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✓✓ (§,4.2 a*t1fituttra Water analysis reveals a very high nitrate (as nitrate -NO3) concentrationo 12 ppm forHomesite Parcel domestic well. Dibromochloropropane (DBCP), and Dibromide(EDB) were found to be Below Detectable Levels (BDL). The Maximum Contaminant Level(MCL) for nitrate in drinking water is 45 ppm. This nitrate concentration originated from surrounding agricultural inputs and production. Since: 1.) The groundwater is shallow, and 2.) Surrounding agricultural production land density is high, nitrate impact from the new Chavez residence could be attenuated as much as possible by installing the leachlines as high in elevation as possible. (§ 7.0) CONCLUSIONS The perc test results for proposed Parcel 1 and the Designated Remainder show acceptable percolation for the management of anticipated septic system effluent flows. As noted from the shallow tests indicative of leachline trenches, effluent percolation will readily occur at the leachline depth. However, when the soil becomes saturated,percolation will be retarded, as was evidenced by the percolation tests for the future disposal area for the Chavez residence. 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 leachline at 42 inches and the current groundwater depth of 15 feet(180 inches - 42 inches = 138 inches, or 11.5 feet). //(Q6.8) he number of leachlines, and septic tank size will be determined at the time the septic cr applies for the permit. It is my understanding the new Chavez residence will have four bedrooms. Z� No problems are anticipated for the future septic system on the property, other than typical lifespan concerns. An engineered septic system will not have to be installed for the Chavez home, unless there are continual failures for an unforeseen reason. The new system must have a 50% standby replacement area incorporated into the area of the disposal field. This will be easily accomplished since the area surrounding the proposed disposal area is an almond orchard. All related septic system structures and the new domestic well must comply with the published "distance" requirements from property borders, roads, irrigation fields and structures. 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. Page -4- jj Chesney Consulting