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L � March 13,2000 Job Number: LG00-067 Page 7 VII. NITRATE LOADING STUDY A build up of nitrates in the upper ground-water zones can cause a temporary blood disorder in infants called methemoglobinemia(blue baby). Serious and occasionally fatal poisonings of infants have occurred following the ingestion of water containing nitrate concentrations greater than 10 mg/1 nitrate as N or 45 mg/I nitrate as NO3. The nitrate loading analysis is conducted to estimate the average nitrate concentration for the parcel for an average year period. The nitrate sources include the septic effluent and rain water. The concentration of the septic effluent is estimated after denitrification in the leach lines (prior to mixing and dilution with existing ground water). The method is based on a simple mass balance formula which takes into account soil denitrification factor, rain fall, and the proposed waste effluent quantity and nitrate level. Assumptions and calculations for the analysis are shown on Plates 9 and 10. The units of nitrate used in the mass balance equation is nitrate-N whose maximum drinking water contaminate level is 10 mg/l. '- Denitrification is the biological process in the soil 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 25%. Soils with higher clay content, moist soil conditions, and organic material denitrify about 25% or more but soils with very high sand content and fast peculation rates are estimated to denitrify about 10%to 15%. Due to the presence of brown sand followed by brown sand with clay, the denitrification factor is estimated to be about 20%. To estimate the average concentration of the waste stream, the nitrate level of onsite well water is added to the average waste level, normally considered to be 45 mg/1-N. The nitrate level of the well water well was found to be 0.9 mg/1-N(4.2 as NO3). Therefore the total nitrate ,. concentration of the waste stream is estimated to be 45.0+0.9 =45.9 mg/1-N for the site. In our approach to estimate the nitrate concentration, we used the following information for our calculation. Fifteen (15) gallons per day per employee and seven and one-half(7.5) gallons per day per truck driver since they will be present only at the beginning and end of the work day. The existing residence is currently occupied by two people and the value of fifty(50) gallons per day per person was used. � 4 2 ` p w V