SITE INFORMATION AND CORRESPONDENCE FILE 1

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Executive Summary Cox & Cox (595 E. 11' Street, Tracy, CA 95736) is a former gas station site where fuel leaked from underground tanks. The tanks were removed and the site has been investigated to determine the extent of contamination migration. The dissolved ;• groundwater plume is no longer moving (stable)however, Total Petroleum Hydrocarbons as Gasoline (TPHG) concentrations in the shallow groundwater have been rising and are attributed to residual soil contamination around two of the monitoring wells (MW). These wells, MW-3 and MW-9, are northerly of the building still remaining on site and down gradient (in the mobile home park) from the former tank pit that was located on the east side of the building. The site currently has several constraints upon it including, mobile home trailers, numerous unplotted domestic water supply lines, unplotted electric and natural gas subsurface utilities, a large diameter agricultural irrigation water pipeline, and City of Tracy subsurface utilities ("utilities"). i Wright Environmental Consultants proposes to implement an interim remedial action s (IRA) to clean up the residual contamination around the two monitoring wells. This IRA will be limited excavations (removal of contaminated soil) to depths of about 9 to 14-feet around and between MW-3 and MW-9. The contaminated soil would be excavated, sampled, and removed while clean excavated soils near the surface would be segregated, stored on site, and eventually used to refill the excavation. The presence of the-mobile homes, loose flowing sands in the upper portions of the excavation, and the presence of numerous utilities are three constraints that could impact this approach. The excavations would be advanced to the nearest safest point considering these constraints. If needed, the utilities would be temporarily relocated and/or supported with beams across the excavation area. The site will be fenced with 24-hour security during the period when excavations are open_ Open excavations would be kept to a minimum, backfilled at the close of each workday, thereby minimizing displacement ,and discomfort to affected F tenants. Groundwater is anticipated to flood the bottom few feet of the excavations. The excavations will be allowed to flood and water will be pumped out to remove contaminated water. The subsurface irrigation pipeline that feeds the canal in front of the Former Heinz Plant is to be turned off on or about October 31, 2003. The feasibility of removing soil within feet of the pipeline in the summer months when the pipeline is full is not an option. Excavation work must be done when the pipeline is empty. It is anticipated that the utility relocation, contaminated soil excavations and hauling, and- backfilling and compaction immediately following the excavation work would take place over a two-week period. This time frame could be shortened if contaminated soil is I. allowed to be immediately transported and stored prior to disposal at a permitted off site f location(Forward Landfill). I After excavation work is completed the site will remain in its current uses. Some additional cleanup work may be required depending on the effectiveness of the Interim �' Remedial Action work described above.