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25288 N Cherokee Lane Project No.2018-00018 Page 16 ' <br /> wastewater concentration of 35 mg/L-N,therefore,it is estimated that residential domestic ' <br /> wastewater concentration will be approximately 35 mg/L-N. ' <br /> 4.4.2 Denitrification Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain ' <br /> bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N2) to the <br /> atmosphere. Denitrification is expressed as a percentage, and the normally accepted range ' <br /> is 10 percent to 35 percent. Soils with higher clay content, moist soil conditions, high pH, <br /> and organic material denitrify by about 35 percent,and soils with high sand content and fast <br /> percolation rates are estimated to denitrify at a lower rate,about 10 percent to 15 percent. ' <br /> The San Joaquin Complex soil is primarily a clay loam/loam, with moderate pH levels and <br /> low permeability; the San Joaquin Complex soil is therefore estimated to denitrify at ' <br /> approximately 35%. <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. The following table presents a <br /> summary of the nitrate loading calculation for the parcel: <br /> Table 3. ' <br /> Summary of Nitrate Mass Balance Anal sis. <br /> Parcel 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) (Plate 7) (in.) <br /> N) (mg/L-N) ' <br /> 1 9.0 1.84 420 35.00 35% 5.29 <br /> * Maximum contaminant level(MCL)for nitrate in drinking water is 10 mg/L-N. <br /> 1 <br /> 4.6 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 1 <br /> 10 mg/L-N. The depth to groundwater for this site is approximately 95 to 100 feet below <br /> ground surface, with clay loam as the primary soil type. Based on the mass balance analysis ' <br /> results, in addition to our professional judgement and geologic setting showing the deep <br /> groundwater table and the slow percolating clay loam soil, we believe the proposed project <br /> will not likely cause a build-up of nitrate in the ground water above the US EPA MCL of 10 ' <br /> 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 /> w .petraloglx.com <br />