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EPA' s COMMENTS ON THE <br /> DRAFT QUARTERLY GROUNDWATER MONITORING (MAY 1991) REPORT <br /> DEFENSE DISTRIBUTION REGION WEST <br /> TRACY, CALIFORNIA <br /> (REPORT OF AUGUST 13 , 1991) <br /> Extent of Chemical Constituents in Groundwater <br /> 1. This section discusses the organochlorine pesticides that <br /> have been detected at DDRW-Tracy. Among those mentioned was <br /> delta-BCH. The proper designation for this isomer of <br /> benzene hexachloride is delta-BHC. <br /> Correct the error. <br /> 2 . Also stated in this section is the fact that no maximum <br /> contaminant levels (MCLS) have been established for these <br /> compounds. While this is true, it should be noted that the <br /> California Department of Health Services (DHS) has <br /> established an action level (AL) for the toxicity of <br /> dieldrin at 0. 05 µg/E . <br /> EPA has also proposed ALs under 40 CFR Part 264 Subpart S <br /> (55 FR 30798 , July 27, 1991) for some of these compounds. <br /> Those proposed standards are as follows: <br /> PARAMETER PROPOSED ACTION LEVEL aq/E <br /> Dieldrin 0. 002 <br /> Endosulfan 2 . 0 <br /> DDT 0. 1 <br /> The analysis of aqueous samples performed by Woodward-Clyde <br /> Consultants (WCC) included the following analytical results <br /> for volatile organic compounds (VOCs) and pesticides and <br /> polychlorinated biphenyls (PCBs) . The detection limits used <br /> by WCC were higher, in some instances, than the MCLS <br /> established as a water quality goal by DHS or pending <br /> adoption by EPA. It would benefit DDRW-Tracy to keep <br /> apprised of these proposals and adopt them for future <br /> sampling events. Quite often DHS has standards more <br /> stringent than EPA, which must be considered in the ongoing <br /> Remedial Investigation/Feasibility Study (RI/FS) process. <br /> It would appear from this monitoring data that these <br /> standards are either being disregarded or cannot be met when <br /> establishing detection limits. <br /> 1 <br />