Susanne Arens thought the vacant lot next to a McDonald's restaurant in a Rockrimmon shopping center was the perfect place to build a new car wash.

Springs native Jerry Golden grew up admiring the Cragmor neighborhood near the Colorado Springs Country Club and four years ago, bought a home there.

Bob Syme was hired to engineer and rebuild Interstate 25 at Woodmen Road.

All three ended up confronting Colorado Springs' past as a coal town - a mostly forgotten era that left an underground network of large tunnels and caverns that, today, threaten thousands of landowners decades after the last mine was boarded up.

State experts say about 3,000 homes, a major railroad line and part of Interstate 25, as well as hundreds of commercial buildings in the Springs, rest on land once mined for coal and now prone to subsidence, or collapse.

The magnitude of the threat is a matter of some disagreement. But a spate of collapses in the 1980s raised anxiety levels and put property values at such risk the state spent hundreds of thousands of dollars to locate, map and aggressively fill old mines.

And in 1989, the state landed a federal grant that funded an insurance program for homeowners in coal fields in the Springs, Boulder and elsewhere.

 About 1,100 homeowners from Colorado Springs bought the insurance. But few collected on their policies when houses shifted, walls crumbled and foundations sank because far more home damage in the area is due to soils that expand when wet, not from mine collapse. Only a handful of the dozens of claims have been attributed to mine subsidence.

But the threat remains, experts say, and they are concerned because participation in the mine protection program is dropping - only about 890 participate today.

Tens of thousands of newcomers have bought homes atop the meandering tunnels without knowledge of the possible jeopardy. Others have concluded the potential danger is not sufficient to justify the annual $35 insurance premium.

So the state is considering changing the program to make the insurance less expensive while doubling the maximum benefit to $100,000. A public hearing on the changes is scheduled Wednesday in Denver.

Among other things, the state is proposing the annual premium be waived after three years in the program. The $200 homeowners currently pay for an inspection before being accepted into the program would remain unchanged.

"Participation is falling off at a rate of 2 or 3 percent a year because of the perception there's not a problem," said Dave Bucknam, director of the office of active and inactive mines for the state Division of Minerals and Geology.

Despite the small number of claims paid to homeowners, Bucknam said, the mines are very real and the potential exists for huge problems.

Few signs remain

Urban growth has erased all but a few surface remnants of the area's mining history.

One relic of the era is still standing and visible from I-25: a beehive-shaped coke oven. It's silently deteriorating in the brush on a hillside west of the interstate and just north of Garden of the Gods Road, across a creek from the end of Rusina Road.

The oven was part of the old Pikeview Mine works - the area's largest mine, which was based on land that now holds the Pro Rodeo Hall of Fame.

The oven is now a tombstone of sorts for the coal mines buried nearby.

The mines' vertical shafts, some plunging to depths of 500 feet, lead to miles of tunnels and caverns and more simple, shallow, horizontal mine shafts.

They are leftovers from a sprawling coal field that once supplied the fuel to power foundries that processed gold ore dug in Cripple Creek, steel factories in Pueblo and trains that rumbled to homes along the Front Range.

Miners in the 19th century worked a layer of coal up to 8 feet thick in an arc from what is now Rockrimmon in the northwest to Cragmor and Palmer Park in the north-central neighborhoods to the Rustic Hills area and Colorado Springs Airport to the east.

In what is now Rockrimmon, the coal layer spread out about 3,000 acres at depths of 200 to 500 feet below ground level.

The coal was much more shallow in other areas, actually reaching the surface in spots along the Templeton Gap near Hancock Avenue.

An underground labyrinth

Maps of the mines reveal a network of dozens of major underground roads that led to hundreds of smaller passageways and thousands of caverns or rooms.

Miners would dig a pair of large tunnels into the layer of coal. One of the main tunnels was for hauling miners. The other was used for hauling equipment and coal.

Then they would dig smaller tunnels off the main drag. Those tunnels would lead to a series of rooms, up to 40 feet wide and 100 to 400 feet long, off each side of the tunnels.

The walls of each room were often pillars of coal. To maximize production, the pillars often were removed as miners retreated from a room.

Men and mules worked side by side. The only difference . . . the men left the mine at the end of a shift. The mules stayed underground in large stables. They pulled rail cars full of coal and miners until being replaced by battery-powered electric trolleys.

The mines honeycombed most of Rockrimmon, including the land under Monument Creek and the railroad tracks that run alongside.

