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Section 5 PROPOSED SITE INVESTIGATION OVERVIEW The proposed site investigation will consist of subsurface soil sampling (Phase 1) and, if necessary, an evaluation of ground water quality and hydraulic gradient (Phase II). Phase I will consist of drilling and sampling at least six exploratory soil borings in the vicinity of the former reboiler unit. If ground water is encountered during the Phase I soil sampling, and there is evidence that product has migrated to the saturated zone, the site investigation will include a ground water assessment (Phase 11). Phase II would consist of installing, developing, and water sampling of at least one monitoring well within the first water bearing zone. Additional ground water monitoring wells will be installed based on conditions encountered during the field activities. Borehole advance and soil sampling procedures for both Phase I and Phase 11 assessments are outlined in Appendix B. PHASE I - SOIL INVESTIGATION The vertical and lateral extent of soils containing elevated levels of petroleum hydrocarbons and glycol will be determined by sampling and analyzing subsurface soil samples taken from the exploratory soil borings. Access permitting, a minimum of six soil borings will be drilled and sampled to characterize subsurface soil conditions in the vicinity of the reboiler and discharge line. Tentative locations of the soil borings are shown in Figure 2. The borings will be advanced to depths just below the water table or where observed or measurable levels of organic vapors (above background levels) are no longer detected using a photovac TIP 1 organic vapor analyzer instrument (TIP 1). Additional soil borings will be drilled and sampled, as necessary, to characterize the lateral and vertical extent of petroleum hydrocarbons in subsurface soils at the station. If the results of the Phase I investigation indicate that hydrocarbon constituents are present in the soils that extend into saturation zone, a ground water monitoring well will be installed and sampled (Phase II). If ground water is encountered during the drilling, soil samples will be obtained for grain size distribution analyses of the aquifer material. This information will be used in the design of the monitoring well(s). Two to four soil samples will be selected for chemical analysis from each soil boring. Samples selected will include: a sample taken near the vadose zone/saturated zone interface; samples with high apparent product residue; and a sample from the bottom of each soil boring. These samples will be submitted to Eureka Laboratories, Inc. (a California certified laboratory)for the following analyses:TPH as gasoline (EPA Method 8015); BTEX (EPA Method 8020); and glycol (GC/FID Method). 462891/42/PPU26 5-1