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EPA COMMENTS ON <br /> WELL MONITORING PROGRAM <br /> 1997 ANNUAL MONITORING REPORT <br /> DDRW-TRACY <br /> GENERAL COMMENTS <br /> 1. Section 6.1.1 Program Objectives, page 6-1; Figure 6.1-1 <br /> Program objectives for 1998 should be revised to include initiation of <br /> groundwater monitoring to comply with ROD-specified objectives. This <br /> includes performance monitoring at individual SWMUs to validate that <br /> ROD-identified soil remediation activities are effective at <br /> eliminating potential threats to groundwater, and to validate <br /> "institutional control" monitoring at SWMUs as part of the remedy. <br /> Table 9-2 (or similar) from the Comprehensive ROD should be included <br /> in this section. DDJC-Tracy should confirm that the 1998 sampling <br /> frequency, analytes, and rationale will be consistent with performance <br /> monitoring and institutional controls specified in the ROD. <br /> EPA suggests that Figure 6.1-1 (Sampling Frequency Decision Flow <br /> Chart) include a footnote for the box --nearest well to identified <br /> contaminant source" to indicate this includes areas of identified soil <br /> contamination that pose potential threats to groundwater (as <br /> identified in the ROD) . Another footnote should indicate that where <br /> ROD-imposed institutional controls include monitoring, such monitoring <br /> will continue until the agencies and DDJC-Tracy concur that the <br /> potential threat is no longer of concern. These footnotes should <br /> further clarify that groundwater monitoring also applies to potential <br /> sources identified in the ROD that have not already impacted <br /> groundwater. <br /> 2. Table 6.2-1 (private wells) ; Figure 6.1-1 <br /> EPA recommends that sampling frequency for PWO05 be changed from <br /> annual to quarterly sampling based on the proximity to the plume and <br /> because nearby PW001 has had VOCs detected above MCLS. EPA recommends <br /> that sampling frequency for other private wells with VOC detections be <br /> changed from annual sampling to semi-annual sampling. Wells with no <br /> contaminant detections can continue to be sampled annually. Private <br /> wells, as potential points of exposure, deserve special consideration <br /> for sampling frequency. <br /> Table 6.2-1 indicates that PWO02 through PWO07 require only annual VOC <br /> sampling because "no contaminants [were] previously detected. " EPA <br /> disagrees with this recommendation because PW002, PWO03 and PWO05 have <br /> had recent detections of VOCs: four VOCs were reported below MCLs in <br /> one of two recent quarters at PW002; chloroform was reported below MCL <br /> at PW003; and carbon tetrachloride was reported above MCL in one of <br /> two recent quarters at PW005. The text in Table 6.2-1 should be <br /> 1 <br />