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\... ..� <br /> ATC Associates Inc. <br /> 1117 Lone Palm Avenue,Suite 201 <br /> Modesto,California 95351 <br /> 209-579-2221 <br /> fax: 209-579-2225 <br /> ASSOCIATES INC . <br /> Installation of Soil Vapor Probes <br /> This task includes mobilization to the site, advancing six soil borings, characterizing soil <br /> cuttings, and completing the borings as temporary soil vapor probes. The soil vapor probes are <br /> planned to be located onsite between the identified source area and nearby structures. Estimated <br /> soil vapor probe locations are shown on Figure 2. <br /> To evaluate the potential for vapor intrusion hazards from subsurface soil and/or groundwater <br /> beneath the site between the source area and nearby structures, the six soil borings will be <br /> advanced to approximately 5 feet bgs. The borings will be advanced using truck mounted <br /> —Strataprobe drilling rig employing narrow diameter, direct push technology. Drilling will be <br /> conducted by a State-licensed C57 drilling company. A field geologist will be present to log soil <br /> samples. Descriptions of soil types encountered and sample collection intervals will be recorded <br /> on oring-logs. Soil samples will be collected at the base of each boring location, field screened — ? <br /> with a Photoionization Detection (PID) meter, and submitted for laboratory analyses. ` <br /> .e'" pe ewi "s P4rA I --Af4 A t44,oA-e - S s',l <br /> Following soil vapor sample collection, the direct push drive rods will be removed and the <br /> borings will be backfilled with neat cement grout to the ground surface. Drill cuttings will be Sg <br /> stored onsite in a 55-gallon drum pending laboratory results. <br /> Sampling Methodology <br /> In an effort to appropriately conduct soil vapor sampling on site, ATC will follow the guidelines <br /> established by the Los Angeles Regional Water Quality Control Board (LA RWQCB) and the <br /> Department of Toxic Substances Control (DTSC) in documents entitled Advisory — Active Soil <br /> Gas Investigations dated January 28, 2003 and Interim Final— Guidance For the Evaluation and <br /> Mitigation of Subsurface Vapor Intrusion to Indoor Air dated December 15, 2004, revised <br /> February 7, 2005. <br /> Temporary Soil Gas Probe Design/Connections <br /> The temporary soil gas probe will be advanced to an approximate depth of five feet _bgs,_Once <br /> the probe has been advanced to the predetermined depth, the drive rod will be pulled back to <br /> expose the slotted screen interval of the soil gas probe. Approximately 10 feet of 1/8-inch outside <br /> diameter Nylaflow® tubing will be attached down hole to the soil gas probe tip creating a <br /> continuous seal associated with the soil gas pathway. The tubing will extend from the top cap of <br /> the screened interval to the ground surface. The tubing will be sealed at the surface using a pinch <br /> clamp and/or a threaded cap. Bentonite chips will be applied around the soil vapor probes and <br /> hydrated prior to collecting any samples. Proposed soil vapor probe construction details are <br /> shown on Figure 3. <br /> S:\Environmental\62605\Reports\2007 November.doc 3 <br />