HR: 0830h
AN: H41D-1032    [PDF]
TI: Characterization of Acid Mine Drainage Sources Using Stable and Radiogenic Isotopes, Chalk Creek, Colorado
AU: * Cordalis, D
EM: cordalis@colorado.edu
AF: Institute of Arctic and Alpine Research, 1560 30th St, Boulder, CO 80309 United States
AU: * Cordalis, D
EM: cordalis@colorado.edu
AF: University of Colorado at Boulder Geography Department, 260 UCB, Boulder, CO 80309 United States
AU: Michel, R
EM: rlmichel@usgs.gov
AF: USGS, 345 Middlefield RD, Menlo Park, CA 94025 United States
AU: Williams, M
EM: markw@colorado.edu
AF: Institute of Arctic and Alpine Research, 1560 30th St, Boulder, CO 80309 United States
AU: Williams, M
EM: markw@colorado.edu
AF: University of Colorado at Boulder Geography Department, 260 UCB, Boulder, CO 80309 United States
AU: Wireman, M
EM: mike.wireman@epamail.epa.gov
AF: US EPA Region VIII, 999 18th St Suite 300, Denver, CO 80202 United States
AB: Acid mine drainage (AMD) affects many streams throughout the western United States. Understanding flow dynamics and sources within a fractured rock setting is necessary in outlining a potential remediation strategy for AMD. Radiogenic and stable isotopes of water were used in the Mary Murphy Mine, Chalk Creek, Colorado, in order to characterize flowpaths and sourcewaters. By delineating the sources of the mine water, groundwater, and event water, we may be able to target remediation techniques for individual contamination sources. Moreover, results from this research provide insights into groundwater flow systems in mountain environments of the Colorado Rockies. Tritium, a cosmogenic isotope of hydrogen, has a half-life 12.43y and is useful for studying hydrologic processes at the decadal time scale and can be used as an effective tracer when traditional chemical tracers are non-conservative. Hydrometric information showed that discharge from the mine adit exhibited a hydrograph characteristic of snowmelt runoff. However, mixing models using stable water isotopes (D and $^{18}$O) found less than 7% of the mine's peak discharge was from snowmelt, suggesting a regional groundwater dominated system. Mine interior samples fell into two characteristic groupings: either from the extreme north side of the drift which contained most of the zinc contamination, and all other locations. The waters from the north drift, MVN-3 and MVN-4, had lower $^{18}$O values, -17.62 per mil and -17.17 per mil, respectively, than did any of the other locations, suggesting a seasonal snowmelt input. However, the tritium values associated with MVN-3 and MVN-4 suggest at least some mixing, with values of 13.4 TU and 12.5 TU, respectively. Surface water samples from Chalk Creek show average tritium values of 11.1 TU, and $^{18}$O values of -14.87 per mil. Groundwater samples were captured using monitoring wells, and plotted according to the depth of screening. Alluvial wells carried a seasonal signal similar to the surface water as expected; 11.6 TU and -15.15 per mil averages for tritium and $^{18}$O. In contrast, bedrock wells showed a longer residence time and snowmelt recharge. The combination of radiogenic and stable isotopes within and near the Mary Murphy Mine may provide a useful tool for studying interactions between groundwaters and surfacewaters in a fractured rock setting. Remediation techniques can be directed more appropriately, and cost effectively, by the characterization of flowpaths within the mine as well.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2003 Fall Meeting