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7hN3dwe11&Ro11O <br /> • <br /> Groundwater contamination also presents both cancer and non-cancer hazard risk at Areas 15 <br /> and 16. At Area 15,benzene currently exceeds landscape maintenance worker, commercial <br /> worker, and resident cancer risk levels at Monitoring Well 21, and has historically exceeded <br /> acceptable levels at MW-1, 4, 20A, 20B, and 21B. At Area 16, benzene concentrations in <br /> groundwater exceed cancer risk-based target concentrations for all exposure scenarios at <br /> well MW-3 and for commercial/residential scenarios at wells MW-6 and 9. Non-cancer <br /> hazard-based concentrations for the commercial scenario are exceeded for benzene and toluene <br /> at MW-3. <br /> Arsenic background concentrations for soil at Area 21 were exceeded at two locations <br /> (20TP-4-1.0 and 20TP-5-6.0). Groundwater cancer risk-based concentrations for all exposure <br /> scenarios are exceeded for benzene at wells MW-4 and 5. PNAs exceed construction worker and <br /> resident cancer-risk based concentrations for soil at Boring 2113-9-1.0. <br /> • Non-cancer hazard-based concentrations of copper in soil for residents was exceeded at Area 21 <br /> at 2113-2-1.0. Non-cancer hazard-based concentrations of benzene were exceeded for all but <br /> construction worker scenarios at wells MW-4 and 5. <br /> Areas 15 and 16 may be acquired by the City of Stockton for use as parking lots. End uses will <br /> all be either for recreational or commercial/industrial purposes. Area 21 may also be acquired in <br /> the future, for similar uses. <br /> The screening and evaluation of remedial alternatives for OU 2 must take into account that the <br /> City of Stockton does not currently own or have access to the sites, that source area remediation <br /> in the form of UST removal has taken place at each site, and that site remediation is currently in <br /> progress at Area 16. In keeping with the DTSC's agreement to evaluate reasonable remedial <br /> alternatives, the following remedial alternatives have been evaluated: <br /> 1. No further action <br /> • 2. Installation of an impermeable cap <br /> 20 <br /> 25970318.PGS 15 November 2000 <br />