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Fourth Quarter 1998 Monitoring and Sampling Report and Work Plan for Additional Subsurface Investigation 5 The Southland Cor ration Store#19976, 1399 North Main Street Manteca CA Janna 29 1399 detector(FID/PlD) will be used to determine relative hydrocarbon concentrations from field samples The ' borings wnll continue until two consecutive five foot samples indicate possible non-detectable hydrocarbon concentrations or as deep as field conditions permit The sampling ng will drive a 1 5-inch-diameter by 2- foot-long stainless steel barrel lined with 1-inch-diameter by 6-inch-long brass sample tubes at each location ' Sod samples will be collected at 5-foot intervals for soil characterization beginning at 5 feet BGS All sampling equipment will be cleaned pnor to sampling the sod at each interval Each soil sample will be ' screened for hydrocarbon vapors using a FID/PID Soils encountered during drilling will be logged using the Unified Soil Classification System by a IT Corporation field geologist, working under the supervision of a California registered geologist ' All soil generated through drilling will be placed in Department of Transportation (DOT)-approved 55-gallon drums pending characterization and disposal Water generated by steam cleaning will be temporarily stored on site in DOT-approved 55-gallon drums pending characterization and disposal WELL CONSTRUCTIONIDEVELOPMENTIGAUGING/SAMPLING ' A groundwater monitoring well will be constructed in two of the three borings (MW-4 and MW-5) of 2-inch diameter Schedule 40 poly-vinyl-chloride (PVC) casing with flush threads and 0 020-inch-slot well screen The well screen for monitoring well MW-4 will be installed from approximately 45 to 50 feet BGS A dual- nested well will be constructed in monitoring well MW-5 The shallower well will be screened from 10 to 30 feet below ground surface (BGS), and the deeper screened interval will be from 45 to 50 feet BGS The wells may be installed shallower/deeper depending on hydrocarbon concentrations encountered A sand filter pack will be placed around the well screen to a maximum height of 2 feet above the top of the screen The well annulus will be sealed with approximately 2 feet of bentonite pellets saturated in place on top of the sand pack, and neat-cement grout to approximately 10 inches BGS The wellheads will be protected at the surface by locking,water-tight well caps and traffic-rated street boxes (with watertight bolted lids) set in concrete These wells will be used to characterize and delineate the extent of dissolved petroleum ' hydrocarbons Following Installation, each monitoring well will be developed by using a surge block and hand bailing to ' remove fine-grained sediments from the well and filter pack Water from the development process will be containerized and 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, liquid levels in all monitoring wells will be monitored to measure static liquid levels Liquid levels will be monitored using an ORS Environmental Equipment INTERFACE PROBE T" Well Monitoring System, which consists of a dual optical sensor and electncal conductivity probe that ' distinguishes between water and petroleum products The survey data will be used along with the depth-to- water measurements to calculate water elevation in the monitoring wells, and estimate local groundwater flow direction and gradient ' Following monitoring, 4 well casing volumes of water will be removed from each well prior to sampling of groundwater A log will be maintained that includes measurements of pH,temperature, and conductivity of purged water Once measurements have stabilized, groundwater samples will be collected from each well IT CORPORATION