SITE INFORMATION AND CORRESPONDENCE FILE 2

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Rodger Liston Darpetro Inc. 749 E. Charter Way, Stockton, California Page 2 of 7 1 . The flow direction of ground water on the site and regionally has been consistently toward the northeast and the plume of impacted ground water has migrated toward the northeast; 2. Ground water will migrate approximately 6 . 3 feet in 'any' quarter; 3 . CGG's inability to collect a ground water sample from HP-2 at 50 feet below surface grade (bsg) indicates that the fine-grained soil in the area acts as a barrier to ground water flow, forcing the ground water to flow under and/or around it; 4. The rise of ground water elevation caused the ground water flow direction on the nearby 701 Charter Way site to shift from flowing northeast to flowing south; but ground water more than 55 feet bsg still flowed toward the northeast; 5 . Increasing MTBE concentrations with increasing depth in B-3 indicates an off-site source of contamination ; 6 . The sand unit commonly encountered across the area at 50 feet bsg is the main contaminant migration pathway; 7. CGG's east-west cross section with plotted contaminant concentrations shows "TPH and MTBE concentrations from the 641 E. Charter Way boring is toward our well MW-11 " ; 8. MW-1 on the 701 Charter Way site has displayed a reduction of MTBE concentrations from a range of 2000 µg/I to 8500 µg/I in the time period from 1998 to 2001 , to 350 µg/I during the second quarter 2003; 9. Soil samples from the boring for VW-7, east of the office building , were impacted by petroleum hydrocarbons to a depth of 80 feet bsg , soil samples from B-2, advanced near VW-7, had nondetectable hydrocarbon concentrations in soil samples from 85, 87 and 90 feet bsg ; 10. Dissolution of MTBE into the ground water increases the ground water density causing it to sink at a rate of 1 foot per 20 feet of lateral migration under the gradient at the site; 11 . Maps of tert-butyl alcohol (TBA) and MTBE concentrations demonstrate migration of the contaminants onto the site from the west under the Sun's Garden building and from the south along Charter Way; and 12. Two plumes of impacted ground water are migrating onto the subject site. EHD concurs that the maps for the area prepared by the San Joaquin County Flood Control District indicate a regional ground water flow direction toward the east-northeast for the area. Flow direction on this site is locally variable but generally trends toward the east-northeast based on the site data and modeling by CGG.