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F ey are the typical and prin iple effluent mans emeng t structure installed in this area, 2.} There nificant distance of approximately 100 feet between the bottom of a seepage pit at 25 feet nd the current groundwater depth of 122 feet, 3.) Seepage pits allow head pressure buildup e effluent into the underlying anaerobic clay soils, 4.) If effluent levels rise 10 feet above the Cof the seepage pit, the effluent could then be managed by the more permeable silty gravel strata encountered,particularly Ar Parcel 4. I1 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 age pits. Therefore, sufficient distance exists between the bottom leachlines and 10 feet with seep of a maximum depth seepage pit and the current groundwater depth of 122 feet. The number of leachlines, sumps land/or seepage pits, and septic tank sizes are unknown for each of the Parcels at this time since tie number of bedrooms for each structure is unknown. No engineered septic systems will have to be installed for this proposed subdivision, unless there are continued failures on one, or all of the Parcels. Each new system must have at least a 50% standbyreplacement p 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.important to recognize �I It is m p gnize that a:ll 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 polyuroniIics and polysaccharides. If the soil/effluent interface is well aerated, a variety of soil microfadna such as nematodes and protozoa may digest the clogging mat bacteria. Since the shallow and deeper subsurface soils consist of a silts and clays, anaerobic conditions may prevail over time which may decrease the expectant life of the leachfield. 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. i i . II it I ' I is II � IPage -5- Chesney Consulting