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Work Plan—Site Sampling Page 3 West Weber Site-Stockton GPE Project 536.2 1.4 Potential Problem The previously mentioned Initial Assessment provides details of the past environmental investigations, but potential environmental concerns identified include the following: 1. Former USTs Three of four former underground storage tank sites have been targets of remedial investigations and been deemed adequately mitigated for industrial use. Additional assessment is, however, needed to determine if conversion to residential use might pose a health risk. 2. Rail Spurs There are no known health risks associated with the existing and former rail spurs. In past years, however, it was common to spray a lead arsenate mixture along rail tracks as a weed control measure. This practice has resulted in elevated concentrations of lead and arsenic in the soil along railroad tracks in other sites, and could have done so in this case. In addition,rail cars may carry hazardous chemicals that can be spilled and adversely impact the soil along the tracks. 3. Former Bulk Fuel Terminal From at least 1936 and up to the early 1970s, 1330 W. Weber was the site of a bulk fuel faculty (Raney, 2005). As part of a previous investigation, two borings (actually backhoe-dug potholes)were installed through the former location of the bulk oil facility (see attached site map for approximate locations) and samples were collected from a depth of 15 deep. One sample contained 78 ppm of weathered diesel fuel while the other did not contain detectable gasoline, diesel, or oil range petroleum hydrocarbons. These data are insufficient to make a determination that the area has not been adversely impacted and poses a human health risk. 4. Semi-Volatile Chemicals of Uncertain Origin As part of an environmental assessment completed by American Geophysical Service Inc., in 2004, a soil boring (136) situated just south of the building at 1404 W. Weber, produced samples exuding a strong chemical odor, and one soil sample from the boring contained trace concentrations of the semi- volatile organic compounds naphthalene, pyrene, fluoranthene and phenanthrene. The lateral extent of the possible contamination is unknown. The reported concentrations appear to be too low to represent a health risk,but additional investigation was recommended. S. Waste Oil Areas A former storage area adjacent to 1541 W. Weber was used to store drums of waste oil. A soil boring was advanced through the area and a sample was collected from a depth of 10 feet. The sample contained 49 ppm of motor oil range petroleum hydrocarbons. The lead concentration in the sample may have been slightly elevated at 15 ppm. Soils in the vicinity of the Stockton Cold Storage maintenance and truck shops may also have been impacted by waste oil. 6. Fill Material Portions of the peninsula were built up with imported material, apparently mostly derived from the dredging of the turning basin, but the material may also include construction debris. The area(s) of landfill are not well known, but the SGS Phase I ESA indicated it was particularly notable north of Weber Avenue and east of building 1541. Imported contaminated soil and contaminated soil from Tank Site 4, amounting to several thousand cubic yards of material,was spread over the western part of the Stockton Cold Storage property. It appears that much of the vacant lot to the west of the buildings was used for this purpose. It is possible this material may have contained residual petroleum contamination. 2937 Veneman Avenue, Suite B240 Geo-Phase Environmental Inc. Phone: (209)569-0293 Modesto, Ca 96356 Fax: (209)569-0295