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r . CONCLUSIONS AND RECOMMENDATIONS FOR NITRATE LOADING MITIGATION The Hantzsche/Finnemore Equation predicts a nitrate-nitrogen concentration in the recharge effluent water from the proposed project to be 4.2 ppm as nitrate-nitrogen(NO3-N), or 18.7 ppm as nitrate(NO3). This calculated impact accounts for a maximum of six new single family residences,three of which are to be considered second unit dwellings. The effluent recharge is approximately equivalent to the nitrate concentration found in the underlying tested aquifers. However,the well is screened from 300 feet to 400 feet and from the well log data,may include four separate aquifers. From numerous studies done in San Joaquin County, it has been invariably determined that the water table in most locations within the County have a significantly higher nitrate concentration than the aquifers underlying a respective water table. Consequently, it can be theoretically concluded that the recharge effluent water from the project may produce a dilution effect to the underlying water table nitrate concentration. The percolation test results for the three Parcels indicate acceptable percolation at the shallow depths that are indicative of effluent percolation from leachlines. Therefore, an engineered septic system is not required. Deeper perc tests reveal that sump septic structures may not be applicable in this soil type. Unfortunately, 25-foot test borings,which would have yielded test results representative of seepage pits, could not be drilled on the subject property due to the severe gravel/cobble content. A large drill rig would have severely compacted the clayey-gravel soil within the perc test borings,thus ensuring no infiltration and percolation. The auger used to drill seepage pits,however,has a"cleat"on the outer flight to prevent, or lessen soil compaction. The total length of leachline and the number of seepage pits will be dependant upon the number of bedrooms each new home will have. Additionally, the system should be oversized if it is known before construction that a large number of people will inhabit the new home. This may include an additional leachline and seepage pit. A 50%replacement area must be designated on the respective Parcel in the event of failure. All installed septic systems for this project must abide with Section 10 of the San Joaquin County Sewage Standards. With regard to septic system leachlines, it is recommended to install Infiltrator® Chambers as shallow leachlines. These chambers are not considered by EHD to be an"engineered" septic system. During the spring and summer months, a medium percentage (--50%) of effluent discharged to the chambered system may be evapotranspired during the hot and windy conditions that are common in this locale. Based upon knowledge of EHD staff, seepage pits are typically installed in this area and may be used for this project as illustrated on the"color"map for different regions of the County. The subject property is located in the "orange" or hardpan region which stipulates leachlines and seepage pits. The Long Term Acceptance Rate (LTAR) for installed seepage pits should stabilize at approximately 0.5 gallons/ffz/day due to biomat formation, according to the scientific literature. As a safety factor, infiltration that may occur in leachlines has been omitted. 10 Chesney Consulting