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Draft Remedial Design <br /> Defense Depot San Joaquin Tracy Site, Tracy California <br /> July 1998 <br /> All SWMUs with the exception of two (SMWU 2/3 and SMWU 4) require additional site <br /> characterization to either define the lateral and vertical extent of contamination, identify <br /> groundwater threat due to leachability of contaminants and/or characterize the physical properties <br /> of the soil in the vadose zone. It is unclear why these data gaps remain given that they should <br /> have been resolved for an adequate evaluation in the Feasibility Study (FS) and thus, final remedy <br /> selection, particularly, since the selected remedy is influenced by these factors. While the site <br /> summaries do acknowledge that the sites evaluated in the FS because contaminants posed a <br /> potential threat to either human health and/or groundwater•, the summaries do not provide why <br /> these data gaps were not resolved earlier or why they could not be resolved with the data <br /> collected in the past to enable implementation of the selected remedies. <br /> Recommendation: Include language clarifying the data gaps. <br /> 4.2.3 SMWU 8 Burn Pit No. 2 <br /> A total of 11 soil borings are proposed, seven will be located outside the known areas of <br /> contamination. Three samples from each borehole (5, 10 and 15 feet below grade) will be <br /> collected and analyzed using U.S. Environmental Protection Agency methods SW8081A for <br /> pesticides, SW8082 for Polychlorinated Biphenyl, SW8151A for chlorinated herbicides and <br /> SW8270C for SVOCS. Are these samples, intended to provide preliminary confirmation results, <br /> designed to indicate the residual levels left if the excavation activities were conducted to these <br /> limits? If so, will the outer limits then be expanded if residual levels are found to be above the <br /> cleanup levels? <br /> Recommendation: Clarify the purpose of the sampling event and any subsequent activities. <br /> 6.0 Design Data Collection Plan for Institutional Control Sites <br /> SWMU 7 <br /> Table ES-1 and 6.0 Design Data Collection Plan for Institutional Control Sites <br /> indicates that institutional controls (ICs) will be developed after a Pre-Design Technical Summary <br /> (PDTS) is approved. However neither section clarifies what the contents of the PDTS will be or <br /> why it would impact the development of ICs. <br /> IIM Ap <br /> I HMI: " <br />