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.� California Regional Water -Ouality Control Board <br /> ._ Central Va�le3� Bron <br /> VVk H.Hickox til`j SSperameiito Main Office Gray Davis <br /> �.�retaryfor Interne Address: http:/hvww.swreb.ca.gov/rwgcb5 Governor <br /> Environmental 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Protection Phone(9-16)255-3000•FAX(916)255-3015 <br /> 2 January 2001 <br /> Mr. Richard W. Fish <br /> Del Monte Foods <br /> PO Box 9004 <br /> Walnut'Creek, CA 94598-0904 <br /> REVIEW WORKPLAN FOR ADDITIONAL INVESTIGATION <br /> DISCO PROPERTY, 110 FILBERT STREET, STOCKTON, SAN JOA QUIN COUNTY <br /> Board staff reviewed the 5 December 2000 Work Plan for Additional CPT Investigation, Monitoring <br /> Well and Extraction Well Installation at the Disco Property(Workplan) submitted on behalf of Del <br /> Monte Foods by CH2M Hill. We are assisting the San Joaquin County Environmental Health Division <br /> (County) by reviewing and commenting on this Workplan; however, the County will remain the lead- <br /> oversight agency for future corrective action work at this site. This review was discussed between Board <br /> and County staffs. <br /> �l 'As presented in the Workplan, CH2M Hill proposes to complete seven cone penetrometer test (CPT) <br /> ;:borings to define the lateral and vertical extent of groundwater contamination downgradient and cross- <br /> gradient of the site, install five off-site monitoring wells to monitor downgradient and cross-gradient <br /> contamination, and install one groundwater extraction well to determine aquifer parameters. <br /> I <br /> '.'The seven, duplicate CPT pairs will be-pushed to 150 feet below ground surface to identify lithology and <br /> permeable water bearing zones, then depth-discrete groundwater samples will be collected from <br /> permeable zones that are identified. Cross-gradient CPTs —16 and—17, and—18 will be completed first, <br /> and the sample results from these water samples will determine if additional CPT borings are needed <br /> west of CPT-18 (see attached Figure 2 from CH2M Hill's Workplan). The proposed CPT work is <br /> appropriate and necessary to define the extent of groundwater contamination at the site. <br /> Based on the results of previous site work and the CPTs proposed in this Workplan, CH2M Hili <br /> proposes to install five monitoring wells: one deep (greater than 120 feet) and four intermediate (90 to <br /> 100 feet). A deep and intermediate monitoring well pair are proposed directly downgradient of the site, <br /> and three intermediate monitoring wells will be installed near CPT borings—12, —17, and—22, as shown <br /> on Figure 2. Due to the high concentrations of 1,2-dichloroethane identified directly downgradient of <br /> the site in the intermediate sand zone, the proposed deep monitoring well must be moved approximately <br /> 230 feet southeast, and completed near CPT-12 (see Figure 2). The other four proposed monitoring <br /> wells are appropriately located. <br /> CH2M Hill proposes to install the 2-inch diameter PVC monitoring wells using mud-rotary drilling <br /> methods due to potential flowing sands, and the necessity of continuous core recovery. Previous well <br /> California Environmental Protection Agency <br /> p�� Recycled Paper <br />