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'' <br /> V. ar <br /> a <br /> I <br /> a <br /> FEELD METHODS <br /> A schematic diagram of a vapor•extraction well is shown on Plate P-3. The wells will be <br /> constructed of thread jointed, 4-inch•diamater schedule polyvinyl chloride (PVC) casing. <br /> No chemical cements, glues, or salvents will be used in well construction. The screened <br /> portion of the wells will consist of factary-perforated casing with 0.020-inch-wide slots. <br /> The interval between 10 and 25 feet below grade will be screened using slotted casings. <br /> No. 3 sand will be placed in the annular space opposite the screen to approximately i <br /> foot above the top of the slotted casing. A 2-foot bentonite plug will be placed above <br /> the sand pack, and a cement-bentonite slurry will be used to fill the remaining annulus to <br /> the surface. <br /> A triliic-rated cast-aluminum utility box with a PVC apron will be placed over each <br /> wellhead and set in concrete flush with the surrounding concrete pad. The box has a <br /> watertight seal to protect against surface water infiltration and is opened with a special <br /> wrench. The design of the box discourages vandalism and reduces the possibility of <br /> accidental disturbance of the well. <br /> VaRor-UMglion Te <br /> The vapor-extraction test has two objectives: (1) to collect operational data to evaluate <br /> the efficiency and practicality of vapor extraction as a soil remediation alternative and <br /> �. <br /> (2) to sell.;t the most appropriate off-gas treatment alternative, if the c►pera#ionai data <br /> suggest that vapor extraction is recommended. Applied GeoSystems will perform the <br /> vapor-extraction test in accordance with San Joaquin County Air Quality District <br /> guidelines. <br /> A portable vapor-extraction system will be transported to the site and operated as <br /> required to obtain vapor samples and vacuum pressure and flow rate information. <br /> Vapor samples will be collected into sample bags at the inlet and outlet of the vapor <br /> extraction test system and submitted to a State-certified laboratory for analysis of TPH9 <br /> will be followed throughor-t field and laboratory <br /> and BTEX. Chai�rof-Custody protocol <br /> procedures. <br /> a <br /> ,S <br /> y <br /> 4110/1e0F Geosystems <br />