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the underlying anaerobic clay soils, 4.) If effluent levels rise 10 feet above the bottom of the seepage pit, the effluent could then be managed by the more permeable silty sand strata encountered at the medium depths. r As stated above, 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 122 feet. The number of leachlines, sumps and/or seepage pits, and septic tank sizes are unknown for each of the Parcels at this time since the number of bedrooms for each structure is unknown. (§ 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 continued failures on any of the Parcels. 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. a Since the deeper subsurface soils on the south half of the property, and the shallow soils on the north half of the property consist of silts and clays, anaerobic conditions may prevail over time which may decrease the expectant life of new leachfields. Shallow soils consist of silty, fine sands under the south half of the property. 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 evaporation/evapotranspiration. This was observed with the existing septic system on Parcel 1, whereby the leachline placement was visible due to green grass over the lines. I f Page -5 J. - kChesney Consulting