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4. 0 DISCUSSION OF RESULTS <br /> The laboratory results of soil sampling are summarized on <br /> Table 1, and the laboratory reports and chain-of-custody <br /> forms are presented in Appendix II. <br /> A waste may be classified as hazardous based on either the <br /> total or soluble amount of a constituent that is present. <br /> None of the samples had any total constituent concentrations <br /> at even 50% of the hazardous level (total threshold limit <br /> concentration or TTLC) established by the Department of <br /> Health Services (DHS ) . However, in making a hazardous <br /> determination, DHS typically uses the rule that if the total <br /> amount of a constituent exceeds the soluble threshold limit <br /> concentration ( STLC ) for a hazardous classification by <br /> greater than 10 times, waste extraction test (WET) should be <br /> run. Using this criteria and the fact that the samples are <br /> composites, it is possible that both lead and mercury are <br /> present in soils at hazardous levels. This would have to be <br /> confirmed by resampling and performing an wet for <br /> leachability test. <br /> While the materials at the site may not prove to be <br /> hazardous, they do exceed the Regional Water Quality Control <br /> Board (RWQCB) limits for a designated classification, which <br /> could require mitigation. Ar ury are <br /> present above the RWQCB levels recommended for the <br /> protection of surface waters. These standards are only <br /> recommendations, nonetheless they are generally used by the <br /> Board to determine whether a waste or discharge is expected <br /> to pose a threat to the beneficial uses of surface water. <br /> These designated levels are shown on Table 1. As with the <br /> DHS hazardous classification, the amount of extractable <br /> arsenic, lead or mercury may need to be determined, pending <br /> discussion with RWQCB staff. <br /> An important consideration in assessing the metals levels in <br /> soils is whether they represent background concentrations or <br /> are related to improper waste disposal, either during site <br /> reclamation or subsequent ship building activities. It is <br /> possible that the dredge spoils or stream sediments are <br /> naturally high in certain metals, however this must be <br /> confirmed with off site sampling. The presence of arsenic, <br /> lead and mercury is not unexpected given the historical use <br /> of the site, although is is surprising that copper, chrome <br /> and cadmium are not also high. All of these constituents <br /> are associated with former activities at the site including <br /> working of alloy metals, painting, and electrical repair. <br /> The laboratory results of water analysis are summarized on <br /> Table 2, and the laboratory reports and chain-of-custodies <br /> are presented in Appendix III . The state maximum <br /> contaminant level (MCL) for drinking water is also shown and <br /> is exceeded for cadmium, total chromium, and selenium. Lead <br /> is present at the MCL and arsenic is at 90% of MCL. The two <br /> 3 <br />