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Y The-in oundin caleulations also demonstrate that a s aration.disiance of five et between the s1) oil/effluent interface and the static water table should_be maintained. This is provided, however, that.septic disposal fields are not installed too close to heavily irri aced fields, or tot e referenced ponds,particularly the irrigation pond to the south. T✓ NLS§ 4.2 : Considering the history of upgrdient and surrounding agricultural land use, a higher water table nitrate concentration would have been expected. The groundwater nitrate concentrations were low in compare on to other similar projects. This lower-than-expected nitrate concentration. :may be attributed td'l.) Careful application of nitrogen on the surrounding, and sub'cct property acreage,.) Irrigation recharge with cleanwater causing a dilution effect, and/or Nitrification prevention due to wet, clayey soils, in addition to promoting greater denitrification potential. From the analytical soil test results, the 12- 24 inch depth, the 42 inch depth, and the 7 foot depth soil samples reveal very low nitrate-nitrogen-concentrations,thus indicating nitrogen uptake by the last crop grown on the property, in addition to highly probable denitrification. Consequently, nitrate loading from the indigenous nitrate-nitrogen soil concentrations may be considered inconsequential. Suppression of nitrification and the promotion of denitrification may inhibit and mitigate nitrate loading from the future on-site septic systems, and from any agricultural production that may occur on the remaining acreage. Any nitrogen applications to these remaining areas must be done very carefully under agronomic rates that have been pre-determined through soil analysis. It will be the requirement of EHD to install_a specified out seal of 200 feet for all new domestic wells serving the proposed residenfial structures on each of the subj ect Parcels. It will be at the r discretion of EHD to require testing for fiArate and DBCP for domestic wells drilled on each Parcel. Y' SSS§,'�6& The numberof leachlines and septic tank sizes are unknown for each Parcel at this time since the number'of bedrooms for each structure is unknown.: Sss� 7 o engineered,septic'systems are anticipated for this protect;unless there were continual k failures due to unforseen conditions. For example,-a sudden and prolonged increase in the water table elevation over the entire region due to a series of heavy rainfall winters. Each new system must have a 50% standby replacement area incorporated into the primary disposal area. All related septic 1' system structures and the new domestic wells must comply with the published "distance" requirements from property borders,roads, irrigation fields,irrigation canals, and all pipelines. It is important to recognize that all septic systems have a lifespan, which is dependant on several factors and is therefore difficult to determine. Septic system failure would primarily result from the advanced formation of a "biomat" or "clogging mat" on the wetted soil/effluent interface. This mat is composed mostly of aerobic and anaerobic bacteria and bacterial products consisting of a slime of polyuronides and polysaccharides. If the soil/effluent interface is well aerated, a variety of soil microfauna such as nematodes and protozoa may digest the clogging mat bacteria. Since the shallow surface soils consist of a fine-grained soil material (primarily silts and clays), anaerobic conditions may prevail over time because of low oxygen diffusion levels. This may decrease the expectant life of each leachfield. If the leachlines are installed high in elevation, there. may be a greater opportunity for oxygen infusion from the atmosphere, thus theoretically assisting in biomat degradation, along with promoting evapotranspiration. Page -12- Chesney Consulting