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v S ECOR 7-Eleven Store#14117 Work Plan for Additional Site Assessment July 27, 2004 Page 5 In boring CPT-1, soil samples will be collected at approximately 60, 70, and 80 feet bgs from the CPT boring. The soil samples will be collected by driving a closed piston-type sampler into the soil. The sampler tip is retracted approximately 12 inches into a locked position, then pushed downward into soil to collect the sample in 6-inch long by 1.25-inch diameter sample rings. All soil samples collected will be sealed with Teflon® sheets and plastic caps, labeled and placed on ice in an insulated container for delivery to Kiff Analytical located in Davis, California. Soil samples will be analyzed for BTEX, TPHg, and MtBE using EPA Method 8260B. Groundwater samples collected form the CPT borings will be analyzed for BTEX, TPHg, and fuel oxygenates using EPA Method 8260B. The borings advanced for the CPT and collection of soil and groundwater samples will be grouted through the drive rods from total depth to grade with neat cement. Monitoring Wells SECOR will supervise the drilling and installation of two offsite groundwater monitor wells (MW-9 and MW-10) at the locations shown on Figure 2. The wells will be drilled to a depth of approximately 20 feet bgs using a truck-mounted drilling rig equipped with 8-inch- diameter hollow-stem augers. Soil samples will be collected from the monitoring wells at 5- foot intervals using a split spoon sampler lined with 2-inch diameter by 6-inch-long brass sample tubes. Three soil samples per boring will retained and analyzed for TPHg, BTEX, and MtBE using EPA Method 8260B (Table 4). The monitor wells will be completed with 2-inch diameter Schedule 40 poly-vinyl chloride (PVC) casing and screened from 5 to 20 feet bgs with 0.020-inch slotted well screen (Table 3). The monitor wells will have a sand filter pack placed within the annulus of the well from the bottom of the boring to approximately one foot above the top of the well screen. The annulus of each well will be sealed with one foot of bentonite on top of the sand and capped with a Portland cement/bentonite grout to the surface. The wells will be secured at grade with an 8-inch-diameter traffic-rated street box. Well Development, Surveying, and Sampling Following installation, the monitoring wells will be developed by surging and bailing using a surge block and bailer to remove fine-grained sediments from each well and sand pack. Periodic measurements of pH, conductivity and temperature will be made during development to establish baseline values for groundwater. Approximately 10 well volumes will be removed from each well during development. All water generated during the development activities will be stored in Department of Transportation (DOT) approved 55- gallon drums pending disposal. Following installation, the new wells will be professionally surveyed to establish horizontal position in relation to pertinent site features and elevation with respect to mean sea level. File:7-11114117 WP for additional assessment(July 04).doc SECOR International Incorporated