JEFFERSON COUNTY, Colo. — If it wasn't for the name of the road, residents in Jefferson County, Colo. likely wouldn't question if there's history beneath Coal Mine Avenue.
Next viewer Gail let us in on an interesting conversation on her Nextdoor, the app for neighborhood chatter. A group of her neighbors was wondering if there’s a coal mine near some new development at the corner of Coal Mine and Kipling Parkway.
The simple answer is yes. There are three coal mines in that little part of Jefferson County: the Economy Mine, the Littleton Mine and the Virginia Mine.
The Economy Mine is the closest to that precise corner Gail and her neighbors wondered about, according to Jeff Graves, director of the state’s mine office.
“I imagine it goes unnoticed because most of those issues or the coal mine itself is all underground,” Graves said. “There’s very little above ground to suggest there was a historic mine here.”
The area was heavily mined in the 1920s, when there wasn’t much in this part of the metro area. Graves said it would have been described as the outskirts of Denver back then, far from the popular suburb its become these days. Graves said miners would go down 500 to 600 feet and hoisted the coal up through shafts. Operations ended in the late 1930s.
Graves confirmed another rumor Gail and her neighbors heard - that homes had sunk in the area after they were built on top of these mines. In the industry, they call that kind of ground collapse subsidence.
Since the 1980s, state regulators have a much better handle of where mines are located and cities do a good job of zoning areas around coal mines.
“For the most part, counties and cities have done a reasonably good job of designating areas as open space or through land use trying to avoid having construction over those areas,” Graves said.
Jefferson County even designed Coal Mine Road with the mine in mind.
According to an engineer with the county’s highway department, the portion of Coal Mine Road that travels over the historic mine is essentially built like a bridge, with extra steel and concrete that would support traffic were the ground underneath the road to collapse.
When the county extended the roadway, the developer who owns the plot of land there put plans on hold for a neighborhood above the mine area, according to the same engineer, because of concerns about subsidence.
A golf course was built there instead.
A developer who currently owns the property did a survey of areas that may be susceptible to subsidence, the traffic engineer told us. Any area with risk will be back-filled with concrete to prevent a potential collapse.
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