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California Regional Water Quality Control Board Central Valley Region 0 Robert Schneider,Chair Gray Davis Winston H.Hickox Governor Secretaryfor Sacramento Main Office Environmental Internet Address: http://www.swrcb.ca.gov/rwgcb5 Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 ., Phone(916)255-3000•FAX(916)255-3015 30 October 2001 I`l7v � 1 2OO, �s Mr. Richard W. Fish F Del Monte Foods PO Box 9004 Walnut Creek, CA 94598-0904 REVIEW OF WORKPLAN ADDENDUM FOR ADDITIONAL INVESTIGATION DISCO PROPERTY, 110 FILBERT STREET, STOCKTON, SAN JOA QUIN COUNTY I reviewed the 16 October 2000 Addendum to the Work plan for Additional Investigation at the Disco Property(Workplan Addendum) submitted on behalf of Del Monte Foods by CH2M Hill. I am currently assisting the San Joaquin County Environmental Health Division(County)by reviewing and commenting on this Addendum; however, the County will remain the lead oversight agency for future corrective action work at this site. This review was discussed between Board and County staffs. hi August 2001, CH2M Hill completed nine cone penetrometer test (CPT)borings to define the extent of groundwater contamination downgradient and cross gradient of the site. Based on this added investigation, CH2M Hill proposes to move three of the previously approved intermediate wells to new locations. • MW-12 is proposed to be moved next to CPT-20 along the centerline of the plume. The proposed location for MW-12 is approved. • MW-13 is proposed to be 240 feet northeast of CPT-21 on Lafayette Street. MW-13 is required to define the eastern edge of the plume in the intermediate water-bearing zone at approximately 90 to 100 feet below ground surface. Depth discrete water samples collected at 85 and 136 feet in CPT-21 were non-detect for 1,2-dichloroethane (1,2 DCA) and all other constituents; therefore,I believe this location is well suited to monitor the eastern edge of the 1,2-DCA plume. Please install MW-13 near CPT-21. MW-14 is proposed to be next to CPT-24. The depth-discrete water sample collected from CPT-24 at 106 feet was non-detect for all constituents, and the log for CPT-24 does not show a water-bearing unit below 106 feet. CPT-23 was completed approximately 150 feet east of CPT-24, and 1,2-DCA was identified at 44 micrograms per liter(µg/1) in a depth discrete water sample from CPT-23 at 144 feet. The groundwater flow direction is consistently to the southwest, and the proposed well at CPT-24 will not monitor the contamination identified at 144 feet in California Environmental Protection Agency Cfecycled Paper The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can reduce demand and cut your energy costs,see our Web-site at http://www.swrcb.ca-gov/rwgcb5