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Based on four bedrooms total at 140 gallons per bedroom per day, the maximum <br /> average daily flow for the Site was estimated to be 560 gallons per day (gpd). <br /> A typical residential concentration of 35 mg/L of nitrate as N was selected (Crites and <br /> Tchobanoglous, 1998). <br /> Denitrification Reductions <br /> Denitrification is a process that occurs in the septic system drain field whereby certain <br /> bacteria oxidize the nitrate (NO3) in the waste water and release nitrogen gas (N2) to the <br /> atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain <br /> field may undergo a reduction between 10 percent to 35 percent. Soils with higher clay <br /> content, moist soil conditions, high pH, and organic material denitrify by about 35 <br /> percent, and soils with high sand content and fast percolation rates tend to denitrify at a <br /> lower rate of about 10 percent. <br /> The soil on the Site was found to be silty sand with clay to a depth of 3.37 feet. A <br /> denitrification factor of 35 percent was selected for the Site because of the clay content <br /> of the shallow soil encountered. <br /> Nitrate Loading Estimate <br /> A nitrate loading scenario was employed to determine the impact from the project to <br /> ground water. The scenario utilizes the variables discussed previously, which represent <br /> the estimated conditions and uses associated with this project. <br /> The assumptions and details of the nitrate loading calculation for the Site are presented <br /> in Plate 13. The following table presents a summary of the assumptions for the <br /> calculation: <br /> LOGE 1918 Page 7 <br />