Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Evaluation of permeable reactive barrier (PRB) integrity using electrical imaging methods.
AU - Slater, Lee
AU - Binley, Andrew M.
PY - 2003/5
Y1 - 2003/5
N2 - The permeable reactive barrier (PRB) is a promising in-situ technology for treatment of hydrocarbon-contaminated groundwater. A PRB is typically composed of granular iron which degrades chlorinated organics into potentially nontoxic dehalogenated organic compounds and inorganic chloride. Geophysical methods may assist assessment of in-situ barrier integrity and evaluation of long-term barrier performance. The highly conductive granular iron makes the PRB an excellent target for conductivity imaging methods. In addition, electrochemical storage of charge at the iron–solution interface generates an impedance that decreases with frequency. The PRB is thus a potential induced polarization (IP) target. Surface and cross-borehole electrical imaging (conductivity and IP) was conducted at a PRB installed at the U.S. Department of Energy's Kansas City plant. Poor signal strength (25% of measurements exceeding 8% reciprocal error) and insensitivity at depth, which results from current channeling in the highly conductive iron, limited surface imaging. Crosshole 2D and 3D electrical measurements were highly effective at defining an accurate, approximately 0.3-m resolution, cross-sectional image of the barrier in-situ. Both the conductivity and IP images reveal the barrier geometry. Crosshole images obtained for seven panels along the barrier suggest variability in iron emplacement along the installation. On five panels the PRB structure is imaged as a conductive feature exceeding 1 S/m. However, on two panels the conductivity in the assumed vicinity of the PRB is less than 1 S/m. The images also suggest variability in the integrity of the contact between the PRB and bedrock. This noninvasive, in-situ evaluation of barrier geometry using conductivity/IP has broad implications for the long-term monitoring of PRB performance as a method of hydrocarbon removal.
AB - The permeable reactive barrier (PRB) is a promising in-situ technology for treatment of hydrocarbon-contaminated groundwater. A PRB is typically composed of granular iron which degrades chlorinated organics into potentially nontoxic dehalogenated organic compounds and inorganic chloride. Geophysical methods may assist assessment of in-situ barrier integrity and evaluation of long-term barrier performance. The highly conductive granular iron makes the PRB an excellent target for conductivity imaging methods. In addition, electrochemical storage of charge at the iron–solution interface generates an impedance that decreases with frequency. The PRB is thus a potential induced polarization (IP) target. Surface and cross-borehole electrical imaging (conductivity and IP) was conducted at a PRB installed at the U.S. Department of Energy's Kansas City plant. Poor signal strength (25% of measurements exceeding 8% reciprocal error) and insensitivity at depth, which results from current channeling in the highly conductive iron, limited surface imaging. Crosshole 2D and 3D electrical measurements were highly effective at defining an accurate, approximately 0.3-m resolution, cross-sectional image of the barrier in-situ. Both the conductivity and IP images reveal the barrier geometry. Crosshole images obtained for seven panels along the barrier suggest variability in iron emplacement along the installation. On five panels the PRB structure is imaged as a conductive feature exceeding 1 S/m. However, on two panels the conductivity in the assumed vicinity of the PRB is less than 1 S/m. The images also suggest variability in the integrity of the contact between the PRB and bedrock. This noninvasive, in-situ evaluation of barrier geometry using conductivity/IP has broad implications for the long-term monitoring of PRB performance as a method of hydrocarbon removal.
KW - geophysical techniques
KW - electrical conductivity
KW - polarisation
KW - imaging
KW - groundwater
KW - permeability
KW - contaminated site remediation
U2 - 10.1190/1.1581043
DO - 10.1190/1.1581043
M3 - Journal article
VL - 68
SP - 911
EP - 921
JO - Geophysics
JF - Geophysics
SN - 0016-8033
IS - 3
ER -