Underground Tunnels Challenge Hot Springs Engineers from Past to Present

The darkness is absolute. Steam fogs your vision as it curls off the surface of water that rushes past your feet. Your boot slips on stone made slick by the rushing water.

The ceiling is far above your head and sometimes, in your flashlight’s glare, you spot the tendrils of seeds that have grown in piles of sediment but won’t survive past germination. You hear the gurgling of waterfalls created by long-built-up deposits of minerals.

And, coming from above, there’s the rumbling sound of motors: The place isn’t one of Arkansas’ many natural caverns, but instead a vast man-made tunnel, built to contain the mineral-rich waters that supply the famous bathhouses of Hot Springs.

The Hot Springs Creek Tunnel is an engineering marvel, a nearly 130-year-old behemoth that dwarfs in size many of the town’s better known architectural feats.

It snakes 7,050 feet along Central Avenue through Hot Springs’ historic downtown area, where it splits two ways and continues along Whittington Avenue and Park Avenue. Including those streets, the tunnel’s full length is about 2 miles. At its widest, the pipe is nearly 17 feet from top to bottom.

Arkansas is home to other structures like this: A tunnel system runs like a spider web throughout downtown Eureka Springs; the Rock Street Tunnel in Little Rock was completed in 1974 and drains water from the Interstate 630 corridor.

These systems represent architectural accomplishments that carry their unique engineering challenges into the present, but often go unnoticed.

Obscure Marvels

Burt Parker, an engineer at North Little Rock’s Garver, worked on the Rock Street Tunnel as it neared completion. He said structures like this are obscure but monumental jobs.

“There are a lot of large culverts around, but the Rock Street Tunnel, it was a pretty large undertaking,” he said. “It was really off the radar when it was built, and it was a pretty major engineering accomplishment at the time.”

This combination of complexity and obscurity is common to the state’s other underground tunnel systems.

Kevin Chitwood, an engineer for Atoka Inc. in Hot Springs, has walked through that city’s tunnel system many times.

Many cities have storm drains in place, Chitwood said, and they are often served by large concrete pipes. The difference in Hot Springs is that there was a creek already in existence.

In 1882, a federal appropriation allowed for enclosing Hot Springs Creek with an arch.

Work began in 1883 and was completed in 1884 at a cost of $136,745. The original arch ran for 3,500 feet.

As a contrast, the tunnels in Eureka Springs stretch 1,250 feet throughout the town’s infrastructure, snaking under businesses and other structures, varying in width and height.

“Most of it is native stone,” said Dwayne Allen, director of public works for the city. “Some areas you can stand up, and some areas you’re going to crawl.”

Many parts of the system are about 100 years old, Allen said, and were built to alleviate the frequent flooding experienced during the town’s booming development in the late 19th century.

Some parts of the pipe were actually built over the first floors of businesses. “There are storefronts down below,” Allen said. “There are business windows and doors from that era, underneath along the sidewalks in that area.”

Engineering Challenges

These tunnels present unique challenges in upkeep as they age.

The need for maintenance of the Hot Springs Tunnel was apparent by 1963, when a study showed it needed major repairs. The next year, McRae Construction Co. of Hot Springs completed an $11,194 project removing debris and clearing boulders from the creek’s bed, as well as repairing the walls and ceiling.

The next major repairs were completed in 2001, a $795,000 improvement job on the tunnel’s arch.

That job was done by Atoka, which has since become the local expert on the tunnel.

Chitwood said it’s difficult to find firms that will work on a structure like the tunnel. “You have to find somebody that can stretch themselves a little bit and perform some maintenance work that they normally don’t do,” Chitwood said.

Despite its size, it’s still considered a confined space, he said.

“You have to go through confined space permitting to enter it,” he said. “If you have a certain area to look at, it takes some planning to access that area because it is very limited access. Various stretches of the tunnel are constantly being eroded away at the foundation where you’ll have to have grout repairs done once every 10 or 20 years.”

It’s dangerous, too. Not only are the walkways slippery, but the water flowing through the tunnel is so hot that, in the summertime, it’s possible to be overcome by the heat. Chitwood said some workers have had to be lifted out of manholes after fainting.

This year, Atoka’s job, paid for by a $53,678 federal disaster recovery grant, will be to repair some cracks and perform some general maintenance work, Chitwood said. But there are other, more difficult issues plaguing the tunnel.

Max Sestili, stormwater manager for Hot Springs, said a crack in the tunnel’s ceiling along Park Avenue has appeared underneath a pair of hotels, one vacant and one an active Relax Inn. As a result, part of the active hotel had to be condemned.

But the city has had a hard time performing work: “No contractors in their right mind are willing to send guys down there to perform that kind of repair,” Sestili said. “We are looking into purchasing the vacant hotel and tearing it down, then opening up the creek again. At that point we’ll be able to access the cracked portion under the active hotel and find some people willing to do it at that point.”

Eureka Springs faces even steeper challenges. Because of the lack of oversight in building the rambling tunnels, some areas have ended up being littered with debris.

“Finding junk metal and stuff was one of the big problems,” Allen said.

Some of the tunnel is in great shape, he said, but some limestone walls and ceilings are failing, putting some buildings and parking lots above at risk.

Because of the businesses above, maintenance is extremely difficult. “You can’t do any excavating there,” Allen said.

He said the city has considered installing modern storm drains and filling in the tunnels with concrete.

“But cost-wise it almost seems like we’re going to have to stay with this tunnel and improve it as we go on,” he said.

He said the city is working on a mitigation plan, and Allen hopes there will be some money allotted to work on the tunnels.

Full repair will require a lot of money: In 2011, McClelland Consulting Engineers Inc. of Little Rock estimated the job would cost around $4 million, and the city shied away from that.

“We didn’t do the work they recommended,” Allen said. “From that point on we’ve had our hands tied. We’ve had some flooding, but we’ve just been kind of observing it until we can get a mitigation plan.”

But through the difficulties, the city officials and engineers attached to these projects expressed enthusiasm for their history and mystique.

“It’s a cool project,” said Chitwood in Hot Springs. “It’s something you don’t get to work on every day.”