HOLDEN VILLAGE — Building an underground wall that’s a mile long and reaches 60 to 70 feet down to the bedrock to divert acid mine drainage from the old Holden Mine will not be an easy task.
“It will be a big, big challenge for us to get this wall in. But it’s not new technology at all. It’s used all over the world,” said Dave Cline, Holden Mine Cleanup project manager for Rio Tinto.
Cline was speaking to a crowd of almost 90 people who toured the $100 million mine reclamation project Saturday, as the company’s first major year of cleanup winds down.
Rio Tinto has no direct connection to Howe Sound Mining, which mined copper, zinc, gold and silver there from 1938 to 1957. Intalco Aluminum Corp. is responsible for the cleanup, but Rio Tinto will spend more than $100 million to clean up the old mine it up for them as part of acquisition agreements.
Cline said about one-third of that — about $30 million — is being spent locally, on wages and services.
Some of those taking Saturday’s tour are regular guests at Holden Village, a remote mountain town just across the creek from the cleanup work at the mine that was built by miners, and bought by Lutherans as a retreat over 50 years ago.
Others were curious residents from North Central Washington, including Chelan council members, museum officials, and staff representing state and federal lawmakers.
Alice Ott, of Manson, was in the crowd. Her father worked at the Holden Mine and her mother was a school teacher in Holden, where she went to school beginning in the second grade.
“I used to play in the tailings, until my mother said, ‘You can’t do that anymore.’ She couldn’t get it washed out of my clothes,” Ott recalled.
Those tailings are one of the main focuses in Rio Tinto’s cleanup work, which this year prompted Holden Village to close its retreat, and use the time to replace roofing and an aged water, irrigation and fire suppression system. Volunteers are also putting overhead electric lines underground, and remodeling a lodge. Holden hopes to continue its summertime programming in 2015.
Stephanie Carpenter, co-director of Holden Village, said the cleanup work has been disruptive. But the village is happy about the cleanup work, too. “It’s been a shadow that’s been in the valley for a very long time,” she said.
On the mine side of Railroad Creek, some 200 mine reclamation workers developed a rock quarry this summer, and built new roads and bridge over Railroad Creek so heavy trucks aren’t traveling through Holden Village.
They also demolished the old mill building, and capped the mine’s entrances so water that collects in the 57 miles of tunnels inside can be controlled, and diverted to a yet-to-be-built water treatment plant.
They also plan to redirect almost a mile of Railroad Creek into a new channel about 50 feet away to make way for the new wall.
Currently, the creek is next to three piles that contain about 8 million tons of tailings from the old mine. They’ve been the source of some of the pollution that has left the water in Railroad Creek clean enough to drink by federal standards, but not clean enough to support a healthy population of fish and other aquatic life.
The creek runs into Lake Chelan, and next to the tailings piles, the rocks have turned an orangish brown from the acid drainage.
Cline said the wall won’t be a rigid structure, but is made of more pliable soil and clay mixed with cement. “It’s actually fairly flexible,” he said, so it can move instead of break in an earthquake.
He said the geography of this area is what will make it difficult to build. Rio Tinto expects to find huge boulders that they’ll have to chisel into, dig around, or pry out of the earth to build the wall.
It’s tough to get enough leverage to pull boulders out when you’re digging a trench that deep, he said.
The equipment that it will take to dig it weighs 450,000 pounds, has a 90-foot boom, and will take three barge loads to haul it to Holden.
Once snow prevents continued work this year, the company will send its workers home, move out 95 pieces of heavy equipment, and come back next spring for what it hopes will be the last summer of major construction.
About half as many workers will return in 2015 to wrap up the mine cleanup project.
But Cline said that won’t be the end of Rio Tinto’s involvement at Holden, as its water treatment obligations will continue for decades to come.