This summer, the Roseburg Bureau of Land Management is working to stop the flow of heavy metal contaminants from the Formosa Mine southwest of Riddle into nearby creeks.
BLm Project Manager Susan Lee said copper, zinc, mercury and gold had been mined from the site off and on from the early 20th century until the mid-1990s.
Cheyne Rossbach, spokesman for the Roseburg BLM, said the mine fills up with water, so the agency had tried to close off the access point to the mine when the site closed.
“But there’s a drainage port, so water from inside that mine comes up and drains out and leaks heavy metals,” Rossbach said. He added this toxic water has been flowing from out of the mine to the Middle Creek drainage, then on into Cow Creek.
“The remediation at the time of closure was not successful and now we have some ecological concerns there with the damage to natural resources, specifically the contamination of the water,” Lee said.
The Formosa Mine has been listed on the Environmental Protection Agency’s National Priorities List as a Superfund site. This means the area is a nationally-recognized candidate for a cleanup because it has been contaminated by hazardous waste and poses an environmental risk.
After years of preparations and working with the EPA, the Roseburg BLM has started to work on the site to stop the contaminated water from flowing out of the adit, which is the tunnel-like access point to the mine.
This tunnel had previously been plugged by a combination of wood and dirt, which Lee said was insufficient.
So far, crews with the BLM have begun to prepare the site, and Lee said they will soon work to open up the tunnel and clear out the wood and dirt plug.
“Then they’ll go in and do an investigation and some design about the exact placement, then put in a bulkhead and let that concrete cure and make sure it’s functioning the way everybody hopes it will,” Lee said. The bulkhead is an underground, 100-foot-thick concrete wall meant to hold back the water from getting through the tunnel.
Lee said the goal is to stop the contaminated water from coming out of the tunnel and spilling into the nearby streams.
“We want to make sure it’s successful,” Lee said. “We’ll have a valve in it in case the water rises and starts coming out somewhere else that’s not desirable, so we can drain it off and address that.”
Lee added the work will continue through the summer and the BLM plans to have the project finished this fall.
For public safety reasons, Lee said she discourages people from visiting the site while work is ongoing.