SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

CLEANUP AND ABATEMENT ORDER NO. 93-712 -2- NESTLE BEVERAGE COMPANY SAN JOAQUIN COUNTY 7. Ground water is encountered at about 35 feet below ground surface (bgs). The ground water flow direction and downward vertical gradient vary seasonally due to the large regional pumping center to the north and pumping by Simpson Paper Company to the southeast. During the dry season (summer) at the peak of major agricultural withdrawals, the ground water flow direction is to the north-northwest, whereas, during the wet season (winter), the flow direction shifts southeasterly. 8. TCE and its derivatives have been detected in the ground water below the Discharger's property and off-site. VOC constituents are found in ground water approximately 3000 feet to the southwest toward the Stanislaus River and to a depth of about 150 feet bgs. 9. As a result of the historical regional ground water flow, the net movement of the contaminant plumes is to the south-southwest. However, the contaminant plumes have also extended to the southeast and north due to seasonal pumping, as shown in Attachment C. 10. TCE is the primary VOC in ground water. The historical high total VOC concentration was approximately 10,000 micrograms per liter (µg/1) and was detected in ground water samples from monitor well M-IA in 1987. In October 1992, the maximum total VOC concentration was 3452 µg/l and was 3380 µg/l for TCE in this well. 11. Two potential causes for the presence of VOCs in ground water have been identified: accidental spills associated with the above ground tank and unanticipated leaks in the industrial sewer system. 12. In April 1986, the Discharger met with the Board for the first time regarding the VOCs ground water contamination. The Board subsequently issued a letter stating that a remedial action plan for the cleanup of the ground water would be required at a later date. 13. Since 1986, the Discharger has conducted seven phases of remedial investigation (RI). The Discharger installed 54 monitor wells on- and off-site to determine the lateral and vertical extent of VOC contamination. 14. The Discharger conducted soil gas investigations in 1987 and 1989 to determine potential . sources and boundaries of the VOC ground water contamination. The results of the investigations revealed that there were elevated TCE concentrations in the vapor phase in the unsaturated zone in the area near the decaffeination building and along the southern portion of Stockton Avenue. No additional source areas were defined by the soil gas data. 15. The Discharger installed eight vacuum extraction wells as part of pilot vapor extraction systems (VES) to remove TCE from the unsaturated zone in the assumed source areas. The systems have proved to be effective in the removal of TCE and the Discharger has