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L! <br /> 0 March 16, 2006 <br /> NOA Project Number: E0601 1A <br /> Table 2. <br /> Summary of Nitrate Mass Balance Analysis. <br /> Result Acres Average Daily Effluent Concen- Leachfield Deep Percolation.of <br /> (Nc)* (A) Flow(Q) (Table 1) tration(Nw) Denitrifi- Rainfall(R) <br /> (mg/ (gpd) (mg/L-N) cation(d) (Plate 9) (in.) <br /> i 2.05 490 40 25% 1.27 <br /> 18.1 2.05 280 40 25% 1.27 <br /> Rum contaminant level(MCL) for nitrate in drinking water is 10 mg/1—N. <br /> 3.6 ImP g Y act of Nitrate Loading to Nearby Water Sources <br /> PThe result of the nitrate loading balance indicates that the proposed use could potentially cause a <br /> buildup of nitrate in the ground water above 10 mg/L-N over.the term. According to the <br /> Hantzsche and F{enne ore equation and approach, there s a potential ora buildup of nitrates in <br /> �� the ground waterll�to 21.8 mg/L-N if a second dwelling unit is cores cted in addition to a two to <br /> three bedroom residence. Withe second dwelling unit there is still a potential for a buildup of <br /> nitrates in the groundwater t /18. mg/L-N. <br /> F <br /> 4.0 DISCUSSION OF NITRATE LOADING RESULTS <br /> F, <br /> 4.1 Total Nitrate Impact <br /> FjAccording to the Hantzsche and Fennemor equ tion and approach there is a potential for a <br /> buildup of nitrates in the ground water up o 21.$mg/L-N over the long term. Without,the-second <br /> dwelling unit there is still a pote�ti�l fora b d o� ni`5rates in the groundwater up t,�8.1�mg/L- <br /> N. The calculated Nc values of 21.x$mg/L-N and 18.1 g/L-N axe higher than the safe drinking <br /> water standard. , <br /> 4.2 Methods of Mitigation <br /> To mitigate the percolating nitrate, some simple measures should be utilized to improve the <br /> �E retention time and digestion of the waste water in the septic system. To accomplish this,we would <br /> recommend installing a double septic tank and utilize a modified filter bed septic system. The <br /> modified filter bed septic system should maintain five feetseparation from first groun ter. The <br /> rriodifred filter bed should contain appxoximatc y f urs loo- ompost-or pear t provide a <br /> carbon s8 rce and`slow i e percolation rate. We re c mmend the following septic system size based <br /> on-the-proposed us _as follows: <br /> k <br /> 0 6 ',0A4 <br /> ! 1 <br />