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W_ 11%/ __W' December 18,2001 ` Job Number:LGOI-375 Page 9 prediction of seasonal changes." The Hantzsche and Fennemore7 equation takes into account development area, soil denitrification factor, rainfall volume, rainfall nitrate concentration, the waste effluent quantity, and waste effluent nitrate concentration. The formula, assumptions and calculations used for the analysis are shown on Plates 8 & 9. The units of nitrate used in the mass balance equation are him nitrate-N whose maximum drinking water contaminate level is 10 mg/l. Denitrification is an important process in septic systems that normally occurs in the leach •• line whereby certain bacteria utilize the oxygen in the nitrate(NO3) and release nitrogen gas(NO to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 percent. Soils with higher clay content,moist soil conditions, high pH, and organic material denitrify about 35 percent and soils with very high sand content and fast percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. Due to the common occurrence of clayey surface soils, the denitrification factor is estimated to be about 25 percent. An estimate of the quantity and quality of effluent is required for the analysis therefore the following information was used in the calculation. The deep percolation of rain was estimated to be 5.65 inches and the calculation is shown on Plates 8 & 9 The nitrate concentration of rain fall was estimated to be 0.17 mg/L-N.7 Nitrates from Septic System The quantity of effluent waste water was estimated to be 15-gallons per employee per day. The proposed use of the new building was designed to include 12 employees Monday thru Friday. Visitors are expected to utilize 5-gallons per person per daily visit. It is estimated that 10 visitors per day(Monday thru Friday) will utilize the restrooms. Since the building will be occupied Monday thru Friday, therefore the average daily flow was adjusted to reflect the Saturday's and Sunday's non-use. A factor of 5/7 was multiplied to the Monday thru Friday daily flow to reflect an average rate over for the week(See Table 5). The average nitrate concentration of the typical residential septic waste is normally considered to be 45 mg/L-N.'°8 8 Otis,RJ.,Boyle,W.C., 1980,Design manual,onsite wastewater treatment and disposal systems:U.S. Environmental Protection Agency,EPA 625/1-80-012. (See page 100,table 6-1). ?pERS0 � 1 > .n o � sso��