SITE INFORMATION AND CORRESPONDENCE

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PUBLIC HEALTH SERVICES SAN JOAQUIN COUNTY ENVIRONMENTAL HEALTH DIVISION Karen Furst, M.D., M.P.H., Health Officer 304 East Weber Avenue, Third Floor • Stockton, CA 95202 209/468-3420 THE EARTHGRAINS COMPANY THERESA LANCTOT `it J IIJJ PO BOX 1830 APR 2 4 2000 ST LOUIS MO 63118-0830 Re: The Earthgrains Company (previously Rainbow Bakery) Site Code: 19093 2651 S. Airport Way Stockton, CA 95206 San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) has reviewed the Remedial Action Work Plan (RA WP) dated April 10, 2000 prepared by Phillips Services Corp. for the above referenced site. The RA WP is not approved, a modified Work Plan should be submitted to PHS/EHD by June 1, 2000. Air Sparging and Soil Vapor Extraction with Vapor Treatment (AS/SVE/VT) was proposed as a remediation method for the above referenced site in the RA WP. Data collected during a November 1994 pilot test for this method. (refer to Pilot Test Results in the Final Remediation Plan Addendum dated March 23, 1995 prepared by Burlington Environmental), was usedas the basis for the SVES design. The 1994 data for the radius of influence for Vapor Wells (VWS) and Air Sparge Wells (ASWs) installed at the site was measured when the groundwater depth was approximately 53 feet below surface grade (bsg). The most recent quarterly monitoring event at the site on March 14, 2000 evidenced groundwater depth readings at approximately 36 feet bsg. Groundwater has risen considerably at the site and the 1994 data may not represent current site conditions because of the change in groundwater depth. Current contaminant concentrations in soil vapor and water for all contaminants of concern should be determined and presented in the Work Plan. Clean-up levels designated in the water quality control plan for this basin should be stated as well. Depending on the data collected from a new pilot test the remediation system should be modified in design so as to operate at maximum efficiency. Calculations for determining numbers of ASWs and VWs to be placed at the site should be provided to PHS/EHD in the Work Plan. The radius of influence shown for the proposed VW 1 location in the RA WP is unsubstantiated by relevant data. Also, the groundwater contamination evidenced in other locations at the site, such as MW4, was not addressed by the remediation system proposed in the RA WP. More than one new VW and the proposed two ASWs may need to be constructed and/or added to the remediation system design to provide coverage of the contaminated area. ASWs 3, 4, 5, and 6 may need to be incorporated into the proposed remediation system to address contamination farther away from the source area. Sparging compressor and soil venting blower mechanical abilities as stated in the RA WP may need to be reevaluated due to greater groundwater head pressure from increased groundwater levels at the site. Another pilot test should be conducted to determine the radius of influence for VW vacuum and ASW pressure/ratio effects with respect to the current groundwater level. Cross sections should be provided in the Work Plan showing the proposed system design and placement, site lithology; groundwater level, updated soil and water contaminant concentrations, and current radius of influence for VWs and ASWs. Also provide updated aerial view diagrams. A Division of San Joaquin County Health Care Services