The mines also extend under I-25 from Woodmen south to the Rockrimmon exit, according to a 1985 study by engineering consultants Dames & Moore, which compared historic mining maps to aerial photos and used borings to pinpoint locations of shafts and tunnels and their depths.

History of collapse

It's been 45 years since the Pikeview - the biggest and most productive of the region's mines - shut down.

Although a couple of smaller mines continued to operate into the late 1960s, the Pikeview's demise ended major coal-mining activity in the Springs.

During 80 years of continuous mining, an estimated 15.5 million tons of coal was taken.

And the miners disappeared as quickly as they arrived, leaving hastily dug and constructed catacombs deep beneath the earth upon which houses, businesses and golf courses eventually were built.

One of the last of the underground miners still alive is Levi Green, 88, who started working in the mines when he was 14, after relocating to the Springs with his parents from Gunnison.

Green still likes to recall his days underground at the Pikeview to his wife, Opal, and the nurses at the rest home where he now lives.

He can describe how he drove mules that hauled men and coal cars down large tunnels deep under Rockrimmon, how he handled dynamite and drove wagonloads of coal to St. Francis Hospital and then-Camp Carson.

And he was aghast as he watched homes spring up atop the ground he knew was fragile from decades of mining.

"Levi has always warned that they never should have built on that land in Rockrimmon," Opal Green said during one of her daily visits to Levi's room.

The fragility of the mining legacy soon was apparent. Headlines from the 1960s through the 1990s chronicled Colorado Springs' long history of mine collapses - the sudden appearance of shallow sinkholes, cave-ins under the foundations of homes, and shaft openings in driveways and streets.

Aerial photos taken over the years document everything from thousands of shallow sinkholes to large cave-ins.

There was a dramatic case of the land disappearing from beneath the corner of a house on Country Club Circle.

On the same street, a homeowner came back from a weekend trip to find a gaping hole in his driveway.

"The concrete busted and the earth just dropped straight down," said Terry Hitt, who bought his home on Country Club Circle in 1980 and stopped his neighbor from driving into the mine shaft.

He also recalls watching sinkholes develop in a nearby vacant lot.

Other hot spots included Portal Park, where a hole 12 feet wide and 7 feet deep opened in the outfield of a ball field in 1979. Massive borings discovered mine shafts just 31 feet below the surface of the park and its swimming pool, built in 1974-75.

The pool was found to be slipping into the mine shaft. Ultimately, engineers ordered tons of cement grout pumped into the shafts to shore up the pool and close the sinkholes.

Then there's Ascension Lutheran Church, which sits on 2 1/2 acres on North Circle Drive over the old Keystone mine. It has experienced many collapses over the years, mostly shallow sinkholes in the lawn. One hole, however, opened under the corner of the old church building.

When a new church building was built about 12 years ago, architects used earthquake-type construction involving a special gridwork under the building to support it, said Pastor Keith Hedstrom.

"About 10 years ago, the state came in and pumped literally tons and tons of concrete into the old mine shafts," Hedstrom said. "Since then, we've had no cave-ins."

Still the building continued. Now, about 500 residences - homes, condominiums and townhomes - sit in areas rated high for possible collapse. Nearly 300 are at moderate risk and another 2,200 are considered at low risk, said Bucknam of the state mine program.

The question facing homeowners is whether the danger remains.

"The majority of subsidence seems to have taken place and peaked about 40 years after the close of the mine," Bucknam said.

The reason: Experts suspect 40 years was the approximate length of time it took the timbers used to hold up the roof of the mine to rot away or for the coal pillars left to support the mine roof to flake off.

Does that mean there will be no more mine collapses?

The 1985 Dames & Moore study found 90 percent of the area's coal shafts had "significant voids or pockets of loose debris below the surface."

And weather conditions above ground can have a big impact on the mines below the surface.

For example, a drought can cause changes in groundwater, leaving timbers exposed after decades being submerged. The result is rapid deterioration and probable collapse.

A long rainy season can have the same impact on a mine that has been dry for years, experts say.

Mines scare some away

While the state can offer insurance to pay for damage caused by a collapse, it's up to landowners to decide whether they want to pay to recoup their losses, gamble that nothing will happen or pay for the extra engineering and construction needed to prevent subsidence.

Those are the choices that faced Arens, Golden and Syme.

All had different reactions when they learned their property was sitting over mines.

Arens was frightened by the thought the ground 185 feet below her planned car wash had been burrowed out, leaving caverns 4 to 8 feet tall supported by timbers or pillars of coal.

She backed out of the deal at the last minute.

"We found out that there's coal mines all over in that area," Arens said of the Village Center at the intersection of Vindicator Drive and Rockrimmon Boulevard.

