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Nestl6 USA Inc. - 3 - • 16 June 2005 Regional Board staff request that Nestle provide a Draft Work Plan by 19 August 2005 to define the extent of the Lower Aquifer plume and install additional monitoring/extraction wells to monitor and contain the plume., Regional Board staff expects Nestl6 to complete investigation and implement necessary corrective actions by the end of 2005. 5. At the request of Regional Board staff, Mann-Kendall (MK) analysis was added to the Annual Reports. In order to make the best use of these results,Nestl6 should augment the VOC isoconcentration maps (Figures 6 through 13) with the results. Wells that have an increasing or decreasing trend should be marked with an up or down arrow showing there is a significant trend. Posting this trend data to the figures will make it easier to identify areas where the plume is migrating. Please make these revisions to the Final Annual Report and future annual reports. 6. The Draft Annual Report shows that concentrations of TCE and chloroform still exceed applicable water quality objectives in the Caltrans irrigation well along Parallel Avenue. Regional Board staff request that Nestl6 provide suitable replacement water to Caltrans by 29 July 2005. Potential replacement water alternatives include installing wellhead treatment or connecting the Caltrans sprinkler system to the City of Ripon's water supply system,but Nestl6 needs to contact Caltrans to determine which replacement alternative will best satisfy their needs. If wellhead treatment is not selected and Caltrans will no longer be using the impacted well, then Nestl6 needs to properly decommission the well in accordance with State and County requirements. 7. For many years, Regional Board staff has requested that Nest16 provide isoconcentration maps for TCE, DCE, and VC that interpret the full extent of the groundwater plumes. This means adding a 0.5 1tg/L contour to each figure so the reader can see the full extent or edge of the plume. The latest Draft Annual Report still provides figures showing the 3 gg/L contour instead of the 0.5 µg/L contour. The 3 gg/L isoconcentration contour is completely arbitrary and is 6X greater than the State MCL for vinyl chloride. Nestl6 should implement this revision in the Final Annual Report for 2004 and all future reports submitted to our agency. 8. Nestle' still hasn't submitted the Revised Indoor Air Vapor Intrusion Report, even though Regional Board staff provided written comments on the Draft indoor Air Vapor Intrusion Report approximately 7 months ago. Also, the Final Groundwater Model Report has not been submitted even though Nestle' agreed to complete it by the end of 2004. Regional Board staff request that Nestle' provide the Revised Indoor Air Intrusion Report by 30 June 2005. Given the recent and unexpected discovery of Nestl6's plume on the south side of the Stanislaus River, the Final Groundwater Model Report can be delayed for a few months until the full extent of the plume is determined. It appears that Nestl6 needs to provide more resources to investigate and cleanup their groundwater plume. The deadlines for documents requested in this letter and other documents required in the revised CAO (in preparation)will be impossible to meet unless Nestle' significantly increases its level of effort in meeting deadlines on submittals. 9. The Draft Annual Report proposes reductions in monitoring frequencies for some wells. Regional Board staff support optimization of the monitoring program and elimination of excessive monitoring,but Nestle' still has not provided their decision logic for well monitoring frequencies.