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ppm), and total xylenes (0.007 ppm). Analytical results of soil samples collected from the borings are summarized in Table 2. The distribution of soil sample analytical results is illustrated on Figure p Y� g 3. Copies of certified analytical reports for each soil sample submitted to the laboratory during this C.: phase of work is contained in Appendix D. 4.2 Groundwater A groundwater sample from each newly constructed and existing monitor well was collected on July 19, 1996, with the exception of MW-10. MW-10 was sampled on August 1, 1996, as a result of remobilizing with a limited access rig. Results of the groundwater analyses collected from monitor wells MW-2,MW-7, and MW-10 were i- all reported below the method detection limits for each analyzed constituent. TPHg concentrations in groundwater samples ranged from below the laboratory method detection limit [(<50 parts per billion(ppb)] in monitor wells MW-2,MW-7,MW-8,MW-9, and MW-10,to 13,600 ppb in MW-1. Benzene concentrations ranged from below the laboratory method detection limit (<0.5 ppb) in monitor wells MW-2,MW-7, and MW-10 to 1,130 ppb in MW-1. The distribution of groundwater sample analytical results is presented on Figure 4 and summarized in Table 3. Copies of the certified laboratory analytical reports and chain-of-custody forms are included in Appendix D. S.0 CONCL USIONS . I Based on the data collected during this investigation, the following conclusions are presented: '� ■ The highest levels of petroleum hydrocarbons in groundwater samples collected from the newly installed monitor wells was detected in the sample collected from off-site monitor well MW-6 (1,370 ppb TPHg and 143 ppb benzene). This well is located -' on the north side of Highway 88. In general, chemical analytical results indicate concentrations are the highest in the vicinity of on-site monitor wells MW-1 and => MW-3, and off-site monitor well MW-6. ■ The distribution and extent of dissolved hydrocarbons in groundwater remains undefined northwest of the site. 6.0 FORTHCOMING ACTIVITIES During the fourth quarter of 1996, SECOR will conduct additional well monitoring, purging, and sampling activities. The results of these activities will be summarized in a quarterly monitoring report to be submitted to you in January 1997. Based on the results of this investigation, it is the opinion of SECOR and Time Oil Company that future efforts at the site should be directed toward remediation of hydrocarbon impacted soils. With the approval of the PHSIEHD, an interim soil remediation work plan will be prepared for regulatory consideration. -- - lab No-]0710-001-01C SECOR 5 LOCKEFORD.INV Ociober 9,1996