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0 0 <br /> corrected to reflect these results. These wells should be monitored <br /> more frequently, as further discussed below. <br /> Figure 6.1-1 should be modified by adding a box under "location <br /> criterion" to separately identify private wells (potential points of <br /> exposure) . EPA suggests a quarterly monitoring frequency for wells <br /> where VOCs have been reported above MCLs in the previous year's <br /> samples, or if an increasing trend is indicated, or if the well is <br /> near a site-related plume (i.e. , PW001 and PW005) . Semi-annual <br /> monitoring should apply if VOCs were detected in the previous year's <br /> samples (i.e. , PW002 and PW003) . Annual monitoring should apply if no <br /> VOCs were detected in the previous year's samples (i.e. , PW004, PWO06 <br /> and PW007) . <br /> DETAILED COMMENTS <br /> 3. Section 6.2.2.12, page 6-5 <br /> The statement that ". . .sampling [for dioxins/furans] will be <br /> terminated after two consecutive samples have no compounds above <br /> reporting limits. . . 11 should be eliminated. Monitoring should continue <br /> at least through the initial five-year review period, and follow the <br /> sampling frequency guidelines in Figure 6.1-1. <br /> Groundwater should be sampled and analyzed for dioxins/furans at least <br /> during the initial 5-year review period for SWMUs 7 and 8. <br /> Dioxins/furans were identified as potential threats to groundwater at <br /> SWMU 7 (historical impact to groundwater) and SWMU 8 (potential impact <br /> to groundwater determined by analytical leaching model) . The ROD <br /> remedy includes institutional controls for SWMU 7 and excavation for <br /> SWMU S. Because of the low mobility of dioxins/furans, the duration <br /> of performance monitoring following soil excavation and implementation <br /> of institutional controls should not end after two non-detects. <br /> 4. Table 6.2-1 (grouping by well purpose) <br /> It would be helpful if wells in this table were grouped according to <br /> their more general purposes, i.e. , extraction wells, OU-1 monitoring <br /> wells, SWMU-specific monitoring wells, private supply wells, and <br /> off-site source monitoring wells. Grouping by extraction wells, <br /> monitoring wells, and private wells is currently provided, but <br /> additional grouping of monitoring wells by OU-1, SWMUs, and off-site <br /> sources, would be quite helpful (similar to ROD Table 9-2) . <br /> 5. Table 6.2-1 (1998 extraction wells) <br /> Extraction wells EW013 through EW037 should be individually listed, <br /> and extraction wells to be sampled for pesticides should be <br /> specifically identified. <br /> 2 <br />