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d 1 FED c r c E6 i TEC-CAC- I HC PAGE 00 0 a Site History/Previous Work The subl,ect property has been under investigation since 1987. Both soil and groundwater contamination investigations have been performed at the site and were summarized in a report to the Region]_ Water Quality Control Board (RWQCB) dated July 21, 1988, and prepared by Groundwater- Technology, Inc. (GTI ) . This report served as the basis for a Soil Remediation Workplan dated February 6, 1-989, which was approved for implementation by the RWQCB on February 17, 1983 . This plan called for the installation of soil venting (vapor extraction) system. The July 21, 1.988 report indicated the presence of groundwater contamination. In January of 1989, four additional monitoring wells were installed at the site. To date a summary report on these well installations has not been prepared. The locations and boring logs of these wells are contained in Appendix A. 2.0 Groundwater. Conditions All seven wells at the site were resurveyed and monitored for water level and product thickness using an interface probe (Table - 1 ) . Only one well contained free product (MW5 ) and one well was dry (MW3) . Using the elevation data a gradient map was generated using the Kriging method ( Figure 2 ) . Figure 2 shows a easterly gradient of approximately 0.002 ft/ft on 9 . 68 ft/utile. This is relatively low gradient and is consistent with the data collected by GTI in February of 1989 (Appendix A) . The gradient direction is also consistent with published data for 1987 and 1989 for this area ,SJCFC & WC Dist) . rhe easterly-southeasterly flow is controlled by a groundwater depression apparently caused by pumping near the center of Township 2 North, Range 6 East. 3.0 Sample Collection/Analysis Samples were collected frow 5 of the 7 wells. Well 3 was dry and _ well 5 was omitted since it contained free product. Samples were collected, preserved and transported in accordance with WaterWork standard protocol (Appendix 8) . Sample analysis was performed by Sequoia Analytical for organic lead ( Luft Manual Method), total low-medium bailing point hydrocarbons (EPA, 8015) and benzene, toluene, ethyl benzene and xylenes (EPA 8020) . Organic lead was not detected in any of the 5 samples (D.L. of 0.05 ppb) . Above action Level concentrations of benzene were present in two wells (MW1 and MW4) . A summtary of all water sampling done at the site to date is shown on Table 2. Although there are variations from round to round the following general interpretations can be made: 1 y _-