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P. 4 4 Page 3 Mr. Meleyco March 1.9, 1997 suggests that the 1ea:hfieid Itself creates these conditions,and therefore a high denitrification .etc can be assumed. This is incorrect. The soil conditions may be right for denitrification at the leaching zone; however, there s no nitrate at this poinr - all of the nitrogen is still in the ammonia and organic forms. The drnitrification process can not occur until several feet below the leaching trenches, after the percolating effluent has been allowed to undergo nitrification. At this point, the Co.ididons are no longer favorable for dentrification, and a lower rate (e.a., 10 to 25%) must be assumed. • Rainfall-Runoff and Dilution. The nitrate study done `or the EIR assumed on-;ice retention and infiltration drainage of rair-fall-runoff from the proposed development, which was the proposed plan for the original 39-let, 59-acre subdivision. This is an important factor in the nitrate loading analysis, since rainfall infil ratior. ;i.e., groundwater r--charge; is the source for dilution of the nitrate concentration in the percolating-wastewarer effluent. The Kleinfelder study assumed approximately the same rate of rainfall-runoff infiltration for the revised 37-lot, 40-acre project as was assumed for the original project with on-site dranage retention, and did not adjust this 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, t5:s results in an overestimation of the amount cf dilution/recharge water on the site under the developed conditions; and this adds to an t:nderestimzt:on of the projected nitra:t loading effect on rhe local groundwater. The rainfall dilution factor ji.e., deep percolation) should be reduced by approximately 15 to 20% (i.e., about 2 inches of runoff), as compared to the assumption used by Kleinfelder; this would properly reflect the conditions that Wisl 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 irrtrl-diate project area. This is inadequate for this type of analysis. it is very common to find local variations in groundwater flow that vary from the regional trends. For instance, the existing domestic water supply wells may create a localized drawdown condition. The groundwater flow needs to be investigated for local conditions in the irrunediate prosect area through a suney of water level elevations at existing wells. Without this inform4on, the safe assumption for environmental analysis is that the groundwater from beneath rhe proiect site could flow in the direction of the any of the nearby wells that border the project. REVISED CALCULATIONS Following are my calculations of the predicted nitrate effects on local gr oundw ter fro the revised 37 lot, 40-acre Morada Meadows subdivision. 'vfv calculations differ from those in the Kleinfelder report in regard to the selection of values for :he various assumptions as discussed above. The