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V. CONCLUSIONS, RECOMMENDATIONS AND MAINTENANCE SSS§ 5.4. The soils underlying the proposed mound system disposal area for the primary and second unit dwelling on the subject Parcel show unacceptable permeability due to the native clay soil type. Other types of clay in the Tracy area exhibit exceptional permeability, but this clay type possesses slow permeability. Additionally, soil compaction from machinery may have occurred under optimum soil moisture conditions and contributed to this slow permeability. NLS§ 4.2, SSS§ 6.7. From the soil chemistry test results, the denitrification potential within the native soils is significant and substantial, based upon the clay content, organic matter content, soil pH, and the soil cation exchange capacity. In addition, it is well-documented in the scientific literature (Ref. 2 and 5) that mound systems have significant nitrogen reduction capabilities ranging from 32% to 70%. This is primarily due to the fact that the ammonium fraction of the septic effluent can nitrify through the sand layer and because of the high clay content native soils, readily denitrify. Consequently, a factor of 70% nitrogen reduction was factored into the nitrate loading calculations. SSS§ 6.8. The new mound system basal area must be designed to accept the highest average daily flow. Pursuant to EHD guidelines in Section 9.19.3 of the OWTS Standards, the absorption area is to be 6000 ft2. The Application Rate at the native soil depth of 36 inches was determined to be 0.100 gals/ft2 /day. With a mound system basal area of 200 ft N-S x 30 ft E-W (6.7:1; L:W Ratio), the ADF = 6,000 ft2 x 0.1 gals/ft2 /day = 600 gals/day. This acceptance rate corresponds with an extremely high average wastewater generation rate of 25 gals/hr/day, every day of the year. The effluent pumps will operate under a "time dose" system, not "demand dose." This will allow the effluent to equally distribute and allow the native soil to process the percolating effluent without creating saturated soil conditions. NLS§ 4.1. The nitrate loading potential calculated in Section BIB indicates the percolating effluent may have a resultant nitrate-nitrogen concentration of 4.9 ppm, which is 5.1 ppm under the drinking water Maximum Contaminant Level (MCL) of 10 ppm nitrate-nitrogen. MAINTENANCE Since the project is in an area that may be prone to power outages, a backup generator should be installed for each residence so that power for potable well water and power to dispose of septic tank effluent through the mound system is always available. A maintenance program must be established for the entire wastewater disposal system. The septic tank pump-out interval has been calculated to be between 2.5 and 3.0 years. However, this is a theoretical pump-out interval and should be field-verified by a sewage contractor. Additionally, the effluent filter in the 2000 gallon tanks should be cleaned at the time of pump-out. Clean-outs must be installed at the distal ends of each lateral as noted on the attached plan detail notes. By using a "snake" device, the interiors of the laterals can be cleaned of biomat build-up, if needed. The distal clean-out valves should be opened and allowed to flush each year. A sewage contractor should perform this operation to observe biomat buildup and adjust clean-out intervals accordingly. 12 Chesney Consulting