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[5[ CONCLUSIONS With regards to the nitrate and chloride concentrations in the tested wells,it is evident there has been nitrate impact. However,the chloride impact is at lower concentrations than what would be expected if there was septic system influence occurring within the study area. If septic systems were causing a greater influence,chloride concentrations should equal or exceed nitrate concentrations. Although there is not a significant density of housing upgradient from the subject property,it is our opinion that the housing which exists at the above-referenced location of South and Cottage Avenues,along with the housing around the subject property would have contributed a greater concentration of chlorides than those observed. Therefore,it is our opinion that the majority of nitrate influence is originating from agricultural inputs,with a minor contributing influence from septic systems. The percolation rate obtained for Parcel 1 suggests there is sufficient percolative capacity of the soil to manage normal effluent flows. The Repairs/Additions that were made for failures can probably be attributed to biomat impermeability or to a thicker stratum of hardpan than what was encountered in our test boring. As referenced earlier,there are no plans to build on Parcel 1 or the Designated Remainder and it will remain in almond production. We are recommending that if there should ever be plans to build on the Designated Remainder,there must be a percolation test done in the proposed location of the leachfield. The leachfield(s) must consist of the proper square footage. This leachfield area will be largely dependent upon the number of bedrooms a proposed house or commercial structure will have. Additionally, if there will be several people inhabiting the residence,particularly children,a septic system should be oversized to accommodate additional wastewater flows. A 50% standby replacement area must also be incorporated into the design of any septic system. All related septic system structures and any domestic well must comply with the published"distance"requirements from property borders,roads, irrigation fields, etc. A properly sized leachfield area will help ensure stability and guard against leachfield failure. 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 biomat bacteria. Since the subsurface soils consist of sandy soil material,aerobic conditions will probably prevail which may impede leachfield failure. Valley Ag Research