Officials give nod to bridge design

Designs for a new Maroon Creek bridge that can be constructed outward from the bridge deck on either side until the span meets in the middle won a conceptual nod Thursday from local elected officials.The so-called “single-box concrete segmental” design floated to the top as the recommended alternative because the impacts on riparian and wetland areas in the Maroon Creek gorge are minimized, Colorado Department of Transportation officials explained yesterday.Various designs considered for the 610-foot-long span were the focus of a pair of open houses at the Rio Grande meeting room.By building the bridge in segments from above, only a relatively small crane will need to work from the bottom of the gorge. Constructing the bridge using either massive steel or concrete girders would require a gigantic crane and roughly twice the disturbance zone along the creek, said Tom Stelmack, senior project manager with Parsons, a consulting firm to CDOT.”If there was nothing to save underneath, this wouldn’t be the recommended alternative,” said Ralph Trapani, former CDOT engineer and now deputy project manager with Parsons.Two A-frame piers will be placed in the gorge to support the bridge.The bridge will cost an estimated $7.2 million to $8.2 million to construct, according to Joe Elsen, CDOT program engineer. The added costs of engineering, traffic control, contingency funds, etc., bring the total price tag to about $11 million, he said.Those funds aren’t currently available, but CDOT and local officials hope having the bridge designs and environmental clearances in place will help move the project forward quickly if state and/or federal money suddenly becomes available. It’s a strategy that has worked before in the Highway 82 corridor, Elsen noted.In fact, that’s why the upper valley put in $1.5 million to get the design work done. CDOT didn’t have the money.If the plans get stuck on a shelf for a while, they won’t become obsolete, Elsen said. “It wouldn’t take a whole lot of dusting off,” he said.The recommended design received the blessing of City Council members and Pitkin County commissioners after a presentation yesterday afternoon. “This is such a no-brainer,” said Commissioner Dorothea Farris.But City Councilman Terry Paulson expressed concern that the existing bridge, a historic railroad trestle that now supports the two-lane highway, won’t be kept in adequate condition by CDOT once the new bridge is built. The trestle is slated to carry light rail if that transit alternative ever comes to pass in the upper valley.For the time being, the old highway deck would remain on the existing bridge, but it would be closed to all use, according to Trapani.”This bridge does need to be preserved. There’s no doubt about it,” he added.The new bridge deck would be 73-feet wide – enough to accommodate four lanes of traffic, including dedicated bus lanes in each direction. However, voter approval for the bus lanes is not in place. Instead, the new bridge is initially expected to carry just two lanes of traffic, one in each direction, plus 8-foot shoulders, a 12-foot bike/pedestrian lane and a 12-foot median. The existing pedestrian bridge will be removed to make way for the new bridge.The projected life of the new span is 75 years, Stelmack said.Janet Urquhart’s e-mail address is janet@aspentimes.com