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January 11, 2022 BGG No. G130.09B 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 9.467 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 use of the new residence 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 6.67 minutes per inch was recorded from a percolation test conducted in the proposed septic system area, in accordance with SJCEHD OWTS Standards 2017. The depth to groundwater from nearby well observations is reported to be approximately 20 to 25 feet bgs, fluctuating seasonally. Groundwater flow direction in the general site region is toward the south-southeast. 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. Based on the proposed residential site improvements and the studies discussed herein, the septic system and leach field is expected to contribute a long-term buildup of nitrate in the aquifer of approximately 9.467 mg/L-N. This level falls 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 Valdovinos Development, Inc. and has been conducted in accordance with current professional 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 exploration location, and professional judgment. This report is not an environmental assessment; it does not claim to identify recognized environmental conditions or health and safety concerns for the site. The values discussed herein should not be used for the design and sizing of the septic system. The design and sizing of the septic system should adhere to the San Joaquin County Environmental Health Department Onsite Wastewater Treatment Systems Standards.