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Facility and PBR Units Closure Work Plan r. 1848 and 1856 Field Ave., Stockton, California 2.3.3 Potentially Elevated Copper in Concrete One concrete sample,BL 1-05,contained what may be an elevated level of copper,370 mg/kg.This may also be a natural copper level, depending on the source and copper level of the aggregate material used in the concrete. However, based on an evaluation of potential exposure using the procedure detailed in the Preliminary Endangerment Assessment(PEA)Guidance Manual(DTSC, 1994),a copper level of 370 mg/kg in soil results in a Hazard Quotient(HQ)of 0.007 for the adult industrial worker,or risk less than one in one hundred million.Because there is no equation for HQ calculation for concrete in the PEA Manual,the HQ for concrete was calculated assuming exposure to soil.The HQ calculation for soil assumes ingestion of soil and dermal exposure to soil,which are exposure assumptions that overestimate the actual hazard from concrete. Therefore,calculations using PEA guidance for exposure to soil equate to a higher,more conservative hazard than the actual hazard from concrete.Further information about calculating the HQ for copper in concrete is presented in Appendix B. Based on our analysis,the 370 mg/kg of copper detected is well below the cleanup goal of 3,100 mg/kg(see ` Section 4)for copper in concrete,and there is no significant risk. Therefore,Tyco intends to take no further action regarding this potential issue. 3.0 1856 FIELD AVENUE r. 3.1 Use History r The building located at 1856 Field Avenue (also known as "Building 2")mainly was used for dry process equipment,primarily drilling and lamination of printed circuit boards.Office areas,maintenance facilities and storage areas were also located at this address. The machinery located within the drilling room was fed by air compressors located on the eastern side of the building. Dust from drilling was carried by vacuum to a baghouse area on a concrete pad just to the north of the air compressors.Lamination equipment was present in the western half of the building.There was also chemical storage area connected to the southeastern comer of the building. Besides dry manufacturing processes,there were two closed-loop wet processes(deburring and plate scrubbing to remove epoxy),but the wastewater was treated at 1848 Field Avenue.A site plan for 1856 Field Avenue is shown on Figure 3. L:IW0W690991CeneraRRe1d WPFieldAve WPAug03rev2.doc 8 August2003