August 29, 2010 - Three thousand feet above the city of Riddle is Silver Butte, a quiet mountaintop with panoramic views of Douglas County's vast forestland. The mountain is breathtaking. It's also home to one of the most contaminated sites in the nation — the abandoned Formosa Mine.
"If you walk in the water flowing out of the mine, the soles of your shoes will be mush," said Denise Baker-Kercher, the Environmental Protection Agency official in charge of the cleanup. "That's how acidic the mine drainage is."
When the mine closed in 1993, the operators failed to clean up the waste they left behind after extracting copper and zinc. For nearly two decades, rain and ground water have been absorbing the waste and flowing into Middle Creek at the base of Silver Butte.
The site produces each year five million gallons of acid drainage, containing up to 30,000 pounds of dissolved copper, zinc and other metals, according to an EPA study. The runoff has poisoned Middle and Cow creeks, killing all aquatic life along 18 miles of habitat.
"If the problem is left unattended, the contamination will eventually reach Riddle's city water source," Baker-Kercher said.