SITE INFORMATION AND CORRESPONDENCE

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Mr. Thomas I Bois March 13, 1997 Page 2 the sewers laterals, and the sewer lines that serviced the Building. Additionally, the PCE contamination may have migrated into the groundwater and caused groundwater contamination beneath the Site. Following are the rationales for DTSC's findings. 1. Attachment B-3 of the Report shows that the Building that housed the two former dry cleaners had a dimension of 50' (width) X 78' (length), and occupied an area of 3900 square feet. Based on this dimension, DTSC concludes that only one sample (VP27)was collected within the Building area(Attachment A). Furthermore, Figure 3 in Appendix C of the Report indicates that a branch sewer line may have been located to the west of the Building (Attachment A). Therefore,wastewater containing PCE may have also been discharged into this sewer line. Soil gas samples should be collected in this area to determine if wastewater containing PCE was discharged into this sewer line and if the discharge has caused any soil contamination. Again, only one sample was collected in the area west of the building. The sample appears to have been collected at a location upgradient from the branch line. Due to the lack of adequate soil gas samples being collected beneath the Building, and in areas west of the Building, DTSC believes that soil gas data collected by Montgomery Watson may not be representative of the soil contamination caused by the former dry cleaners. 2. Areal distribution of the PCE detected at the Site indicates that PCE was released from the Building that housed the two former dry cleaners operations, the sewer lines, and the sewer laterals that serviced the Building. To determine levels of the soil contamination at the Site,DTSC categorized the levels of PCE detected into three ranges: high (5 to 16 ug/l, medium (1.1 to 4.9 ug/1), and low (less than or equal to 1.0 ug/1). DTSC found that high levels of PCE (VP9, VP10,VPI 1, and VP12) were found in areas adjacent to the sewer laterals (sewer discharge point). Medium levels of PCE were found beneath the Building, along the sewer lines that serviced the Building, and in areas immediately downgradient of the sewer laterals that serviced the Building. Low levels of PCE were detected in areas that were the greatest distance from the Building,the sewer laterals, and the sewer lines that serviced the Building. The detection of high and medium levels of PCE in areas adjacent to the Building, the sewer laterals, and along the sewer lines serviced the Building, and the presence of low levels of PCE in areas that were the greatest distance from the Building indicate that PCE was released from operations of the two former dry