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-3- estimate on the magnitude of contamination. It will not give vertical or horizontal extent of contamination. Sampling depth The sampling plan proposes that soil samples are to be collected over a depth interval of one foot. Because CDD and CDF have a high organic carbon absorption factor, soil migration is very low. Faster migration rates are possible if a carrier like oil is provided. Sampling should be focused within the top four inches of soil . Depth profiles should be performed in areas where a carrier would be present. Based on descriptions of the process, poles were removed from the cellon and retorts that still were dripping with oil . Profiles would then be necessary in front of these exits. Indicator compounds The Department is concerned over the approach of using PCP as an indicator of CDD and CDF contamination. The chemical properties of the compounds are markedly different, with half-lives also differing dramatically. The Department agrees that CDD and CDF contamination will be highest in areas of highest PCP exposure. However, areas with low PCP concentrations do not exclude the presence of CDD and CDF. The stormwater ballast ponds show fairly low levels of PCP, but metal levels are elevated. Sampling should be expanded to include this area, rather than collection of stormwater to determine CDD and CDF levels. The Department considers the sampling for CDD and CDF as a crucial task with regards to mitigation of this site. Pentachlorophenol has been used at the site since 1946. Accumulation of CDD and CDF has been occurring for over forty years. CDD and CDF contamination at McCormick and Baxter is extremely under estimated. Issues which were not accurately addressed in the report include: a) the large difference in biodegradation between PCP and CDD/CDF, b) that past composition formulation for PCP contaminants is unknown, c) the analytical results of past samples collected for CDD/CDF are not evaluated or used, and d) sampling locations and depths at the site of CDD/CDF vs. PCP are not accurately defined. The current proposal for sampling at McCormick and Baxter would not be acceptable for characterizing contamination at the site. Before sampling activities proceed at McCormick and Baxter, revisions of the preliminary site assessment for dioxins should be made.