Re-Claiming a Dream

What’s a Canadian oil and gas company doing reclaiming hundreds of acres around a gold and silver mine in Washington state? That’s what Lin Callow of ConocoPhillips asked himself 10 years ago. His answer came when he was recently presented with a Department of Natural Resources (DNR) Award from the State of Washington for leadership in his company’s program to reclaim the exhausted Cannon mine as a spectacular natural area.

DNR has called the reclamation a model for other mining projects based on the innovation and technology used in the project.

Callow, senior manager of environment and regulatory major projects for ConocoPhillips, became involved with the Cannon mine in 1994. That was when Gulf Canada (now ConocoPhillips) moved to shut down mining operations, because the only gold and silver reserves left were located directly beneath the Wenatchee town site. Gulf had been operating the mine since 1987, when it purchased the Asamera companies, including prized petroleum operations in Indonesia and the decidedly non-core Cannon mine.

During its operating history, the mine had more than 250 full-time employees and produced more than 1.4 million oz of gold and 2 million oz of silver. The mine’s permitted areas encompassed more than 1,700 acres of land, of which approximately 280 acres were leased state land managed by DNR.

Callow and ConocoPhillips could have walked away from the mine by forfeiting a US$2 million bond. Instead, they spent almost eight years and US$6 million to give the people of Wenatchee back their “pretty little valley”.

“We decided as a company that we were going to do the right thing,” says Callow. “We made a conscious ethical decision to reclaim this area and we feel good about what we’ve accomplished.”

He continues: “This was an entirely different and unique reclamation operation from what we had been used to in the past. Here we were taking on the reclamation of a gold and silver mine in Washington state, and one that sat surprisingly close to the town itself.”

To ConocoPhillips’s advantage, the mine had never employed cyanide extraction common in other gold mining operations, because it wasn’t effective on the Cannon ore. Another element working in its favour was how the dynamite blasting technique had broken down part of the cement-filled support pillars, causing the crumbled cement (calcium carbonate) to mix with and neutralize the metal-bearing tailings material. As a result, there was virtually no opportunity for acid mine drainage to occur. Even so, the state’s Department of Ecology expressed concern that this buffering capacity might be insufficient one day.

That’s when Callow and his team decided to draw on their oil and gas experience. They had been developing “engineered wetlands” to treat hydrocarbon contamination on several projects in Gulf’s Canadian operations, and realized that a different type of engineered wetland could be used at the Cannon mine to mitigate any possible metals contamination.

“As far as these wetlands are concerned, we don’t ever expect them to contain any significant amount of metals because there had been no metals leaching from the site,” said Callow. “The wetlands are there purely as a backstop, and they are, in my view, the primary reason why the Department of Ecology was willing to sign-off on all our future monitoring requirements. We had done all the scientific studies to show that we did not expect anything to go wrong, but this provided further insurance to mitigate the faint chance of anything going wrong.”

A second and more significant challenge, reclaiming a 60-acre wet tailings pond, required some creativity. Even though the previous owners had committed to reclaiming the tailings area, there was no known method for accomplishing it.

Callow’s team came up with an innovative approach that involved emptying the ponds by spraying the water into the air to accelerate evaporation. Once the ponds were dry enough, about the consistency of moist clay, the team rolled out and stitched together massive sheets of geo-textile fabric to cover the whole 60-acre surface!

Then came the risky part. The fabric was covered with about a foot of gravel, which serves as a capillary break to prevent the tailings water from migrating to the surface. Great care had to be taken to distribute the gravel evenly over the entire area since it effectively was floating on the moist ground underneath. Putting too much weight on any one area would have caused parts of the 60-acre gravel layer to sink or flip over, bringing to the surface the contents of the tailings pond. Using light equipment, Bobcats at first, the crews began spreading the first of an additional five feet of soil on top of the gravel. As the ground became more solid, larger equipment was used to spread the final few feet of soil, which was taken from hills around the old mine site.

The weight of the gravel cap and five feet of soil has now solidified the materials of the tailings pond deep below the surface. Liquids from the former tailing pond are trapped in their own groundwater layer well below the surface of the reclaimed land.

Once that was accomplished, crews began revegetation trials using different mixtures of vegetation native to the area. The result is a natural vegetation mixture that was approved by the Department of Ecology and has taken firm hold in the formerly disrupted land.

“You would be hard-pressed to ever tell there were mining activities in that area,” says Callow. “The work we’ve done blends in beautifully with the surrounding area.

“For me, it’s further proof that when a team approaches this kind of challenge with imagination and innovative thinking, they can reclaim these difficult sites and eliminate the need for ongoing monitoring and compliance requirements over time. Because of our approach, our technical innovations and our understanding of regulations and regulators, we were able to come up with a way that would allow us to get all our approvals in place and remove all our monitoring requirements, and ensure that the site’s wildlife and recreation values are restored and will remain intact for the enjoyment of future generations.”

To that end, ConocoPhillips is currently negotiating with a local equestrian association and the Washington State Land Conservation Trust to ensure the land is preserved and used appropriately. The Trust will ensure the land is used only for conservation purposes, recreation and wildlife habitat, and that no development occurs in the future.

The equestrian association will likely be responsible for day-to-day management of the site to ensure the area is only used for hiking, walking, riding and wildlife viewing. Vehicles such as ATVs and dirt bikes will be prohibited in order to maintain the vegetation and the integrity of the immense amount of work that’s been done.

Callow gives full marks to his company as well as the Seattle-based firm of Pincock, Allen & Holt for their construction work and Hart-Crower for their design of the wetlands area. “All companies involved are to be commended for their ongoing and diligent commitment to ‘doing the right thing’ and following through with reclamation completion,” he comments.

Callow is proud to note that ConocoPhillips is currently discussing plans to install a self-guided interpretive centre to give the public a first-hand look at how the land reclamation was designed and implemented to achieve the remarkable transformation of the site.

“The Recognition for Reclamation Award is a great honour for me, the team and ConocoPhillips,” says Callow, “but the satisfaction we feel from getting this job done right, and maybe even advancing reclamation science, is a tremendous reward in itself.”

Washington state officials couldn’t agree more. Doug Sutherland, commissioner of public lands, acknowledges that “this is the way it can be done,” and Ron Teissere, a DNR geologist, agrees that the Cannon mine reclamation plan sets an example for other mining projects.

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