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ROCK SPRINGS — When Carl Demshar’s children were growing up in the early 1980s, they’d often run back to tell their parents about the latest hole that opened up near their home.

“They’d come in and say, ‘Dad, Mom, mine shaft’s open again,” said Demshar, now the mayor of Rock Springs. “You couldn’t see mine timbers or anything like that, but you knew it was an entry point to a mine .... Fortunately for us, none of the kids in the neighborhood ever got hurt because of that.”

Rock Springs’ existence is due to the honeycomb of coal mines that run under and around the city. But now, almost half a century after the last mine closed, the remnants of the city’s former glory have become one of its biggest concerns.

It’s not unusual for subsidence holes — sometimes big enough to park a truck in — to occasionally open around town as the mines sink or cave in. Some residents live only 10 feet above a blackened underground void, and suffer cracks in their walls, sinking floors and carbon monoxide poisoning.

For the past 30 or so years, the state has spent $160 million to try to fix the subsidence problem in Rock Springs and the surrounding area — from identifying where the mine shafts are to pumping in grout to act as support columns.

But one of those efforts — in the Tree Street neighborhood in the southwestern part of the city — has created its own set of problems, and has given new prominence to the issue of mine subsidence in the city.

History

The city of Rock Springs was first populated in the late 1860s to supply coal to the newly constructed Union Pacific Railroad. Over the next century, more than 100 million tons of coal was hauled out of a maze of poorly built mine shafts that twisted and snaked for miles underneath the city.

When the last mine closed in 1963, Rock Springs had moved on to new thriving industries — oil and gas. But the mines themselves remained. And as the years passed and the city expanded, inevitably, collapses began to happen.

“You could either call it short-sightedness, or you could call it ... I’m trying not to say raw stupidity,” said Charlie Love, professor of geology at Western Wyoming College in Rock Springs.

In January 1949, a 60- by 80-foot-wide hole about 40 feet deep opened in front of the downtown Catholic church during Sunday Mass, forcing the priest to hastily finish the rest of the service before evacuating his parishioners.

By early 1968, subsidence got so bad that in one Rock Springs neighborhood, 10 of 17 homes sustained moderate to severe damage from sinking mines.

Not all subsidence damage comes from sudden sinkholes: Even a drop of a few inches can wreak havoc on a house sitting above it, cracking walls, warping door frames and bending floors into fun-house-shaped dimensions.

As Demshar noted, it’s not inherently unsafe to live over an old mine shaft, so long as there’s several dozen feet of earth and rock in between. But if the void is within a dozen or so feet of your basement, he said, that’s a different story.

Solutions

Rock Springs officials and longtime residents say that thanks to efforts by the state, instances of sinkholes and damaged homes around the city have, well, subsided during the past few years.

The first efforts started in 1970, when Rock Springs became the test city for an experimental process in which workers pumped more than 200,000 tons of a sand-water slurry into the mines to fill them.

But the slurry only made matters worse, Love said, for the water accelerated the subsidence and knocked out mine support timbers.

Better help started coming after 1977, when Congress passed the Surface Mining Control and Reclamation Act, under which coal companies gave millions to assist thousands of communities nationwide with the reclamation and cleanup of coal mines. The funds in Wyoming are administered by the Abandoned Mine Lands Division of the Department of Environmental Quality.

The DEQ has found a more effective way to stabilize old voids: Drill holes every few yards down to the mine shaft, then pump in grout to create a series of stabilizing columns.

As a result, said Margie Smith, owner of Rock Springs Realty, mine subsidence “went from a very strong issue to a nonissue.”

DEQ is now focusing less on shoring up houses and concentrating on grouting roads, water mains and other infrastructure, Demshar said. The state is currently drilling and grouting along the Belt Loop road and plans to continue that work into next year, said DEQ Administrator Alan Edwards.

A big part of the problem, though, is that officials don’t have a clear picture of where all the underground mine shafts are under the city. To avoid paying more in taxes, mine owners would often underreport how long their shafts extended, so official maps often aren’t reliable.

About the only way to discover if a dangerous mine shaft’s underneath an area is to drill down to find out. AML contractors will be doing just that in downtown Rock Springs for 30 days starting Monday.

Tree Street

In the mid-2000s, another idea for a solution was hit upon: Pound the ground with massive weights to cave in the shafts underneath.

But when that process, called dynamic compaction, was tried in the summer of 2007 on a 61-acre plot of land in southwestern Rock Springs, it created new problems that endure today.

For more than two weeks, workers repeatedly slammed 25- and 35-ton weights against the ground. Nearby residents in the Tree Street neighborhood claim that nearly 20 homes in the area were damaged — not only because of the vibrations of the weights themselves, but also because it destabilized voids under their houses, causing subsidence issues in an area that previously hadn’t seen any such problems.

On a tour last week of some Tree Street houses, outraged residents point to cracked walls, warped window frames and sinking driveways they say were caused by the ground rising and falling underneath them.

The state offered compensation, but several homeowners said the offers were far too low and filed suit against the state in July. They’re seeking about $6 million in AML money for repairs and to pay homeowners for houses they say are unrecoverable.

The state, however, has offered each of them only several thousand dollars in compensation. Tree Street resident Donna Maynard said after lobbying for so long, she wants to move forward on a lawsuit against the state to get fair market value for their homes.

“It’s been four-and-a-half years,” Maynard said. “I’m done.”

Today

With Sweetwater County in the middle of an oil and gas boom, the Rock Springs housing market is thriving these days, Smith said.

But now, new development is being concentrated on the west and north ends of town, where fewer subsidence issues exist. Demshar said that’s a coincidence, and that the city’s growth plan didn’t factor in mine subsidence.

In talking with a number of Rock Springs residents, it appears that most of the city is aware of the potential threat beneath their feet.

But ask residents if their lives have been affected at all by mine subsidence, and you’ll get a wide range of answers.

Tree Street resident Becky Kelley is dreading the thought of spending another winter with cold Wyoming wind whipping in through the cracks in her house.

“They’ve ruined our lives, our whole investments — everything,” Kelley said.

But James Klein, who lives just south of downtown, said he’s lived his entire life in Rock Springs without seeing a single sign of any effects from a century of mining beneath the city’s feet.

“I haven’t noticed anything,” Klein said, grilling outside his house on a sunny early fall day.

Contact capital bureau reporter Jeremy Pelzer at 307-632-1244 or email jeremy.pelzer@trib.com.

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