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Draft Sampling & Analysis Plan - 4 - 13 July 2022 Stockton Propeller, Inc. 2478 Wilcox Road, Stockton be a priority and occur as soon as SPI receives Assistant Executive Officer's concurrence on the Final SAP. Section 3.3- Leach Field does not explicitly state that SPI will locate the leach field. However, the section does state the use of geophysical, camera, tracer dyes, or other means may be used as necessary to assess the connectivity of SPI's tank with other tanks. It is unclear if the same methods will be applied to locating the leach field. Additionally, several sections state the on-Site septic tank may not be connected to a leach field. However, it is unheard of for a septic system to be designed without a corresponding leach field. Required Action: Please revise Section 3.3 to include information regarding how the corresponding leach field will be located and remove all references stating the septic tank may not be connected to a corresponding leach field or provide information supporting the septic system was designed without a corresponding leach field. COMMENT 5 Issue: Section 3- Proposed Investigation Tasks states depending on the results of field activities, decisions in the field will be based on professional judgement of the field staff. Requested Action. Central Valley Water Board staff plans to be on-Site during most of the field work. However, if the Central Valley Water Board staff is unable to be on-Site, it is requested that the field staff attempt to contact Central Valley Water Board staff via telephone for concurrence if significant changes to the approved Final SAP occur. All deviations from the Final SAP shall be documented in the Site Investigation Report (SI Report). COMMENT 6 Issue: The Draft SAP proposes to collect a single composite sample from two (2) depths in each of the two septic tank compartments. Central Valley Water Board staff previously requested three samples be collected from the contents of the septic tank (a sample near the influent, effluent, and effluent screen; Central Valley Water Board, 2022a). Collecting a single composite sample will not be sufficient to evaluate the concentrations of contaminates in each compartment of the septic tank. As previously mentioned in the Water Board Response to Stockton Propeller Sampling Plan, the samples collected from the septic tank on 20 December 2021 by SPI staff provide some information, but there is uncertainty whether the septic tank contents had previously been tampered with prior to collecting these samples (Central Valley Water Board, 2022a). Recommended Action. Central Valley Water Board staff recommends collecting at least two discrete liquid samples from the septic tank (one sample from the influent compartment and one sample from the effluent compartment). Central Valley Water Board staff recommends collecting a third sample from the effluent screen if it is