High stream flows and heavy rainfalls created a 20-sq.-ft. (1.8 sq m) sinkhole in the westbound lanes of Interstate 70 in Eagle County, CO, on Sunday, June 1. Colorado Department of Transportation crews immediately closed the interstate in both directions in what could be the longest period that the interstate has been closed in its 40-year history.
The sinkhole developed after Bighorn Creek in Eagle County spilled over its banks, flooding a culvert under the highway and flushing dirt and rocks from under the highway down the slope below. The culvert is a 6-ft. (1.8 m) wide corrugated metal pipe that channels water from the creek under the highway and back into Gore Creek below. More than 400 people were evacuated from homes below the interstate because highway crews weren’t sure how much debris might plummet down the slope.
“Our first concern was that it would go at any moment,” said CDOT spokeswoman Stacy Stegman. “We were concerned that any amount of weight would cause it to slide down the hill.”
Water poured through Vail, flooding about a dozen homes. Preliminary estimates put damage to town roads at approximately $1 million. While Vail residents scurried about placing sandbags around million-dollar homes, nearly 20 federal and state maintenance and engineering crews began pumping water from the sinkhole and diverting the creek from the pipe’s opening.
Stegman said crews needed to lower the water level within the sinkhole nearly 20 ft. (6m) in order to find the break and assess the stability of the culvert in the eastbound lanes. Initial reports stated that the damage might have been caused by something puncturing the pipe or by water pressure funneling into the creek. CDOT likely will need to replace the culvert. Officials at the state agency will tabulate the costs of repairing the damage.
“It’s going very, very well,” Stegman said of stabilizing the situation. “Everyone’s pretty optimistic we’re making good progress.”
Meanwhile crews have paved part of the median on either side of the sinkhole so drivers can access the two eastbound lanes. Traffic has since been diverted to those lanes while CDOT crews finish repair work in the westbound lanes. Stegman said engineers are confident the eastbound lanes are stable and can carry the 25,000 to 30,000 vehicles that usually travel over Vail Pass each day.
During the initial closure CDOT detoured vehicles to SH 91 (Fremont Pass) to Leadville and U.S. 24 (Tennessee Pass) to Minturn. Commercial truck drivers were advised to avoid the interstate altogether by using Interstate 80 through Wyoming or Interstate 40 in New Mexico. CDOT officials did allow an ambulance that needed to go from Vail to Denver access through the area.
CDOT has no idea how long it will take to repair and reopen the highway although Stegman said that the stretch of highway between mile marker 180 in Eagle County and 195 at Copper Mountain wouldn’t be completely reopened for at least two weeks.
Earlier this year I-70, which serves as a major East/West corridor passing through the Rocky Mountain region, was closed for three days in mid-March after a severe snowstorm dumped up to 6 ft. of snow in the High Country, triggering avalanches that swept across the highway. A second storm later this spring closed the highway for 13 hours after a gasoline tanker truck slid off the highway near Copper Mountain.
The area has since realized warmer than usual spring weather, creating high water runoffs. CDOT spokesman Bob Wilson said oftentimes spring and summer weather can take a bigger toll on the state’s roadways than winter weather.
“The summer stuff takes the road with it,” he said of high water in the spring runoff. “The winter just blocks it up with some snow.”
Wilson explained that sinkholes are holes in the ground where water dissolves salt layers deep within the ground away the underlying rock layers. The land then gives way, usually violently, and the hole fills with water. At least two sinkholes were reported in nearby Summit County during the 1995 floods. Sinkholes can also form when cracks in asphalt allow water to seep into the road base and erode the underlying rock or if water moving underneath the ground gets to be so great it eats away at the wet soil and causes it to sink.
