SITE INFORMATION AND CORRESPONDENCE_2

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Del Monte Stockton Property Assessment and Remediation RFP Section III, Page 3 engine was removed, and the SVE wells were connected to two tanks of activated carbon. However, the carbon reached breakpoint far faster than originally calculated, and excessive water vapor was thought to be the problem. Numerous modifications to the system were made to reduce the water vapor entering the carbon tanks. In July 1996, the system was shut down when rising groundwater levels submerged the SVE wells. An estimated 8,787 pounds of TPH gasoline were removed during the period of system operation. When it was obvious that the treatment system would not be used for some time in the future, the two leased carbon tanks were returned to the supplier. Don Light, Del Tech Geotechnical, was the treatment system operator. The electrical line to the treatment system was knocked down in 1997 by a truck turning around in the area adjacent to the treatment compound and has not been reinstalled. The system (including control panel,pumps, etc.) has not been run since 1997. A diagram of the AS/SVE system is shown in Attachment 6. E. Additional Investigation The additional investigation started with one row of CPT soil borings on the north shoulder of the freeway, but two more rows further south were required to reach nondetect. The BTEX plume appeared to end at the freeway on-ramp south of the freeway, while 1,2-DCA was found at one location on Lafayette Street (2.6 ppb at 85 feet bgs). 1,2-DCA was also found in one CPT boring at the southwest corner of Filbert and Myrtle Streets, so additional borings were made 200 and 400 feet further west on Myrtle Street. 1,2-DCA was found only at the 200-foot boring location at 1.1 ppb at 107 feet bgs and 45 ppb at 144 feet bgs. No 1,2-DCA was found 400 feet from Filbert Street. Shallow monitoring wells were recently installed in the on-ramp south of the freeway and along Lafayette Street. One shallow and one deep monitoring well were installed at the northwest corner of the freeway off-ramp and Filbert Street. These wells were sampled on November 30, 2001. The shallow monitoring well at the off-ramp south of the freeway contained 8.1 ppb 1,2-DCA while the shallow monitoring well in the on-ramp south of the freeway contained low levels of TPH gasoline and Benzene, and 180 ppb 1,2-DCA. The last deep monitoring well at the leading edge of the plume was installed in the on-ramp south of the freeway on December 10 and 11. It will be sampled on December 28 during the fourth quarter monitoring well sampling event. We will request a rush analysis, and the results will be faxed to you as soon as we receive them. All details on the CPT borings, analyses, and plumes can be found in the Additional Site Characterization Report dated June 2000 (Attachment 7),Del Monte Disco CPT Investigation and Monitoring Well Installation Results dated December 4, 2001