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476 N Patton Avenue Project No. 2021-00084 Page 18 <br /> 5.5 Nitrate Loading <br /> A nitrate loading scenario was performed to determine the impact from the proposed <br /> project. The scenario utilizes the variables discussed previously which represent the <br /> estimated conditions and uses associated with this project. The following table presents a <br /> summary of the nitrate loading calculation for the parcel. <br /> Table 4. <br /> Summary of Nitrate Mass Balance Analysis. <br /> Parcel Result Acres Average Daily Flow Effluent Leachfield Deep Percolation <br /> (Nc)* (A) (Q) Concen- Denitrifi- of Rainfall(R) <br /> (mg/L-N) (gpd) tration(Nw) cation(d) (Plate 7) (in.) <br /> (mg/L-N) <br /> 1 11.2 2.20 400 35.00 1 30% 3.21 <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 12 mg/L-N, which is <br /> above the MCL of 10 mg/L-N set by the EPA. As discussed above, the depth to groundwater <br /> is approximately 110 to 115 feet below ground surface at the site. <br /> The background concentration of nitrate detected in the domestic well for the site is 12 <br /> mg/L-N. Based on the methods and assumptions described, the project will result in nitrate <br /> of 11.2 mg/L-N. However,the depth to groundwater for this site is approximately 110 to 115 <br /> feet below ground surface. Based on the moderate percolating clayey loam layers <br /> underneath the site, 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 background level <br /> reported from the domestic well onsite of 12 mg/L-N above the total nitrogen over the long <br /> 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 background detected concentration of total nitrogen 12 mg/L <br /> over the long term. <br /> Petralogix Engineering,InC. <br /> 26675 BruelIa Road,Galt,Ca 95632 <br /> (209)-40o-5729 <br /> www.petralogix.com <br />