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• Sup�lEmental Site Investigation Scoping Document
<br /> Pittman Elementary School,Stockton,Califomia
<br /> January 23,2004
<br /> Page 4
<br /> Tabulated summaries of the PEA sample analytical results are included in Appendix B. Figures 3 through 5
<br /> (Appendix A)present selected sample locations with selected analytical results from the PEA report.
<br /> The following constituents were identified as chemicals of potential concern (COPC) and underwent human
<br /> health risk assessment (HHRA) analysis: barium, beryllium, chromium III, cobalt, copper,nickel, hexavalent
<br /> chromium, aldrin, alpha-BHC, beta-BHC, delta-BHC, gamma-BHC, alpha-chlordane, chlorobenzilate, DDD,
<br /> DDE, DDT, dieldrin, endosulfan II, endrin aldehyde, endrin ketone, heptachlor, heptachlor epoxide, acetone,
<br /> benzene, 1,3-butadiene, 2-butanone [methyl ethyl ketone (MEK)], carbon disulfide, chloroform,
<br /> cyclohexane, 1,3-dichlorobenzene, 1,2-dichloroethane (1,2-DCA), ethanol, ethyl benzene, 4-ethyltoluene,
<br /> heptane, hexane, methylene chloride, methyl tertiary-butyl ether (MTBE), propylbenzene, tetrachloroethene
<br /> (PCE), toluene, 1,1,1-trichloroethane, trichloroethene (TCE), 1,2,4-trimethylbenzene, 1,3,5-
<br /> trimethylbenzene, m,p-xylenes, and o-xylene.
<br /> Cancer risk and hazard quotients were calculated for each COPC and summed (Table 2, on the next page).
<br /> The cumulative lifetime cancer risk for all COPC is 1.49E-05 (14.9 in one million). The cumulative hazard
<br /> index is 0.524, which is less than the level of significance of 1.0 (unity). Therefore, the combined COPC
<br /> pose a lifetime cancer risk greater than one-in-a-million, but do not pose a significant health hazard. The
<br /> COPC that appear to pose the greatest cancer risk include hexavalent chromium, cobalt, dieldrin, and 1,3-
<br /> butadiene. Lead in soil near structures at the proposed school site was analyzed separately for health risk
<br /> using the DTSC Leadspread 7 Model, which indicates that lead concentrations pose a significant risk to
<br /> human health.
<br /> i
<br /> The assessment revealed evidence of recognized endangerment in connection with the property that may
<br /> result in a lifetime increased cancer risk greater than one-in-a-million and adverse health effects from lead.
<br /> Condor concluded the following:
<br /> Lawn Area
<br /> Concentrations of chromium and cobalt in some soil appear to pose a potential health risk. Past use of pest
<br /> control and gardening chemicals adjacent to structures has resulted in a residual concentration of chemicals
<br /> in soil with some health risk.
<br /> Structure Driplines
<br /> Soil sampling around site structures identified certain areas where lead concentrations pose a significant
<br /> health hazard.
<br /> Northern Soil Gas Anomalv
<br /> Elevated cancer risk is indicated by soil gas sample results along the northern site boundary.
<br /> Condor recommended further action in the form of a Supplemental Site Investigation (SSI) to characterize
<br /> the extent of soil contamination in the lawn area and the structure driplines. A removal action to remove the
<br /> lead contaminated soil was also recommended. Additional removal actions may be required based on the
<br /> results of the SSI.
<br /> Based on subsequent discussions with the DTSC project manager, further evaluation of hexavalent
<br /> chromium at the site has not been included in this SSI Scoping Document due to the lack of a known source.
<br /> The site boundary definition was changed subsequent to submittal of the PEA, excluding a northwest portion
<br /> and decreasing the size of the site as defined in the PEA (Figure 2, Appendix A). Due to this boundary
<br /> �.� CONDOR
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