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July 31, 2023 BGG No. G130.09D GROUNDWATER INFORMATION Groundwater Depth and Gradient We reviewed groundwater elevation information available from the California Department of Water Resources Water Data Library(CA WDL),the Sustainable Groundwater Management Act(SGMA) data viewer website, and the San Joaquin County Flood Control and Water Conservation District (SJCFCWCD)to determine the ground water levels near the site. Recent data indicates that ground water at the site is approximately 60 to 70 feet below ground surface(bgs) and ground water flows predominantly toward the south-southeast. A detailed evaluation of these and other factors, which may be responsible for groundwater fluctuations,was beyond the scope of this study. Potential Ground Water Contamination Issues The Soil Suitability Study is not intended to serve as an investigation into groundwater contamination sources, and no such investigation was conducted. Many sources can contribute to ground water contamination, including underground storage tank leaks, agricultural applications, dairy activities, septic systems, and storm water infiltration. BGG reviewed the SJCEHD Water Well Data Table dated March 10,2009 for nearby addresses that have been tested for nitrate and dibromochloropropane(DBCP),which are identified groundwater contaminants in San Joaquin County. The Maximum Contaminant Level(MCL)established by the US EPA for nitrate as NO3 is 45 mg/L(10 mg/L-N) and the MCL for DBCP is 0.2 µg/L. For wells identified within approximately 1 mile of the subject site, the following summarizes the reported results: • Nitrate was detected in the wells identified, at concentrations of 25.0 to 48.0 mg/L-NO3. • DBCP was not detected. Wells Onsite No wells are currently present at the site and no well permits were identified for the site from among files at the San Joaquin County Environmental Health Department. Water Sample No wells are currently present at the site; hence, a water sample was not collected for this study. SOIL PROFILE AND GEOLOGIC SETTING The site is shown on the Geologic map of the San Francisco-San Jose quadrangle of California (Wagner, et al., 199 1)to be underlain by Holocene age alluvial fan deposits. According to the USDA NRCS Web Soil Survey, the proposed residence site is mapped as being mantled by the Delhi loamy sand and Veritas fine sandy loam soil series. Infiltration rates for these soil series are reported to be up to 20 inches per hour in the upper 4.5-feet, with a locally present, nearly impermeable layer between 4.5 to 6-feet deep with infiltration reported to be nearly zero. The Web Soil Survey report is contained in Appendix C,and the following is a summary of the reported characteristics of these soil series. BAEZ GEOTECHNICAL GROUP Soil Suitability Study&Nitrate Loading Study-Becerra Residence,18163 S.Carrolton Road Page 3