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January 21, 2021 BGG Job No. G130.09 GROUNDWATER INFORMATION Groundwater Depth and Gradient We reviewed ground water elevation information available from the California Department of Water Resources Water Data Library (CA WDL) 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 40 to 60 feet below ground surface (bgs) and ground water flows predominantly toward the northwest. 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. Agricultural activities and the use of septic systems in the area are known groundwater contamination sources with the potential for impacting to the site. BGG reviewed the SJC EHD 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 gg/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 There are currently no wells located at the site. No well permits were identified for the Site from among files at the San Joaquin County Environmental Health Department. Water Sample There are no wells located 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 Web Soil Survey, the proposed residence site is mapped as being mantled by the Galt -Urban land complex soil series. In the upper 21/2 feet below the ground surface (bgs), this soil series is reported to have 100% passing the No. 4 sieve (sand -sized particles), contain 71 to 95 percent fines (silt- and clay -sized particles), and be highly to very highly expansive with a Plasticity Index (PI) of 28 to 44. Cemented hardpan is reported between about 21/2 to 5 feet deep. The saturated hydraulic conductivity of this soil series varies between 0.06 to 0.2 inches per hour in BAEZ GEOTECHNICAL GROUP Soil Suitability Study and Nitrate Loading Study - Valdovinos Residence Page