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Soil Suitability / Nitrate Loading Study <br /> 11065 North Alpine Road I Stockton, California r rerracon <br /> June 30, 2026 1 Terracon Project No. NA267068 <br /> 1.4.4. Groundwater Sample Analysis <br /> One groundwater sample was collected from the on-site well and analyzed for nitrate as <br /> N and DBCP. Nitrate as N was reported at a concentration of 12 mg/L, which is above <br /> the California maximum contaminant level (MCL) of 10 mg/L for safe drinking water. <br /> DBCP was not reported above the laboratory reporting limit (RL) of 0.010 micrograms <br /> per liter (pg/L). Groundwater analytical reports are presented in Appendix G. <br /> 1.4.5. Groundwater Sample Handling <br /> Groundwater samples collected onsite were placed directly into laboratory containers <br /> and placed on ice. Samples were delivered via chain-of-custody procedures to a <br /> California certified laboratory for analysis. <br /> 1.5. Soil Profile and Geologic Information <br /> The site is depicted on the Geologic Map of California website, as within generalized <br /> early quaternary and tertiary strata deposits which are comprised primarily of upper <br /> member undivided alluvium deposits. <br /> Terracon reviewed the United States Department of Agriculture (USDA) Natural <br /> Resources Conservation Service (NRCS) Web Soil Survey and USDA Soil Survey of San <br /> Joaquin County (2023) for information regarding soil properties. Based on information <br /> obtained from the USDA sources, site soils consist of the following soil type. <br /> Hollenbeck silty clay (1.3 acres) <br /> Hollenbeck silty clay soils are located across much of the northern and eastern portions <br /> of the site with 0 to 2 percent slopes. Parent material consists of alluvium derived from <br /> mixed rock sources. The typical soil profile consists of silty clay from 0 to 10 inches bgs, <br /> underlain by clay to a depth of 37 inches bgs, underlain by silty clay loam to a depth of <br /> 42 inches bgs, underlain by cemented material to a total depth of 60 inches bgs. <br /> Drainage class is considered moderately well drained with high runoff and very low <br /> permeability. <br /> Galt Clay (0.2 acre) <br /> Galt clay soils are located on the southwestern portion of the site with 0 to 1 percent <br /> slopes. Parent material consists of clayey alluvium derived from igneous, metamorphic <br /> and sedimentary rock. The typical soil profile consists of clay from 0 to 32 inches bgs, <br /> underlain by cemented material to a total depth of 60 inches bgs. Drainage class is <br /> considered somewhat poorly drained with high runoff and low permeability. <br /> Facilities I Environmental I Geotechnical I Materials 9 <br />