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Geclagual recluiics lnc. Page 3 <br /> ' Additional Site Characterization and <br /> 3rd Quarter Groundwater Monitoring <br /> Project No.989.2 <br /> October 31,2002 <br /> ' Drilling (C57# 720904). The monitoring well was constructed using 2.0-inch diameter <br /> schedule 40 PVC casing with flush threads. The details of construction are listed in the <br /> ' table below. <br /> WeR No. Dia. creen S1of Sand Fac rans. Searout Seal <br /> sand - -sur ace <br /> Groundwater was first encountered at approximately 10 feet below grade. A#12 sand filter <br /> pack surrounded and extended one and a half feet above the 0.010 inch screened interval <br /> and was topped by a two foot bentonite pellet transition seal installed on top of the filter <br /> pack. A surface seal was achieved by pumping a neat cement grout (augmented with <4% <br /> bentonite). The well was surged using a clean surge block to achieve maximum filter pack <br /> density prior to installing the bentonite transition seal. The well was secured with a locking <br /> watertight cap encased in a flush mounted traffic rated well box. The boring log (Appendix <br /> B) contains the details of construction. <br /> Shallow Monitoring Wells <br /> On July 30, 2002, Geological Technics Inc. supervised the installation of two shallow <br /> groundwater-monitoring wells (MW-7 and MW-9). The additional shallow monitoring <br /> ' wells were installed to further define the lateral migration of the plume. The locations of <br /> the new monitoring wells are included on the site map (Figure 2). <br /> Monitoring well permits were secured from the San Joaquin County Public Health <br /> Services/Environmental Health Department (SJC PHS/EHD). An encroachment permit was <br /> required by and obtained from the City of Stockton Public Works Department for the <br /> installation of MW-8 on a city sidewalk. The local regulatory agency was notified 48 hours <br /> prior to commencing work. The subsurface was cleared of underground utilities by <br /> notifying Underground Service Alert. <br /> ' On July 30, 2002, two of the shallow monitoring wells (MW-7 and MW-9) were installed to <br /> a depth of 22 feet bgs using an 8-inch outside diameter (o.d.), hollow stem auger drill rig <br /> owned and operated by V&W Drilling (C57# 720904). The monitoring wells were <br /> constructed using 2.0-inch diameter schedule 40 PVC casing with flush threads. <br /> On August 12, 2002, MW-8 was installed to a depth of 22 feet bgs using an 8-inch outside <br /> diameter (o.d.), hollow stem auger drill rig owned and operated by V&W Drilling (C57# <br /> ' 720904). The mast of the drill rig could not be raised due to trees covering the borehole <br /> area. MW-8 was drilled with the mast down, which did not allow soil sample collection and <br /> interpretation. The monitoring well was constructed using 2.0-inch diameter schedule 40 <br /> 1 PVC casing with flush threads. <br /> The details of construction are listed in the table below. <br /> 1Well No. ia. --Screen Slot Sand PackTrans. Seal Grout Seal <br /> - sand -sur ace <br /> - - #3 sand _ -sur ace <br /> sand - -sur ace <br /> Groundwater was first encountered at approximately 17' bgs in MW-7, 15' bgs in MW-8 <br /> and 9' bgs in MW-9. A #3 sand filter pack surrounded and extended two feet above the <br />