Wed July 11, 2012

Sinkhole Near Leadville Turns Out To Be Century-old Railroad Tunnel

With the summer travel season well underway in Colorado, US24 north of Leadville is now closed by a little bit of history. A long forgotten and collapsed railroad tunnel finally revealed itself with a sinkhole.

At an estimated 100ft, the sinkhole is certainly a surprise. Initially, it was thought to have been caused by the heavy rains, but a mix of experts and engineers examining the hole determined it was a railroad tunnel. The method by which they deduced this was something straight out of MythBusters.

As the Vail Daily explains:

CDOT engineers and maintenance crews used mirrors Tuesday morning to bounce around reflections of the sun, all the way to the bottom of the sinkhole. That enabled them to get an accurate measurement.

The long lost tunnel is apparently part of theĀ Denver and Rio Grande Railway and a mining route from 1880. This route map from 1881 shows the spur going over Tennessee Pass connecting with the Royal Gorge Route in the south. According to DRGW.net the original tunnel was replaced after collapse with a second one, lined with concrete, built in 1945 and remains today [google map].

The most telling quote from DRGW.net's history of the Tennessee Pass Route is "The new tunnel was just geographically west of the original tunnel (by probably 50 feet or so). Also, at some point [sic]The old tunnel remains today, ...".

That is certainly confirmed now that ground thaw has opened up an enormous sinkhole. If you are looking for a time sink today, pun intended, then reading the history of the Denver and Rio Grande Railway is certainly a worthy pursuit. Both DRGW.net and the Royal Gorge Route have some history to pique your interest.

Modern day concerns still exist though as motorists have been driving over this forgotten tunnel for years. US24 remains closed indefinitely at mile marker 165, just south of Red Cliff, until CDOT can figure out how to fix the issue. Traffic is diverting to Highway 91 now.