Hazen, J M
Institute of Arctic and Alpine Research,
University of Colorado at Boulder
Campus Box 450, Boulder, CO 80309-0450
Stover, B K
Division of Minerals and Geology,
Department of Natural Resources
1313 Sherman Street, Room 215,
Denver, CO 80203
Wireman, M
Environmental Protection Agency - Region VIII,
999 18th Street,
Denver, CO 80203
Williams, M W
Institute of Arctic and Alpine Research,
University of Colorado at Boulder
Campus Box 450, Boulder, CO 80309-0450
The legacy of acid mine drainage continues to affect stream water quality throughout the western United
States. Traditional remediation, involving treatment of water draining from portals, is not feasable for the thousands of
abandoned mines in the West as it is difficult and expensive. Here we present preliminary results from an attempt to control
acid mine drainage within the source area of the mine. Source waters and flowpaths within the underground Mary Murphy Mine
were characterized using an innovative mixture of water isotopes, solute concentrations, and hydrometric techniques.
The abandoned Mary Murphy Mine is located in the Colorado Rocky Mountains and consists of an intruded pyritic vein running
through quartz monzonite porphyry country rock. Its raises span an elevation range of 10,000 ft to 12,500 ft., and 14 levels
of workings total approximately 15 miles. Elevated levels of zinc are experienced in the main adit each melt season,
affecting the water quality in nearby Chalk Creek.
Hydrometric measurements show that while discharge from a central level adit increased by a factor of 9 during peak melt
(from 0.29 m$^{3}$/sec to 2.48 m$^{3}$/sec), Zn concentrations increased by a factor of 5 (from 5.8 mg/L to 28.3 mg/L).
However, mixing model analysis using water isotopes shows that less than 15\% of this increase was from new water. Within
the mine, almost 100\% of the high flow Zn loading was caused by a single source characterized by extremely high Zn
concentrations (235.7 mg/L) and low pH (3.6). Somewhat suprisingly, mixing models using water isotopes show that new water
composed nearly 50\% of flow in this high Zn source during the melt season. Diversion of this high Zn source within the mine
resulted in a decrease in Zn concentrations at the portal to 2.5 mg/L, lower than base flow levels.
These results suggest that in some mines remediation efforts can be concentrated on specific areas within the mine itself,
either through treatment, diversion, or capping of waste rock, greatly reducing costs.