Water quality improving in Upper Clark Fork Basin
FRISCO — There are hopeful signs that the ongoing cleanup of abandoned mines around the West will pay off.
The U.S. Geological Survey, reported decreased levels of toxic heavy metals in the streams of Montana’s Upper Clark Fork Basin that have been targeted by remediation efforts.
The USGS and the EPA conducted the study to measure cleanup results. The report analyzes data collected at 22 sites during 1996-2010 from streams in the Upper Clark Fork Basin. The study found that metals tended to enter waterways in larger quantities from areas where historical mining wastes had accumulated. A few of these stream reaches contributed most of the metals that entered into the entire basin.
Some of the metals evaluated, cadmium, copper, lead, and zinc, primarily move through streams attached to sediment.
“Arsenic is different from the heavy metals because it was more widely distributed in the soils and groundwater, and is typically dissolved in the water rather than attached to sediment. So arsenic tends to enter streams more uniformly, rather than in localized areas,” said Steve Sando, USGS hydrologist and lead author of the report.
This difference is important because it shows the complexities involved in remediating the mining impacts. Federal, State, and local agencies, as well as the British Petroleum Company are involved in the massive clean-up efforts in the Basin.
Although evaluating water quality with respect to regulatory standards was not the focus of the study, concentrations of metals and arsenic were compared to U.S. EPA aquatic life criteria and drinking-water standards.
Historically, many of the streams have had concentrations of the contaminants that were higher than the standards. Some sites still have concentrations of some contaminants that exceed standards, but especially in sites with remediation, the water quality is substantially improving.