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L *M01 I.W4 <br /> LNovember 8,2004 <br /> NOA Project Number: E040110A <br /> LTable 1. <br /> Typical Quantity of Effluent per Parcel from Residential Sources. <br /> L Total People Average Quantity per Average Daily Flow <br /> per Day Person Per Parcel <br /> 8 70 gal/day/person 8 residents/day* 70 gpd/person <br /> = 560 d <br /> i' Note —gpd is gallons per day. <br /> 4 The daily waste water quantity is estimated to be 560 gallons per day for each parcel. <br /> L <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 /> 1--3.4.2 Denitrification Estimate <br /> L <br /> Denitrification is an important process which occurs within the leach field whereby certain bacteria <br /> utilize the oxygen in the nitrate (NO,) 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 /> LA denitrification factor of 25 percent was selected for the Site. <br /> 3 5 Nitrate Loading Scenario <br /> LA 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 /> L uses associated with this project. The following table presents a summary of the nitrate loading <br /> calculation for each parcel. <br /> Table 2. <br /> Summary of Nitrate Mass Balance Analysis. <br /> Plate Result Acres Average Daily Effluent Leachfreld Deep <br /> L (Nc) * (A) Flow(Q) Concen- Denitrifi- Percolation of <br /> (mg/L-N) (Table 3) tration(Nw) cation(d) Rainfall(R) <br /> (gpd) (mg/L-N) (Plate 9) (in.) <br /> 10 6.9 5.0 560 45 25% 6.84 <br /> * Maximum contaminant level(MCL) for nitrate in drinking water is 10 mg/L-N. <br /> 6 <br />