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August 31, 2006 <br /> NOA Project Number: E06091A <br /> 3.5 Nitrate Loading Scenario <br /> A nitrate loading scenario was performed to determine the impact from the proposed project. The <br /> scenario utilizes the variables discussed previously which represent the estimated conditions and <br /> uses associated with this project. The following table presents a summary of the nitrate loading <br /> calculation for the parcel. (P6X7CC 11�I o) <br /> R." Table 2. <br /> Summary of Nitrate Mass Balance Analysis. <br /> Parcel Result Acres Average Daily Effluent Leachfield Deep <br /> (Nc)* (A) Flow(Q) Concen- Denitrifi- Percolation of <br /> (mg/L-N) (Table 3) tration(Nw) cation(d) Rainfall(R) <br /> (gpd) (mg/L-N) (Plate 9) (in.) <br /> 1 10.8 5.0 730 56.50 30% 5.76 11 <br /> * Maximum co ant level(MCL) for nitrate in drinking water is 10 mg/L-N. <br /> 3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> Since the site is relatively flat,we do not foresee percolating effluent affecting any surface waterFit, <br /> resources. <br /> , 6 <br /> 4.0 DISCUSSION OF NITRATE LOADING RESULTS <br /> 4.1 Total Nitrate Impact <br /> Based on the method and assumptions described, the result of the nitrate loading balance indicates <br /> that the p:Foposed"development on the proposed parcel maycause a-b`Luld up of nitrate in the <br /> tgxotind water above 10.8 mg/L-N over the long term. The existing aquifer, from which the water <br /> well draws, has experienced elevated nitrates. These soils appear to be susceptible to rapid leaching <br /> of waste water. <br /> 4.2 Methods of Mitigation <br /> To mitigate potential buildup of nitrate in the aquifer, some simple, cost effective measures should <br /> be utilized to improve the retention-time, digestion within the septic tank, and improvethe <br /> conditions.in the leach field. To accomplish this,we would recommend installing ddoublc septic <br /> ,_tank and the utilization of a modified filter bed septic system. We recommend using EHD criteria <br /> for sizing the septic disposal field.The.modified filter bed should contain approximately,four niches /-� <br /> F1of loose compost or peat to provide a carbon source and slow the percolation rate? <br /> D. 7 <br />