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t <br /> CONCLUSIONS <br /> The percolation test results reveal acceptable permeability at both the shallow and deeper depths <br /> representative of leachlines and backhoe-dug sumps,respectively. Although it is my <br /> understanding that a second unit dwelling cannot be built upon the proposed Homesite Parcel, <br /> these test results give replacement information in the event of failure of the exiting leachfield <br /> which serves the Polk's residence. <br /> EHD requires that there be sufficient distance for treatment of septic effluent before it encounters <br /> the groundwater table. This distance is normally regarded to be five feet for leachlines and 10 <br /> feet for sumps and seepage pits. As noted on the attached Lines of Equal Depth, groundwater is <br /> approximately 115 ft below grade. Therefore, sufficient distance exists between the bottom of a <br /> maximum depth leachline trench at 42 inches, or a sump at 10 feet in depth, and the current <br /> groundwater depth of-115 feet. <br /> It is important to recognize that all septic systems have a lifespan, which is dependant upon <br /> several factors and is therefore difficult to determine. Septic system leachline failure would <br /> primarily result from the advanced formation of a "biomat" or "clogging mat" on the wetted <br /> soil/effluent interface. This mat is composed mostly of aerobic and anaerobic bacteria and <br /> bacterial products consisting of a slime of polyuronides and polysaccharides. If the soil/effluent <br /> interface is well aerated, a variety of soil microfauna such as nematodes and protozoa may digest <br /> the clogging mat bacteria. <br /> Since the shallow subsurface soils on the property consist of clays and silts, anaerobic conditions <br /> may prevail over time which may slightly decrease the expectant life of a septic system. Lifespan <br /> will also be dependant upon the efficiency of the septic system to manage typical, or atypical <br /> effluent flows. <br /> In addition, soil moisture content of the subsurface soils will play an important role in septic <br /> system operational capacity. For example, if heavy rains are experienced in any given winter, <br /> subsurface soil moisture content will increase,thus decreasing permeability. <br /> In unsewered areas and/or areas that have been, or currently are under agricultural production, it <br /> is highly recommended that bottled water be used for drinking and cooking purposes. <br /> Page 3 of 4 <br />