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GeotoguafTeckmcs Inc Page 3 Soil Groundwater Investigation Report George s Service Project No 425 2 August 5 1997 Details on the geology encountered during the completion of the sampling event as well as the field observations are included in Section 3 2, Geology and Field Observations 2.1.2 Soil Laboratory Analyses Based on field screening observations, one to two soil samples from each shallow borehole and five soils samples from the deep borehole were submitted to Sherwood Laboratories of Hilmar (State Certified Laboratory #1400) for analysis for benzene. toluene, ethylbenzene and xylene (BTEX by EPA method 8020), gasoline range petroleum hydrocarbons (TPH- Gasoline by EPA method 8015(m)), and diesel range petroleum hydrocarbons (Total Extractable Petroleum Hydrocarbons, TEPH, Diesel, Kerosene and Motor Oil by EPA method 3540/8015m) The detection limits for these compounds are listed below A Chain of Custody was completed for all samples collected and tracked to ensure sample integrity ' etection units - aso ine TEPH or Fp-g-/&g) , 2.2 Monitoring Well Ilnstallation To investigate the lateral definition of gasoline and diesel range petroleum hydrocarbons in the groundwater at this site, Geological Technics Inc installed five shallow groundwater monitoring wells from the southwest to the east of the former UST's and one deeper, discretely screened, monitoring well on the edge of the former UST pit (Figure 2, Site Map) Shallow Wells The shallow monitoring wells were constructed using 2 0 inch diameter PVC casing with flush threads The screened intervals extended from one foot above the water table to fourteen feet below the water table Groundwater was encountered at approximately 7 to 8 feet below grade A #3 sand filter pack surrounded and extended one foot above the 0 020 inch screened interval and was topped by a two foot bentonite chip transition seal installed on top of the filter pack and hydrated A surface seal was achieved by pumping a neat cement grout (augmented with <4% bentonite) on top of the transition seal The wells were secured with locking watertight caps encased in flush mounted traffic rated well boxes During the installation of the filter pack on MW-8 it was noted that the filter pack would only nse to eight (8) feet below ground surface in the annular space The driller added a total of eight (8) sacks of sand After consulting with Ms Mary Meays of San Joaquin County and Ray Kablanow of G T I it was decided to add two (2) additional sacks of sand This was done with no rise in the filter pack, to fact, it dropped six (b) inches The augers were pulled from the hole and a cave-in was noted in the side of the borehole starting at 7 5 feet below ground surface After discussion with the land owner it was decided that thts subsurface structure was a vertical drain for part of the sewer septic system that was thought to be located elsewhere The drain is no longer in use but it is still attached to the septic system It was decided to abandon the this borehole and re-dill about 10 feet to the west The well casing was pressure grouted and the casing was cut off approximately 3 feet below ground surface The cave in was plugged with a combination of bentonite chips and dry cement Once this had setup a neat cement grout (<4% bentonite) was pumped into the borehole A concrete cap was added to bring it to grade The name of this borehole was changed to MW- 8A and the new borehole/morutonng well was named MW-8 Due to the proximity of the