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CONCLUSIONS AND RECOMMENDATIONS The shallow subsurface soils underlying the subject property where the new filter bed disposal area is to be installed, reveals a silty sand soil structure with medium permeability at the 3.42 ft depth. Sufficient area exists for the 100%replacement area, as detailed on the aerial photo in Appendix A. The nitrate loading calculations show the resultant effluent from the primary dwelling will theoretically possess a concentration of approximately 13.53 ppm as nitrate-nitrogen, which is 3.53 ppm over the drinking water MCL of 10 ppm nitrate-nitrogen. Calculations demonstrate that the nitrogen uptake by the Fescue lawn grass that must be planted over the filter bed area to mitigate the nitrate loading, will readily meet the 50%N reduction requirement as imposed by the EHD through the Regional Water Board's Policy. This 50% reduction must occur between the raw wastewater influent and the vadose zone effluent after vegetative nitrogen uptake. Based on this 50%reduction in total nitrogen requirements, 13.3 lbs of nitrogen(50%of 26.6 lbs)would have to be treated by vegetative uptake; readily achieved by the Fescue grass by removing 29.2 lbs N in 18 cuttings. Grass clippings from mowing the Fescue grass must be transported off-site, otherwise the nitrogen cycle will be completed. A 1,600 gallon septic tank has been specified. This tank size will supply sufficient hydraulic residence time (HRT) and promote nitrogen retention within the tank. It is recommended the septic tank be pumped out every three to four years. In addition, due to the design of the D-box, particulate matter can be retained preventing discharge to the filter bed and should also be pumped out at the same time as the septic tank. The application rate was determined from the perc rate of 17.86 min/in to be 0.686 gallons/ftZ/day. The total filter bed area is 875 ft' of floor area. Therefore,the filter bed can readily manage: 0.686 gallons/ft2/day x 875 ft'=600 gpd. The Average Daily Flow(ADF)was determined to be 250 gpd. Therefore,the filter bed design is 2.4x the area needed to accept the ADF of 250 gpd. It is recommended that the kitchen sink should not have a disposal. All food waste should be handled as solid waste and disposed of in the garbage. All onsite wastewater treatment systems (septic systems)will eventually fail. A reasonably long lifespan of the disposal area can be expected based on the perc rate obtained and the incorporated design factors. Pae -5- Chesney Consultin-