Reclaiming the environment after coal
Reclaiming the environment after coal
Reclamation is just something TransAlta does — we plan for it when looking at the entire life cycle of a mine. But when mining ended almost 19 years early; the area around the Centralia mine in Washington, U.S. looked nothing like the original blueprint for reclamation and the team there had to start from square one.
When TransAlta bought the mine in 2000, they inherited a reclamation permit from 1985 with a plan for returning approximately 7,000 acres of disturbance around the mine back to its original state. Geological issues around the mine site led to the end of mining in 2006, much earlier than expected, and the area looked very different than planned. The reclamation permit was no longer valid.
“Our old plan had a small lake intended for where the mine pit was only 28 acres in size, but when mining stopped, we didn’t have enough material to backfill the pit for that,” says Dennis Morr, senior environmental specialist, Centralia. “We had to get creative and ended up proposing a larger lake which actually allows us to establish a more diverse habitat for fish and wildlife.”
A new permit had to be approved for the reclamation and the team launched into the extensive process needed. To start, a three dimensional model of the area is created and working closely with state and federal departments, the depth of the lake and the topography of the area is determined. This includes the shallow and deep zones, water temperature and the way the lake spills and flows into established creeks and channels.
“Lakes have to be commensurate with other lakes of the region because of depth so native species can survive. If it’s too deep it means slow turnover of the water and it’s hard for the habitat to survive,” says Ken Johnson, supervisor engineering and compliance, Centralia.
“We ended up raising the mined-out pit bottom about 100 feet to meet the average lake depth criteria set by fish and wildlife agencies. We wanted to fit in well with other lakes that showed positive results for supporting fish and wildlife habitat.”
Creating the area for the approved new permit proved a whole other ballgame. With only five to six months out of the year when it’s typically dry, the design has to accommodate the heavy rainfalls typical to the area. It took several years moving dirt into the pit to form the lake and to stabilize the slopes around it.
“One of the biggest challenges was working the large equipment in the dirt when it gets wet,” says Johnson. “Once there are large amounts of rainfall, it can severely impact some of the dirt that is placed and the drainage structures; we have to design and plan for this.”
The long steep slopes of the area also proved challenging when working with big equipment, but the team was able to complete this work, and the entire reclamation project thus far with no lost time safety incidents, a testament to TransAlta’s commitment to safety.
Once the area is created, vegetation is planted and the variety of these species is designated by the reclamation permit. What is called the Central Packwood Lake area was designated as upland forest, lowland forest and wetlands on some channels near the lake. This meant planting everything from Douglas firs to underwater species for the aquatic habitat.
TransAlta is required to show, amongst many reclamation success standards, a specific survival rate for Douglas fir trees of 190 stems per acre after five years. This demonstrates that the vegetation is progressing as it should. It isn’t as easy as it seems.
“We’ve learned a lot as we’ve gone along. There were some areas with too much compaction, which is really hard on trees and their success,” says Tony Briggs, manager, mining, Centralia.
“We’ve adjusted our practices and broken up the ground more to allow the tree roots to get the oxygen and water that they need.”
With the Central Packwood Lake area now showing progress, the team will continue to plant vegetation until 2020 and monitor the survival rates until 2025. As the vegetation grows and the lake begins to fill with water from rainfall and groundwater, animals begin to visit and graze, and fish will eventually begin to migrate through the channels.
“There is already a fair migration of birds: eagles, hawks, and Canadian geese,” says Johnson. “We see big herds of elk — they like to walk down newly vegetated slopes and eat the vegetation and drink out of the lake — it’s pretty cool.”
Winning a TransAlta President’s Award for Environmental Leadership, the Central Packwood Lake reclamation team has certainly demonstrated TransAlta’s commitment to environmental stewardship wherever we do work. The team at Centralia took an innovative look at solving how to reclaim an area they had not planned for and was able to create an area with even more ecological diversity than expected.
“Our plans changed quickly and people here worked really hard on solutions to make it work,” says Briggs. “We worked as a team and that’s what made it so successful. I think it’s a testimony to TransAlta’s people; the kind of people we are, that we took this on and just didn’t quit until we found the best solutions.”