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Sampling Plan - 3 - 25 March 2022 <br /> Stockton Propeller, Inc. <br /> 2478 Wilcox Road, Stockton <br /> septic tank contents fluctuated by several feet in mid-December. The contents of the <br /> septic tank have remained stable ever since. As previously mentioned in the <br /> introduction, the samples collected on 20 December 2021 contained concentrations of <br /> cadmium and lead above the USEPA MCL, and concentrations of copper, vanadium, <br /> and zinc above the SFBRWQCB Tier 1 ESLs. Although these samples provided some <br /> information, it is unclear if the septic tank contents had been tampered with in mid- <br /> December prior to the collecting the samples. Additionally, the samples were collected <br /> without having a regulatory approved work plan/sampling and analysis plan. Central <br /> Valley Water Board staff are unsure how and where the samples were collected within <br /> the septic tank. Therefore, Central Valley Water Board staff request additional samples <br /> be collected from the septic tank. <br /> Currently, the septic tank contents are near capacity and may require pumping before <br /> an approved sampling and analysis plan is approved. On 10 March 2022, Central Valley <br /> Water Board staff approved the contents of the septic tank to be pumped only if there is <br /> a risk of the septic tank overflowing. The approval included the following requests 1) <br /> samples should be collected prior to pumping, 2) the condition of the septic tank be <br /> evaluated and documented with photos after the contents are removed, 3) the contents <br /> of the septic tank be treated as hazardous waste and disposed of properly until <br /> laboratory analysis indicates otherwise. SPI staff is continuing to monitor the contents of <br /> the septic tank and will inform Central Valley Water Board staff if the tank requires <br /> pumping. Further details regarding sampling and evaluating the septic tank are provided <br /> below. <br /> Requested Actions: <br /> Leach Field Investigation: Revise the SAP to include a geophysical investigation or <br /> alternative method to identify the location of the leach field. The Site is in a mixed used <br /> property complex that includes several other businesses with septic tanks. It is possible <br /> SPI's leach field may be shared with other septic tank discharges at the property. <br /> Therefore, please ensure to investigate all potential contributors to the leach field from <br /> which SPI's septic system discharges. Once the leach field is identified, submit another <br /> work plan or addendum to investigate and sample discharges of hazardous waste to the <br /> leach field. <br /> Groundwater Investigation: Revise the SAP to include a groundwater investigation. <br /> Central Valley Water Board staff recommend at least two (2) grab groundwater samples <br /> to be analyzed for power of hydrogen (pH), California Administrative Manual (CAM) 17 <br /> Metals, chromium VI, cyanide, mercury, fish bioassay, fecal coliform, and volatile <br /> organic compounds (VOCs) by an Environmental Laboratory Accreditation Program <br /> (ELAP) accredited laboratory, using industry standard methods, such as the USEPA <br /> methods. <br /> Septic Tank Investigation: Revise the SAP to include sampling the septic tank. Central <br /> Valley Water Board staff recommend at least three (3) samples collected within the <br /> septic tank to be analyzed for pH, CAM 17 Metals, chromium VI, cyanide, mercury, fish <br />