|
Preliminary Environmental Assessment Report
<br /> Pittman Elementary School,Stockton,CA
<br /> December 10,2003
<br /> Page 26
<br /> determined not to pose a significant cancer risk or health hazard. The compound 1,2-DCA was detected
<br /> in one groundwater sample (VB-7) collected closest to the former UST site (Figure 13, Appendix A),but
<br /> does not pose a health threat at this site because groundwater occurs too deep (40 feet) to be exposed by
<br /> construction activities, and will not be used for irrigation or consumption at the school.
<br /> Northern Former i inderground Storage Tanks Site
<br /> Twenty VOCs were detected in the soil gas samples and identified as COPC. These chemicals were
<br /> evaluated for risk and hazard using the Johnson and Ettinger Vapor Intrusion Model. The chemical 1,3-
<br /> butadiene was determined to pose a cancer risk of 4.30E-06. The other detected VOCs were determined
<br /> not to pose a significant cancer risk or health hazard. Acetone, benzene, 2-butanone (MEK), chloroform,
<br /> methylene chloride, and toluene were detected in the groundwater samples (Figure 13, Appendix A),but
<br /> do not pose a health threat at this site because groundwater occurs too deep (40 feet) to be exposed by
<br /> construction activities, and will not be used for irrigation or consumption at the school.
<br /> Polychlorinated Ri hn enols
<br /> No PCBs were detected in any of the surface samples collected by the electrical switching stations
<br /> (transformers).
<br /> Hydraulic Flevator
<br /> No PCBs were detected in the sample of hydraulic oil collected from the concrete floor in the hydraulic
<br /> elevator shaft.
<br /> 10.0 CONCLUSIONS AND RECOMMENDATIONS
<br /> • The metals identified by statistical tests as COPC are barium, beryllium, chromium, cobalt, copper,
<br /> nickel, and vanadium. Table A, Statistics of Metals Data and COPC Determination (Appendix C), shows
<br /> the statistical calculations performed including means, standard deviations, minimums and maximums,
<br /> coefficients of variation, and the Wilcoxon Rank Sum Test. Table A also details the determination of
<br /> metals as COPC according to DTSC guidance.
<br /> In addition, the following 43 constituents were also identified as COPC based on their detectable
<br /> presence in soil, soil gas or groundwater samples collected from the site: hexavalent chromium,
<br /> organochlorine pesticides (aldrin, alpha-BHC, beta-BHC, delta-BHC, gamma-BHC, alpha-chlordane,
<br /> chlorobenzilate, DDD, DDE, DDT, dieldrin, endosulfan II, endrin aldehyde, endrin ketone, heptachlor,
<br /> heptachlor epoxide, and methoxychlor), and VOCs [acetone, benzene, 1,3-butadiene, 2-butanone (MEK),
<br /> carbon disulfide, chloroform, cyclohexane, 1,3-dichlorobenzene, 1,2-DCA, ethanol, ethyl benzene, 4-
<br /> ethyltoluene, heptane, hexane, methylene chloride, MTBE, propylbenzene, PCE, toluene, 1,1,1-
<br /> trichloroethane, TCE, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, m,p-xylenes, and o-xylene]. Only
<br /> detected chemicals were evaluated as COPC.
<br /> All 50 COPC underwent HHRA analysis in accordance with DTSC guidelines. Cancer risk and hazard
<br /> quotients were calculated for each COPC and summed. The cumulative lifetime cancer risk for all COPC
<br /> is 1.84E-05 (18.4 in one million). The cumulative hazard index is 0.824, which is less than the level of
<br /> significance of 1.0 (unity). Therefore, the combined COPC pose a lifetime cancer risk greater than one-
<br /> in-a-million, but do not pose a significant health hazard. The COPC that appear to pose the greatest
<br /> cancer risk include hexavalent chromium, cobalt, dieldrin, and 1,3-butadiene. Lead in soil near structures
<br /> at the proposed school site was analyzed separately for health risk using the DTSC Leadspread 7 Model,
<br /> • which indicates that lead concentrations pose a significant risk to human health.
<br /> 1
<br /> +.A CONDOR
<br />
|