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Case Closure Summary Page 2 �I <br /> I` dng Underground Fuel Storage Tank Pro! <br /> (III Release and Site Characterization Information, continued) <br /> Maximum Documented Contaminant Concentrations -Before and After Cleanup (in this case,the over-excavation) <br /> I <br /> Contaminant Soil Soil Water Water Contaminant Soil Soil Wateri Water <br /> (ppm) (ppm) (ppb) (ppb) (ppm) (ppm) (ppb) (ppb) <br /> Before After Before After Before After Before After <br /> TPH (Gas) 33 00 --- 17,000 59 MTBE 15 0.13 6.4 4.4 <br /> TPH (Diesel) 330 --- 200 <50 Mineral Spirits ---- -- <br /> Benzene 39 2.4 3,100 8.2 Oil &Grease ---- 10 <1.0 i <br /> Toluene 170 4.9 2,000 <5.0 Heavy Metals 37 _ — <br /> Ethylbenzene 110 8.0 670 1.3 Lead 19 <br /> Xylenes 600 41 2,400 6.2 <br /> Comments (Depth of Remediation, etc.): Tanks were removed in 1993. Investigation showed soil impact to be limited to <br /> 15 feet with most of the hydrocarbon mass concentrated at 10 feet and above. 450 cubic yards of contaminated soil from a <br /> 30 feet wide by 40 feet long by 12 feet deep excavation had since been removed from site in 1998. <br /> IV. Closure , <br /> Does completed corrective action protect existing beneficial uses per the Regional Board Basin Plan? Yes <br /> Does completed corrective action protect potential beneficial uses per the Regional Board Basin Plan? Yes iff <br /> Does corrective action protect public health for current land use? Yes l <br /> Site management requirements: none <br /> i <br /> Should corrective action be reviewed if land use changes?Yes <br /> Monitoring wells decommissioned: Number Decommissioned: 1 Number retained: L# f <br /> List enforcement actions taken: NOR sent <br /> List enforcement actions rescinded: None <br /> V. Local Agency Representative Data li <br /> Name: Donna Heran 11V o Title: Director of Environmental Health lsrrVlzl <br /> r <br /> Signature: L" Date: /,I-/-z2?/ <br /> VI. Central Valley Regional Water Quality Control Board (RB) Notification <br /> r <br /> Date Submitted to RB: Response Date: <br /> RB Staff: Mark List Response: <br /> Title: Engineering Geologist <br /> VII. Additional Comments, Data, etc. <br /> One Monitor well was destroyed when site was over-excavated in 1998. Remaining monitor wells will be destroyed once <br /> concurrence from CVRWQCB has been received. Closure will not be issued until all monitoring wells have been destroyed <br /> by C-57 licensed contractor under permit.. <br /> i <br /> i <br /> This document and the related CASE CLOSURE LETTER,Shall be retained by the lead agency as part of the <br /> official site file. (08124193) Exhibit N Page 2 of 2 <br /> t <br /> r <br />