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Contingency Work Plan For Excavation of Soil @ Chevron Station #9-3232 January 21 1999 characterization . Should the backfill material be sand or soil it will be stockpiled separately onsite and the appropriate samples collected and analyzed for characterization . Depending on sample results Chevron may elect to re-use the material onsite as backfill. If necessary, the sand or soil may be aerated onsite and then re-used as backfill material . Should the soil be aerated onsite, the appropriate permits will be obtained from the San Joaquin Unified Air Pollution Control District (SJUAPCD). Concurrence will be obtained from SJCPHS prior to re-using any sand or soil as backfill onsite. In the event the sand or soil backfill material is not re-used onsite, Chevron will arrange for proper transportation to a licensed landfill for disposal . Task 3. Soil Borings Upon receiving the analytical results from the compliance soil sampling and the excavations (if necessary), GR proposes to drill soil borings to delineate the lateral and vertical extent of onsite . impacted soil. An addendum to this work plan will be prepared depicting the boring locations with a permit application and appropriate fee. We anticipate that one boring will be drilled near the source of impact to approximately 70 feet bsg (historical low depth to groundwater) to delineate the vertical extent of impacted soil. j Additional onsite borings will be drilled to approximately 40 feet bsg to delineate the lateral j extent of soil impact as necessary. Drilling will be performed by Bay Area Exploration, Inc. (C57 #522125). A GR geologist will monitor the drilling activities and prepare a log of each boring. Soil samples for description and possible chemical analysis will be obtained from each boring at five-foot intervals, as a minimum . Sample handling procedures are described in Appendix A. Although the actual number of samples submitted for chemical analysis will depend on site conditions and field screening data, we anticipate a minimum of three soil samples collected from above groundwater in each boring will be submitted for chemical analysis as described below. Two saturated samples will also be collected from the boring drilled below groundwater. Borings will be drilled with 8-inch-diameter hollow-stem augers and will be backfilled to ground surface with neat cement containing approximately 5 % bentonite powder upon completion of drilling. Neat cement will be placed using atremie pipe. Soil from each sampled interval will be screened in the field for the presence of volatile organic compounds using a photoionization detector (PID). These data will be collected for reconnaissance purposes only, and will not be used as verification of the presence or absence of petroleum hydrocarbons . Screening data will be recorded on the boring logs. Drill cuttings will be stored at the site pending receipt of chemical analytical data for disposal. The drill cuttings will be stockpiled on and covered with plastic sheeting. Soil samples from the drill cuttings will be collected for disposal characterization as described below. Steam cleaning rinsate wastewater will be transported bylmegrated WastestreamManagement (IWM) to McKittrick Waste Management in McKittrick, California. CH93232.WP2 3 346463 .02