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CLOSURE REQUEST REPORT Section No 5 0 <br /> Former American Forest Products Company 07/31/01 <br /> 2801 West Lane Page 5-2 <br /> Stockton,California <br /> 5 If monitoring wells were installed and no contamination was found in the monitoring wells, <br /> the estimated transit time for contamination to leach to groundwater and reach the closest <br /> downgradient monitoring well. <br /> TPH has been detected in monitoring wells installed at the Site <br /> 6. if a vapor extraction system was used include: plan views showing the radius of influence <br /> of each vapor extraction well; graphs showing the dechne in influent concentrations vs. time <br /> showing system reached asymptotic concentrations if system was pulsed, graphs must <br /> include peaks if there were any; date when system ceased to operate; plan views showing <br /> the lateral extent of remaining contamination; and cross-sections showing vertical extent of <br /> remaining soil contamination. <br /> A vapor extraction system was not used at the Site <br /> 7 If groundwater extraction was used include: plan views showing the original groundwater <br /> contamination plume, and the remaining plume; plan views showing the radius of influence <br /> of each groundwater extraction well, graphs showing the decline in concentrations vs. time <br /> for each monitoring well; an estimate of when remaining contamination concentrations (if <br /> there is any) will reach Water Quality Objectives by passive bioremediation i.e. Primary <br /> MCL for Benzene, Taste and Odor Thresholds for TPHg, TPHd, and Toluene, <br /> Ethylbenzene,and Xylenes; and date when system ceased to operate. <br /> A groundwater extraction system was not used at the Site <br /> 8 If passive bioremediation is to be used to remediate remaining contamination or was the <br /> only remedial action include: plan views showing the original groundwater contanunation <br /> plume, and the remaining plume; graphs showing the decline concentrations vs. time for <br /> each monitoring well; and an estimate of when remaining contamination concentrations (if <br /> there are any) will reach Water Quality Objectives by passive bioremediation (i e.,Primary <br /> MCL for Benzene, Taste and Odor Thresholds for TPHg, TPHd, and Toluene, <br /> Ethylbenzene,and Xylenes). <br /> Passive bioremediation is the remedial action that is currently being used at the site A persistent, well <br /> defined TPH plume has not been identified at the site during the 11 years of groundwater monitoring <br /> TPH was only detected in one sample prior to 1998 TPH detections in the samples collected since 1998 <br /> indicate that the majority of detections are below or near the taste and odor theshold of 100 µg/]L for <br /> diesel A steady, increasing trend in TPH concentrations resulting from rising groundwater is not <br /> apparent, indicating that TPH impacts are liley to remain near the 100 gg/L level (Appendix B) <br /> Groundwater analytical data also indicates that the diesel is degrading, as documented by the <br /> chromatogram patterns which correspond to weathered diesel instead of fresh diesel <br /> 10. If contamination remains in the soil, and if there were no momtoring wells installed, fate <br /> and transport modehng to determine if groundwater will be impacted, and by what <br /> maximum concentration. The input sheet shall be included with the fate and transport <br /> output sheets. <br /> Monitoring wells have been installed at the Site <br /> K 1840191afp1afp_c1osure_rpt doe 07131/0I 3 24 PM <br />