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Mr. Ken Price - 3 - • 14 June 2004 contingency plan to "address potential future changes in site conditions that could result in loss of hydraulic control or plume migration beyond the existing monitoring system". We concur that on-site phytoremediation is a reasonable remedial strategy for groundwater at this site, provided that the recent trends of decreasing concentrations of constituents in off-site downgradient monitoring wells continue. If,however, increasing concentration trends in these off-site downgradient wells become apparent, then MSRM will be called upon to enact a contingency plan that implements an alternate or supplemental remediation strategy. The existing phytoremediation plot consists of about 1,500 eucalyptus trees that are about one year old. MSRM needs to provide a Cleanup Plan, including a contingency plan that identifies what criteria will determine an apparent increase in constituent concentrations in downgradient monitoring wells, what remedial action will be implemented if the contingency is triggered, and what additional preparation will be needed to fully execute this alternative. The Cleanup Plan also needs to include photographs of the existing trees. Analyses for 1,2,3-Trichloropropane In the Analyses for 1,2,3-Trichloropropane Report, Geomatrix presents a comparison of duplicate groundwater samples obtained from this site over two sampling events. The samples were analyzed for 1,2,3-trichloropropane by two different Department of Health Services (DHS) methods: Fumigant Method and Low Level Method. The Fumigant Method has a detection limit of 0.01 ug/l, and the Low Level Method has a detection limit of 0.005 ug/l. Thirty eight samples were analyzed in duplicate, with results ranging from 1.3 ug/l to less than 0.005 ug/l. The comparison of these sample sets shows that the Low Level Method typically results in a higher concentration of 1,2,3-TCP than the Fumigant Method. For detectable results, the concentration differences between the two analyses ranged from 8% to 82%. Twenty-two sample sets did not contain 1,2,3-TCP by either method. For two samples, the Fumigant Method returned an unqualified ND, and the Low Level Method returned a trace amount (below the quantitation limit). In conclusion, Geomatrix states that the additional cost of the Low Level Method ($250 per analysis versus $95 per analysis by the Fumigant Method) is not commensurate with the benefit of the lower detection limit possible with that method. We concur that for the majority of the monitoring, a detection limit of 0.01 ug/1 as is provided by the Fumigant Method is appropriate. The existing Monitoring and Reporting Program No. R5-2002-0831 (MRP) does not require the Low Level Method for 1,2,3-TCP. When MSRM requests that the MRP be ievised, or when otherwise asserting that the 1,2,3-TCP plume is reduced or stable, then the Low Level Method will be needed to support such statements. Summary The soil excavation and treatment that MSRM and Geomatrix conducted in late 2001 has reduced the extent of the groundwater plume such that on-site phytoremediation appears to be a reasonable remediation strategy to remove groundwater constituents. The phytoremediation plot that MSRM established for soil remediation in 2003 may serve the dual purposes of soil and groundwater remediation.