HR: 14:55h
AN: H43J-06    [Abstracts]
TI: Synthetic and field based electrical tomography of a permeable reactive barrier: implications for monitoring barrier performance
AU: * Slater, L D
EM: lslater@andromeda.rutgers.edu
AF: Rutgers University, Earth @ Environmental Sciences, 101 Warren St., Newark, NJ 07102 United States
AU: Binley, A
EM: a.binley@lancaster.ac.uk
AF: Department of Environmental Science, Lancaster University, Lancaster, LA1 4YQ United Kingdom
AU: Wu, Y
EM: yuxinwu@pegasus.rutgers.edu
AF: Rutgers University, Earth @ Environmental Sciences, 101 Warren St., Newark, NJ 07102 United States
AB: We performed a study of the sensitivity of electrical imaging to geochemical alteration of a zerovalent iron permeable reactive barrier (PRB) over time. Complex resistivity measurements on laboratory cores from an operational PRB defined the electrical properties of both unreacted and geochemically altered (reacted) iron as well as the growth rate of the reacted front on the up-gradient edge of the barrier. Laboratory results were used to generate models of the electrical structure of the PRB at 0, 15 and 30 years of operation. Synthetic cross-borehole resistivity and induced polarization data were generated and perturbed with errors representative of noise at the site. In order to generate reliable images of the engineered structure, a complex resistivity inversion was employed with a 'disconnect' in the regularization between the part of the finite element mesh (FEM) representing the internal structure of the barrier and the remainder of the FEM mesh. Synthetic results show that, although the internal structure of inverted images at 15 and 30 years does not accurately reflect the width of the reacted front modeled along the up-gradient edge of the barrier, perturbations to the internal structure of the imaged PRB are diagnostic of the growth of the reacted front. Cross-borehole electrical data obtained at the field site over a 15 month period demonstrate that the complex resistivity algorithm can reliably resolve the PRB target. Both resistivity and induced polarization reciprocal errors are low and the induced polarization data highly repeatable over this period. Changes in the electrical properties of the PRB over time were small, but consistent with growth of a reacted front based on the synthetic study.
DE: 0925 Magnetic and electrical methods (5109)
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: Fall Meeting 2005