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ARCADIS GERAGHTY&MILLER ' concentrations are observed A schematic piezometer construction diagram is provided as Figure 2. A summary of field methodologies is provided in Attachment A ' Preparation of a Corrective Action Plan(CAP) Upon completion of the focused subsurface investigation, UNOCAL will prepare and submit a CAP. The CAP will propose a course of action designed to ' result in cleanup of the impacts and that has been determined to be the most cost- effective. The CAP will be designed such that its implementation will restore or protect beneficial uses of the aquifer. The CAP submitted to SJCPHS'wdl include • An assessment of the vertical and lateral extent of impacts based on the ' previous site investigations and the focused subsurface investigation proposed herein. • A feasibility study. • Applicable cleanup levels based on the numerical obJectives designated in the Basin Plan of the Central Valley Regional Water Quality Control Board The assessment component of the CAP, in addition to that referred to above, will address the physiochemical characteristic of the constituents of concern, toxicity, persistence and potential for migration in groundwater The CAP will also ' discuss the hydrogeology of the site and the surrounding area where the unauthorized release has migrated or may migrate The current and potential beneficial uses of the waters beneath the site and vicinity will also be presented ' along with the associated background quality of groundwater in the vicinity of the site Lastly, the assessment will address the potential effect of residual impacts on groundwater in the site vicinity ' A feasibility study will be included in the CAP and will evaluate alternatives for remedying or mitigating adverse effects of the release As indicated in Title 23, each alternative will also be evaluated for cost-effectiveness. At least two alternatives will be identified and evaluated as methods to restore or protect the beneficial uses of groundwater in the site vicinity. It is the opinion of ARCADIS Geraghty and Miller that sufficient data is available, from scientific literature sources and site-specific data at similar sites in California and in the local vicinity of this site, to conduct the methodology evaluation without further implementation of site pilot testing The most cost-effective corrective action will be selected and ' submitted to SJCPHS as the action to implement. 1 our ret_ page WAA SANTA_aM BARA{DATAVAPRO SSOVJNOCALW VALLEY%WPS_REVWACW0AbOC 7/11