Changes come to long-forgotten tunnel

AUSTIN (KXAN) - It runs for 15 blocks beneath the west side of Austin’s downtown, but almost no one had ever heard of it before city work crews started digging part of it up.

The history

The Little Shoal Creek Tunnel started out, possibly as long ago as the 1800s, as a series of bridges over a tributary that ran into the main Shoal Creek before that stream emptied into the Colorado River.

The original bridges were constructed of large limestone bricks. Later versions used more traditional clay bricks. Eventually, the city connected the bridges with arched concrete, forming the tunnel.

• Photos: Inside the underground passage

The technique enabled engineers to cover the entire stretch of Little Shoal Creek, creating lots of new real estate on the surface.

The best we can determine,” said Glen Taffinder, a city supervising engineer for the Watershed Protection Department, “it was designed in the 1920s and constructed in the 1930s. The best we can tell, it was to encourage or to allow more development to occur in a more centralized location in the downtown area. It looks very much like they followed the original path or alignment of Little Shoal Creek and then just enclosed it in concrete.”

The bank

Now modern-day construction crews are digging up part of their ancestors’ handiwork to move a three-block stretch of the tunnel slightly to the west. The city insisted on the altered route before developers could start work on a new Austin high-rise headquarters building for IBC Bank.

“The tunnel currently goes under what's a parking lot now,” said Taffinder. “So they could not build their building there because of the footing and the foundation requirements. So they needed to move the tunnel out from under that parking lot to be able to build it.”

It’s not that the project would endanger the tunnel, necessarily, but if it became necessary to dig down to the structure for maintenance or repair in the future, that would be hard to do with a 13-story building sitting on top of it.

“Certainly from a structural engineer standpoint, you could design something that could go around it, but then we've lost all of our access to the surface. And so we can't excavate down to find an issue. If something collapsed or something like that, it would be very difficult.”

The agreement

So, working together, the city and the developers found a mutually beneficial solution.

“We didn't have funding for it at the time,” Taffinder said. “However the private developer came to us and presented an opportunity that they would cost-share with us to relocate the tunnel out into the right-of-way. And so we looked at that as a win-win situation.”

The tour

So with the long buried and mostly forgotten tunnel re-emerging from the mists of time, KXAN News asked the Watershed Protection Department for a guided tour. Department officials agreed, with the caveat that our crew would have to gear up in reflective vests, harnesses and hard hats, carry flashlights and receive a ten-minute safety briefing.

So, at the mouth of the tunnel along Fourth Street, City Safety Engineer Mike Millsap let loose with a long list of things that could go wrong in the tunnel. To begin with, the buried passageway is designed to direct street storm water runoff to Shoal Creek and then into the section of the Colorado now known as Lady Bird Lake.

“So in the rain,” said Millsap, “this would fill up with water going at a very rapid pace and that would, you know, overwhelm anyone.”

“Overwhelm” in that context translates into “drown."                  

The hazards

But even in the middle of a drought, the tunnel can be treacherous. It is a haven for spiders and cock roaches. The arachnids tend to hide in crevices but the roaches, some of them appearing to be as large as small rats, regularly gather for conventions along the tunnel walls and floors.

Then there are the razor sharp pieces of cut iron protruding from the concrete and sections of jagged cut pipe sticking up along the floor.

“You can touch anything you want to,” said Millsap, putting the visitors briefly at ease before adding, “Just be aware it may be contaminated.”

With that, the safety engineer pulled out a loud air horn.

“This is going to be used in case of an emergency,” Millsap said. “So we're going to blow this and then…the attendants (on the surface) have been instructed, if they hear the air horn, that's going to mean call 911. So AFD (Austin Fire Department) will come and they'll rescue us.”

Fortunately, the tour ended without incident, though if not for the hard hats, there would definitely have been some bloodied scalps as the visitors passed through the narrower and shorter sections.

The video

For the curious, a click on the television version of this story to the left on this page will offer up a trip down into the tunnel.

Try it on your own, though, and even if you do avoid trouble inside, beware: Unauthorized entry into the Little Shoal Creek Tunnel is a crime. If you’re caught, you could be charged with a Class B misdemeanor, under Penal Code section 30.05. Conviction carries a penalty of six months in jail and/or a fine of up to $2,000.

Just watch the story.