07/13/2012 06:12 pm ET Updated Dec 06, 2017

'Sinkhole' Beneath Colorado Highway Growing, Pieces Of Highway 'Crumbling' And Falling Into It (PHOTOS, VIDEO)

The giant sinkhole that opened up alongside Highway 24 near the top of Tennessee Pass on Monday continues to grow. As of Thursday afternoon it had grown to 30 feet by 30 feet and remains 100 feet deep.

On Facebook, CDOT posted some new photos and said they are working on figuring out a plan of action:

Our crews have been working hard on finding a repair solution and we will let you know as soon as one has been found!

CDOT estimates that the repairs to US-24 to take a little over a month and is prepared to offer financial incentives to the right contractor to encourage them to complete the job ahead of schedule. USA Pro Cycling Challenge is expected to pass through the area in about a month and CDOT is hoping to have the project completed before the race. Costs are estimated between $1 and $2 million.

According to the Colorado Department of Transportation, pieces of asphalt from the highway have started to crumble and fall into it.

CDOT also issued a statement on Thursday saying that the "sinkhole" isn't really a sinkhole at all, rather it's just a hole caused by the soil giving way above an abandoned railroad tunnel.

After several engineers, maintenance supervisors and geological experts examined the sinkhole on Monday, it was determined that it is actually a century-old railroad tunnel that collapsed decades ago, CDOT said in a press release.

CDOT is also working with state historians and is referencing archival materials to build a full history of the tunnel and roadway.

The depth of the hole is estimated to be about 100 feet, and since the depths reach so far into the earth, much of the soil was still frozen until very recently -- when the soil thawed, the hole was exposed.


7News spoke with Rex Goodrich, a CDOT engineer who explained why engineers decided it was safer to shut the highway down completely. "It's the unknown. Twenty feet away, there could be another hole like this ready to break through," Goodrich said to 7News.

The collapsed tunnel was reportedly once part of the old Denver and Rio Grande Western's Tennessee Pass Route. It was constructed as part of the Royal Gorge Railroad route in the 1880s, The Denver Post reports.

According to 9News, Union Pacific now owns it and said the tunnel has been abandoned since the 1950s.

All of US-24 is not closed between Red Cliff and Leadville, however it is closed at the section near the sinkhole from mile marker 166 to 162. Crews remain on-site to enforce the closure 24 hours a day, seven days a week. Access to all local roads and businesses remain open. CDOT is recommending using State Highway 91 as an alternative route.

The Colorado Department of Transportation (CDOT) posted photos of the giant sinkhole on their Facebook page.

LOOK: Giant sinkhole alongside US-24 near Leadville, via CDOT:
colorado sinkhole

Additional photos of the US-24 sinkhole and more giant sinkholes from around the world: