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Considering the intensely farmed land upgradient to the subject property over the past 60 years, a higher nitrate concentration would be expected in the shallower aquifers. High nitrate impact to the shallower aquifers and significantly lower nitrate concentrations in the deeper aquifers is often observed throughout San Joaquin County. CONCLUSIONS T}u;.rA*� +P�+ rrc„ttc fpr Parcels 1 and 2 show acceptablepercolation for the manavemenr of peptic affluent flows that can be expected at near the maximum and leachlineeath of 42 inc dhes. Evidence from the perc tests reveal that percolative capacity of the on-site soils decrease with extreme soil saturation. The 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 typical leachline depth of 42 inches and the current groundwater depth of 27 feet. It is recommended that Infiltrator® Chambers be considered for installation for the new septic system on Parcel 2 to keen the soil/effluent interface as hien in elevation as possible and to take advantage of the evaporative and evapotranspiration capacit}+ during favorable weather conditions throughout the year. The actual number of Infiltrator Chambers or conventional leachlines and septic tank sizes are unknown at this time since the number of bedrooms for Mr. Kearsey's house is unknown, along with the potential for a second unit dwelling. The new septic system for Mr. Kearsey's house will have a 50% standby replacement area incorporated into the design,which will be easily achievable. 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. It is important to note 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 consist of a sandier grained soil material, aerobic conditions may prevail over time which may extend the life of the leachfield. If the Infiltrator leachlines are installed high in elevation, there will be a greater opportunity for oxygen intrusion from the atmosphere, thus theoretically assisting in biomat degradation. ,Regardless of the nitrate concentration ultimately tested for in each of the new domestic wells, bottled water should always be used for drinking and cooking purposes. Page -4- Chesney Consulting