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• <br /> Draft Ground Water ROD Memorandum -3- 21 May 1992 <br /> DDRW, Sharpe <br /> The cleanup levels for xylene, as well as other petroleum based contaminants, and <br /> bromacil need to be removed from this table or revised to 20 µg/l and 90 µg/1 , <br /> respectively. If it is determined that these constituents are to remain a part of <br /> this ROD, then we will be unable to be sign the ROD, unless the aquifer cleanup <br /> levels are changed. <br /> Plume Capture. The ROD states that the existing extraction systems are adequate <br /> (page 52) in the North and South Balloon Areas. Based on the most recently <br /> submitted quarterly plume capture maps (Third Quarter 1991) , the existing extraction <br /> systems do not capture all of the TCE plumes in the North and South Balloon Areas. <br /> The text of the ROD needs to be revised to reflect the most recent information <br /> regarding plume capture. We have previously written that the capture of the plumes <br /> from the North and South Balloon Areas is inadequate (letters dated 2 January 1992, <br /> 20 December 1991, 16 October 1991, and 16 September 1991) . <br /> SPECIFIC COMMENTS <br /> Declaration of the ROD. The Statement of Basis and Purpose and the Statement of <br /> Determination need to clearly reflect the limited scope of this ROD. This ground <br /> water ROD addresses existing solvent contamination, except for potential <br /> contamination in the area of the two waste solvent tanks (discussed in more detail <br /> below) . <br /> The section on the Scope and Role of the Operable Unit (OU) should reflect that the <br /> OU Response Action is limited to solvents, except for the two solvent tanks. It <br /> also should address how this response action ties in to the site-wide ROD which will <br /> address the remaining soil and ground water contamination. <br /> The Declaration for the ROD did not included signature blocks for the Regional Water <br /> Quality Control Board and the Department of Toxic Substances Control . Both of these <br /> State agencies are signatory parties to the Federal Facilities Agreement (FFA) and <br /> therefore must have separate signature blocks. We request that the signature page <br /> be changed to reflect this. <br /> Site Conceptual Model . The Draft ROD presents a conceptual model of the site by <br /> describing the different water bearing zones and the interconnection between the <br /> zones in Section 1 .0 (Site, Name and Description) of the Decision Summary (page 3) . <br /> However, the ROD also states the sedimentary deposits are not entirely saturated. <br /> We have previously written (letter dated 19 July 1991) regarding the apparent <br /> confusion between saturated sediments and hydraulic connection. This issue has <br /> never been resolved. Therefore, references to saturated or unsaturated sediments <br /> should be deleted from the ROD. <br /> Metals Concentrations at Background Levels. The ROD states that metals are believed <br /> to be present at background levels (page 6) . This statement should be removed from <br /> the text of the ROD because of the recent findings in the Soils FS regarding heavy <br /> metal contamination in soil and ground water. The WMU and UST investigations showed <br /> that there is extensive lead soil contamination, some above the hazardous <br /> concentration, and that chromium and nickel are present in the ground water above <br /> the Primary Maximum Contaminant Level (MCL) at one location. Until additional <br /> investigation of the WMUs and USTs associated with the heavy metal contamination is <br />