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Publications > Mwakanyamale and others, 2010.

Use of the time-domain induced polarization method to map the spatial distribution and depth of the Hanford-Ringold contact in the Hanford 300 Area–Results from 2D complex resistivity inversion

K.E. Mwakanyamale (kisam@pegasus.rutgers.edu)
Earth and Environmental Science, Rutgers University, Newark, NJ, USA

L.D. Slate (lslater@andromeda.rutgers.edu)
Earth and Environmental Science, Rutgers University, Newark, NJ, USA

D. Ntarlagiannis (dimntar@andromeda.rutgers.edu)
Earth and Environmental Science, Rutgers University, Newark, NJ, USA

A. Binley (a.binley@lancaster.ac.uk)
Lancaster Environment Centre,, Lancaster University, Lancaster, United Kingdom

F.D. Day-Lewis (daylewis@usgs.gov)
Office of Groundwater, Branch of Geophysics, U.S. Geological Survey, Storrs, CT, USA

A.L. Ward (andy.ward@pnl.gov)
Pacific Northwest National Laboratory, Richland, WA, USA

J. Heenan (jheenan@pegasus.rutgers.edu)
Earth and Environmental Science, Rutgers University, Newark, NJ, USA

E. Placencia (edmundo.placencia@tkk.fi)
Earth and Environmental Science, Rutgers University, Newark, NJ, USA

Abstract

The transport of Uranium [U(VI)] contaminated groundwater to the Columbia River in the Hanford 300 Area, Washington, is influenced by the depth and location of the Hanford-Ringold contact. Ringold Formation sediments have distinct physicochemical properties compared to the Hanford Formation sediments through which contaminated groundwater flows. Better definition of the spatial variability and the depth to the Hanford-Ringold contact across the site is crucial to improve understanding of contaminant transport between the aquifer and the Columbia River. In particular, there is only very limited information on the spatial variability of the contact between the river and the Hanford Integrated Field Research Challenge (IFRC) site where controlled experiments on U (VI) transport are being conducted. Data collected with land-based electrical resistivity, induced polarization (IP), and ground penetrating radar have only been of limited use for mapping this critical hydrological contact. However, recent waterborne IP imaging along the river corridor proved successful in characterizing the distribution of the Hanford-Ringold contact beneath the river due to the strong contrast in polarization between the Hanford and Ringold units. Therefore, a high-resolution IP survey was conducted along five 2D lines using static cables on the land, parallel to the shore; full resistivity and IP reciprocal datasets were collected. Here, linear IP error models that describe the increase in error with increase in measured chargeability are constructed to provide appropriate data weights in the inversion, and a 2D complex resistivity inversion of the resistivity and time domain IP data is performed to image the spatial distribution of electrical conductivity and normalized chargeability (proportional to the imaginary conductivity representing polarization) between the IFRC and the river. The Hanford-Ringold contact is clearly identified from the sharp contrast between the weakly polarizable Hanford Formation and the highly polarizable Ringold Formation. The results suggest that, given appropriate care to quantify and model measurement errors, IP is a very effective tool in mapping the key lithologic units at this site.

Final copy as submitted to the American Geophysical Union for publication as: Mwakanyamale, K., Slater, L., Ntarlagiannis, D., Binley, A., Day-Lewis, F.D., Ward, Andy, Heenan, J., and Placencia, E., 2010, Use of the time-domain induced polarization method to map the spatial distribution and depth of the Hanford-Ringold contact in the Hanford 300 Area–Results from 2D complex resistivity inversion [abs.], in 2010 Fall Meeting, San Francisco, California, 13-17 December 2010, proceedings: American Geophysical Union, Washington, D.C., abstract H23C-1199.