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stantec September 11, 2009 Page 4 of 6 Reference: Work Plan for Site Closure,Caltrans Shop 10 Maintenance Facility. Stockton,California borings will be logged continuously and soil samples will be screened in the,field for volatiles using a photo- ionization detector(PID). Selected soil samples will be capped, labeled, and placed in a cooler at 4°C for 1.� transport to TestAmerica, Inc. laboratory for analysis. Soil cuttings will be placed in labeled 55-gallon drums and stored onsite, pending analysis results. Soil cuttings will be disposed offsite following local, State, and ' I Federal regulations. i Soil Sample Analysis Soil samples collected from depths similar to those.previously found to contain high levels of contaminants (at 20 ft, 30 ft, and 40 ft bgs)will be analyzed from each boring.. In addition, soil samples found by PID to contain volatiles above background during field screening will also be analyzed. Selected soil samples will be analyzed for TPH-g, TPH-d, benzene,toluene, ethyl benzene and xylenes by EPA Method 8015 (modified) and fuel oxygenate compounds using EPA Method 8260B. Solt Vapor lnyestloatlon Soil vapor samples will be collected to evaluate soil vapor levels near the former UST area at the Site. Vapor sampling will follow the procedures outlined in the January 28, 2003 "Advisory—Active Soil Gas Investigations" published by the Department of Toxic Substances Control avid Los Angeles RWQCS, and F described further below. Stantec will drill and install three soil vapor wells acyacent to the Site building near the former UST location (Figure 2). Soil Vapor Well Installation and Sampling Barings for three temporary soil vapor sampling probes will be advanced using a 3-inch hand auger to a ` a depth of approximately 5.5 bgs. The hand auger will be decontaminated prior to drilling each vapor well. The temporary soil vapor wells will be constructed by filling the borehole for each vapor well with an approximately 3-inch layer of sand and installing '/,-inch-diameter Teflon tubing, attached to a 6-inch-long stainless steel screen. The screen will have perforations to allow the flow of soil vapor into, the tubing and will be located approximately 5 ft bgs in each boring. The annular space surrounding the well screen and tubing will be filled with#2112 sand to approximately 6 inches above the screen (approxi'mate 15-inch sand pack interval), followed by hydrated granular bentonite to surface, w Vapor wells will be allowed to sit for 48-hours to allow subsurface vapors to equilibrate. Following equilibration,the vapor well head and sampling equipment will be placed be"neath a sealed shroud and filled with helium as a field test for leaks during vapor sampling. The vapor wells 11 be purged of approximately five well volumes and vapor samples will be collected. Soil vapor samples for volatile organic compounds 1� (VOCs) analysis will be collected in 6 liter Summa canisters equipped with flow regulators, supplied by the lab. Sample flow rates set by the summa canister flow regulator will''be betiiveen 100 to 200 milliliters per minute. Start and stop times, and sampling rate will be recorded in field notes and the chain-of-custody . (COC). Soil vapor samples will also be collected in a diesel sampling tube from each location. Diesel samples will be collected through-a calibrated air sampling pump and a field blank will also be collected-and accompany diesel samples to the lab. Pump times and flow rates will be recorded and used to calculate sample volumes. Soil vapor samples will be sent overnight under COC to TestAmerica; Inc. laboratory for VOC analysis by E Method TO-15 (low level standard), diesel analysis by Method NIOSH 1550;` and helium (for the leak check). One duplicate sample will be collected and a trip blank will be included and shipped with the VOC samples. i The duplicate sample and trip blank will be analyzed for VOCs by Method TOI A 5 (low level standard). In ! addition, at least one soil sample will be collected at the same depth as the vapor samples are to be collected from each of the temporary soil vapor probe borings and analyzed for physical parameters. The list for ' l:1Prolects\CALTRAN51Shop 10120091Closuretloaure work plan fnl.doe