SITE INFORMATION AND CORRESPONDENCE

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wf • '� _ III Release and Site Charact6oeation Information (continued) �t Maximum Documented Contaminant Concentrations--Before and After Cleanup Contaminant Soil (ppm) Water (ppm) Contaminant Soil (ppm)After Water (ppm) Before After Before4 After5 Before Before4 After5 TPH (Gas) 1901 460 <0.05 <.05 Ethylbenzene <0.25 <2,500U— <0.0003 <0.0003 TPH(Diesel) 2,2001 12,0003 <0.05 <.05 Xylene 0.592 <2,5003 <0.00034 <0.0003 TPH(Motor Oil) 2,4002 8,3003 <2.0 <2.0 Benzene <0.251 <2,5003 <0.0003 <0.0003 Toluene 1<0.251 1<2,5003 1<0.0003 1<0.0003 1 MTBE NA NA Comments: 1Sample from B2 at 25'collected on 5110195. 2Sample collected from B1 at 25' on 5/10/95. 3Sample collected from B4 at 15' on July 9, 1996. 4Groundwater sample collected from MW1 on 7/10/96. 5Groundwater sample collected from MW1 on 3/12197. The concentrations after are higher despite the excavation attempt in part because the sampling was more focussed in an effort to characterize the remaining contamination. The contamination appeared to have attenuated at depths of 23 feet. IV. Closure Does completed corrective action protect existing beneficial uses per the Regional Board Basin Plan? Yes Does completed corrective action protect potential beneficial uses per the Regional Board Basin Plan?Yes Does corrective action protect public health for current land use? Yes Site management requirements: None Should corrective action be reviewed if land use changes? No Monitoring/Vapor wells: 1 Number Decommissioned: 1 Number retained: List enforcement actions taken: Notice of Reimbursement sent 8/31/94 List enforcement actions rescinded: None V. Local Agency Representative Data Name: Donna Heran Title: Director of Environmental Health Signature: Date: VI. Central Valley Regional Water Quality Control Board (RB) Notification Date Submitted to RB: 6/16/97 Response Date: 7/8/97 RB Staff: J. Brathovde Response: Concurrence-No Further Action Required Title: Assoc Eng Geologist VII. Additional Comments, Data, etc. Registered Geologist William Millar#6175 with Cape Environmental stated that the clay barrier that is present between 30 and 35 feet with its low transmissivity may limited the vertical migration of petroleum hydrocarbons into existing groundwater. He estimated that there was two areas of remaining soil contamination, approximately 5.78 cubic yards under the building comprising 2.12 gallons of TEPH-diesel and 2.15 gallons of TEPH-motor oil and 2.67 cubic yards under the concrete electrical vault comprising 2.3 gallons of TEPH-diesel, 2.42 gallons of TEPH-motor oil and 0.08 gallons of total volatile hydrocarbons. This document and the related CASE CLOSURE LETTER, Shall be retained by the lead agency as part of the official site file. Case Closure Summary Page 2 of 2