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I 4 1 2 Extraction Well Construction The well was constructed within the hollow stem augers using 6-inch diameter flush-threaded, schedule 40, 0 020-inch slotted PVC well screen and blank casing The well was screened between 4 and 19-feet bgs t o allow for vapor extraction as well as pumping the entire unconfined water bearing zone The well casing was lowered through the augers and #2/ 12 Ifilter pack sand was placed in the annular space between the well casing and the borehole from the bottom of the boring to 1-foot above t h e screened interval Prior to placing the sanitary seal, the well was developed using surge block agitation and evacuation with a bailer Once the sandpack was settled and there was a significant reduction in the I amount of fine sediment in the purged water, 05-feet. of bentonite pellets were placed on top of the sand pack The bentonite was hydrated with water prior to placing the cement sanitary seal Cement mixed with 3 to 5 ' percent bentonite powder by volume was used to fill the annular space between the bentonite layer and the surface to prevent surface water from infiltrating into the well The well head is protected with a locking well plug beneath an at-grade, traffic-rated well box 4-2 install an Air STging Well to Conduct an Air Snarging Test On August 15, 2000, Gregg Drilling of Martinez, California constructed air ' sparge well AS-1 at the site (Figure 4) The purpose of this well was to provide the air sparging well required to conduct an air sparging test at the site 4 2 1 Air Sparge Well Drilling d Sampling g an The boring for the air sparge well was drilled using a Mobile B-61 drill rig equipped with 8-inch diameter hollow-stem augers The drilling was ' directed by ASE senior geologist Robert Kitay, R G Undisturbed soil samples were collected continuously as drilling ' progressed for lithologic and hydrogeologic description and for possible chemical analysis The samples were collected by driving a split-barrel ' sampler lined with 2-inch diameter brass tubes using repeated blows from a 140-pound hammer dropped 30-inches Selective soil samples were immediately cut, trimmed, sealed with Teflon tape, plastic end caps a n d duct tape, labeled, sealed in plastic bags and stored on ice for transport to Kiff Analytical, LLC of Davis, California (ELAP #2236) under chain of custody Soil from the remaining tubes were described by the site geologist using the Unified Soil Classification System and were screened Frank's One Stop Interim Remediation System Workplan — September 2000 -S-