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[51 CONCLUSIONS The percolation rates for the subject property suggest that if septic systems are eventually installed on the subject Parcels, they should consist of 6,000 to 8,000 square foot leachfield areas, with sumps at the ends of the leachlines. This design should allow the systems to operate successfully. The final square footage of the leachfield area will be largely dependent upon the number of bedrooms a proposed house 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. All related septic system structures must comply with the published "distance" requirements from wells, property borders, roads, irrigation fields, etc. Since the perc tests were performed in the areas most likely for future development, additional percolation tests will not be necessary. The referenced leachfield area will help ensure stability and guard against leachfield failure. A failure would primarily result from the formation of a "biornat" 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 subsurface soils consist of a sandy/silty material with potentially aerobic conditions, this type of biological digestion activity may occur and lessen the possibility of failure from the biomat. An important issue with this study is the impact to the underlying groundwater from nitrogen in the form of nitrate. Two nitrate promoting factors indigenous to this area are relatively sandy, permeable soils and a large amount of agricultural production land. Although the depth to groundwater varies over the two Parcels, it is probably 35 feet below grade where the domestic well is currently situated. It is our opinion that septic systems which may be installed in the future will have a small impact upon the underlying groundwater in comparison to the amount of nitrogen fertilization which occurs in the area. The septic system density is low and in our opinion, not a significant contributing factor to nitrate contamination of the underlying groundwater. {,* C /unlity Control Inspection