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2 the nitrogen removal within the leachfield system, providing up to approximately 30% additional nitrogen reduction as compared with standard gravity flow systems. This is due mainly to the wetting-drying cycles (from pressure dosing), maintaining an aerobically active gravel-soil interface along trench bottom, and making maximum use of the available soils for wastewater contact and treatment. Calculations indicate that with this mitigation approach, the resultant Nr value would be reduced to 9.73 mg/l, below the 10 mg/L compliance criterion. The following assumptions used in my analysis:  Recharge Area: 2.5 acres (1.0 acres vegetated, 1.5 acres hardscape)  Wastewater flow:  Proposed project (2 bed): 150 gpd  241 French Camp Rd (4-bed) 250 gpd  255 French Camp Rd (Store) 150 gpd Total 550 gpd Annual wastewater volume: (550 gpd*365/325,851) = 0.62 ac-ft/yr  Nitrogen effluent concentration, Nw = 62 mg/L  Soil denitrification rate for standard OWTS, d = 0.20  Soil denitrification rate for pressure distribution leachfield, d=50%  Rainfall recharge, R = 10.68 inches per year, or 2.23 ac-ft/yr for 2.5 acre area  Background nitrate Nb = 0.1 mg/L Based on this extended analysis of wastewater nitrate loading for the entire “block”, I would revise my prior recommendations to still include the use of a pressure distribution system for nitrogen mitigation, but eliminate the requirement for an advanced nitrogen-removal treatment unit. Sawdust Mitigation Proposal The OWTS designer (Don Chesney) has proposed the use of a layer of sawdust over the entire bottom soil-infiltrative surface of the proposed leaching beds as a means of mitigating nitrate- nitrogen loading impacts from the percolating wastewater. I have previously reviewed this proposed mitigation idea for another property, and found no technical information or examples to support this approach. In my opinion this proposal is without merit and would do more harm than good.  Chesney’s proposal is to line the bottom of the leaching bed with sawdust to create a heavy anaerobic layer to capture nitrogen. The supporting theory for this is missing, but more importantly this would directly interfere with the maintenance of aerobic soil conditions which is essential for long-term infiltration and drainage of wastewater and pathogen removal. The anaerobic layer will lead to early soil clogging and failure of the leachfield.