SITE INFORMATION AND CORRESPONDENCE

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}erlt Sy: 8ASELINE; 510 420 1707; Nov-9-99 17:04; Page 8113 REPRESENTATION OF SITE CONDITIONS Potential Duman receptors are assumed to be exposed to the maximum concentration ofcontaminants in soil and groundwater, and the entire thickness of the surface and subsurface soils are assumed to be wntarninated by the maximum concentration of COPCs. This adds to conservatism in the human health assessment. Also, the PEA was conducted assuming future residential use of the site and default:exposure assumptions. Potential exposure to COPCs, and resulting risks and hazards under proposed redevelopment of the site as a water square/public meeting place,would be less than those for residential development. In addition,inclusion of groundwater ingestion and dermal contact with shallow groundwater is considered a conservative assumption,since shallow groundwater underlying the site is not currently or proposed to be used as a drinking water source under proposed redevelopment of the property. TOXICOLOGICAL DATA Conservative slope factors for carcinogens were used in the assessment, as is the currently, recommended approach by the U.S. EPA. These slope factors are based on the 95`h percent upper confidence limit on the low-dose portiori of the chemical's dose response curve,as extrapolated from high-dose human or animal response data using the U.S. EPA's linearized multistage model. This assumption means actual risks are likely to be lower than Clic risk estitnatcs calculated in the human health risk analysis. In addition, results of animal studies are often used to predict the potential human health effects of a chemical.There may be important,but unidentified differences in uptake, metabolism,distribution, and elimination of chemicals between a test species and humans. Animal studies are also usually conducted under high dose conditions, where the high dose itself may be responsible for the observed carcinogenic effects. UNCERTAINTIES ASSOCIATED WITH COMBINATION OF CONSERVATIVE ASSUMPTIONS The uncertainties and conservatism associated with the various components of the human health risk analysis discussed above are additive. This,combined with conservative exposure parameters and exposure assumptions ensures that estimates of health risks are greater than those actually or potentially occurring at the site. PUBLIC PARTICIPATION COMMUNITY ASSESSMENT The Weber Block property is located in the Stockton Environmental Master Plan Area. Thepurpose. . of the Environmental Master Plan is to establish protocols for future environmental work(including remediation)within the Master Plan area,identify financing mechanisms far redevelopment,develop a marketing plan for properties in the waterfront area, and develop an action plan to ensure redevelopment. It is the intent of the Environmental. Master Plan to reduce uncertainty associated with environmental contamination for developers, lenders, and others in the private :sector, thus facilitating redevelopment of the area. It is believed that, in the long run, this will speed up the redevelopment process by providing pre--approved remedial actions for the conditions that exist in . the waterfront area,.and by providing a range of possible costs for the actions to be implemented. 973699tk.poa.wpd-11!9!99 Y)