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V. CONCLUSIONS AND RECOMMENDATIONS SSS 5.4V.8.t The soils underlying the area proposed for wastewater effluent dispo show acceptable pe ea ' he shallow depths representative of a filter bed. From the soil chemis st resu appears there is some denitrification potential from the soils,but not as significant as has been observed in other areas of S oaquin County. �§ , ,S S§6.7 Since the water table is relatively deep in this locale at approximately 56 ft below filte ffluent disposal system will allow the greatest distance between the soil-effluent interface and the depth to the water table. Consequently,filter beds are the best option for the septic system structure to be installed for this project. By installing the filter bed as high in elevation as possible, evapotranspiration may be expedited depending upon the plant types that are grown over and near the disposal area, and downward migration of nitrate may be impeded. Additionally, a filter bed reduces the footprint of the disposal area in comparison to conventional leachlines and sumps. The new buildings should be built as high in elevation as practical and/or have the influent wastewater lines plumbed through the footings of the buildings. This is to ensure that the septic tanks are as high in elevation as possible so there is sufficient fall between the tank outlet and the furthest disposal point without exceeding the maximum allowable filter bed depth and allowing for gravity flow. The general contractor, plumber and septic system contractor must coordinate on these construction details. The filter bed sizing requirement calculations demonstrate there is ample area as denoted on the RJM Design Group Site Plans for the primary disposal and the 100%replacement areas. The exact dimensions of the filter bed systems may be orientated prior to construction to conform with the setbacks from trees, parking areas,fence lines,etc. It is noted, as depicted on the Site Plans,that large trees cannot encroach within 10 ft of the filter bed disposal areas. As also noted on Site Plans, perimeter fencing is near the effluent disposal area. If additional area is needed for disposal, more area is south of this fence line. NLS§4.1. itrate loading calculations demonstrate that if the toilets in both the Office and ance Buildings were flushed 400x per day(1.5 gals/flush x 4.00 flushes=600 gpd ADF),the nitrate loading remains well below the Maximum Contaminant Level(MCL). It appears from the nitrate loading calculations,that nitrate loading potential could be significantly greater from lawn and landscaping nitrogen fertilization than from the disposal of on-site wastewater effluent. "Slow release"nitrogen fertilizers,or"dosing"nitrogen fertilizers should be used for all lawn/landscape nitrogen fertilization. It is imperative that any food and food by-product wastes from the Office and Maintenance Buildings must be handled as solid wastes and not be disposed of into the septic system. This will prevent concentrated organic loading,prolong the lifespan of the wastewater disposal system-and reduce nitrate loading potential. It is important to recognize that all septic systems have a lifespan,which is dependant on several factors and is therefore difficult to determine. Septic system 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 polysaccharides. Since the filter beds will be installed high in elevation,there will be a greater opportunity for oxygen intrusion from the atmosphere, thus theoretically assisting in biomat degradation,along with promoting evapotranspiration, as discussed above. 10 1 Chesney Consrdltifng