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September 27, 2000 Job Number. LG00-312 Page 8 balance equation are nitrate-N whose maximum drinking water contaminate level is 10 mg/l. Denitrification is an important process that mostly occurs in the septic system leach line whereby certain bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N2) to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10% to 35%. Soils with higher clay content, moist soil conditions, high pH, and organic material denitrify about 35% and soils with very high sand content and fast peculation rates are estimated to denitrify at a lower rate, about 101/6 to 'o. Due to the presence of brown fine to medium sandy soils, the denitrification factor is estimated to be about 15 %. In our approach to estimate the quantity of effluent, we used the following information for our calculation. Fifteen (15) gallons per day per staff/employee and fifteen (15) gallons per day per student were the estimated use for this type of facility. Since the building is operating 6 hours per da a fetor of�6/8.was applied to the usage reducing to 11.25 gallons per day per stafflemployee and student. The average nitrate concentration of the typical septic waste is- normally consideirA to be. 45 mg/L..-N.6 An adjustment must be added because the ground water Fwa nd to contain nitrates at a concentration of 45.6 mg/L-NO3 (10.1 mg/L-N)therefore a f 55.1 mg/1-N was used (45 +_10.1 = 55.1 mg/L-N, estimated level of wasi' 'stream). The amount of students and staff that the site could occupy the site without exceeding the or Nitrate was determined to be twenty-five (25) students and eight (8) staff/employees e present septic system. Several trial runs were performed using thirty-six (36) students er the MCL for nitrates was exceeded. The analysis indicated that a maximum of twenty- 5) students and eight (8) staff/employees could occupy the facility with respect to nitrate using the a typical, non-engineered septic system. The following tables present the input d results of the nitrate loading analysis. A result under 10 mg/L-N (the MCL for drinking is considered acceptable. 6 U.S.Environmental Protection Agency(EPA). 1980. Design Manual: On-Site Wastewater Treatment and Disposal Systems. Report No. EPA-625/ 1-80-012. 390 pp. pEts�y F