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George F. Schuler, Inc. 1705 N. Broadway, Stockton, California August 17, 1993 Phase I Remedial Report Page: 5 Immediately prior to sampling, water levels and well depth measurements were taken in all wells at the site. Each was evacuated using a stainless steel bladder pump, which does not introduce air into the water column. The pH, temperature, and electrical conductivity of the water were monitored as the well was evacuated. These parameters are noted on a field log (Appendix E). Instruments calibrated to known standards were used to monitor these parameters. At least 5 well volumes were evacuated from each well, and more, if necessary, until the above parameters were stabilized. The samples were carefully poured from a Teflon bailer into clean glass vials with Teflon-lined screw caps and half gallon plastic containers provided by the laboratory. Care was taken to ensure that no air space existed in the vials by inverting to check for bubbles and re-sampling if necessary. The samples were analyzed or extracted within 14 days according to their EPA methods. Water samples collected for analysis were analyzed by EPA method 602 for BTX&E compounds, and method 3550 for gasoline range hydrocarbons. All analyses were conducted by Geo-Monitor, Inc., a state certified laboratory. 3.6 Vapor Well Construction All materials used in vapor well construction were thoroughly cleaned prior to introduction into the boring. A two inch (2") diameter well casing (PVC) with end cap and factory perforations for placement in the contaminated zone was placed in the boring. The screen and filter pack sizes are as noted in the boring logs (Appendix D). The casing and end caps were threaded; no PVC cement was used. The filter pack extends two feet (2) above the well casing perforations. A bentonite seal three feet (3') thick was placed in the annular space above the filter pack followed by a cement grout to the surface. I 4.0 Soil Conditions The subsurface geology of the George Schuler, Inc. site in Stockton, California is characterized by interbedded inorganic micaceous clayey silts and silty clays with numerous sand lenses. This is typical of the valley fill deposits in the region (Figures 4 and 5). Analysis of soil samples show xylene and gasoline contamination in B-2 at 36 feet and at the remedial excavation pit floor near MW-1 at 30 feet. Additional samples from B-1 / MW-1 show contaminates to 50 feet (Figures 6 and 7). 5.0 Groundwater Conditions The water table was approximately 70 feet below ground level as the borings were being drilled. Subsequent water sampling of MW-1 recorded a water level at 70.45 feet (Appendix E). The analysis of the July 7, 1993 sampling event show benzene and E- benzene contamination of 1.0 and 19 pg/kg, respectively (Table I / Appendix B and C).