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CONCLUSIONS AND RECOMMENDATIONS The shallow subsurface soils underlying the subject property where the new filter bed disposal structure is to be installed, reveals a clay loam and sandy clay loam soil structure with acceptable permeability determined by the perc rate of 13.2 minutes/inch. The underlying soils have significant denitrification capabilities. Although a denitrification factor of 30% was used in the original study, it is my professional opinion that this 30% parameter could have been increased at least 1.5x, or even doubled based on the observed soil characteristics. Sufficient area exists for the 100% replacement area, as detailed on the architectural Site Plan. Although it may be many years or decades before failure of the primary system, when the replacement area is activated, it must also be constructed as a filter bed arrangement, as illustrated. The septic tank has been increased in size from the required 1,200 gallon tank to a 2,000 gallon tank to increase hydraulic residence time (FIRT) and promote nitrogen retention within the tank. The wastewater characteristics are anticipated to be those normally found in typical domestic or household systems. The recommendation of installing a larger tank is based on the following premise: ' From the September 2004 Symposium "University Curriculum Development for Decentralized Wastewater Management - Onsite Nitrogen Removal," Dr. Stuart Oakley of California State University Chico stated that "approximately 20% of the total nitrogen generated is removed in the septic tank." If Dr. Oaldey's premise of an approximate 20% nitrogen removal occurs in septic tanks, then if the tank size is increased a specific percentage from a baseline size, then it is reasonable to assume that the percentage increase in tank size will remove that percentage of nitrogen above the 20% baseline. This nitrogen removal occurs from anaerobic digestion of organic material and scheduled tank pumping. Therefore, increasing the septic tank size for this project from the required 1,200 gallon to 2,000 gallon is a 67% increase in capacity, thus substantiating a 67% increase above this 20% N reduction: 20% + (20 x 0.67) = 33% decrease in nitrogen concentrations by installing a 2,000 gallon tank in lieu of a 1,200 gallon tank. As referenced in the AdvancedGeo document, the biomat removes another 10% of the nitrogen, totaling a 43% decrease from the 45 mg/L nitrogen influent concentration of the wastewater: 45 -43% = 25.7 mg/L N concentration. The initial nitrate loading calculations from AdvancedGeo show the resultant effluent from the proposed SFR will theoretically possess a concentration of approximately 16.28 ppm as nitrate- nitrogen. The following calculations demonstrate that changing the NRR exclusively (excluding increased denitrification potential and decreased total wastewater nitrogen concentration, as discussed above), lowers the nitrate loading potential to below the MCL: HANTZSCHE/FINNEMORE EQUATION IN,(I - d)+ R N Nr = (I + R) Where: tav - Chesney Consulting