Over the last two decades, ongoing remediation efforts throughout the Upper Clark Fork Basin have allowed the river to gradually rebound from its polluted past. The going has been slow and expensive—estimates put the cost of the next major phase at $100 million—but advocates for a cleaner Clark Fork have reason to believe it will pay off.
Last week, the U.S. Geological Survey released the results of a 15-year study of water quality from Silver Bow Creek all the way to Missoula. The findings show that arsenic and heavy metal pollution in the Clark Fork has dropped dramatically near Butte and Anaconda, where remediation efforts have primarily focused thus far. At one testing location on Silver Bow Creek, levels of zinc fell from 1,100 micrograms per liter in 1996 to 42 micrograms per liter in 2010.
"The contaminate concentrations in the upper reaches have come down pretty substantially," says USGS hydrologist Steve Sando, the chief author of the report.
The data itself is nothing new; the USGS releases results from its monitoring stations annually. But the 15-year breadth and scope of Sando's report offer a more historic and detailed sense of what's going on along the Clark Fork than has been available in the past.
"It reaffirmed and showed us in a very specific way how Silver Bow Creek is slowly but surely cleaning up as they've removed the tailings," says Clark Fork Coalition science director Chris Brick. "That project is almost done now, but the years of this study ... That was a period during which cleanup was occurring."
While the prevalence of copper and zinc has declined significantly, Sando notes that the reduction in arsenic hasn't been "quite as dramatic"only about 50 percent. Sando's report also indicates that contaminants remain a major concern farther downstream from Silver Bow, namely between Galen and Deer Lodge. For Brick, that makes perfect sense—the next phase of remediation covers that stretch and was only started last year. The whole project covers 45 miles, Brick says, and will take about 15 years to complete.
"It's good to see that where we've done Superfund cleanup, the river's improving," she says. "And where we haven't started yet or are just starting, there's a lot of room for improvement."