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v Geological Technics Inc. Page 2 C&B Equipment Monitoring Well Installation Work Plan Project No.336.2 June 15,1995 2.0 PROPOSED INVESTIGATION 2.1 Monitoring Well Installation To further investigate the extent of gasoline and diesel range petroleum hydrocarbons in the soil and groundwater environments, Geological Technics Inc. proposes to install three groundwater monitoring wells surrounding the former UST location (Figure 2 Site Map). Based on surface topography (Figure 1 U.S.G.S. Topographic Map) we suspect that the groundwater exhibits a predominately north direction of flow. San Joaquin County Flood Control Maps (1986) indicate a relatively flat groundwater surface approximately 10 feet below grade. The well borings will be drilled using a 8.00 inch outside diameter continuous flight hollow stem auger owned and operated by V&W Drilling (C57# 658786). Soil cuttings will be stockpiled on site within the fenced yard and underlain and covered with plastic. The monitoring wells will be constructed using 2.0 inch diameter PVC casing with flush threads. The screened interval will extend from five feet above the water table to ten feet below the water table. Groundwater is expected to be located between 5 and 10 feet below grade. If a significant clay unit is encountered during the drilling of the well, the well may be seated no greater than 3 ft into that fine grained unit. A #3 sand filter pack will surround and extend two feet above the 0.020" screened interval. A granular bentonite transition seal will be installed and hydrated. A surface seal will be achieved by pumping a neat cement grout (augmented with < 4% bentonite) via a tremie tube. The well will be secured with a locking watertight cap encased in flush mounted traffic rated well box. After the well sealing materials have set (>24 hours) the well will be developed (using mechanical surging and pumping methods) until a clear stream of water is obtained. The well will be purged and groundwater samples collected no sooner than 24 hours after well development. All development and purge water will be containerized in 55 gallon DOT approved containers and stored on site until their disposition can be arranged. The top of casing measuring point for each well will be surveyed into an arbitrary plane by a licensed land surveyor. 2.2 Groundwater Sampling Procedure The groundwater in the new wells will be sampled no sooner than 48 hours after well development. The following is a procedure for the sampling of groundwater from the well: