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' 0 0 yeofogicalTeckwsW Page 6 Feasibility Study&Investigation Work Plan Cardoza(Main St) Project No 662 2 lie Apnl 19,2004 ' groundwater extraction starts the water table drawdown will leave the screen dry and then vapor extraction will be applied to the fine grained sediments beneath the former ' excavation The top of the screened section at 22 feet bgs leaves enough buffer distance so that the vapor extraction does not immediately short circuit straight up into the excavation fill ' 3.2 Extraction Well Development After the well sealing materials have set (>24 hours) the new well will be developed (using mechanical surging and pumping methods) until a clear stream of water is obtained All ' development and purge water will be containerized in 55 gallon DOT approved containers and stored on site until their disposition can be arranged ' 4.0 DUAL PHASE EXTRACTION TEST/FEASIBILITY STUDY Soil vapor extraction and groundwater extraction are two proven technologies for the ' remediation of gasoline impacted sites Dual phase extraction involves the use of both technologies simultaneously from one well - extracting groundwater induces a cone of depression that exposes more impacted soil to vapor extraction For the purpose of this ' pilot test, GTT proposes to utilize a mobile treatment unit for a period of one week Extracted vapors will be treated with a thermal oxidizer and groundwater will be hauled off site for disposal 4.1 Dual Phase Extraction System The general process for dual phase extraction is as follows ' ■ Extract vapors and water using a liquid ring vacuum pump ■ Separate the influent vapors and water in a portable vacuum tank ■ The contaminated vapor is then oxidized in a thermal oxidizer ' ■ The captured contaminated groundwater is transferred to a tanker truck trailer via a high vacuum pump The tank trailer will be emptied at regulator intervals by a licensed hauler for transportation to a waste disposal facility ' = Collect data for actual vacuum flow and contaminant concentrations and temperature ■ Delineate the area of influence from the applied vacuum and groundwater draw down through use of observation wells ' Note Three bids will be requested from dual phase equipment contractors in accordance with UST Cleanup Fund (USTCFP) requirements ' 4.2 Dual Phase Extraction Test GTT proposes conducting a 5-day pilot test utilizing existing well EW-1 and proposed ' extraction well EW-2 To optimize the pilot testing process, we propose to perform two separate tests using the ' dual phase equipment The tests will include 1 Vapor Extraction Test - measuring vacuum influence at surrounding monitoring wells to determine the effectiveness of soil vapor extraction for vadose zone 1