There are two major scenarios by which exposure to soil contaminants might occur at the St. Francis Auto Wreckers property. The first is exposure to people, especially children, visiting the vacant lot, as discussed under the child health statement. The second is to workers within the salvage yard. Of these, exposure via the vacant lot is the greater risk to public health. It is also the area where more information is needed to conclusively assess the public health threat. Based on currently available data, much of the known health risk at this site is to workers within the fenced salvage yard and would result from direct contact with contaminants in the upper 2 inches of soil. However, more environmental assessment is needed here as well. Only a few soil samples from the 6" soil depth within the salvage yard have been analyzed. A sample from 6" deep may not be representative of PCB contamination at the soil surface, where exposure is likely to occur. The samples, which were taken in 1991, contained elevated PCBs ranging from approximately 1-50 µg/gm throughout the salvage yard (2). An environmental comparison value, the cancer risk evaluation guide (CREG) for PCBs, has been established by the Agency for Toxic Substances and Disease Registry. The CREG is an estimate of a contaminant in an environmental medium in which an excess 1 in 1,000,000 cancer risk might occur following a lifetime exposure to soils that contain 0.4 µg/gm PCBs. Because the salvage yard is an active work site, the current contamination in surface soil may not be similar to that found ten years ago. Subsequent samples have not been shallow enough (approx. 2" depth) to support an evaluation of possible effects from direct contact with surface soils. If additional investigation identifies contaminants in surface soils similar to that found at depth, the direct contact risks can be addressed. The need for surface soil tests emphasizing PCBs, metals, and PAHs are appropriate because the presence of each of those classes of compounds can be expected in surface soils around an auto salvage operation of this type. Each compound class includes substances that are toxic and are persistent in soil. In this case, VOCs are less likely to be a direct contact concern because they are not persistent in surface soil.
Because PCBs, petroleum hydrocarbons, and metals are present in the soils, there is concernover the potential for exposure to these compounds. This exposure could occur through eitherdirect contact with these soils or through incidental ingestion or inhalation of these soils. Thepotential for exposure would range from minimal, such as to someone walking casually throughthe property, to a large exposure to someone digging or playing in these soils. The potential forcasual exposure can be assessed by (1) knowledge of the contamination at the soil surface (1-2inch depth) and (2) the thickness of plant cover. At the St. Francis Auto Wreckers property thereis known soil contamination in both the salvage yard and the vacant lot. However, sampling datathat adequately addresses contamination in the direct contact zone at the soil surface isincomplete. Previous soil surveys suggest that significant surface contamination is present, andthe lack of soil cover, either plant or barrier, allows the possibility of incidental contact withsurface contaminants.
The Wisconsin Bureau of Environmental Health was asked by the Wisconsin Department ofNatural Resources to evaluate the St. Francis Auto Wreckers property. The property consists ofa fenced auto salvage yard and an unfenced wooded vacant lot adjacent to a residentialneighborhood. Children use the vacant lot as a play area. Subsurface soils (below one foot deep)on both parts of the property are contaminated with elevated levels of polychlorinated biphenyls(PCBs), , lead, and chromium. Surface soil at the salvageyard contains PCBs that are a direct contact . Bare foundry sand at the soil surface of thevacant lot suggests a contact hazard also exists there; however, the soil data for that area areincomplete. The Wisconsin Bureau of Environmental Health (BEH) recommends further soilcharacterization and that the vacant lot be fenced and posted with hazard signs to limit access.
The owner of the St. Francis Auto Wreckers has retained an environmental consultant to furthercharacterize the soil and groundwater beneath the property. These results will be submitted toWDNR; BEH will review additional sample results.