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Addendum-Revised Nitrate Mass Balance Analysis Nitrate Loading Study 16475 Tide Road Page 12 Table 1. 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 15.3 0.94 250 35.00 25% 2.74 * Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N. Discussion of Revised Nitrate Loading Results The nitrate maximum contaminant level (MCL) set by the US EPA is 45 mg/L-NO3 or 10 mg/L-N. Based on the methods and assumptions described,the project will result in nitrate 15.3 mg/L-N.As discussed in the Nitrate Loading Study submitted, the depth to groundwater for this site is approximately 55 to 60 feet below ground surface.Although the soil is a fine sandy loam, there is a thick layer of hardpan reportedly underlying the area from approximately 50 to 70 inches below ground surface, as indicated by Soil Survey's and confirmed by review of a nearby well completion report geologic log. Based on the mass balance analysis results,in addition to our professional judgement,low septic tank density, and geologic setting showing the deep groundwater table and thick layer of hardpan underlying the Site,we believe the proposed project will not likely cause a build-up of nitrate in the ground water above the background concentration of total nitrogen above 10 mg/L over the long term. Conclusions In summary, the total quantity of effluent is revised to represent 100 gallons for the first bedroom and 50 gallons for each additional bedroom; the proposed 4-bedroom residence is estimated to contribute 250 gallons per day,which was incorporated into the revised nitrate loading calculation presented above. We appreciate the opportunity to submit this addendum and revised calculation which incorporates the new guidelines recommended by the San Joaquin County Environmental Health Department. Daniel E.Kramer,President Professional Geologist 8657 Certified Engineering Geologist 2588 Professional Geophysicist 1078 Attachment A-Revised Nitrate Loading Analysis Results Cc:Jennifer De Jong Petralogix Engineering,Inc. 26675 Bruelia Road,Galt,Ca 95632 (209)-400-5729 www.petralogix.com