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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 /> 10999 <br /> 700 Feet North 77 697 New Septic 1,600 3 75 (3) 3.5, 25 --- <br /> South Alpine System <br /> Rd <br /> 11121 <br /> West North NF --- --- --- --- <br /> Alpine <br /> Rd <br /> Note: NF = No septic permits found <br /> Based on a review of the permits, septic systems in the area appear to utilize leach lines <br /> 40 to 75 feet in length and seepage pits approximately 3 feet in diameter and 25 feet <br /> deep. <br /> 1.3.6. Septic Repair Permit History in the Vicinity <br /> Based on the EHD file review permits, septic repairs in the vicinity appear to be for the <br /> addition of leach lines and seepage pits. Copies of septic permits can be found in <br /> Appendix C. <br /> 1.3.7. Expected On-Site Maximum Septic Tank Usage <br /> Residential Land Use <br /> According to information provided by the client, the proposed ADU will be a 3-bedroom <br /> 2-bathroom. Based on a review of the San Joaquin County Onsite Wastewater Treatment <br /> Standards (OWTS) and the findings of this SSNLS, a septic tank capacity of 1200 gallons <br /> and a conventional septic system design is recommended. <br /> Terracon estimates the maximum flowrate for the proposed ADU to be 420 gallons per <br /> day (gpd). This estimate is based off a daily flow rate of 70 gpd per person with two <br /> people per bedroom. <br /> 1.4. Groundwater Information <br /> 1.4.1. Groundwater Depth and Gradient <br /> Groundwater was not encountered within soil borings which were drilled to an <br /> approximate maximum depth of 25 feet below ground surface (bgs) using a track- <br /> mounted drill rig. According to the California Department of Water Resources <br /> Sustainable Groundwater Management Act (SGMA) Data Viewer, depth to groundwater <br /> was reported approximately 70 to 80 feet bgs in Fall of 2025, with a general hydraulic <br /> gradient toward the east. According to the Department of Water Resources (DWR) Water <br /> Data Library, a well located on the southern-adjoining property (10799 North Alpine <br /> Road) had historic depth to groundwater level of 96.3 feet bgs in November 2014. <br /> Facilities I Environmental I Geotechnical I Materials 7 <br />