SITE INFORMATION AND CORRESPONDENCE

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William S. Peters Peters Enterprises Page 4of4 (CVRWQB) is not granting closure to sites with incompletely assessed 1,2-DCA or MTBE. EHD notes that the highest MTBE concentration detected to date by EPA Method 8260 was not from the Chevron site, but from a water sample from the former Kwikee UST pit at 9,200 ppb. The highest concentration detected by EPA 8260 on the Chevron site has been 260 ppb, detected in MW-1 on the east margin of the Chevron site when ground water flow was inferred to be toward the west. MTBE analyses by EPA 8020 appear to over-quantify the concentration, perhaps due to high hydrocarbon concentrations, as MTBE concentrations determined by both methods are generally lower for the 8260 analyses. A hole was noted in the Kwikee UST during its removal, providing a prima facie source for the contamination that has not been well assessed. As noted above, EHD believes the site to warrant further characterization and directs you to conduct further investigation of the release. However, if you feel the site is ready to close and can account for all the data, EHD will consider an updated closure request presented in the context of a site conceptual model that effectively demonstrates your conclusions. Either the work plan or the updated site closure request is due in this office 02 December 2002. The SCM for the work plan or closure request should account for all the data and demonstrate the geological controls on contaminant transport, the contaminant sources, migration and transportation pathways, contaminant transportation rates (velocities). The model should provide reasonable estimates of the seepage velocities in the areas of concern during operation of the DPE system, i.e. near KW-3, KW-1, KW-2 and KW-5, and possibly near the Chevron wells MW-6 and MW-1. EHD notes that responsible parties that do not agree on who is responsible may face litigation, so the data should be collected and presented with that potential in mind. You may contact Michael Infurna at (209) 468-3454 should you have any questions and to schedule any field activities. Donna Heran, REHS, Director Environmental Health Divisi n Michael J. Infurna Jr., Senior REHS Nuel C. Henderson, Jr., RG LOP / Site Mitigation Unit IV LOP / Site Mitigation MI/ c: CVRWQCB — Marty Hartzell, Sacramento c: SWRCB—CUF — Mark Owens, Sacramento c: Upgradient Consulting —V. Cherven PO Box 8002 Stockton, 95208