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v u EHD requires that there be sufficient distance for"treatment' of septic effluent before it encounters the groundwater table. This distance is normally regarded to be five feet in leachlines and 10 feet with seepage pits. Therefore, sufficient distance exists between the bottom of a maximum depth seepage pit and the current groundwater depth of 105 feet. (§ 6.8) The number of leachlines, sumps and/or seepage pits, and septic tank sizes are unknown for �(�,C each Parcel at this time since there is no proposal to build. (§ 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 continual failures. Each 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 the new domestic wells must comply with the published "distance" requirements from property borders, 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 silts, clays and hardpan, anaerobic conditions may prevail over time which may decrease the expectant life of new leachfields. �� 1 Lifespan will be dependant upon the efficiency of the deep septic system structures (i.e., seepage pits)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 lifespan. For example, if heavy rains are experienced in any given winter, subsurface soil moisture content will increase dramatically, thus decreasing permeability. Page-5- Chesney Consulting