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Soil Suitability Report BSK Job E21-002-01B Cascade BESS Project August 26, 2021 Stockton, California P a g e | 6 4.5 Groundwater Analytical Report The nitrate concentration of the groundwater sample obtained was 2.11 milligrams per liter (mg/L). The analytical data from the USGS for this well is included in Appendix C. The proximity to the creek may impact the concentrations of nitrate and other constituents compared to the site. Based on the nitrate loading analysis performed earlier in the year (Nitrate Loading Analysis, 2482 Carpenter Road, Stockton, California, BSK Project No. E21-002-01B,dated July 13, 2021), the estimated average concentration of nitrate-nitrogen in recharge water will be 19.76 mg-N/L. A chain of custody or laboratory report was not prepared since no actual samples were obtained from the site. 5.SOIL PROFILE INFORMATION 5.1 Field Exploration and Site Description The field exploration for this investigation was conducted under the supervision of a California licensed Geotechnical Engineer and field oversight of a BSK engineer. Nine (9) borings were drilled at the Site on February 1, 2021 using a CME 75 drill rig provided by Baja Exploration of Escondido, CA. The borings were drilled to a maximum depth of 31.5 feet beneath the existing ground surface (bgs) and have a diameter of 8 inches. Three (3) of the borings were set up for percolation tests on February 1, 2021 and tested on February 2, 2021. The location of the borings is presented on the Boring Location Map, Figure 1-C. The soil materials encountered in the test borings were visually classified in the field, and the logs were recorded during the drilling and sampling operations. Visual classification of the materials encountered in the test borings was made in general accordance with the Unified Soil Classification System (ASTM D 2488). 5.2 Soil Lithology Description The subsurface material in the vicinity of the planned leach field generally consisted of sandy and silty clay with low to moderate plasticity to the maximum depths of exploration (31.5 feet bgs). A soil classification chart is presented in Appendix D. Boring logs are also presented in Appendix D and should be consulted for more details concerning subsurface conditions. Stratification lines were approximated by the field staff based on observations made at the time of drilling, while the actual boundaries between soil types may be gradual and soil conditions may vary at other locations. 5.3 Soil Lithology Relating to Future Onsite Septic Uses The soil at the site is generally silty to sandy clay with low hydraulic conductivity in a semi-arid environment. Based on this information and comparisons to other semiarid regions with sandy clay soil, the transport of contaminants like nitrate would be lower than that of soils with higher sand content, higher rainfall and/or soil saturation, or more permeability. Since the septic system size and usage will not change at the adult care facility, which is the producer of the nitrate-nitrogen containing recharge water that is discharged to the onsite system, the total nitrate impact would not differ.