19,200 mg/LAN gal i Residential flow sidential concentration Flow concentration 490 gallons per day * 45 L-N = 22,050 mg/L-N gal Sum of Com. and Res. Flow Concentrations 19,200 m L-N ga1 + 22,050 mg/LAN gal = 41.250 mg/L-N gal Sum of Com. and Res.gallons per day average 240 gallons per day age + 490 gallons 12cr da -average = 730 gallons per dad average g klheighted Average of mg/L-N Concentration inflow of on-site waste water 41,250 m L-N al ' 730 gallons ner day average =56.50 mg/L-N 14 I Based on the weighted average of mg/L-N concentrations in the flow of waste water,it is estimated Z4_3that the average concentration for total nitrogen from both sources in waste water for the project is approximately 56.50 mg/L-N over the long term. 3.4.2 Denitrification Estimate Denitrification is an important process which occurs within the leach field whereby certain bacteria utilize the oxygen in the nitrate (NO.) and release nitrogen gas (N� to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 percent. Soils with higher clay content,moist soil conditions, high pH, and organic material denitrify by about 35 percent, and soils with high sand content and fast percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. A typical denitrification fact r of 30 pence t was selected for the calculation because of the fine- grained silty sands containin that exist at the site. 6