North Dakota researchers and industry are aiming to apply agriculture practices to coal mine reclamation.
Soil compaction, often resulting from heavy equipment, is one of the biggest challenges mining companies seek to remedy during any reclamation project.
“Following the mining process, heavy machinery is used to move soil, which applies compressive pressure during the reclamation process,” said Jay Volk, environmental manager for BNI Coal’s Center Mine, in a statement.
“We knew this compaction was occurring, but we thought, with time, the soils would loosen as crops were planted, rains fell and the ground froze in the winter and thawed in the spring," he said. "But, instead, we found that the compaction problems continue to linger as long as four decades after mining.”
While coal mines in the state have received multiple national awards for reclamation programs, many are investing in further improvements. North Dakota State University researchers are aiming to reduce soil compaction by scaling up agricultural practices for the mining industry in order to create better water movement, vegetation and increase root penetration.
Volk says companies try to decrease the compaction by changing traffic patterns but it still exists to a certain level. So the industry is turning to Ryan Limb, project director and principal investigator, and three other researchers from North Dakota State University’s Department of Natural Resources.
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“Agriculture has long had the same problems but on a much smaller scale,” Limb said.
As part of a five-year, $1.1 million state- and industry-funded study, researchers will test the practices of deep ripping, polymer and mulch soil additions and seeding changes to determine whether they can make a difference. The last time research was done on reclamation in the state was the early 1990s.
Limb said companies have started to use some of these practices but no one has quantified the benefits, if any.
Researchers also will experiment with a change to how companies are seeding. Kentucky bluegrass is prevalent on reclaimed lands. It meets production benchmarks but its shallow root system puts it at risk in drought and wet conditions.
More than 27,000 acres of rangeland has been mined and gone through formal bond release. To be released from bond, the land must be as productive or more productive for 10 years than it was prior to mining. Limb said the research being conducted will be proactive, finding ways to maintain and extend production on reclaimed lands should a drought occur.
For property going back to rangeland rather than cropland, researchers will seed native flowers to improve root structure, bringing back more native prairie plants, Limb said. These aren’t being planted with pollinators in mind but it could also help North Dakota’s beekeepers by providing an additional source of forage. The biggest limit will be commercial seed availability.
The team will also change soil respread depths. At current depths, Limb said companies have “basically created a perfect storm” for Kentucky bluegrass to grow. New depths may change that.
Limb said the study is not specifically looking at the economics of these methods but they’re designed to not add additional expense for companies.
“Farmers operate under the same small margins (as coal companies) already,” Limb said, so what farmers can afford, mines can, too.
Extending the benefits
And the benefits of the study will not be limited to coal mines.
“Soil compaction is soil compaction,” Limb said, and if researchers can find a fix on a mine site, other industries, such as oil and gas and wind producers, could use it as well.
North Dakota has more than 10,000 active oil wells and 12 wind farms. Associated with these energy sources are pad sites, access roads, pipelines and transfer stations, which will all need to be reclaimed, according to the Lignite Energy Council.
All of these trials will be run on actual mine reclamation sites, for which companies are currently seeking research variances. The plots will be at least an acre so equipment can be run at production rates.
Ultimately, if solutions are found, North Dakota Public Service Commission approval will be needed to make changes to reclamation practices.
North Dakota Public Service Commissioner Randy Christmann holds the coal industry portfolio for the PSC and also sits on the state’s coal tax-funded Lignite Research Council, which provided half of the $1.1 million in funding for the research. BNI Coal’s Center Mine and North American Coal’s Coyote Creek, Falkirk and Freedom Mines have all invested in the rest of the necessary funding and will provide the test plots acreage and labor.
“After speaking with the PSC’s division of reclamation manager, I decided to support the study,” Christmann said in a statement. “He told me that more research is needed to prevent the occasional compaction problems and non-native grasses growing on land that has bond released. When I learned that, I changed my mind. While we reclaim mined land well, we can always learn to do it better.”
The result of the study will be a best management practices document.
Reach Jessica Holdman at 701-250-8261 or email@example.com
While we reclaim mined land well, we can always learn to do it better.”
-- North Dakota Public Service Commissioner Randy Christmann