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F - L Pastor Matt Linder !' May 5,2003 Page 5 k _ a , Table 2.,Summary of Nitrate Mass Balance'Analysis. F Scenario Result Acres Average Effluent Leachfeld Deep.Percolation (Nc) * (A) Daily Concen= Denitrifi- of Rainfall(R) Flow(Q) tration cation.(d) (Plate 1) (Table 1) (Nw) Standard Septic - . 5.4 mg/L-N 16.7 4369P 75 mg/L-.N 10% 5.01 in . System(Plate 2). r k OSI Treatment System 3.3 mg/L-N 16.7 436 gpd 38 mg/L-N 5% 5.01 in (5001.removal of Total Nitrogen)(Plate 3) ** ` OSI Treatment System 2.1 mg/L-N 16.7 436 gpd I9 mg/L-N 5% 5.01 in (75%removal of Total Nitrogen)(Plate 4) ** * Maximum contaminate level(MGL)for Nitrate in drinking water is 10 mg/L-N., ** Please note that 50%removal of nitrogen(75 mg/GN x 50%)is conservative,nitrogen removal may be up to 751/o+if conditions are optimal according to OSI. Discussion and Recommendations Because of the sandy coriditions,the rapid percolation rate measured,the shallow depth to r' ground water, and the pre-existing nitrate condition of the ground water, our previous report had recommended the use of an engineered septic system to reduce the nitrate concentration of the effluent in order to minimize the impact to the existing aquifer. Our office has evaluated several treatment systems and believes the.Orenco Advantex system is well suited for'the proposed facility. It'has a relatively low capital cost low maintenance cost reliable, and obtains performance consistency. Considering-that treatment_goals below 10 m for nitrate are e difficult o achieve and a grew ae endent on 'n uent concentrations of waste water,w �e believ that itis much more realistic to set treatment goals of 50%to 75%total nitrogen reduction of(Nw)over the long term. This is what Orenco Systems Inc. AdvanTex system has achieved. Based on the assumptions of the Hantzshe&Finnemore equation,we believe the proposed project will not cause a long term buildup of nitrates above 10 mg/L-N in the ground water regardless of the type of septic system. However, a short term build up is possible due to the rapid percolation rate , measured, the shallow depth to ground water. A water quality test of the aquifer indicates,it has been ` impacted by nitrates. The use of an OSI,AdvanTex treatment system will greatly.reduce these short term impacts and improve the long term water quality level(Nc)estimated by the Hantzshe&Finnemore equation. Our office believes the site is suitable for development unitizing an OSI Advantex waste water treatment system or an equivalently performing system.. Please refer to the soil suitability/nitrate loading 9SSOL1 r