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Questa identified certain assumptions used in the Condor analysis that contributed to an overestimation of the nitrate loading impact. These included: (a) use of peak rather than average annual wastewater flow; (b) adjustments (reductions) that should be made in the accounting of actual evapotranspiration (e.g., for paved surfaces, bare soil, and other non -turf landscaping). The Condor analysis also included a low value 35 mg-N/L for septic tank nitrogen concentration, which significantly below the normal concentrations found at schools. Questa also provided information on the use of pressure distribution in the leachfield as a practical means of improving the nitrogen reduction in the leachfield and soil over that achieved by conventional gravity leaching trenches. Revised Design Submittal Based on technical references and methodologies provided through Questa's initial review, MCR modified the leachfield design to incorporate pressure distribution, and prepared revisions to the water balance and nitrate loading calculations. The following documents were provided for Questa's review: • Pressure Distribution Civil Design - Site Plan • Pressure Distribution Design Calculations • Sewer Pump Station Design Calculations • Rainfall Recharge Water Balance Calculations • Updated Nitrate Loading Calculations My review of the drawings and calculations found the pressure distribution design to be appropriate and in accordance with EPA guidelines and common practices in the OWTS industry. The revised water balance calculations incorporated more current rainfall data and adjustments to the evapotranspiration factor based on site specific landscape conditions, which I found reasonable. The calculations give a revised rainfall -recharge ("deep percolation") estimate of 8.50 inches per year. This was incorporated in updated nitrate loading calculations along with two other changes - annual wastewater flow volume of 1,940 gpd, and effluent nitrogen concentration of 100 mg-N/L. Calculations of the resultant nitrogen concentration (Nc) were made for (a) standard leachfield design (at 15% denitrification), and (b) mitigated pressure distribution leachfield design (at 50% denitrification), with the following results: • Standard Leachfreld: Nc = 14.98 mg-N/L • Pressure Distribution Leachfreld: Nc = 9.16 mg-N/L I'm in agreement with the assumptions and calculations presented in the revised design submittal. With the proposed change to a pressure distribution leachfield design I believe the groundwater nitrate impacts from the School's OWTS will be adequately mitigated consistent with San Joaquin County Environmental Health Department requirements.