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18340 E Rodeo Drive Project No.2018-00037 Page 17 <br /> Montepellier-Cometa soil is a primarily sandy loam and sandy clay loam with low <br /> permeability and moderate pH levels; the Montpellier-Cometa complex soil is therefore <br /> estimated to denitrify at approximately 30%. <br /> 4.5 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. Because both soil types are <br /> estimated to have the same denitrification percentage, a single nitrate loading calculation is <br /> considered sufficient for the nitrate mass balance analysis. 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 /> Result Acres Average Daily Flow Effluent Leachfield Deep Percolation <br /> (Nc)* (A) (Q) Concen- Denitrifi- of Rainfall(R) <br /> (mg/L- (gpd) tration(Nw) cation(d) (Plates 8 and 9) <br /> N) (mg/L-N) (in.) <br /> 10.1 5.10 1,260 1 35.00 1 30% 5.29 <br /> * Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N. <br /> 4.6 Impact of Nitrate Loading to Nearby Water Sources <br /> The nitrate maximum contaminant level (MCL) set by the US EPA is 10 mg/L-N or 45 <br /> mg/L-NO3. Nitrate was found in groundwater at 1.4 mg/L-N and 6.4 mg/L-NO3; the <br /> background groundwater quality concentration of nitrate is above the MCL of 10 mg/L-N <br /> and 45 mg/L-NO3, respectively. Based on the methods and assumptions described, the <br /> project will result in 10.1 mg/L-N. The depth to groundwater for this site is approximately <br /> 160 to 165 feet below ground surface, with sandy loam/sandy clay loam as the primary soil <br /> type. Based on the mass balance analysis results, in addition to our professional judgement <br /> and geologic setting showing the deep groundwater table and the severely slow percolating <br /> rate sandy loam/sandy clay loam soil, we believe the proposed project will not likely cause <br /> a build-up of nitrate in the ground water above the maximum contaminate level <br /> concentration of 10.0 mg/L-N 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 /> Petralogix Engineering,Inc. <br /> 26675 Bruella Road,Galt,Ca 95632 <br /> (209)-400-5729 <br /> wwwpetralogix.com <br />