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Ivor 0. 1uu 19• C/HM 11) ion Lee 916-566-SMO• UIUD N 4/Gp.3 SIGAhE l STL Project No_ 0010711Appendix D Teadog Lah5 Page D.1 A,PPE"1 C D NITRATE LOADING STUDY (Revised ll")Joi) Tho principal concern with respect to the build-up of nitrates within the groundwater is methemoglobinemia, which is of particular concern with infant children. Methemoglobinemia, also known as "blue baby syndrome," occurs whet' bacteria in the digestive system transforms nitrate to nitrite and the nitrite oxidizes iron in hemoglobin of red blood cells to form mcthcmoglobin. Methemoglobin lacks the capacity to carry Oxygen and the resulting condition can uhimate}y lead to death if undetected. Therefore,the Environmental Protection Agency has set the maxunum contaminant level(MCL)for drinking water of 10 mglL or 1 p parts per million for nitrate i itrogen. Because of the concern for nitrate leaching into the groundwater system, a nitrate loading study was performed to estimate the average nitrate concentration of percolating water for the subject sits. The sources included in our loading study included the percolation from the on-site sewage disposal system and recharge due to rainfall. To this end,we utilized a simple mss balance formula,often referred to as the Handsche and Finnemore Equation- The equation is somewhat conservative and is often thoughl of as a worst-case approximation for the chronic effects of groundwmer-laden nitrate-nitrogen resulting hom the combined effect of rainwater and septic system percolations. The equation takes into consideration the development area and laird use, soil chemistry,rainfall criteria and sewage system effluent characteristics. The Hantzsche equation and design parameters utilized herein are as follows: Nitrate-nit:ogen(M)=(INw( I-D)+RNb)t(I+R) where I= Amount of wastewater entering subsurface for subject area(in/year) Nw= Nitrate-nitrogen concentration in wastewater (mg/L) D= denitrification as a percent of original concentration(%%) R= Recharge due to procipitation(in/year) Nb= Background concentration of nitrate-nitrogen in rainfall(mg/L) The amount of wastewaIVT that enters the subsurface was determined on the basis of the following criteria: The per capita flow to a septic tank is 8o gallons per day (US EPA Publication Nn. 62511-80- 012, Dqa o Manual & On-Site Wastewater Treatment and Disposal Systems, page 51. 1980; Kaplan O- Elmjamin, Se is Systems Kandbook, pages 147-148, 1988, Lewis Publishers). We have assumed 2.5 residents per household at 80 gpd, a working staff of 4 persons at 15 gpd, and 10 customers pot day at 5 gpd, resulting in 9 net average of 310 gpd for 16.5 persons- The average rate of discharge of nitrogen Per person per day is 15 grams as N (Kaplan, 4. Benjamin, Se tic SHendboo pages 1.47-149, 1998, Lewis Pab[isbers; State Water Resources Control Board, Identification and Evaluation of Methods for Determining Sources of Nitrate Contaminatiou of Groundwater page 18, 1994). t