Structure problems strike bridge
Aspen Times Staff Writer
The Colorado Department of Transportation briefly closed the Maroon Creek bridge yesterday to vehicles larger than a pickup truck after inspectors found cracks in the stone abutment that holds up the bridge.
Although weight restrictions were later loosened to allow midsize trucks, it appears the primary access in and out of Aspen will remain open for only limited use for at least a week and quite possibly longer.
“We’re working as fast as we can to make these repairs,” said Joe Elsen, CDOT’s program engineer. “This is the main route into Aspen, and we don’t want to lose it.”
The limited closure began Sunday after CDOT inspectors discovered that two giant sandstone blocks that support the downvalley end of the bridge were crumbling.
The inspectors immediately replaced the most compromised of the blocks with hydraulic jacks designed to lift a semitruck.
The 115-year-old Maroon Creek bridge has long been considered one of the shakiest in the state highway system and is therefore inspected once a year instead of once every other year, as are most bridges.
The closure forced most construction traffic in and out of Aspen onto a detour that goes through the Cemetery Lane neighborhood, on to McLain Flats and back to Highway 82 via Smith Way.
Pitkin County lifted its usual weight restrictions on McLain Flats Road to accommodate the detour. Traffic-control crews from the Snowmass Canyon four-laning project were dispatched to help direct traffic to the detour.
Throughout the day yesterday, restrictions were tightened as CDOT engineers sought to reduce stress on the bridge, the crumbling abutment and the hydraulic jacks that were being used to replace it.
In the early morning, the detour affected only large trucks, weighing 20 tons or more. By afternoon, the maximum weight allowed across the bridge was lowered to 10 tons. And by late afternoon CDOT lowered the bar again to allow just one-ton pickups and smaller vehicles.
For most of the afternoon, CDOT officials considered forcing public transportation, including school buses, onto the detour route but changed their minds at the end of the day. CDOT spokeswoman Nancy Shanks announced late yesterday that public transit and school buses would be allowed across the bridge, and the weight restriction had been raised to allow vehicles up to 5 tons.
Large pickup trucks, SUVs with trailers and almost all commercial trucks will be required to use the McLain Flats detour until further notice. Trucks and large vehicles traveling from Snowmass Village to Aspen will also be required to detour around the bridge.
Aspen’s assistant city manager, Randy Ready, said police would step up enforcement of the speed limit along Cemetery Lane, the main access road to one of Aspen’s largest residential neighborhoods.
Two members of CDOT’s bridge crew were dispatched to assist local engineers. Jeff Anderson, a member of the CDOT bridge department, said the sandstone blocks, which are normally more sturdy than concrete, were crushed by the bridge itself, which stretched 3 to 4 inches beyond its normal range.
He said bridges are designed to allow for considerable expansion and contraction of steel and other materials with changes in temperature. But he questioned whether the ancient Maroon Creek bridge had those design safeguards in place. He pointed out that most bridges are designed to last 50 to 75 years.
Anderson lowered the bridge’s sufficiency rating, which takes structural integrity into account, to just 9 out of 100. For several years the bridge’s integrity rating has been at 24, low enough to prompt the annual inspection schedule.
Ames Construction, the lead contractor on the Snowmass Canyon/Highway 82 widening project, has been hired to make the necessary repairs, Shanks said.
Crews are also trying to find the source of a small stream of water that’s flowing out of the hillside a few dozen feet below the compromised abutment.
Ready said the damage and detour highlight the importance of replacing the bridge.
“It’s CDOT’s bridge, but we’ve been working on a new design for a year,” he said. “This makes it all the more obvious that we need to move ahead and build a new bridge.”
[Allyn Harvey’s e-mail address is email@example.com]
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