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April 17, 2019 BGG Job No. G001.05 Table 6—Results of Nitrate Loading Calculation Variable Value Units Description Nc 1.0 mg/L-N Estimated long-term average concentration of percolating effluent The US EPA recommended MCL for nitrate in drinking water is 10 mg/L-N. The expected worst- case scenario would result in a calculated maximum buildup of nitrates in the aquifer of 1.0 mg/L-N from the use of the proposed onsite septic system. The result of the nitrate loading estimate is below the maximum drinking water standard. DISCUSSION OF NITRATE LOADING RESULTS Based on the method and assumptions described,the result of the nitrate loading estimate indicates that the proposed guard station septic system would not likely cause a buildup of nitrates in the aquifer above 10 mg/L-N for the site. As this result is satisfactory, mitigation measures are not recommended. SUMMARY AND CONCLUSIONS The soil conditions encountered near the proposed septic system and leach field appear to be suitable as designed. A satisfactory soil percolation rate of 11.5 minutes per inch was recorded from a percolation test conducted in the proposed septic system area. The depth to groundwater from recent well readings and exploratory borings is approximately 35 to 45 feet bgs, fluctuating seasonally. Groundwater flow direction is the general site region is North- Northeast. Due to the percolation rate recorded, the San Joaquin County Environmental Health Department will require a 20-foot separation from the bottom of the dispersal system to ground water. Based on the anticipated depth of the leach field to be less than 5 feet deep, modifications from a standard septic system should not be required. No wells are currently located at the subject site; as such, a water sample was not collected. ------ Based ---Based on the proposed project and the study discussed herein,the proposed septic system and leach field is not expected to cause an unsatisfactory buildup of nitrate in the aquifer above 1.0 mg/L-N. This level falls well below the US EPA drinking water recommendation of 10 mg/L-N. It is our opinion that the site is suitable for the use of a standard septic system utilizing leach lines. - LIMITATIONS This report has been prepared exclusively for the use of Baez Design Group. This study has been conducted in accordance with current professional geotechnical engineering standards; no other warranty is expressed or implied. The conclusions and recommendations contained in this report are based upon the information provided to us regarding the proposed improvements,subsurface conditions encountered at the field BAEZ GEOTECHNICAL GROUP Soil Suitability Study and Nitrate Loading Study-DFV Guard Station Page 10