SITE INFORMATION AND CORRESPONDENCE

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However, in Section 6.4.2, the Report states that EW036AU will not be replaced because it was producing low volumes of water. This rationale is unclear. If contaminant concentrations at this well location continue to indicate that groundwater is adversely impacted, a replacement well should be installed in the area of former EW036AU. In addition, the Report does not discuss whether a replacement well was installed for well LM066A and when well LM019A will be repaired so it can be sampled again in accordance with Table 6.5-1. For completeness, please indicate whether a replacement well was installed for well LM066A and when well LM019A will be repaired and provide justification for why well EW036AU should not be replaced or a schedule for replacement. 6. As noted in EPA's comments (dated January 14, 2000) on the 1999 Annual Monitoring Report, the EPA requested that the location of the infiltration features (i.e., infiltration gallery(IGI), chimney drain(CDI), percolation ponds, injection wells and the northern and southern infiltration galleries)be added to the groundwater contour maps of the Above-Upper and Upper Horizons to facilitate the review of the groundwater contours. Since applicable Figures in Section 5 and Appendix H do not show these features,please revise the figures to include the infiltration features. 7. The comments on the 1999 Annual Monitoring Report noted that the time-series plots presented in Appendix C are difficult to review quickly due to the use of different vertical (concentration) scales on the plots. EPA has previously requested that, in all future monitoring reports, as many of the time series graphs as possible be plotted using the same vertical scale. Each of the plots should still be readable to the point where trends in the data can be seen. For TCE, this will likely require plotting data on scales of 0 to 1, 0 to 10, 0 to 100, and 0 to 1,000 ug/l. All of the plots that have the same vertical scale should be grouped together. 8. While EPA concurred with the recommended changes to sampling frequency discussed in the conference call January 23, 2001, Table 6.5-1 does not always sufficiently explain the rationale for the changes. For example, the sampling frequency for VOCs at well LM032AU was decreased from quarterly to semi-annually but the rationale states "Significantly increasing trends in cis-1,2-13CE." Please revise the table to provide rationale consistent with the recommended changes in sampling frequency. 3