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15 November 2019 AdvancedGeo <br /> AGE Project No. 19-4912 Environmental <br /> Page 13 of 14 <br /> A total of 15.37 ppm of additional nitrogen is estimated to be added to the site over the <br /> long term through waste water recharge from the existing and proposed septic systems. <br /> The nitrogen loading value is above the desired value of 10 ppm. <br /> 10.0. TOTAL NITRATE IMPACT FROM PROPOSED PROJECT <br /> Based on the method and assumptions described, proposed NO3_N mass of wastewater <br /> and the calculations of the NO3_N loading predicted, the proposed development may <br /> negatively impact NO3_N loading rates within the aquifer. The soil at the site appear to <br /> be adequate for nitrate degradation and proper leaching of wastewater. A total of <br /> 15.37 ppm of additional nitrogen is estimated to be added to the site over the long term <br /> through waste water recharge from the existing and proposed septic systems. <br /> 11.0. MITIGATION METHODS PROPOSED <br /> To mitigate any known or potential future impacts to soil and groundwater of nitrate from <br /> the existing and proposed septic systems, the following mitigations could be <br /> implemented: <br /> • Maximize wastewater hold time where practical (retention). <br /> • Avoid use of bioattenuation chemicals (bleach etc.). <br /> • Properly and regularly maintain property septic systems. <br /> • Use EHD criteria for sizing the septic disposal field. <br /> If re-location or expansion of leach fields becomes necessary, leach lines should include <br /> high organic substrates under and surrounding the lines installed. <br /> 12.0. CONCLUSIONS AND RECOMMENDATIONS <br /> Based on this Soil Suitability and Nitrate Loading Study, AGE concludes the following: <br /> • The percolation rate meets the minimum EHD standards in the proposed septic <br /> system disposal field. <br /> • The nitrogen loading rate is above the desired value of 10 mg/I. However, the <br /> groundwater table is a minimum of 25 feet bsg and the parcel appears suitable for <br /> the use of a standard septic system. <br /> • All approved septic system use should follow the EHD Onsite Wastewater <br /> Treatment System Standards. <br />