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I4 A futurero osal to build on Parcel.2 will require a erc test in that specific location. Potential P P q p p homebuilders on this Parcel must be made aware that any future leachfield must be installed within 100 feet of the perc test location. Item"C" of the Conditions of Approval state that agricultural discharge pipes utilizing an air gap for back-flow prevention shall maintain an air gap equal to the size of the discharge pipe,but not less than 6 inches. This applies to both the east and west on-site irrigation wells. The underlying soils possess increasing moisture content with increasing depth. This is due to the rainfall that has occurred in March 2006. High moisture content soils are beneficial for the suppression of nitrification, and the promotion of denitrification of nitrate molecules that may have formed through nitrification in the upper soil environments. 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. Therefore, sufficient distance exists between the bottom of a maximum depth leachline trench at 42 inches and the current groundwater depth of greater than 9.5 feet (114 inches), as evidenced by the backhoe test pit (114 inches minus 42 inches = 72 inches = six feet). (§ 6.$) The number of leachlines and septic tank size is unknown for the future residential structure since the number of bedrooms is unknown at this time. (§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 well must comply with the "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 sands and silts, aerobic conditions may prevail over time which may increase the expectant life of the 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. Page -5- Chesney Consulting