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<br /> URS
<br /> Mr Harlin Knoll Page 3
<br /> San Joaquin County Environmental Health Department
<br /> December 22, 2005
<br /> rOn November 30, 2005, through December 2, 2005, the task of concrete surface completions was
<br /> performed The vault lids were removed, sand was used to backfill the well vaults to approximately
<br /> 4 inches from ground surface, and fast-set concrete, reinforced with rebar, was used to complete the
<br /> i surfaces
<br /> On December 7, 2005, National Concrete Cutting Co , of Stockton, California, cut 2-foot by 2-foot
<br /> squares into the concrete sidewalk around monitoring well locations ATR-9, ATR-10, and ATR-12
<br /> These locations were then hand cleared for utilities to 5 feet bgs by water-knife (on December 7 and
<br /> December 8, 2005) completely encircling the well to the diameter of the concrete cut A piece of 4-foot
<br /> by 4-foot, 1-inch thick plywood was placed on top of the well location with delineators and caution tape
<br /> for safety The driller was able to pull the entire casing string from well locations ATR-9 and ATR-12
<br /> prior to drilling out the seal materials with 8-inch HSAs and a 9-inch bit to 27 feet bgs The borings
<br /> were then grouted through the augers with neat cement grout containing <5% bentonite powder, the
<br /> augers pulled, additional grout added to near ground surface, and a dry bag of grout was used to create a
<br /> surface whereas concrete could be poured for a temporary surface in the sidewalk
<br /> Well location ATR-10 was pressure grouted with neat cement grout containing c5% bentonite powder,
<br /> and pneumatic pressure was applied at the top of casing for filter pack infiltration, however, due to the
<br /> amount of surface material removed during utility clearance activities, the pressure was lost as evident
<br /> by bubbles at the base of the excavation The casing was cut down to approximately 4 5 feet bgs,
<br /> backfilled with additional neat cement grout containing <5% bentonite powder to near ground surface,
<br /> and a dry bag of grout was used to create a surface whereas concrete could be poured for a temporary
<br />�J surface in the sidewalk
<br /> On December 14, 2005, National Concrete Cutting Co , of Stockton, California, removed the full
<br /> concrete squares of the sidewalk at the former locations of ATR-9, ATR-10, and ATR-12, per the
<br /> requirements of the City of Tracy encroachment permit, and replaced the sidewalk squares with new
<br /> concrete to match the existing sidewalk
<br /> Waste Disposal
<br /> Drill cuttings, wastewater, and well vault box waste generated during well destruction activities were
<br /> placed in labeled 55-gallon Department of Transportation (DOT)-approved steel drums and stored on
<br /> site A composite soil sample was collected from the soil cuttings and submitted to the Sequoia
<br /> Analytical Laboratory in Morgan Hill, California, for analysis of gasoline range organics (GRO),
<br /> benzene, toluene, ethylbenzene, total xylenes (BTEX), methyl tert-butyl ether(MtBE), tert-butyl alcohol
<br /> (TBA), ethyl tert-butyl ether (EtBE), di-isopropyl ether (DIPE), tert-amyl methyl ether (TAME), 1,2-
<br /> r, dichoioroethane(1,2-DCA), 1,2-dibromoethane(EDB), and ethanol by EPA Method 8260B (preparation
<br />' K 1WprocessUS BP ARCO\020931Well Destr12093 Well Destruction Report draft doc
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