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Geafo ica(7eclnics Inc. y Well Installation Report Page 4 City of Escalon Project No. 750.2 �••y January 30,2001 2.2 Monitoring Well Installation 2.2.1 Groundwater Monitoring Wells To investigate the lateral extent of gasoline-range petroleum hydrocarbons in the groundwater at this site, GTI installed two water table groundwater monitoring wells (MW- 4 & MW-5). The boring, MW-4, was drilled north of the building, doowngradient of the former tanks. The boring for MW-5 was drilled north of MW-1 to prove ed definition in tH_aT To investigate the vertical extent of gasoline-range petroleum hydrocarbons in the groundwater at the site, GTI installed one, deep, discretely screened, monitoring well to a depth of 89-feet bgs. The boring, (MW-101) was installed east of MW-1 in the former tank pit. See Figure 2, Site Map for locations of the wells. The monitoring wells were constructed using 2-inch diameter PVC casing with flush r,. threads. The table below shows the construction details. The filter pack was surged during placement to insure maximum filter pack density. Well No. Dia./TD Screen lot San Pack Trans. Seat Grout Seal MWS.-. - - N4W_-7_0 $37 . _ . 86-5-99 T7 . . Pre-pack 8Y589' - 0-82.5" A surface seal was achieved by pumping a neat cement grout via a tremie tube (augmented with <4% bentonite) from the top of the Transition Seal to the surface. Weighted bentonite �' pellets (Pel-Plug) were used for the transition seals in MW-4 because there was a significant amount of water left in the borehole from trying to control the heaving sands. The same pellets were used for the transition seal in MW-101 because the transition seal was installed �., below the water table. Note: These pellets do contain ethanol and it has been observed to show up in laboratory testing. However, they are currently the best technology for installing transition seals below the water table. +- 3.0 RESULTS OF INVESTIGATION The analytical results and field observations are discussed below. Tabular summaries of all analytical data are included in Appendix A, and the boring logs are included in Appendix B. A site map with monitoring well locations is included as Figure 2. 3.1 Analytical Results Soil Sample Analysis In summary, none of the soil samples collected during this latest round of drilling showed �. �. the presence of contamination. Table 1 in Appendix A is a full summary of all soil analytical data collected at the site.