"The geologist told us a building could drop 6 inches to 4 feet. There's a continuous shaft and it winds around all over in that area. I live just a couple blocks away. I had no idea it was this bad."

The owner of the lot, Paul Cohen, said Arens should not have dropped her car wash plans so quickly. In fact, the debate over that vacant lot captures the complexity of the mine subsidence issue.

Cohen notes a large Safeway grocery store built in 1985 and several other large buildings housing a library, liquor store, bank, restaurant and a McDonald's have avoided serious subsidence damage at the shopping center.

They have used creative, and expensive, engineering to compensate for groundwater and expansive soils - the far bigger geo-hazard threatening buildings across Colorado Springs.

Cohen hired geo-hazard experts who studied the vacant lot and rated it suitable for building if certain precautions are taken in the design and construction.

"We know that Dames & Moore rated this area a high risk for mine subsidence," Cohen said. "So we hired geologists to conduct detailed study of the site. They drilled all the way down to the coal mine and found it. There is a 6-foot cavern that has collapsed at 185 feet below the surface.

"Rubble has filled it in. It is below 163 feet of bedrock. Our geologists believe the risk of subsidence is low and rated it a low risk for commercial construction."

Still, Arens wasn't interested in the property after learning what's underneath, or the price tag of building a car wash that wouldn't be vulnerable to collapse.

Some simply deal with it

Like Cohen, Jerry Golden was aware of the mines beneath the Cragmor area when he was house-hunting and chose one on Country Club Place, site of several collapses over the years.

"I wondered about the truth of all those stories," he said. "But I always liked the area and bought this house in July 1999. The mines were never an issue with me."

Since moving in, he has watched his driveway crack, buckle and heave. He wonders if a mine collapse is at fault.

"My driveway has gotten progressively worse," he said. "We bought the insurance, but it only covers your house, not your driveways and sidewalks."

About a year ago, he said, neighbors were talking about a collapse on a nearby fairway at the Colorado Springs Country Club golf course.

Still, he wasn't scared. He's seen houses bought and sold there for years without any dramatic collapses. And he watched a neighbor build a new house on a vacant lot a few doors down using a "monolithic pour" of concrete that binds the foundation footers and  basement together to protect against damage resulting if the mine collapses.

Now he hopes to find someone with a similar attitude as he tries to sell his house so he can move to Denver to be near his grandchild and his business.

"I was never too worried about the mines," he said.

That's similar to the attitude engineering consultant Bob Syme adopted when he was hired to rebuild a section of I-25 that includes the Woodmen Road interchange.

The new northbound on-ramp will run over the air shaft of the old Klondike Mine - a 500-foot-deep shaft.

The state capped the shaft in 1979 after it collapsed and left a gaping hole just 15 feet off the existing on ramp.

A 3-foot-thick concrete cap was built using double-reinforced steel to seal the shaft and prevent future collapse. But the old cap sticks up too high and must be lowered to allow for the new on ramp.

"We will be removing the cap and rebuilding it," Syme said, though he didn't have a specific cost for the work. "It's something we have to fix. It's the first time in my 25 years of building highways that I've encountered anything like it."

No hard-sell from state

Bucknam understands why Arens is frightened at the thought of mines under her property. He's seen the damage mines can cause to buildings.

And the state doesn't encourage building over old mines.

In fact, the state mine subsidence protection program only covers houses built before Feb. 22, 1989, when the program started with a federal grant. The state didn't want to give developers incentive to deliberately build over mines, thinking homeowners could simply buy insurance.

But Bucknam also knows modern engineering can compensate for many of the risks, as Cohen suggests, making land over mines liveable and buildable. For a price, of course. Hiring geologists and engineers and paying for additional construction materials can add tens of thousands of dollars to the price tag of a project.

"You can probably build on some of these lots if you take proper precautions," Bucknam said.

Often it requires special foundations, as Cohen said were used on buildings at the Village Center, and sometimes drilling caissons, or concrete piers to the bottom of the mine to support the building.

"It's expensive work, but it can be done," he said. "But you need an engineering geologist to really figure it out."

And he acknowledges few claims have been paid since the program was established. Most damage to homes is the result of expansive soils, not subsidence.

"It's like flood insurance," Bucknam said. "If you live in a 100-year floodplain, you have a 1 percent chance of suffering a loss. But it can happen two years in a row.

"Unfortunately, we can't put a high degree of precision on hazard assessment. But the program is there if people want to participate. It's cheap peace of mind."

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