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Parkwoods Shopping Center - 2 - 20 November 2017 1762 West Hammer Lane, Stockton 5. Allow soil gas probes to equilibrate for at least 2 hours, and then collect soil gas samples for analysis of VOCs using USEPA Method 8260B or USEPA Method TO-15; and 6. Following sample collection, destroy temporary soil gas probes by removing tubing and probes, then filling the borings with granular bentonite hydrated with potable water. Sims-Grupe plans to summarize field activities and sample results in a report to the Central Valley Water Board. The Work Plan states that if investigation results indicate that a deeper assessment is needed to characterize the extent of VOCs at the Site, then recommendations for additional investigation will be included in the report. Comments Central Valley Water Board staff has the following comments on the approach outlined in the Work Plan: 1. Required Action #2 of the Order requires submittal of a "work plan to investigate soil gas and groundwater beneath the Site." The Work Plan does not include a plan for groundwater investigation, and instead states, "Based on the results of this investigation, a groundwater sampling program will be designed and submitted to the Water Board, if warranted."A plan to investigate groundwater is absent from the Work Plan; therefore, the Work Plan does not satisfy Required Action #2 of the Order. 2. The Work Plan states "The soil gas investigation will be conducted in general accordance with the July 2015 California Environmental Protection Agency's Advisory— Active Soil Gas Investigations (Advisory)." However, the Work Plan does not address certain key details of the proposed investigation approach, including the proposed floor penetration technique, soil gas sample container type, purge rate, applied vacuum, or leak testing approach. 3. Required Action #2 of the Order states "The work plan should propose a schedule for conducting investigation activities within 120 days of the issuance of this order." The Work Plan does not include a schedule for conducting the proposed field activities. 4. The Work Plan provides a general description of soil gas probe installation and destruction techniques, but it does not mention soil gas probe permitting or conformance with San Joaquin County Environmental Health Department guidelines. Central Valley Water Board staff requests that Sims-Grupe submit a work plan addendum to address the deficiencies identified in Comments#1 through #4 above. As stated in Required Action #2, the Order requires "a work plan to investigate soil gas and groundwater beneath the Site" which includes "a schedule for conducting investigation activities within 120 days of the issuance of this order." In the work plan addendum, please include the required plan for investigating groundwater within 120 days of Order issuance (i.e. completing investigation by 11 January 2018). To ensure continued progress towards meeting the deadline in the Order, please submit the work plan addendum by 4 December 2017. Central Valley Water Board staff recommends that Sims-Grupe proceed with soil and soil gas investigation preparation activities (planning, permitting, etc.) while the groundwater component of the investigation is being prepared. If you