From the Colorado Independent (Katie Redding):
In 1997, under pressure from media, including NBC Nightly News, as well as from citizens, preservationists and state representatives, incredulous EPA authorities agreed to leave several remaining tailings piles in the Leadville Mining District in place, divert most runoff around them, and send any contaminated runoff down Stray Horse Gulch, into an old mine shaft and through a series of convoluted mine workings to a treatment plant on the other side of town.
But in the intervening years, according to EPA Remedial Project Manager Stan Christensen, dye tracer tests have shown that not all the 300 to 500 gallons of contaminated water generated each year actually makes it to the plant. Depending on the day, the plant recovers somewhere between 12 percent and 75 percent of the contaminated water that comes its way, he said. No one is sure where the rest of the water goes.