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F3.4times no on the attached Filter Bed and 100% Replacement Area Schematic, there are vailable for primary filter bed area and 100% secondary replacement area. This is area needed for both the primary and secondary filter bed area with over 1,130 sq ft ,720 sq ft- (795 sq ft+ Z9 sq ft) = 1,130 sq ft. When constructing the primaryere should be a "stul� u or the 100%replacement area in case of failure. Conventional leachlines cannot be used for two reasons: 1.) There is no remaining area to place the septic tank 'outside" of the 100 ft radius from the on-site well, and if the tank were placed outside the 100-ft radius in the "primary" leachfield area,this would leave insufficient room to install 265 lineal feet of leachline. 2.) Conventional leachlines would leave no area for secondary 100% replacement, unless the parking area was designated as the 100%replacement area in the event of a septic system failure. NITRATE-NITROGEN IMPACT MITIGATION Environmental impact from nitrate-nitrogen will be mitigated through the septic system design by the following: First,the use of a filter(e.g., Zabel®or OSI®Filters) installed in the second compartment of the septic tank before the effluent is pumped to the filter bed will retain a higher percentage of solid organic material. Secondly,the three main factors most favorableTor the denitrification process are: l.) An organic carbon substrate (organic matter), 2.) High soil moisture content, and 3.) High soil pH. As has been shown from the soil chemistry of the indigenous surface soils,there is a high organic matter content and a high soil pH. In addition, the filter bed area will be landscaped with domestic irrigation, thus creating a high soil moisture content. These factors should promote the denitrification process. IV. CONCLUSIONS It is our opinion the proposed septic system is suitable for effective effluent management and that potential environmental impact from nitrate-nitrogen will be mitigated to the highest possible extent without additional effluent treatment. The proposed filter bed will allow greater treatment of effluent by the environmental parameters documented, and since the on-site domestic well ? TDbe downeradient from the filter bed area, greater treatment is warranted. Without sophisticated groundwater monitoring over a long period of time, it is unknown as to the exact groundwater depth at different times of the year, and the groundwater directional flow. However, sufficient data has been collected and analyzed to determine that the groundwater table is currently an acceptable distance below grade for there to be adequate biological treatment, according to published scientific literature. The nitrate loading calculations demonstrate that the theoretical nitrate impact will be under the drinking water Maximum Contaminant Level by 32%. Groundwater analyses of the on-site well and the Post Office well indicate that nitrate impact to the underlying aquifers exceeds the Maximum Contaminant Level. This nitrate impact has most likely occurred from the high density housing upgradient, or to the southwest of the subject property. Page -7- Va!!ey Ag Research