New pedestrian bridge to span Maroon Creek | AspenTimes.com

New pedestrian bridge to span Maroon Creek

Janet Urquhart
Aspen Times Staff Writer

The longest bridge of its type in the state will be erected over the Maroon Creek gorge this year, providing a key link in Aspen’s trail system.

The Aspen City Council last week approved a $2.1 million contract with BTE Concrete Formwork of Glenwood Springs to build the span, which will link Iselin Park and the Tiehack parking lot at Buttermilk.

The bridge’s construction will be something of a technical marvel, according to Jeff Woods, city parks director.

“It will go 605 feet without a pillar in the middle,” he said. “We can build the bridge from both edges without going into the canyon floor.

“It’s quite a technological feat,” Woods said. “When it comes down to dollars and cents, it was actually the cheapest option, as well.”

The span will be the longest arch bridge in Colorado, according to Terry Ostrom, general manager for BTE. It will be the second-longest bridge of any type in the state, he added. The suspension bridge over the Royal Gorge will retain its distinction as the longest in Colorado.

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Concrete abutments will anchor the bridge on either side of the gorge, but the supports will be drilled into benches far above the deepest cut of the creekbed, Woods said. No abutments will be extended to the floor of the gorge, 175 feet below. That way, the bridge construction will not disturb sensitive riparian areas along the creek. Mature trees in the gorge will be avoided, as well.

“This bridge is basically going to be put in with very minimal impacts,” Woods said. “We’re not taking out a single tree as we build this bridge. It’s sited in a gap in the canopy.”

The actual construction, however, won’t go unnoticed. It will require the use of a 270-ton crane, to be delivered in 13 truckloads and assembled at the site, according to Ostrom.

“It will be by far the biggest crane that Aspen has ever seen,” he said.

BTE has begun excavation work at the site and will start pouring concrete in June, Ostrom said. The firm has subcontracted with Pioneer Steel of Glenwood Springs to assemble the steel arch, which will be prefabricated by a Denver company.

The steel work is scheduled to begin in September. That’s when the giant crane will be assembled first on the Iselin side for about three weeks. The arch will be extended about halfway over the gorge and suspended in place by temporary cables, according to Ostrom. Then, the crane will be taken apart, trucked to the Tiehack side and reassembled so the other side of the arch can be extended outward, he said.

While that is being done, two smaller cranes will be used to put steel floor beams in place on the Iselin side. When the arch is complete, the two small cranes will be moved to the Tiehack side to complete the flooring for the bridge deck. BTE will then pour the concrete deck this fall, weather permitting.

If the deck can’t be poured this fall, it will be delayed until next spring, Woods said.

The bridge, designed by engineer Jeff Simmons of Carter-Burgess in Denver, will take on the look of weathered steel. The steel mesh railing on either side will be 5 feet 7 inches high.

The new connection has long been part of the city’s trail plans and was included in the Maroon Creek Club approvals, according to Woods.

The $2.1 million construction contract will include $475,000 from the Maroon Creek Club, $377,401 from the city Water Department and $34,974 from the city’s electric utility. A new water line and electrical conduits will be extended across the creek on the underside of the new bridge.

Currently, the sole water line serving Aspen west of Maroon Creek runs beneath the Highway 82 bridge over the creek, Woods said. A major break in that line would cut off water to the west side of the city.

The bridge deck will be 14 feet wide and structurally capable of accommodating emergency vehicles as large as a fire truck, according to Woods.

The bulk of the cost of the construction contract, $1.5 million, will come from the Parks Department via a recreation bond issue approved by voters in 2001. With preconstruction costs, fees and a $50,000 contingency budget, the total cost of the span is $2.4 million.

The bridge will provide a missing link in the city’s recreational trail system, accommodating bicyclists on the Government Trail and Nordic skiers on the city’s groomed trail system.

“You will be able to ski from Iselin and the whole schools complex across the bridge to the Maroon Creek Club and the Owl Creek Trail,” Woods said. “This has been in the planning stages for many years.”

Currently, crossing the creek requires a steep decent into the canyon to a U.S. Forest Service bridge and up the other side. The Forest Service plans to abandon the existing trail on the Tiehack side because it crosses private property and is subject to erosion problems, according to Woods.

A new trail down to the creek from the Tiehack side will be constructed beneath the new bridge, he said.