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33503 S Koster Road Project No. 2021-00073 P a g e | 8 <br />Table 4. <br />Summary of Nitrate Mass Balance Analysis. <br />Parcel Result <br />(Nc) * <br />(mg/L-N) <br />Acres <br />(A) <br />Average Daily Flow <br />(Q) <br />(gpd) <br />Effluent <br />Concen- <br />tration (Nw) <br />(mg/L-N) <br />Leachfield <br />Denitrifi- <br />cation (d) <br />Deep Percolation <br />of Rainfall (R) <br />(Plate 7) (in.) <br />1 18.5 1.26 350 35.00 30% 1.28 <br /> * Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N. <br />5.6 Impact of Nitrate Loading to Nearby Water Sources <br />Based on the relatively flat topography of the site, we do not foresee percolating effluent <br />affecting any surface water resources. <br />6.0 DISCUSSION OF NITRATE LOADING RESULTS <br />6.1 Total Nitrate Impact <br />The nitrate maximum contaminant level (MCL) set by the US EPA is 45 mg/L-NO3 or <br />10 mg/L-N. The domestic well reported groundwater at the site was 4.3 mg/L-N. As <br />discussed above, the depth to groundwater is approximately 70 to 80 feet below ground <br />surface at the site. <br />The background concentration of nitrate detected in the domestic well for the site is 4.3 <br />mg/L-N. Based on the methods and assumptions described, the project will result in nitrate <br />of 18.5 mg/L-N. However, the depth to groundwater for this site is approximately 70 to 80 <br />feet below ground surface. Based on the very low background nitrate concentration <br />detected, the low-density septic systems for the area, the moderate percolating clayey loam <br />layers underneath the site, and the depth to groundwater, we believe the proposed project <br />will not likely cause a build-up of nitrate in the ground water above the nitrate maximum <br />contaminant level (MCL) set by the US EPA of 10 mg/L-N above the total nitrogen over the <br />long term. <br />Based on the methods and assumptions described, in addition to our professional judgement <br />and geologic setting, we believe the proposed project is unlikely to cause a build-up of nitrate <br />in the ground water above the USEPA maximum concentration level of total nitrogen <br />10 mg/L over the long term. <br />6.2 Nitrate Loading - Methods of Mitigation <br />Based on the very low background nitrate concentration detected, the low-density septic <br />systems for the area, and the depth to groundwater, we believe the proposed project will not <br />likely cause a build-up of nitrate in the ground water above the nitrate maximum <br />contaminant level (MCL) set by the US EPA of 10 mg/L-N above the total nitrogen over the <br />long term. It is our professional opinion that mitigation measures such as an engineered <br />septic are not warranted at this time, however, a standard septic system with an oversized