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Fracture Enhanced Soil Vapor Extraction:
GeoSierra provides complete Design/Build services for soil and groundwater
remediation including site investigation, treatability studies, design
documents, agency approval, and installation. Iron PRBs at depths beyond
the reach of conventional construction methods are GeoSierra’s particular
specialty for large-scale groundwater remediation projects. |
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Each PRB design activity requires additional
data beyond conventional site characterization; namely, column reactivity
data and iron permeability design data. These data are generated from
laboratory tests conducted from site groundwater and soils. Laboratory
column tests quantify the degradation reaction rates and pathways (daughter
products) of the particular contaminant specie in the presence of iron
filings. Tests also address additional issues such as potential precipitation
and clogging of the reactive barrier. The design methodology for each
PRB incorporates a probabilistic fate and transport model for VOC natural
attenuation downgradient of the PRB. Probabilistic distributions for the
design input parameters (formation hydraulic conductivity, groundwater
flow gradient, VOC concentrations, VOC degradation half lives, iron PRB
porosity and iron PRB effective thickness) are developed, resulting in
computed probabilistic distributions for PRB effluent VOC concentrations.
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Project List
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Iron PRBs are installed by GeoSierra's trenchless
construction technology. Conventionally drilled wells are spaced at an
average of 15 ft along the desired azmiuth for the PRB alignment. Specialized
frac casings are then grouted into the boreholes. A controlled vertical
fracture is then initiated at the required azimuth orientation and depth
in each well. The iron filings are blended and injected with the vertical
fracture pathway in the form of a highly viscous gel to form a coalesced
PRB wall. Real time quality assurance monitoring of the injections validates
the PRB geometry and iron-loading densities are to design specifications. |
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