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404 WEST FREMONT STREET WKA No. 1628 .09 August 31 , 2001 - Page 10 be used to remove petroleum hydrocarbons and VOCs before discharge into the atmosphere. The filters will consist of two 55-gallon drums filled with 400 pounds of 4 x 6 mesh coal based activated granular carbon pellets. The carbon filters will be equipped with two-inch diameter -J influent and effluent piping, sampling ports, temperature gauges, pressure gauges and a 6-foot high exhaust stack. The filters will also be equipped with diffuser manifolds designed for - uniform vapor flow and maximum exposure to the carbon bed. r-P j � Vapor Extraction Wells lExisting vapor extraction wells VEWl through VEW3 will be used to extract residual VOCs from I" the subsurface soil. Two additional vapor extraction wells will be installed in the vicinity of monitoring wells MW4 and MW5 as part of the remediation process. Two soil borings will be drilled to depths of 12 feet below surface grade using abuck-mounted drill rig equipped with hollow-stem augers. The borings will be converted into vapor extraction wells at the locations shown on Plate 3 to be used as a part of the remediation process for extracting subsurface soil contaminated with petroleum hydrocarbons beneath the site. The vapor extraction wells will be constructed using two two-inch diameter, flush jointed, ("" I Schedule 40 PVC casing; 0.02-inch slotted casing will be used for the screened interval. The j I screened interval will extend from approximately 7 feet bsg to 12 feet bsg. Number 3 Monterey sand will be placed as a filter pack in the well annulus. The filter pack will extend from the bottom of the screened interval to approximately two feet above the top of the screened interval. A minimum two-foot thick bentonite seal will be placed in the well annulus above the filter pack. A grout seal consisting of Portland cement and bentonite slurry will be placed into the well annulus above the bentonite seal. Each well will be completed with a locking well cap and a flush- mounted, traffic-rated well cover (Plate 5). All drilling equipment will be steam cleaned as described above. All soil cuttings generated during drilling will be placed on a stockpile and stored on site. it The vapor extraction wells will be connected to underground piping and stubbed-up and manifold and connected to the vapor extraction unit inside the treatment enclosure. The soil vapor extraction INK L ` aIX-LACE • KUHL �. . . . E= PoSSoaATES INC.