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v <br /> L September 30,2002 <br /> Job Number:LG02-335 <br /> Page 8 <br /> The Hantzsche and Fennemore'equation takes into account development area, sot <br /> denitrification factor,rainfall volume,rainfall nitrate concentration, the waste effluent quantity, <br /> ` and waste effluent nitrate concentration. The formula, assumptions and calculations used for the <br /> analysis are shown on Plates 8 and 9. The units of nitrate used in the mass balance equation are <br /> nitrate-N whose maximum drinking water contaminate level is 10 mg/l. <br /> Nitrates from the Septic System and Rain Fall <br /> .. The total average nitrate concentration of the typical septic waste is normally considered <br /> to be 45 mg/L-N s (This concentration is not related to the maximum contaminate level for <br /> drinking water of 45 mg/L-NO3). The average daily flow of influent into the septic systems on <br /> the site was determined by assigning a flow rate of seventy-five(75) gallons per day per person. <br /> The primary residence is a three(3)bedroom home which can be occupied by 4 people. In <br /> addition to the primary residence, a legal two (2)bedroom second dwelling unit(SDU)up to <br /> 1,500 SF may be placed on the site at some time in the future. Three(3) people were estimated <br /> to occupy the SDU should one ever be built. The following table presents the anticipated daily <br /> ` usage for the property. <br /> Table 5. <br /> Total Estimated Daily Usage of Septic System. <br /> Category Effluent usage People Effluent quantity per category <br /> for each per day <br /> category <br /> Existing 3-bedroom home 75 gals 4 4 people*75 gal/person-day=300 gal/day <br /> 2-bedroom,second dwelling 75 gals 3 3 people* 75 gal/person-day=225 gal/day <br /> unit <br /> Average Daily Flow: 525 gals/day <br /> Denitrification is an important process in septic systems that normally occurs in the leach <br /> line whereby certain bacteria utilize the oxygen in the nitrate(NO3) and release nitrogen gas (NZ) <br /> to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range <br /> is 10 percent to 35 percent. Soils with higher clay content, moist soil conditions,high pH, and <br /> organic material denitrify about 35 percent and soils with very high sand content and fast <br /> 8 Otis,RJ.,Boyle,W.C., 1980,Design manual,onsite wastewater treatment and disposal systems:U.S. <br /> Environmental Protection Agency,EPA 625/1-80-012. (See page 100,table 6-1). <br /> � ttso <br /> 4 <br /> i <br /> ♦� <br /> �Z50�� <br />