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Workplan for Nunan - O'?7-15/97 1U./ Pale 7 22 Rationale for Proposed Borehole Locations and Laboratory Analyses Former Gasoline UST Point Source I This project includes the drilling four (4) soil borings to a depth of approximately 20 feet bgs around the former gasoline UST and one 30 foot deep borehole to a depth of 30 feet in the center of the former pit. Since low levels of gasoline related contaminants were identified previously, the vertical and lateral extent can be ascertained by this array of boreholes. Three soil samples will be collected and analyzed from each of the 20 foot boreholes and four from the 30 foot borehole.The 16 soil samples will be analyzed for TPHg/BTEX/MTBE by approved EPA methods at a State Certified Laboratory. The soil samples will be collected at the tank backfill/natural soil interface, at significant changes in soil stratigraphy, at vertical L depths where obvious olfactory evidence of hydrocarbon contamination is identified, and at the capillary fringe if groundwater is encountered. Soil samples may be collected in the UST gravel backfill in the 30 foot deep borehole, to be placed at the center of the former gasoline UST pit, if obvious hydrocarbon contamination is identified during borehole logging. Former Waste Oil UST Point Source One 20 foot deep borehole will be drilled through the former waste oil pit.Since waste oil does not migrate very easily through the subsurface, one borehole through the former pit should suffice in determining if soil removal process was complete. Since no chlorinated solvents or PC33s were identified in soil at the former waste oil pit, they will not be tested r. again.The previous gasoline related testing at the former waste oil pit revealed insignificant concentrations of gasoline in soil. The sample collected as "waste oil west"revealed TPHg concentrations that may not even be related to gasoline.The previous results did not yield any benzene which suggests that if gasoline is present at the former waste oil pit, it is very degraded and most likely not related to discharges associated with the former gasoline USTs. Two(2) soil samples will be collected and analyzed for TPH(mo) (motor oil ranged organics). The shallowest of the two samples will be analyzed for CAM metals. ` Former Gasoline Dispenser and Associated Piping Point Source The previous piping soil samples revealed no gasoline constituents in soil and will therefore L not be investigated. Contingency Plan L The former gasoline UST pit will be investigated first during drilling. If high levels of gasoline are identified, then analysis of gasoline constituents in the former waste oil pit borehole will 6' be performer) and appropriate step out boreholes will be drilled. L 6.