CDOT rebuilding flood-damaged Glenwood Canyon bike path
September 9, 2011
GLENWOOD SPRINGS – The Colorado Department of Transportation has launched a $1.5 million project to repair stretches of the Glenwood Canyon bike trail damaged by sustained high runoff this spring and summer.
State officials hope to have the project on the two-mile stretch from the Shoshone Power Plant (mile marker 123) and Hanging Lake Tunnel (mile marker 125) complete by late October or early November.
Driving up the project cost is the extensive damage to the cantilevered trail sections, as well as the difficulty of accessing the path with heavy equipment.
Major erosion to the embankment below the path, for example, will require transporting and using a crane to place an estimated 1,800 cubic yards of rock material to stabilize the area.
Nearly every year, the Shoshone-to-Hanging Lake stretch of the canyon trail must be closed for a few weeks during the peak of spring runoff, when floodwaters swamp the trail.
This year, however, huge late season snowfall in the high country led to spring runoff flows that were much higher than usual and lasted for more than two months. Along the path, water was up to the railing in places (about 48 inches high on the path) and through the path’s eight-foot-high tunnel under I-70, the water reached a depth of six feet.
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By mid-June, with the floodwaters still raging, it was clear that sections of the concrete trail had buckled or collapsed. It wasn’t until water finally receded in late July that highway engineers could get a complete picture of the damage.
“We originally thought the damages were minor. But after detailed examination, we realized this would be a more difficult engineering project,” CDOT Region 3 Transportation Director Dave Eller said.
“It has required extensive design work, much like any other highway reconstruction project, and construction access is going to be challenging.
“We will rebuild the path to its original cross-sections and design. In the path’s 20-year history, this is the first major repair project we’ve conducted,” Eller added.
CDOT brought in Lawson Construction of Longmont in August to clear debris from the path. Crews found large, damaged sections of concrete along the path’s two cantilevered sections west of the Hanging Lake Tunnel. Some concrete sections and railings had completely washed away.
CDOT engineers have coordinated with White River National Forest and U.S. Army Corps of Engineers officials on a repair plan, and Lawson Construction started work this week.
During repair work on the path (or “sidewalk”), Lawson’s crews will:
• Replace 60 square yards of concrete sidewalk panels on the cantilever sections west of the tunnel.
• Repair support beams on the cantilever sections.
• Replace about 300 square yards of on-the-ground concrete sidewalk, including embankment and fill material.
• Repair scouring caused by water erosion under the concrete wall footers (or support bases).
• Replace about 700 linear feet of timber railings and posts, and repair additional sections that are damaged but still in place.
• Rebuild a 45-cubic-yard concrete abutment where the on-the-ground sidewalk meets the cantilevered sidewalk.
• Repair sections underneath the sidewalk that have eroded, using a procedure call “slab jacking.” The method is essentially drilling holes into the concrete and filling voids underneath with grout.
The work will require a closure of the right lane of eastbound I-70 from the Shoshone exit to the Hanging Lake Tunnel for the duration of the project. Some parking spaces in the overflow parking area at Hanging Lake Rest Area may also be closed to provide a storage space for stockpiled material.