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L %kill, <br /> LSeptember 21,2005 <br /> NOA Project Number: E05104A <br /> Table 1. <br /> 6. Typical Q antity of Effluent for Parcels 8-20. <br /> Category Total People per Average Quantity per Average Daily Flow <br /> LDay Person Per Parcel <br /> Residential 8 residents*70 gpd/resident <br /> L <br /> is 1- 8 70 gal/day/resident = 560 d <br /> Note —gpd is gallons per day. <br /> L For lots 1-7,the total daily waste water quantity is 560 gallons per day. �3'J <br /> The average total nitrogen concentration of domestic waste water is normally considered to be <br /> L 20-85 mg/L-N (Crites and Tchobanoglous, 1998). For the purposes of the nitrate loading estimate, <br /> the long-term average concentration for total nitrogen in waste water is estimated to be 45 mg/L-N. <br /> L3.4.2 Denitrification Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain bacteria <br /> L utilize the oxygen in the nitrate (NO3) and release nitrogen gas (ND 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 /> L estimated to denitrify at a lower rate,about 10 percent to 15 percent. <br /> ` A typical denitrification factor of 25 percent was selected for the Site due to the presence of dark 2 <br /> Ladobe surface clays. <br /> L3.5 Nitrate Loading Scenario <br /> A nitrate loading scenario was performed to determine the impact from the proposed project. The <br /> scenario utilizes the variables discussed previously which represent the estimated conditions and <br /> Luses associated with this project. The following table presents a summary of the nitrate loading <br /> calculation. <br /> I <br /> � Table 3. <br /> Summary of Nitrate Mass Balance Analysis. <br /> Result Acres Average Daily Effluent Concen- Leachfield Deep Percolation of <br /> (Nc)* (A) Flow(Q) (Tabic 1) tration(Nw) Denitrifi- Rainfall(R) <br /> (mg/L-N) (gpd) (mg/L-N) cation(d) (Plate 9) (in.) <br /> 13.9 2 560 45 25% 5.76 <br /> Maximum contaminant level(MCL) for nitrate in drinking water is 10 mg/L-N. <br /> 5 <br /> r <br />