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Stantec Further Assessment Work Plan Stockton Charter Way Commingled Plume February 15, 2011 other pertinent geologic information will be recorded on soil boring logs. Down-hole drilling equipment will be decontaminated with high pressure steam following the completion of each soil boring. Down-hole sampling equipment will be decontaminated between samples using an Alconox detergent solution and a tap water rinse. Selected soil samples will be submitted for chemical analyses and will be based on visual observations, soil type, and VOC measurements. At least two soil samples will be analyzed from each boring based on highest PID and directly above the water table. Additional samples will be collected and analyzed as warranted. The samples will be placed on ice in an insulated cooler until relinquished, under documented chain-of-custody control, to a certified analytical laboratory. Select soil samples will be analyzed for gasoline range organics (GRO) using Environmental Protection Agency (EPA) Method 8015B(M) and benzene, toluene, ethylbenzene, total xylenes (collectively BTEX), methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), di-isopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), ethanol, 1,2-dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) using EPA Method 82608. Additional soil samples in the permeable layer (within the screen interval) will be collected and analyzed for a hydraulic conductivity package for the saturated zone, which includes native- state permeability to water (hydraulic conductivity), grain density, total porosity, air-filled porosity, and total pore fluid saturation (reported as water only) by American Petroleum Institute Recommended Practice 40, dry bulk density by ASTM D2937, moisture content by ASTM D2216, grain size (sieve analysis) by ASTM D422, and TOC and FOC by Walkley-Black. At the terminal depth of each well boring, one groundwater monitoring well will be installed within the annulus of the auger. The following table summarizes the anticipated well construction details; however, these details may be modified in the field based upon the actual soil stratigraphy encountered. A sand filter pack will be placed in the annular space surrounding the entire screened interval, and will extend approximately two foot above the top of the screened interval. A bentonite annular seal will be placed and extend approximately two ft above the filter pack and hydrated. The remainder of the annular space will be filled with cement and/or grout from the top of the bentonite seal to within 12 inches of the surface. The wells will be secured with a locking well cap and completed with a watertight traffic-rated well box installed at grade. Table 4.1: Well construction details Boring Casing Slot Screen Filter Bentonite Cement Well ID Size Interval Pack Seal Seal Depth p Interval Interval Interval (ft bgs) ( " ) Type ( " ) ( " ) (ft bgs) (ft bgs) (ft bgs) (ft bgs) SMW-24B 55 10 PVC 4 0.010 40 - 55 38 - 55 36 - 38 0 - 36 SMW-25B 55 10 PVC 4 0.010 40 - 55 38 - 55 36 - 38 0 - 36 SMW-26B 60 8 PVC 2 0.010 45 - 60 43 - 60 41 - 43 0 - 41 SLMW-10B 60 10 PVC 4 0.010 45 - 60 43 - 60 41 - 43 0 - 41 SMW-25C 85 10 PVC 4 0.010 65 - 85 63 - 85 61 - 63 0 - 61 Stockton Charter Way Commingled Plume Further Assessment Work Plan.doc 9