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Anary Environmental Assessment Report
<br /> Pittman Elementary School,Stockton,CA
<br /> December 10,2003
<br /> Page 21
<br /> • 8.2 RISK AND HAZARD CHARACTERIZATION
<br /> 8.2.1 Identification of Chemicals of Potential Concern
<br /> Two tests were applied to determine whether the CAM 17 Metals met criteria to be considered chemicals
<br /> of potential concern (COPC). The criteria are:
<br /> 1) Compare the highest site concentration with the highest background concentration. If the site
<br /> concentration is equal to or less than the background, then the metal may be eliminated as a
<br /> COPC.
<br /> 2) Perform the Wilcoxon rank sum test, which evaluates whether concentrations from the site
<br /> sample population tend to be consistently larger or smaller than the background sample
<br /> population. This method is described in detail in Selecting Inorganic Constituents as Chemicals
<br /> of Potential Concern at Risk Assessments at Hazardous Waste Sites and Permitted Facilities
<br /> (1997)prepared by DTSC.
<br /> The COPC identified in this manner are barium, beryllium, chromium, cobalt, copper, nickel, and
<br /> vanadium. Table A, Statistics of Metals Data and COPC Determination (Appendix C), demonstrates the
<br /> statistical calculations performed including means, standard deviation, minimums and maximums,
<br /> coefficient of variation, and the Wilcoxon Rank Sum Test. Table A also details the determination of
<br /> metals as COPC.
<br /> In addition, the following 43 constituents were identified as COPC based solely on their presence in soil,
<br /> soil gas and groundwater samples collected from the site: hexavalent chromium, organochlorine
<br /> • pesticides (aldrin, alpha-BHC, beta-BHC, delta-BHC, gamma-BHC, alpha-chlordane, chlorobenzilate,
<br /> DDD, DDE, DDT, dieldrin, endosulfan II, endrin aldehyde, endrin ketone, heptachlor, heptachlor
<br /> epoxide, and methoxychlor), VOCs [acetone, benzene, 1,3-butadiene, 2-butanone (MEK), carbon
<br /> disulfide, chloroform, cyclohexane, 1,3-dichlorobenzene, 1,2-dichloroethane, ethanol, ethyl benzene, 4-
<br /> ethyltoluene, heptane, hexane, methylene chloride, MTBE, propylbenzene, tetrachloroethene, toluene,
<br /> 1,1,1-trichloroethane, trichloroethene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, m,p-xylenes, and
<br /> o-xylene]. Human health risk assessment (HHRH) calculations were performed on the constituents
<br /> identified as COPC. Only chemicals that were detected in site samples were considered as COPC.
<br /> 8.2.2 Exposure Assessment Methods
<br /> Conceptual Site Model
<br /> As shown in Table 16, on the next page, all soil and air pathways discussed in the DTSC PEA Guidance
<br /> Manual were evaluated for residential exposure as mandated by DTSC for school assessments. In
<br /> addition, the soil gas pathway discussed in the Johnson and Ettinger Model was evaluated for residential
<br /> exposure.
<br /> �/� CONDOR
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