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• Mr. Steve Sasson Project 22794-100.001 August 10, 1998 Page 3 Subsurface Investigations During subsurface assessment activities conducted between 1987 and 1995, a total of 36 exploratory borings were drilled Soil sample analytical results are shown on Table 1. HydroPuncho groundwater samples were collected from 15 of the borings. Six borings were converted to groundwater monitoring wells. Three groundwater monitoring wells (MW-1, MW-2, and MW-3) were decommissioned in 1991. Groundwater sample analytical results are shown on Table 2. Eight groundwater monitoring events were conducted in between 1992 and 1995. TPHD concentrations in samples collected from wells MW-4, MW-5, and MW-6 ranged from 150 to 1,200 micrograms per titer (µg/L) BTEX constituents were not detected. Analysis for polynuclear aromatic hydrocarbons (PNAs) was conducted as part of the March 1995 monitoring event. The sample collected from MW-6 contained phenanthrene (0.95 gg/L), anthracene (7 7 gg/L), and pyrene (0.038 µg/L). MW-6 was installed adjacent to one of the two sanitary sewer mains located beneath . Navy Drive. Coliform concentrations were consistently reported above drinking water concentrations in monitoring well MW-6. This indicates that the sewer mains are affecting groundwater quality in the site vicinity, and the detected dissolved petroleum hydrocarbon concentrations In HydroPunch and monitoring well groundwater samples located along Navy Drive likely contain dissolved petroleum hydrocarbons that may have been released from the sewer mains. Chemilsk prepared a Tier 2 Risk-Based Corrective Action (RBCA) Report for the site in February 1996. Chen=k evaluated the volatile and senuvolatile organic chemicals in site soils. The RBCA results concluded the concentrations are below levels that pose unacceptable risk to workers and to groundwater quality. Site-specific threshold levels (SSTLs) calculated for BTEX and PNA constituents are not exceeded by the maximum detected concentrations for the respective parameters. A case closure summary report prepared by Safeway, Inc., m March 1996 recommended closure based on the absence of risks to human health and general poor water quality in the site vicinity, The case closure hearing requested additional activities be conducted at the site. Included in the request were estimation of petroleum hydrocarbon mass in soil and groundwater and evaluating remedial alternatives. As requested by the SJCPHS, copies of certified analytical reports for soil samples that were not provided in Safeway's March 1996 Closure Report are included in Appendix A �1 SACN'NP72\27M7941000 1CS-Wpmsmer8 sEmcon Rev 0.8110/98