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i <br /> �. `/ <br /> November 27,2006 <br /> NOA Project Number: E06087A <br /> The average total nitrogen concentration of domestic waste water is normally considered to be <br /> 20-85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). For the <br /> purposes of the nitrate loading estimate, the long-term average concentration for total nitrogen in <br /> ` residential waste water is estimated to be 45 mg/UN. The long term average concentration for <br /> commercial restaurant use is 65 mg/UN, and a shower would have a concentration of 35 mg/L- <br /> N. <br /> IN. A weighted average is therefore used to calculate the total mg/L-N over the long term in the flow <br /> for the site since this project will include both residential and commercial concentrations. Please see <br /> the following equation for further detail. <br /> Table 3. <br /> Weighted Average Calculation for Total Nitrogen Concentration in <br /> Residential and Commercial Flow On-Site <br /> Category Average Daily Flow Effluent Concentration Total Site Effluent <br /> Concentration <br /> RV&Residential use _1,�i pd+490 gpd= 1;858 gpd x 45 mg/LN = <br /> 1,858 gpd 83,610 <br /> 74 gpd x 65 mg/L-N = (98,220 gpd/mg/L-N)/ <br /> Cafe&Marina Office 74 gpd 4,810 (2,212 gpd) <br /> 44.40 mg/L-N <br /> Showers 280 gpd 280 gpd x 35 mg/L-N= <br /> 9,800 <br /> WHISKEY �gpd 0JV y1g�gOgpd/mg/L-N 45 mg/L-N <br /> _ SLOUGH MARINA v77 <br /> Note —gpd is gallons per day. <br /> Based on the weighted average of mg/L-N concentrations in the flow of wastewater,it is estimated CS � <br /> that the average concentration for total nitrogen from all sources in waste water for the project is <br /> approximately 45 mg/UN over the long term. <br /> 3.4.2 DenittiScation Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain bacteria <br /> utilize the oxygen in the nitrate (NOS and release nitrogen gas (N� to the atmosphere. <br /> Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 <br /> percent. Soils with higher clay content,moist soil conditions,high pH, and organic material <br /> denitrify by about 35 percent, and soils with high sand content and fast percolation rates are <br /> estimated to denitrify at a lower rate, about 10 percent to 15 percent. <br /> A typical denitrification factor of 35 percent was selected for the Site because of the fine grained <br /> Lorganic soils that exist at the site. <br /> 7 <br /> 6W ..44 <br /> L <br />