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FFTheunde,rlying soils possess increasing moisture content with increasing depth, as determined in the g. This is due to the rainfall that occurred in March/April 2006. High moisturee beneficial for the suppression of nitrification, and the promotion of denitrification cules that may have formed through nitrification in the upper soil environments. EHD requires there be sufficient distance for"treatment" of septic effluent before it encounters the groundwater table. This distance is normally regarded to be five feet. Therefore, sufficient distance exists between the bottom of a maximum depth seepage pit and the current groundwater depth of approximately 150 ft, as evidenced by the Lines of Equal Depth Map. A--(§ 6.8) The number of leachlines and septic tank size is unknown since there is no proposal for a future residential structure. -'�(§ 6.7) No problems are anticipated for any future septic system on the property, other than typical lifespan concerns. Engineered septic systems will not have to be installed for this proposed subdivision unless there are failures. Any new system must have at least a 50% standby replacement area incorporated into the design of the septic system. All related septic system structures and any new domestic well must comply with the "distance" requirements from property borders, the domestic well, roads, irrigation fields and irrigation ditches, etc. 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 leachline 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 subsurface soils on the property consist of sands and silts, aerobic conditions may prevail over time which may increase the expectant life of any new leachfield. Lifespan will be 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. 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 decreasing permeability. In this event, deep septic system structures will manage most of the effluent. In unsewered areas and/or areas that have been, or currently are near agricultural production, it is highly recommended that bottled water be used for drinking and cooking purposes. LL�- Page -5- Chesney Consulting