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3 4 Monitoring Well Installation <br /> To monitor the groundwater underlying the Stockton Scavenger site, a <br /> monitoring network consisting of three new wells is recommended (see <br />' Drawing 3-1) These wells will be located to monitor the groundwater <br /> upgradient of the site, adjacent to the excavation area, and downgradient <br /> of the site As described in detail below, in addition to the standard well <br /> construction specifications, each well will include a conductor casing and <br /> a surface vault The conductor casing is recommended to seal off <br /> secondary infiltration from waters other than that of the first groundwater <br /> The surface vault setup will be designed to allow the piping connections <br /> in the event that groundwater extraction or soil vapor extraction is <br /> necessary <br />' Each boring will be drilled with a standard (8-inch diameter) hollow-stem <br /> continuous flight auger to approximate depths of 45 feet below ground <br /> t surface The hollow stem allows the core sampler to be lowered in the <br /> borehole while the auger is in place to prevent caving Boring logs will be <br /> prepared and submitted using the Unified Soil Classification System <br /> (USCS) for soils and unconsolidated materials All drilling, sampling, and <br /> well installation will be conducted under the direct supervision of a <br /> geologist/hydrogeologist who in turn is supervised by a Certified <br />' • Engineering Geologist The appropriate soil descriptions, stratigraphic <br /> changes, geologic notation, sampling intervals and recoveries, blow counts, <br /> drilling conditions, groundwater levels, and other required transient data <br /> will be recorded on the field logs Drill cuttings will be stockpiled on-site <br /> and combined with previously excavated soil for remediation <br />' Each well will include a secondary conductor casing consisting of a 12 inch <br /> diameter, 10 gauge steel surface casing It is anticipated that the <br /> conductor casing will be installed to an approximate depth of 35 feet The <br />' placement of the conductor casing will require the use of direct circulation <br /> rotary drilling because the 12 inch surface casing cannot be set with <br /> hollow-stem equipment Conductor casing will be pressure grouted in <br />' place and the grout will be allowed to cure for 72___^ho 4 After the grout <br /> is cured, the boring will be advanced using 8-inch hollow-stem augers <br /> through the bottom of the grout and to a depth of approximately 45 feet <br />' All wells will be constructed with four inch casing to facilitate groundwater <br /> sampling All points will be flush-threaded The filter material will be a <br /> clean, washed medium to coarse grained sand (Lapis Luster No 2/12) <br /> The sealant immediately above the filter material will consist of 1/4-inch <br /> diameter, Ca-rich montorillonitc clay bentonite pellets The pellets will <br />' be dropped into the annulus and allowed to settle before the <br /> cement/bentonite grout is emplaced by tremie means The sealant above <br /> the bentonite pellets will consist of a cement/bentonite mixture of one <br />' 3-5 <br />' COMPANY OONEMOIrr1AL TRADE SLCRF7 AND PROPRIETARY INFORMATION OF THE MARK GROUP 1m r, <br />