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The domestic well test reveals a medium concentration of nitrate which indicate some impact- most likely from agricultural inputs. It may be that higher nitrate concentrations could have been obtained if the attenuating factors of soil moisture content and intervening strata of clay were not present. The agrichemical DBCP was found to be Below Detectable Limits (BDL). -The n=proposal er of`l'eachl'ires'aiid septic tank•size,is•unknown for any future residential structure ,since there is to build on any of the Lots at this presen imt- (§ 6.7) Potential obfems-that ar�i'"y Fe an-icipated for any future septic system on the property include lifespan concerns, flood zone issues, saturated soil from climatic stress, and depth to groundwater. Engineered septic systems may have to be designed and installed for this proposed subdivision based upon these aforementioned concerns. For example, future residential structures that may be built on Lots 3, 4, 5 and 6 will be built in Flood Zone A. Percolation testing for Lots 1 and 2 were specifically done in Flood Zone C. Any building in Flood Zone A will have to be above this Flood Plain elevation. Consideration should be given to installing the leachfield on the elevated building pad. This may require a civil engineering opinion. In addition,the well casing for any new domestic well should also extend above the Flood Plain elevation so that a house can continue to theoretically function. Each new system must have at least a 50% standby replacement area incorporated into the design of the septic system, which can easily be achieved since the Lots are more than 40 acres in size. All related septic system structures and new domestic wells must comply with the "distance" requirements from property borders, roads, wells, irrigation fields, and irrigation ditches. It is important to recognize that all septic systems have a lifespan (i.e., all systems eventually fail), which is dependant on several factors and is therefore difficult to determine. Septic system leachline failure may 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 ae rated a variety of soil microfauna such as nematodes and protozoa may digest the clogging mat bacteria. Since the shallow subsurface soil on the property consist of clays and silts, anaerobic conditions may prevail over time which may decrease the expectant life of any new leachfield. Lifespan will be partly dependant upon the efficiency of the leachline trench structures to manage effluent flows. If the leachlines are installed high in elevation,there will be a greater opportunity for oxygen intrusion from the atmosphere, thus theoretically assisting in biomat degradation, along with promoting Evapotranspiration. However, has referenced above, consideration should be given to installing the septic tank and leachfield on the raised house pad. i In addition, soil moisture content of the subsurface soils will play an important role in septic system operational capacity. For example, if heavy rains are experienced in any given winter, subsurface soil moisture content will increase, thus significantly decreasing permeability. In unsewered areas and/or areas that have been, or currently are in or near agricultural production, it is strongly recommended that bottled water be used for drinking and cooking purposes. Page -7- Chesney Consulting 1