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100 feet(See Attached) with the perforations from 180 to 200 feet. Considering there are six - significant stratums of brown clay above the well casing perforations and the well is grouted to 100 feet,,this indicates that agricultural production to the south (upgradient) has most likely contributed to this high nitrate level. The agrichemicals DBCP and EDB were below detection limits (BDL) which is equivalent to non-detect(ND). CONCLUSIONS The perc test result for Parcel "A" suggests there will be excellent effluent percolation at the typical leachline depth of 42-inches. This shallow test depth also reveals there will be a greater distance for "treatment" of septic effluent before it encounters the groundwater table. It was evident that percolative capacity did not decrease with soil saturation. It is important to note that all septic systems have a lifespan. This lifespan is dependant on several factors and is therefore difficult to determine. From the repairs and additions on record at the Environmental Health Department, it is evident the septic systems in this area have a definite lifespan. It is recommended that if any structure with a septic system is built on the Designated Remainder, there should be a percolation test done in the area of the proposed leachfield. A shallow perc test at 42 inches should be conducted in the proposed leachfield area. In addition, the leachfield must be hydraulically protected during the rainy season.to prevent inundation. A 50% standby replacement area must be incorporated into the design. All related septic system structures and a possible new domestic well must comply with the published "distance" requirements from property borders,roads, irrigation fields, etc. As noted on the Leachline Requirement Map published by the Environmental Health Department, the subject property is just over the border of the "High Water Table Areas." The map shows that seepage pits are not allowed in this area and there must be 100 feet of leachline for each bedroom. 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 mostly of sandy-silty type soil material, aerobic conditions may prevail over time - which may theoretically extend the life of the leachfield. The nitrate concentrations determined in the underlying groundwater suggests there has been impact to the deeper aquifers and can possibly be attributable to upgradient agricultural inputs. Regardless of the nitrate concentration of any well water in rural areas, itis recommended that bottled water should always be used for drinking and cooking purposes. - Page -3- NaCCey Ag Research