Laserfiche WebLink
• Risk-based cleanup levels established by risk assessments or risk-based corrective action <br /> (RBCA)guidelines, <br /> • Current closure guidelines from the regulatory agencies, such as the RWQCB criteria for low- <br /> risk ground water cases, or <br /> • Asymptotic levels have been achieved for chemical concentrations in ground water extracted <br /> by a remediation system <br /> The proposed remediation objectives in this CAP are a combination of the above criteria Shell's <br /> objectives are to implement the most cost effective approach to remediate site ground water, and to <br /> protect sensitive receptors and human health Therefore, this CAP should control off-site migration <br /> of hydrocarbons, and provide enhanced remediation of residual hydrocarbons beneath and down <br /> gradient of the site <br /> Given the specific site conditions, the specific CAP objectives are to <br /> Remove the most heavily impacted hydrocarbons in the source area in the former tank <br /> complex, <br /> Prevent hydrocarbon migration from the site, <br /> Augment hydrocarbon biodegradation to improve ground water quality, <br /> Continue the ground water monitoring program to monitor water quality, and <br /> Establish a contingency plan to expedite or enhance remediation if necessary <br /> The final objective of this modified CAP is to reduce dissolved hydrocarbons to the point where <br /> natural attenuation can remediate any residual hydrocarbons RBCA guidelines may be used to revise <br /> site cleanup objectives in the future if deemed appropriate by the SJCEHD <br /> EVALUATION OF REMEDIAL ALTERNATIVES <br /> Cambria evaluated several remedial alternatives to achieve the site remedial objectives Presented <br /> below is a description of the technical appropriateness and cost effectiveness of each remedial <br /> alternative <br /> Natural Attenuation (Intrinsic Biorennediation) <br /> The natural attenuation alternative includes allowing hydrocarbons to biodegrade naturally and <br /> implementing a long-term ground water monitoring plan The recent Lawrence Livermore National <br /> Laboratory report indicates that almost all subsurface hydrocarbons releases eventually stabilize and <br /> degrade on their own In response to this report, the SWRCB has recommended focusing on source <br />. area removal, and no longer requests active remediation of dissolved hydrocarbons unless the <br /> hydrocarbons represent a significant threat to human health or other sensitive receptors <br /> 240-0783 20 <br />