Laserfiche WebLink
16475 TIDE ROAD Project No.2019-00072 Page 17 <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 19.8 0.94 560 35.00 25% 2.74 <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 45 mg/L-NO3 or <br /> 10 mg/L-N. The planned domestic well has not been installed yet,therefore,Total Nitrogen <br /> was not tested. Based on the methods and assumptions described, the project will result in <br /> nitrate 19.8 mg/L-N. The depth to groundwater for this site is approximately 55 to 60 feet <br /> below ground surface.Although the soil is a fine sandy loam,there is a thick layer of hardpan <br /> reportedly underlying the area from approximately 50 to 70 inches below ground surface, <br /> as indicated by Soil Survey's and confirmed by review of a nearby well completion report <br /> geologic log. 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 and thick layer of hardpan underlying the Site,we believe the proposed project will not <br /> likely cause a build-up of nitrate in the ground water above the background concentration of <br /> total nitrogen above 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 /> 5.0 DISCUSSION OF NITRATE LOADING RESULTS <br /> 5.1 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 projects is unlikely to cause a build-up of <br /> nitrate in the ground water above background concentration level of total nitrogen 10 mg/L <br /> over the long term. <br /> 5.2 Methods of Mitigation <br /> Based on the Veritas sandy loam soil that includes a hardpan layer from approximately 54 <br /> to 70 inches below ground surface (which is expected to provide a degree of protection between <br /> percolating effluent at the surface and ground water aquifers), the low density of septic use in the <br /> area, and the depth to groundwater being large (50+ feet below the ground surface) mitigation <br /> measures are not warranted at this time. However, it should be noted that mitigation <br /> measures may be recommended and required at a later date based on changes in nitrate in <br /> the groundwater, and long-term monitoring results for the region. <br /> Petralogix Engineering,Inc. <br /> 26675 Bruella Road,Gait Ca 95632 <br /> (209)-400-5729 <br /> www.petralogix.com <br />