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Protect No 58100-06-I I B <br /> April 19, 1996 <br /> 32 Vapor Extraction Well Construction <br /> ' Vapor extraction well VW-2 was installed adjacent to the former UST excavation and pump island to <br /> a depth of approximately 21 3 meters(70 feet) bgs The well was constructed using 101 6-mm (four- <br /> inch) diameter Schedule 40 polyvinyl chloride (PVC) casing The lower portion of VW-2 was <br /> constructed using approximately 16 8 meters (55 feet) of 0 50-mm (0 020-inch) slotted screen PVC <br />' casing placed between the depths of approximately 4 6 to 213 meters(15 to 70 feet)bgs <br /> A filter pack consisting of No 3 Monterey sand was placed around the screen from the bottom of the <br /> boring to an elevation of 0 6 meter (2 feet) above the screen zone The well was developed using a <br /> surge block to densify the sand pack prior to placement of the bentonite seal <br />' A 0 6 meter (two foot) thick seal consisting of hydrated bentonite chips was placed above the filter <br /> pack An 304 8-mm (twelve-inch)diameter,traffic-rated security wellhead cover set in a concrete pad <br /> was used to complete construction Well construction details are recorded on the boring/well logs <br /> presented in Appendix B <br /> 3 3 Monitoring Well Construction <br /> Wells MW-9 through MW-12 were located 35 5 to 47 2 meters(110 to 155 feet)from the perimeter of <br /> the former UST excavation and installed to a depth of approximately 24 4 meters (80 feet) bgs The <br /> monitoring wells were constructed using 101 6-mm (four-inch) diameter Schedule 40 polyvinyl <br /> chloride (PVC) casing The lower portion of the wells were constructed using 6 1 meters (20 feet) of <br /> 0 5-mm (0 020-inch) slotted screen PVC casing placed between the approximate depths of 18 3 to <br />' 24 4 meters(60 to 80 feet)bgs <br /> A filter pack consisting of No 3 Monterey sand was placed around the screen from the bottom of the <br />' boring to an elevation of 0 6 meters (2 feet) above the screen zone The monitoring wells were <br /> developed using a surge block to densify the sand pack prior to placement of the bentonite seal <br /> A 0 6 meter(2 foot)thick seal consisting of hydrated bentonite chips was placed above the filter pack <br /> A 304 8-mm (twelve-inch) diameter, traffic-rated security wellhead cover set in a concrete pad was <br /> used to complete construction Well construction details are recorded on the boring/well Iogs <br />' presented in Appendix B <br /> 34 Well Development and Groundwater Sampling <br />' Monitoring wells were developed using a surge block to densify the sand pack prior to placement of <br /> the bentonite seal Pumping to remove sediment and groundwater was accomplished using a 50 8-mm <br /> (two-inch)diameter Grundfos electric submersible pump <br /> 6 <br />