ARCHIVED REPORTS_PHASE II ENVIRONMENTAL SITE ASSESSMENT

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W GR • Southwest, IIrnc. 11.0 DISCUSSION AND EVALUATION OF FINDINGS 11.1 Soil Conditions Many of the highest concentrations of contaminants were found in areas heavily used for stockpiling and processing recyclable metals, i.e., B-3, B-4, B-6 and B-13 (see Table 1). Metal concentrations above TTLC limits, PCB concentrations exceeding PRGs, as well as elevated levels of O&G, TPH-mo and, to a lesser extent, TPH-d were found in the one-foot samples from these borings. As previously documented, potential contaminants such as residual oils on engine blocks and electric capacitors containing PCBs have been mixed with the metals brought in for recycling. The levels of lead, zinc, copper, chromium and antimony detected in B-13 and the levels of lead and/or zinc found in B-3, B-4, B-6, B-8, B-9 and B-16 classify these soils as hazardous wastes. Mishandling of lead-acid batteries has been documented on site in the past, and is considered a potential source of the lead contamination. B-13, located adjacent to the railroad spur in an area historically used for stockpiling, processing and possibly loading materials onto railcars, contained the highest soil concentrations of PCBs and all but 3 of the CAM 17 metals. • CAM17 metals occur naturally in soils, and detectable concentrations do not necessarily indicate impact from human activities. Naturally occurring levels vary depending on soil type and environment, but can be estimated by examining nearby sites with no known history of metal contamination. Table 3 provides a comparison of the range of metal concentrations detected in soil samples from the Learner site with those of soil samples recovered by WGR approximately a year ago on a nearby Port of Stockton site. Data from this site was selected for comparison due to its proximity to the Learner site and because the samples were collected from locations where metal contamination would not be expected. Table 3 is not intended to provide conclusive data regarding metal background levels in the soil at the Port of Stockton, but to offer a basis for comparison and evaluation of the Learner data. As shown in Table 3, the upper ranges of all 17 metals are higher in the Learner samples than in the reference samples. With the exception of arsenic, beryllium, cobalt and vanadium, the upper metal ranges of the Learner samples are at least an order of magnitude greater. Comparison of Table 1 with Table 3 reveals that concentrations of these metals in most of the five-foot Learner samples fall within the ranges of those in the reference samples. However, in approximately 50% of the one-foot samples from the Learner site, the antimony, cadmium, copper, lead, mercury, nickel and zinc concentrations exceed the upper limits of the • 704. PRI.05 24 July 21, 2008