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21300 MANN ROAD Project No.2019-00095 Page 17 <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 3. <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 10.9 1.66 420 35.00 25% 5.29 <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 /> 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 was not operable; therefore, Total Nitrogen was not tested. <br /> Based on the methods and assumptions described, the project will result in nitrate 10.9 <br /> mg/L-N. The depth to groundwater for this site is approximately 110 to 130 feet below <br /> ground surface. Based on the mass balance analysis results, in addition to our professional <br /> judgement, low septic tank density, and geologic setting showing the deep groundwater <br /> table underlying the Site,we believe the proposed project will not likely cause a build-up of <br /> nitrate in the ground water above the background concentration of total nitrogen above <br /> 10 mg/L over the long term. <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 /> 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 background concentration level of total nitrogen 10 mg/L over <br /> the long term. <br /> 6.2 Nitrate Loading-Methods of Mitigation <br /> Based on the mass balance analysis results, in addition to our professional judgement, low <br /> septic tank density,and geologic setting showing the deep groundwater table underlying the <br /> Site, we believe the proposed project will not likely cause a build-up of nitrate in the ground <br /> water above the background concentration of total nitrogen above 10 mg/L over the long <br /> Petralogix Engineering,Inc <br /> 26675 Bruella Road,Gait,Ca 95632 <br /> (209)-400-5729 <br /> www.petralogix.com <br />