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August 31, 2004 NOA Project Number: E04060A The method utilized for the nitrate loading analysis is based on a simple mass balance formula, discussed in a published article by Hantzsche and Finnemore (1992) which provides a convenient and simplified method to estimate long-term ground-water nitrate impacts on an area-wide basis. Hantzsche and Finnemore found that over a long period of time, water quality in the upper �- saturated ground-water zone closely approximates the quality of percolating recharge waters. They believe that their method is a good planning tool and provides useful information to planners and local officials but with some real limitations. In their article published in Ground Water, Hantzsche and Finnemore mention that "...the equation ignores dispersion, lateral flow, 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 that 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 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 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 the development area, soil denitrification factor, rainfall _ volume, rainfall nitrate concentration, waste effluent quantity, and waste effluent nitrate concentration. The formula, assumptions and calculations used for the analysis are shown on Plate 10. The units of nitrate used in the mass balance equation are nitrate-N, whose maximum drinking water contaminant level (MCL) is 10 mg/L. No information was available from the San Joaquin County Community Development Department regarding the proposed uses of the Site. The project appears to be in its initial stages at this point. As a result, only a rough nitrate loading calculation could be prepared. For the purposes of this calculation, the six parcels which make up the Site were considered to be one parcel 44.59 acres in size. The maximum average daily waste water flow which would not result in a nitrate impact to ground water above the MCL was calculated. 7.1 Quantity and Quality of Domestic Wastewater From Proposed Project The maximum average daily flow was back-calculated from the mass balance of nitrate allowed before the ground water nitrate MCL would be exceeded (Plate 10). The maximum average daily flow allowed was found to be 6,600 gpd. 13