Passive Soil Vapor Extraction - GSI Environmental Inc.

SRNL-STI-2009-00571Rev. 1minimize contaminant transfer to the groundwater. The original MicroBlowerdesign was a 12 V system powered solely by a solar panel. These systems werecapable of extracting contaminant mass only when the sun was shining, andtherefore operated on a periodic basis. In January 2006, 24 V MicroBlowersystems were installed. These systems are designed to operate 24 hours a dayusing a sustainable 24 V power source (a battery bank charged by solar panels).The two enhanced PSVE wells are screened 30 to 40 ft bgs in relativelypermeable soil that underlie the fine-grained sediments where DNAPL wasfound.B.4.2 Results/Performance MetricsPerformance at the MAPSL site following the installation of the 24 V MicroBlower systemis summarized in Table B.4.Concentration Trends:• The periodically-operating 12 V MicroBlower system did not reduce CVOC vaporconcentrations, but as shown in Figure B.4.1, PCE and TCE vapor-phaseconcentrations decreased rapidly and stabilized at a lower level following theswitch to the continuously-operating 24 V system in January 2006.• Soil concentration profiles from sampling events completed in 2003 (prior toMicroBlower installation) and in 2007 (post-installation) are shown in FigureB.4.2. Soil concentrations of both PCE and TCE decreased by an order ofmagnitude in the interval immediately above the screened zone of the extractionwell. This interval consists of fine-grained material, as indicated by the higherCPT (cone penetrometer test) friction ratios measured as part of thecharacterization study. Interestingly, the enhanced PSVE system significantlyreduced contaminant levels in the fine-grained interval despite the fact that it hasthe tendency to trap contaminant mass and DNAPL was present.Concentration, ppmv30020010024 V MicroblowerInstallationPCETCE01/1/04 1/1/05 1/1/06 1/1/07 1/1/08 1/1/09Figure B.4.1: Vapor-Phase Concentration Trends at MAPSL Site during PSVE System Operation(PSVE Well MVE-29 with MicroBlower).B.14 Enhanced Attenuation TechnologiesPassive Soil Vapor Extraction