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1 4350 E.Acampo Road Project No.2018-0043 Page 18 Table 3. t Summary of Nitrate Mass Balance Analysis. ' Parcel Result Acres Average Daily Flow Effluent Leachfield Deep Percolation (Nc)* (A) (Q) Concen- Denitrifi- of Rainfall(R) (mg/L-N) (gpd) tration(Nw) cation(d) (Plate 7) (in.) (mg/L-N) 1 12.2 2.68 840 35.00 25% 5.24 * Maximum contaminant level(MCL) for nitrate in drinking water is 10 mg/L-N. ' 4.6 Impact of Nitrate Loading to Nearby Water Sources The nitrate maximum contaminant level (MCL) set by the US EPA is 45 mg/L-NO3 or ' 10 mg/L-N. Total Nitrogen was found in groundwater at 3.8 mg/L. Based on the mass balance analysis results, in addition to our professional judgement and geologic setting ' showing the groundwater at approximately 75 feet below ground surface,traveling through moderately percolating sandy loam soil,we believe the proposed project will not likely cause a build-up of nitrate in the ground water 2.2 mg/L-N above 10 mg/L-N over the long term. ' Based on the relatively flat topography of the site, we do not foresee percolating effluent affecting any surface water resources. ' 5.0 DISCUSSION OF NITRATE LOADING RESULTS ' 5.1 Total Nitrate Impact Based on the methods and assumptions described,in addition to our professional judgement , and geologic setting, we believe the proposed projects is unlikely to cause a build-up of nitrate in the ground water 2.2 mg/L-N above 10 mg/L-N over the long term. 5.2 Methods of Mitigation ' The nitrate mass balance equation indicates the project would result in 12.2 mg/L-N, t however,based on the depth to groundwater being large(approximately 75 feet below the ground surface), and the moderately percolating sandy loam soil onsite, mitigation measures are not warranted at this time. However, it should be noted that mitigation measures may be ' recommended and required at a later date based on changes in nitrate in the groundwater, and long-term monitoring results for the region. 1 6.0 CONCLUSIONS AND RECOMMENDATIONS Our office concludes that the proposed project will not likely cause a build-up of nitrates above 10 mg/L total nitrogen in the ground water. However, based on the nitrate loading calculation (above the 10 mg/L-N), annual sampling and submission of sampling results to ' the San Joaquin County Environmental Health Department for groundwater from the lnW g-Ctic well onsite is recommended,and will be required by the SJC EHD. Petralogix Engmeent 9,Tnc. 26675 Bmella Road,Galt,Ca 95632 ' (209)-400-5729 it w .petmlogixxom 1