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Work Plan for Subsurface Investigation March 25 1999 The Southland Corporation Store No 14117 Stockton California Page 2 ' SOIL SAMPLING AND ANALYSIS ' Four sod borings will be Installed on site to a depth of 25 feet below ground surface (BGS) using a hollow-stem auger drill rig using 8 Inch outside diameter (OD) augers (soil boring depth will be Increased If groundwater is not encountered above 25 feet BGS) During the drilling, soil samples will be collected at five foot intervals ' from surface to maximum borehole depth and logged using the Unified Soil Classification System by an IT Corporation field geologist, working under the supervision of a California registered geologist Soil at each depth interval will be evaluated on site for relative hydrocarbon content using a field Instrument Samples �C ? ' collected for laboratory analysis will be sealed with plastic caps over Teflon film, taped labeled, placed on ice and sent to a state certified laboratory under chain of custody These will be analyzed for benzene, toluene, ethylbenzene, total xylenes (BTEX), MTBE, and total petroleum hydrocarbons as gasoline (TPH-g) following EPA method 8020/8015(modified) MTBE will be confirmed using EPA method 8260 All sampling equipment will be cleaned between sampling Intervals using detergent and rinsed with deionized water Boreholes will be back filled to grade with bentonite ' WELL INSTALLATION, MONITORING AND SAMPLING N A groundwater monitoring well will be constructed in each boring of 2-:rich diameter Schedule 40 poly-vinyl chloride (PVC) casing with flush threads and 0 020-inch-slot well screen The well screen for each monitoring well will be installed from approximately 10 to 25 feet BGS with groundwater expected at approximately 15 feet BGS A sand filter pack will be placed around the well screen to a maximum height of 1 foot above the top of the screen The well will be sealed with 2 feet of hydrated bentonite, followed by a neat-cement grout to grade The wellhead will be protected at the surface by a locking, expandable cap and traffic-rated street box ' (with watertight bolted lid) set in concrete These wells will be used to characterize and delineate the lateral extent of dissolved petroleum hydrocarbons ' Following Installation, eacn monitoring well will be developed by hand bailing to remove fine-grained sediments from the well and filter pack Water from the development process will be temporarily stored on site in DOT-approved 55-gallon drums The top of casing of each well will be professionally surveyed relative to a mean sea level datum At least 48 hours after development, static liquid levels will be measured In all monitoring wells Liquid levels will be ' monitored using interface probe The survey data will be used along with the depth-to-water measurements to calculate groundwater elevations and generate a potentiometric surface map