SITE INFORMATION AND CORRESPONDENCE_2001-CURRENT

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4-inch-diameter PVC casing and range in depth from 26 to 91 feet. The sealing material will consist of neat cement grout (grout) which will be introduced through the annulus of the augers with a tremie pipe, if required by the SJCEHD grout inspector, and will be added from the total depth of each boring to a depth of approximately 5 feet. The remaining 5 feet of annulus will be backfilled with either grout, sand, or native soil obtained from the drill outs. The top approximately 6 inches of each boring will be backfilled with concrete and dyed black at the surface (as needed) to blend in with the surrounding asphalt. Overdrilling Nested 2-Inch-Diameter and 3-Inch Diameter PVC Wells Using a Hollow Stem Auger Drilling Rig Nested wells VEW-6A/B, VEW-7A/B, VEW-8A/B, VEW-9A/B, VEW-l0A/B, VEW-11A/B, VEW-12A/B, and VEW-13A/B will be destroyed by overdrilling the casing and annulus to the total depth of each well using a hollow-stem auger drilling rig equipped 15-inch-diameter augers with a self- centering "stinger" bit. The larger diameter augers are necessary to ensure that each of the nested wells are destroyed simultaneously. If the self-centering "stinger bit' should malfunction or be deemed unsuitable, appropriately sized drilling rods will be placed down the annulus of the 3-inch-diameter well and augered around to ensure the augers stay centered on the wells. These wells were installed using 10- inch-diameter augers, are constructed of 2- and 3-inch-diameter PVC casing and range in depth from 31 to 60 feet. Grout will be introduced through the annulus of the augers with a tremie pipe, if required by the SJCEHD grout inspector, from the total depth of each boring to a depth of approximately 5 feet. The remaining 5 feet of annulus will be backfilled with either grout, sand, or native soil obtained from the overdrilling. The top approximately 6 inches of each boring will be backfilled with concrete and dyed black at the surface(as needed)to blend in with the surrounding asphalt. Overdrilling 1-Inch-Diameter PVC Wells Using Sonic and Hollow-Stem Auger Drilling Rigs Wells AS-14, AS-15, AS-17, AS18, AS-20 and AS-21 will be destroyed by overdrilling the casing and annulus to the total depth of each well using a combination of a sonic drilling rig and a hollow-stem auger drilling rig equipped 8-inch-diameter augers. Prior to the advancement of any rods or augers, the wells will be filled with cement with a tremie pipe. The wells will then be pressurized at approximately 20 to 40 pounds per square inch (psi) until the grout level stabilizes. This process will be repeated until the grout level stabilizes and each well is completely filled. A sonic drilling rig will then advance 2- or 4-inch-diameter rods down the center of the wells to the total depth of each well. Eight-inch-diameter hollow-stem augers will then be advanced around the sonic drilling rods ensuring that the augers stay centered on the well. These wells were installed using 8-inch-diameter augers, are constructed of 1-inch-diameter PVC casing, and range in depth between 71.5 and 110 feet. The sealing material will consist of neat cement. The cement will be introduced through the annulus of the augers with a tremie pipe, if required by the SJCEHD grout inspector, from the total depth of each boring to a depth of approximately 5 feet. The remaining 5 feet of annulus will be backfilled with either grout, sand, or native soil obtained from the overdrilling. The top approximately 6 inches of each boring will be backfilled with concrete and dyed black at the surface(as needed)to blend in with the surrounding asphalt. Project No.59482-06-02 -2- January 5,2012