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R AR SupplemenTal Investigation Work Plan BP Oil Site No. 11193 J CAM B R I A Stockton, California February 25, 2000 y S In addition, one.4-inch diameter monitoring-well will be installed near soil boring CB-3 using 10-inch diameter hollow-stem augers (see Figure 2). To assess the vertical extent of hydrocarbons and MTBE at the site,this well will be advanced to the top of the clay unit reported at 43 feet bgs in the Caltrans well, or a maximum depth of 50 feet bgs. Depending on the depth to the clay unit, this well will screen from approximately'35'fo`45'feet'bgs or 35 to 50 feet bgs. Soil Sampling: In general, soil samples will be collected using a modified California split spoon sampler at five foot intervals (see Appendix D). The monitoring well near boring CB-3 will be continuously-sampled to,further evaluate-soil stratigraphy at the site. Field screening of hydrocarbons will include visual or olfactory observations, and/or portable volatile vapor analyzer readings. � I Well Construction and Development: The wells will be constructed of polyvinyl chloride and screened with 0.010-inch machine slot. A filter pack consisting of No. 2/16 sand will be installed to 1 to 2 feet above the top of the well screen, which will be overlain by I to 2 feet of bentonite, and 3 i bentonite-cement grout to the surface (see Appendix D). Traffic-rated vault-boxes will be installed i ( to protect each well. The wells will be developed by surging and purging at least 10 casing volumes of water. The elevations of the well-heads will be surveyed relative to existing site datum. 1 Chemical Analysis: Selected soil samples from each boring will be analyzed fo-rTPHg by modified l: EPA Method 8015, and BTEX-and MTBE by-FPA'Method 8260 at a California-certified laboratory. y If encountered, samples of the clay unit will be analyzed for total organic carbon using the Walkley- Black Method. Soil and Water Diaposal/Recyeling: Soil and water produced during drilling activities will be temporarily stored on site. Following review of analytical results, the soil and water will be transported to an appropriate facility for disposal/recycling. A Caltrans Well Assessment As previously mentioned, a Caltrans irrigation well was identified approximately 315 feet west of j the site. The well is constructed with a conductor casing from surface to 50 feet bgs which seats into the clay unit reported from 43 to 80 feet bgs, and is screened from 214 to 238 feet bgs and from 254 3 to 350 feet bgs (see Appendix B). Il 7