HR: 0830h
AN: H31B-0471    [PDF]
TI: Electrical Resistance Tomography to Monitor Mitigation of Metal-Toxic Acid-Leachates Ruby Gulch Waste Rock Repository Gilt Edge Mine Superfund Site, South Dakota USA
AU: * Versteeg, R
EM: VERSRJ@INEL.GOV
AF: INEEL, MS2025, Idaho Falls, ID. 83415
AU: Heath, G
EM: HEATGL@INEL.GOV
AF: INEEL, MS2025, Idaho Falls, ID. 83415
AU: Richardson, A
EM: RICHAN@INEL.GOV
AF: University of Washington, INEEL MS 2025, Idaho Falls, Id. 83415
AU: Paul, D
EM: dpaul@do.usbr.gov
AF: Bureau of Reclamation, P.O. Box 25007 Denver Federal Center, Denver, Co. 80225-0007
AU: Wangerud, K
EM: wangerud.ken@epa.gov
AF: USEPA Region VIII, Superfund Remedial Program Office of Ecosystems Protection and Remediation USEPA Region VIII, Suite 500 999 18th St.,303-312-6703 wangerud.ken@epa.gov, Denver, Co. 80282-2466
AB: At a cyanide heap-leach open-pit mine, 15-million cubic yards of acid-generating sulfides were dumped at the head of a steep-walled mountain valley, with 30 inches/year precipitation generating 60- gallons/minute ARD leachate. Remediation has reshaped the dump to a 70-acre, 3.5:1-sloped geometry, installed drainage benches and runoff diversions, and capped the repository and lined diversions with a polyethylene geomembrane and cover system. Monitoring was needed to evaluate (a) long-term geomembrane integrity, (b) diversion liner integrity and long-term effectiveness, (c) ARD geochemistry, kinetics and pore-gas dynamics within the repository mass, and (d) groundwater interactions. Observation wells were paired with a 600-electrode resistivity survey system. Using near-surface and down-hole electrodes and automated data collection and post-processing, periodic two- and three-dimensional resistivity images are developed to reflect current and changed-conditions in moisture, temperature, geochemical components, and flow-direction analysis. Examination of total resistivity values and time variances between images allows direct observation of liner and cap integrity with precise identification and location of leaks; likewise, if runoff migrates from degraded diversion ditches into the repository zone, there is an accompanying and noticeable change in resistivity values. Used in combination with monitoring wells containing borehole resistivity electrodes (calibrated with direct sampling of dump water/moisture, temperature and pore-gas composition), the resistivity arrays allow at-depth imaging of geochemical conditions within the repository mass. The information provides early indications of progress or deficiencies in de-watering and ARD- mitigation that is the remedy intent. If emerging technologies present opportunities for secondary treatment, deep resistivity images may assist in developing application methods and evaluating the effectiveness of any reagents introduced into the repository mass to further effect changes in oxidation/reduction reactions.
DE: 1719 Hydrology
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting