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'Waste Management Unit Report -3- 10 September 1991 <br /> DDRW, Tracy <br /> ground water samples. The list of parameters in the priority pollutant metals <br /> contains metals that are not considered heavy metals (such as calcium, <br /> magnesium and iron) and for which hazardous concentrations have not been <br /> established. These metals may more appropriately be performed by analyses for <br /> general or standard minerals. <br /> f. Soil samples which are to be analyzed for pesticides and for heavy metals <br /> should be analyzed for soluble concentrations. The soluble concentrations of <br /> these waste constituents will indicate whether the residual waste <br /> constituents, if left in-place, pose a threat to water quality. However, the <br /> total concentrations of these waste constituents are generally needed to <br /> perform a health based risk assessment. Therefore, soil samples which are to <br /> be analyzed for pesticides and heavy metals should have the shallowest sample <br /> split, with one split to be analyzed for total concentrations and the other <br /> split sample to be analyzed for soluble concentrations. The deeper soil <br /> samples should be analyzed only for soluble concentrations. <br /> Analyses for soluble concentrations of heavy metals should be performed using <br /> the Waste Extraction Test (WET) with deionized water, provided the soils have <br /> a neutral pH. If the soils are acidic, such as may be potentially encountered <br /> in the Battery Acid Sump (WMU 21) , then it would be more appropriate to use <br /> citric acid in the WET. Soluble concentrations of pesticides in soils should <br /> be performed using the Toxic Characteristic Leaching Procedure (TCLP) . <br /> g. The Report generally indicates that monitor wells will be installed with a ten <br /> foot screened interval . Considering historical water level fluctuations, a <br /> ten foot screen interval may not be adequate. In addition, if floating <br /> product is found when a monitor well is installed through a former WMU site, <br /> then the screened interval should be across the water table to monitor the <br /> floating product. A different monitor well may be needed to monitor the <br /> dissolved phase of contamination in the aquifer. <br /> h. The list of analytes should be expanded to include dioxins in the samples from <br /> the burn pits. However, analysis for dioxins should not be performed until <br /> the analytical results of chlorinated organics are received. If chlorinated <br /> organics are not present, then it would be unnecessary to analyze for dioxins <br /> because dioxins are thought to be break down products from chlorinated <br /> organics. In addition, if the shallowest soils samples do not have <br /> chlorinated organics then deeper soil and ground water samples would not need <br /> to be analyzed for dioxins. <br /> i . The Report indicates that soils boring will be backfilled with grout, but does <br /> not specify what type of grout. A cement grout should be used instead of <br /> bentonite due to the shrink-swell capacity of the bentonite above the water <br /> table. <br /> SPECIFIC COMMENTS <br /> Table 1-1. Table 1-1 is a list of the WMUs at the site which required additional <br /> characterization or remediation. The list does not include the fuel tanks <br /> adjacent to Building 201. The Building 201 underground tanks (UGTs) , as <br /> well as any other UGTs, should be included in the final investigation of <br /> WMUs. <br />