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- [5] CONCLUSIONS A shallow test was not conducted because the gravelly, silty nature of the shallow soils would not have been conducive for percolation. The deep percolation rate for the subject parcel suggests there would be effluent percolation at the depths of seepage pits and particularly sumps. Based upon the number of repairs and additions to septic systems in the project locale, leachlines in this - area have a limited lifespan. The final sewage disposal area for any proposed structure on Parcel 1 should be dependant upon the type and size of the structure. We are recommending a 10,000 to 12,000 square feet leachfield area to provide treatment of the septic effluent. Seepage pits or sumps must be installed for any future residential or commercial structure. The number of pits or sumps will be dependent on the number of bedrooms or offices the structure will have. If there will be several people inhabiting the structure, particularly children, a septic system should be oversized (increase the number of pits/sumps) to accommodate additional wastewater flows. A 50% standby replacement area (100% for commercial) must also be incorporated into the design of the septic system. All related septic system structures and the domestic well must comply with published "distance" requirements from property borders, roads, easements, irrigation fields, etc. It must be recognized that all septic systems have lifespans. If the leachfield area should fail, the seepage pits/sumps will manage the effluent percolation. Seepage pits can also fail, although over a longer time period. As referenced earlier, a 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 subsurface soils consist of a tight, gravelly/silty material, anaerobic conditions will probably prevail This may hasten leachfield and seepage pit/sump failure. [6) LIMITATIONS The conclusions of this Soil Suitability Study are based upon past and present information concerning the location and results of percolation testing. Results of the perc testing can only be assumed to be representative of the subsurface conditions encountered in the area of testing. It is our opinion the findings included in this study are a reasonable assessment of the current subject property and surrounding study area conditions regarding septic system density, nitrate-nitrogen sources and potential impact to the underlying groundwater. This opinion cannot constitute a guarantee or warranty, either expressed or implied. Respectfully submitted, QUALITY CONTROL INSPECTION, INC. 3