ARCHIVED REPORTS_WELL DESTRUCTION REPORT

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More detailed descriptions of each well destruction method are presented below and summarized on Tables 1 through 5. ' Destruction by Drilling Out 2- and 4-Inch-Diameter PVC Wells ' A total of 15 wells were destroyed by drilling out the casing and grout/sand-filled annulus to the total depth of each well using a hollow-stem auger (HSA) drilling rig (Photo 1). Drilling rods were placed inside the well casings to ensure the augers stayed centered on the wells with the exception of wells ' VEW-2 (A and B) through VEW-5 (A and B) which were destroyed using a self-centering "stinger" bit. The augers used to drill out each well were the same size as were used when the wells were installed (8- and 12-inch-diameter). These wells were constructed of 2-or 4-inch-diameter PVC casing ' and ranged in depth from 26 to 91 feet. The sealing material consisted of neat Portland cement grout (grout) introduced via tremie pipe from the bottom of the boring to a depth of approximately 3 feet. The remaining 3 feet of boring was backfilled with either grout, concrete, or native soil. The top ' approximate 6 inches of each boring was backfilled with concrete that was dyed black (when necessary)to match the surrounding asphalt. Destruction by Pressure Grouting and Installing a `Mushroom Cap' on 2 and ' 4-Inch-Diameter PVC Wells A total of 40 wells were destroyed using pressure-grouting techniques and either a Vacmaster 4000 air ' vacuum excavation system (air knife) or a skid-steer equipped with a 24-inch-diameter solid-stem auger. These wells were constructed of 2- or 4-inch-diameter PVC casing and ranged in depth from 26.5 to 102.5 feet. Each of the pressure-grouted wells was filled with grout via tremie pipe to the top ' of casing. A minimum of 25 pounds per square inch(psi)of pressure was then applied to the wells and additional grout added as necessary until the grout level remained stable and at the top of the well casing for five minutes. Following pressure-grouting, the well box and concrete surrounding the well ' was removed and a hole at least one foot larger in diameter than the original borehole was excavated using the air-knife (Photo 2) or skid-steer (Photo 3) to a depth of approximately 3 feet (Photo 4). The well casing was then cut off 6 inches above the bottom of the excavation and grout was used to fill ' the well and excavation forming a one-foot-thick"mushroom cap". Once the sealing materials had set, the excavation was backfilled with native soil and capped at the surface with either additional native soil or concrete dyed black(when necessary)to match the surrounding ground surface. Well MW-3, originally slated to be completely overdrilled, was instead destroyed via pressure grout as described above due to a nearby decorative stone wall that prevented Gregg's ability to set up and safely operate a HSA drilling rig atop the well. Well AS-15, also originally slated to be completely overdrilled, was instead destroyed via pressure grout upon discovering an underground utility in the immediate vicinity of the well (Photo 5). AS-15 was destroyed as described above with the exception ' that the well was excavated to a depth of 5 feet. Wells MW-25S and MW-25D were destroyed as described above with the exception that 8-inch-diameter augers were used to drill out the top 3 feet of the wells. Each of these modifications was approved by the SJCEHD prior to destroying the wells. ' Destruction by Overdrilling Nested 2- and 3-Inch-Diameter PVC Wells A total of 16 nested wells were destroyed by overdrilling the casing and annulus to the total depth of each ' well using a HSA drilling rig equipped 15-inch-diameter augers (Photo 6). The larger diameter augers were used to ensure that both nested wells were destroyed simultaneously. Drilling rods were placed inside the deeper 3-inch-diameter well casing to ensure the augers stayed centered on the wells to the ' total depth of 60 feet. Grout was introduced via tremie pipe from the bottom of the boring to a depth of ' Project No.59482-06-02 -3 - March 30,2012