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June 10,2002 <br /> Job Number:LG02-164 <br /> Page 9 <br /> The Hantzsche and Fennemore'equation takes into account development area, soil <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 9 through 16. The units of nitrate used in the mass balance equation <br /> are nitrate-N whose maximum drinking water contaminate level is 10 mg/1. <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 (ND <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 /> percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. Due to <br /> the occurrence of sandy soils, the denitrification factor is estimated to be about 10 percent. <br /> An estimate of the quantity and quality of effluent is required for the analysis. The deep <br /> percolation of rain was estimated to be 6.21 inches and the calculation is shown on Plate 8. The <br /> nitrate concentration of rain fall was estimated to be 0.17 mg/L-N.' <br /> Nitrate from Septic System <br /> The nitrate loading study takes into consideration the existing structures on each parcel <br /> and legally permitted construction of new structures on the parcels. Though no construction on <br /> the designated remainder parcel is planned, an estimate of nitrate loading was performed as part <br /> of this study. We estimate a future residence on the designate remainder parcel may contain up <br /> to four(4)bedrooms and as many as five(5)persons. A legally permitted 1500 sq-ft second unit <br /> dwelling(SUD) can exist on either Parcel 1 or the designated remainder parcel and can contain <br /> up to three(3)bedrooms or about four(4)persons. The existing home located on Parcel 1 is two <br /> (2)bedrooms and is estimated to include as many as three(3) persons. The quantity of effluent <br /> waste water was estimated to be 70 gallons per person per day based on a publication by Crites <br /> and Tchobanoglous.$ <br /> Table 6 presents the quality of effluent that could be produced on new Parcel 1 and the <br /> designated remainder parcel. <br /> 8 Crites,R,and Tchobanoglous,G., 1998,Small and decentralized wastewater management systems: <br /> McGraw-Hill Publishing Company, 1084 p. See Tables 4-1 (p.170)and 4-14(p. 181). <br /> �pERSO <br /> r 1 <br /> Z � <br /> O � <br /> Assoc. <br /> r <br />