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' No Further Action Request Section 5 0 <br /> Former American Forest Products Facility 2/16/2006 <br /> URS Project No 17322736 Page 5-4 <br /> There are no surface water bodies In the vicinity of the site or within the range of the <br /> groundwater contaminant plume <br /> • Discuss how background concentrations of chemicals were determined, if considered for use <br /> in the risk assessment (see Section 2 9) <br /> No background concentrations were determined <br /> 6 Selection of Tier I ESLs and Comparison to Site Data (see Section 2 2) <br /> Summarize how Tier I ESLs were selected with respect to the information provided above <br />' and additional assumptions as applicable <br /> Tier 1 ESLs were selected based on the depth to groundwater, which Is significantly greater <br /> than 3 meters, and on the lack of beneficial use of the groundwater, based on shallow <br /> groundwater in an urban setting and demonstrated lack of any downgradient water supply <br /> wells either within the extent of the plume or within a radius of 2,000 feet <br /> • Compare site data to the selected summary Tier I ESLs (presented in volume 1) and discuss <br /> general results <br /> All maximum concentrations for constituents of concern fell significantly below the Tier 1 <br />' ESLs <br /> If desired or recommended, compare site data to detailed ESLs for individual environmental <br /> concerns (presented in Volume 2, Appendix 1) and discuss specific, potential environmental <br /> concerns present at site <br /> Not applicable <br /> 7 Conclusions (see Section 2 10) <br /> Describe the extent of soil and groundwater impacts above Tier 1 ESLs, using maps and <br /> cross sections as necessary <br /> As demonstrated by data in Table 4,no site groundwater Impacts exceed Tier 1 ESLs <br /> • Discuss if a condition of potential risk to human health and the environment exists at the site <br /> The results of previous risk assessments are summarized In Section 4 of the 2001 Closure <br /> Request Report, Former American Forest Products Company, 2801 West Lane, Stockton, <br /> California (URS, 2001) The nsk to human health from TPH residues remaining In the soil Is <br /> low, based primarily on the fact that residual soil Impacts are located at depths greater than 20 <br /> feet Fate and transport modeling Indicates that, at groundwater depths greater than 35 feet <br /> bgs, predicted groundwater Impacts would be less than the MCL for the Indicator parameter <br /> used Risk of exposure to groundwater Impacts Is also limited by distance to active water <br /> supply wells and the fact that water supply wells in the vicinity are screened In deeper, semi- <br /> confined aquifer, not the shallow, unconfined aquifer Impacted by site contaminants The Tier <br /> 1 screening assessment conducted for this report indicates that residual groundwater <br /> concentrations present no human health risk with respect to Indoor air for a residential <br /> scenario <br /> E I'Proiccts\URS1AFP12005 IBCA InvestigationViP Investigation Report\AFP 2005 Report WP-TE-Rev02 doc <br />