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S A N J O A Q U I N Environmental Health Department <br /> -- COUNTY--- <br /> Jasjit Kang, REHS, Director <br /> cgvFoa�'�� Greotrtess grows {sere. Muniappa Naidu, REHS,Assistant Director <br /> PROGRAM COORDINATORS <br /> Jeff Carruesco, REHS, RDI <br /> Willy Ng, REHS <br /> Steven Shih. REHS <br /> Elena Manzo, REHS <br /> Natalia Subbotnikova, REHS <br /> February 24, 2026 <br /> Don Chesney <br /> Chesney Engineering Inc., <br /> P.O. BOX 3794, <br /> Turlock, CA 95381 <br /> RE: Soil Suitability and Nitrate Loading Study Addendum and Onsite Wastewater <br /> Treatment System (OWTS) Design Report <br /> 1901 Patterson Avenue, Stockton, CA 95215 <br /> SU-2601156, APN: 089-091-08 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed the Soil <br /> Suitability and Nitrate Loading (SSNL) Addendum Study and OWTS Design dated February 16, <br /> 2026, and submitted February 17, 2026, and has the following comments for your consideration. <br /> The SSNL was prepared to determine the suitability for onsite wastewater treatment system <br /> (OWTS) usage and the potential long-term impact of nitrate to groundwater from the proposed <br /> new two-bedroom single family residence. The parcel size is 0.23 acres. The report states that <br /> this site cannot support an ADU. <br /> 1 . The SSNL reports a nitrate-loading estimate for the existing and proposed OWTS of 7.5 <br /> milligrams per Liter (mg/L) of NO3-N (Nitrate as Nitrogen); the maximum contamination level <br /> for NO3-N in groundwater is 10.0 (mg/L) set by the Central Valley Regional Water Quality <br /> Control Board. The septic system construction shall follow the San Joaquin County OWTS <br /> where applicable. (SJC OWTS Standard 7.1). <br /> 2. The Percolation tests conducted on February 5, 2026, yielded a percolation rate of 13.2 MPI <br /> for the 40-inch test, 22.7 MPI for the 94-inch test, and 125 MPI for the 268-inch percolation <br /> test. At this rate, a minimum of 8 feet of soil separation is required between the bottom of the <br /> dispersal field and the groundwater as mitigated by the proposed standard septic system. <br /> The SSNL reports the highest reported groundwater level at about 82 to 85 feet below surface <br /> grade, and the most recent groundwater level at more than 100 feet below surface grade in <br /> 2025. (San Joaquin County OWTS Standard Table 1.10.2). <br /> 3. Prior to obtaining the new septic system permit with EHD, the site shall be surveyed to <br /> determine accurate boundaries and setbacks as stated in the report. <br /> 1868 E. Hazelton Avenue I Stockton, California 95205 1 T 209 468-3420 1 F 209 468-3877 1 www.sjgov.org/ehd <br />