SU0004213 SSNL - Laserfiche WebLink

Home Browse Search

April 20, 2004F! �. ...- NOA Project Number' E04002A- - Page 11 and mixing with ground water flow from up-gradient areas. These processes would generally contribute to additional reduction-of nitrate-nitrogen concentrations in ground water to the extent Fjthat the nitrate-nitrogen concentration of ground-water flow from up-gradient-areas is lower." The Hantzsche and Fennemore approach is "..:a conservative (worst case) first approximation of Fi ground-water nitrate-nitrogen concentration resulting from the combined effect of on-site sewage disposal systems and precipitation. This (the equation and approach) is for estimation of 'j long-term effect(i.e., over years) on ground-water quality, and is not intended for prediction of seasonal changes" (Hantzsche and Finnemore, 1992). The method 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 Plate 10. The units F! of nitrate used in the mass balance equation are nitrate-N whose maximum drinking water , contaminant level is 10 mg/L. /7.1 Quantity of Quality of Domestic Wastewater From Proposed Project The average total nitrogen concentration of the domestic waste water is normally considered to ribe 20-85 mg/L-N (Crites and Tchobanoglous, 1998). For the purpose of the nitrate loading: estimate, the long-term average concentration for total nitrogen in waste water is estimated to be �j 35 mg/L-N. ! I / 7.2 Quantity and Quality of Deep Percolating Rain Water An estimate of the quantity and quality of rainfall was required for the analysis. The estimate of deep percolation of rain is based on the average monthly precipitation of rain fall and F! evapotranspiration for Lodi, California. The estimate first determines whether the average � ! monthly precipitation exceeds average monthly.potential ET. If so, then the difference is potential deep percolation. This method does not consider runoff. See Plate 9 for the data and calculation. ! 1 Average potential evapotranspiration was obtained from the California Irrigation Management Information System System(CIMIS). Lodi is located within evapotranspiration zone number 12. The 1 average rainfall for the Lodi area was obtained from the USDA(1992) Soil Survey for San. Joaquin County. FBased on this estimate,the average deep percolation of gain for the Lodi area is estimated to be V 6.84 inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N whose maximum contaminant limit for drinking water is 10 mg/L-N (Hantzsche and Finnemore, 1992). F1