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VI. CONCLUSIONS AND RECOMMENDATIONS The perc test results for the 11 proposed Parcels show acceptable percolation for the management of septic system effluent flows either in the shallow test borings representative of leachlines, or at deeper depths representative of sumps or seepage pits. Potential septic system structures have been denoted in Table 1 based upon the test results obtained. For example, if acceptable pert test results were obtained from both shallow and deeper depths of approximately eight feet, both leachlines and sumps have been specified. If acceptable pert test results were obtained in depths deeper than eight feet, seepage pits were indicated. If shallow percolation was unacceptable, then seepage pits were indicated with leachlines to provide maximum management potential of septic effluent. Sumps may provide a higher level of protection against nitrate loading. Considering a new law that may be implemented which may ban seepage pits (Assembly Bill 885), EHD may require sumps be installed for all of the proposed Parcels. It will be at the discretion of EHD to 1.) Install leachlines exclusively on the Parcels with acceptable shallow perc rates, 2.) Install leachlines and sumps, or 3.)Install leachlines and seepage pits based on the criteria explained 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 of 25 feet and the assumed groundwater depth of 85 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. No engineered septic systems are anticipated for this subdivision. Each new system must have 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, irrigation ditches, and pipelines. 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 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 surface soils consist of a fine-grained soil material (primarily silts and clays), anaerobic conditions may prevail over time because of oxygen diffusion difficulty. This may decrease the expectant life of each leachfield. If the leachlines are installed high in elevation, there may be a greater opportunity for oxygen infusion from the atmosphere, thus theoretically assisting in biomat degradation, along with promoting evapotranspiration. LL�- Page -8- Chesney Consulting