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1 Harding Lawson Associates <br /> III RECOMMENDED CLEAN-UP <br /> This section presents the recommended clean--up levels for <br /> ' petroleum hydrocarbons in near-surface soils and groundwater at <br /> 455 Grant Line Road. <br /> The SJCPHS/EHD has indicated that the target levels are re non- <br /> ' detectable concentrations in soil and groundwater. HLA believes <br /> that such target levels are unattainable and that a remediation <br /> ' system should be installed and monitored to document the <br /> attainable clean-up level . On the basis of the progress of <br /> remediation, clean-up levels should be negotiated. The following <br /> factors should be used in evaluating clean-up levels: <br /> • The physical characteristics of surface and subsurface <br /> features, <br /> • The chemical characteristics of the petroleum <br /> hydrocarbons present in the subsurface material, <br /> • The potential for hydrocarbons to leach from the <br /> vadose-zone soil into the groundwater, and <br /> • The current or potential uses of groundwater that would <br /> be compromised by petroleum hydrocarbons at this site. <br /> • Beneficial uses of groundwater. <br /> Negotiations to establish the clean-up level should take <br /> place approximately 12 months after the installation of the <br /> remediation system. <br /> Although the primary exposure pathway of constituent <br /> chemicals is through ingestion of groundwater, HLA believes that <br /> ' human health is not endangered by the presence of residual levels <br /> of hydrocarbon compounds confined to the site. <br /> 8 <br />