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161 CONCLUSIONS �- The percolation rates for the subject property illustrate that a septic system with a 6,000 to 8,000 square foot leachfield may be utilized for a mobile home or new residential structure to be built on Parcel 2. An 8,000 square foot leaching area is recommended if there is potential influence from a hardpan layer. This will be detected during the installation of the septic system. The number of Permit Applications for additional leachline would indicate a larger leachfield should be installed. Although we do not have knowledge at this point in time as to the size or number of bedrooms the new structure will have, this will also have to be taken into consideration for the final design of the leachfield. For example, a four bedroom house should have between 8,000 and 10,000 i' square feet of leachfield area. A 50% standby replacement area must also be incorporated into a the design. The referenced leachfield areas will help ensure stability and guard against leachfield failure. A failure would primarily result from the formation of a "biomat" or "clogging mat" on the wetted soil where the effluent enters the soil. 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. This type of biological activity will probably prevail due to the sandy nature of the leachfield area soil. ' With respect to the protection of the underlying groundwater from pathogens and nitrates (NO3), ' the shallow depth to groundwater (-18 ft) and the sandy soil structure can be considered a favorable environment for nitrate and DBCP continued contamination. The attached well logs indicate there is a clay layer between grade and the depth to groundwater and this may have some &W attenuation effect on the downward migration of nitrate molecules. However, the high amount of agricultural activity and consequently nitrogen fertilization in the area will certainly contribute L. nitrates to the underlying groundwater to a much greater extent than will the low density housing in the area. W All related septic system structures and the domestic well will have to comply with the published "distance" requirements from property borders, roads, irrigation fields, etc. � X1°0 $ ��uulity `Joniro� �xspection