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s r table was so close to the ground surface. The soil gas survey was followed by the drilling and soil sampling of three shallow borings. Later, three monitoring wells were constructed (Figure 3-1). The investigation activities by HIeinfelder characterized the site- specific hydrogeologic setting and partially characterized the occurrence of the release. Results of analyses performed for Kleinfelder are summarized in Table 3-1. The Kleinfeider report is contained in Appendix A. ERM-West was retained by Catellus Development Corporation in 1991 to complete additional investigation activities and to assess the need for remediation. The activities completed by ERM-West consisted of constructing two additional monitoring wells. These wells were located within and hydraulically downgradient of the tank site (Figure 3-1). The results of the soil and water sampling from new and existing wells were reported to the EHD in May 1991 (Appendix B). Additional quarterly ground water sampling of all five wells was reported to the EHD in October, 1991 (Appendices C and D). Laboratory results from ERM-West activities are summarized in Table 3-1. Copies of the laboratory reports are contained in Appendices B, C, and D. ! �nding5 Findings from investigations performed at 1515 West Weber have resulted in the characterization of soil types, as well as the depth to and direction of ground water flow. Laboratory analyses have resulted in the characterization of the nature of the release, including its lateral and vertical occurrence. These findings are discussed below. The information collected during the construction of monitoring wells and soil borings indicate that the site is underlain by clays and sands. Figure 3-2 presents a cross section of the former tank location at 1515 West Weber. Semi-consolidated tely eytsoil feextend elow the -- _- -_------__ - ground-surface-ta a depth-of-app — clays, unconsolidated, fine-to course-grained sands extend to 2-depth---- - ----of at least 30 feet. Depicted on the cross section is an area of fill soils associated with the former tank. Apparently, the petroleum-affected soils around the 3-2