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-20-1997 8:44PM FRS' P. 4 Page 3 1W. Lmeleyco March 19, 1997 . Suggests that the leachfield itself creates these conditions, and therefore a high denititication rate ` can be assumed. This is incorrect. The soil conditions may be right for derinrirication at the leaching zone; however, there is no nitrate at this point - all of t: e nitrogen is still in the t ammonia and organic forms. The denitrification process car. nor'oeeur until several feet below I the leaching trenciaes, after the percolating effluent has been allowed to undergo nitrification. At this point. rhe conditions are no longer favorable for dentrificat:on, and a lower rate (e.a., 10 to 25%) must be assumed. • Rainfall-Runoff and Dilution. The nitrate study done for the EiR assumed on-,ite retention and infiltration drainage of rainfall-runoff from the proposed developmentw , hich was the Proposed plan for the original 39-lot, 59-acre subdivision. This is animportant factor in the nitrate loading analysis, since rainfall infiltration ;i.e., groundwater recharge; is _he source for dilution.of the nitrate concentration in the percolating wastewater effluent. The Kleinfelder study assumed approximately the same rate of rainfall-runoff infiltmrion for the revised 37-lot, 40-acre project as was assumed for the original project with on-site drainage retention, and did not adjust Lhis to account for the fact that the revised project will ;have a drainage system that collects and discharges runoff outside of the project area. Accordingly, this results it overestimation of the arnount of dilutionlrecharge water on the site urcer rhe developed conditions; and this adds to an underestimation of the protected nitrate 'loading effect on rhe local groundwater. The rainfa:l dilution factor i.e., deep percolations should be reduced by approximately 15 to 20%c (i.e., about 2 inches of runoff, as compared to the assumption used by Kleinfelder; this would properly reflect the conditions that u i;l exist with the project. • Groundwater Flow Direction,The Kleinfelder study assumes that the flow of groundwater is to the south-southeast, away from the existing neighboring residences. This is based on a regional groundwater map, and.not on any local groundwater information in the immediate project area. This is inadequate for this type of analysis. it is very corn non to rind loczl variations in groundwater flow that vary from t're regional trends_ For instance, the existia� domestic water supply wells .nav create a localized drawdown ccnciition. Tine groundvw iter,now needs to be investigated for local conditions in the irm-nediate protect area through a survey of water level elevations at existing wells. Without this informa:ion, the safe assumption for environmental analvsis is that the groundwater from beneath the prvieez site could flow in the direction of the any oe the nearby wells that border the proiect. REVISED CALCULATIONS Following are my calculations of the predicted nitrate effects on local groundwater frorn the revised 37-10t, 40-acre Morada �tMeadows subdivision. 'vIv calcuiations :differ from those in the KIein:eider report in regard to the selection of values °ar :fie various assumptions as discussed above. The