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r <br /> Encountered hardpan at the shallow perc test depths showed some impact on soil permeability, but <br /> not to the extent of preventing acceptable percolation. It is my opinion that the septic system <br /> contractor breach encountered hardpan as the leachlines are being installed. Consideration may be <br /> given to increasing the size of the septic system if heavy effluent flows are anticipated. However, <br /> since the leachfield will be in an almond orchard, there will be sufficient replacement area when <br /> failure occurs. <br /> It is important to recognize that all septic systems have a lifespan, which is dependant on several <br /> factors and is therefore difficult to determine. Septic system leachline failure would primarily result <br /> from the advanced formation of a "biomat" or "clogging mat" on the wetted soil/effluent interface. <br /> This mat is composed mostly of aerobic and anaerobic bacteria and bacterial products consisting of <br /> a slime of polyuronides and polysaccharides. If the soil/effluent interface is well aerated, a variety <br /> of soil microfauna such as nematodes and protozoa may digest the clogging mat bacteria. <br /> Since the shallow subsurface soils on the property consist of silty, sandy soils, aerobic conditions <br /> may prevail over time which may keep the expectant life of the new septic system in equilibrium. <br /> Lifespan will be dependant upon the efficiency of the septic system to manage typical effluent <br /> flows. <br /> In addition, soil moisture content of the subsurface soils may influence septic system operational <br /> capacity. For example, if heavy rains are experienced in any given winter, subsurface soil moisture <br /> content will increase which may lead to a decrease in permeability potential. Additionally. EHD <br /> will require that the future leachfield area be bermed highenough to prevent flood irrigation waters <br /> from the surrounding almond orchard to infiltrate and percolate within the leachfield area. <br /> The opportunity to provide this service for you is appreciated. If there should be any questions, <br /> please contact the undersigned. <br /> R <br /> Respectfully submitted, <br /> Qp <br /> No. 04875 7C <br /> 'CHESNEY CONSULTING <br /> Expires: <br /> 1 �A <br /> -V <br /> Don Chesney, .E.A. " <br /> Registered Environmental Assessor#4575 <br /> Page -3- <br /> I <br /> 1 Chesney Consulting <br />