The North Metro Rail Line will have a total of nine bridges along its 18.5 mile route, and construction began for another one of them in November. Crews have mobilized to start the six-month long construction process on the 104th Avenue Bridge.
What is a "twin" bridge?
Unlike any other bridge on the project, the 104th Avenue Bridge is a twin bridge which means there are two independent bridges allowing trains to go both northbound and southbound simultaneously.
Each single track bridge is 401 feet long and 20 feet wide. The top of the rail is 26 feet above the street at its highest and there will be about 16-and-a-half feet of clearance under the bridge. It will be erected with a total of 18 precast girders.
Rendering of future 104th Avenue Bridge
Why a "twin" bridge?
Studies were done to determine the traffic volume at this station and decide whether it would be an at-grade crossing or a bridge structure. Results showed that the intersection of Colorado Boulevard and East 104th Avenue sees a high volume of vehicular traffic and as such a bridge is clearly the best option for the train to cross this juncture while reducing impacts.
Initial design called for an elevated station on top of the bridge, with a center platform between the two tracks while parking would have been under the bridge. However, once Wadsworth Construction, the contractor building this bridge, was engaged, engineers re-evaluated the bridge design and relocated the station and the parking. By relocating an existing detention pond to the east side of Colorado Boulevard, the North Metro crews will now build a ground level station platform and a new parking structure, which provides the surrounding community with easier access to the train.
Casings for the bridge caissons
Originally the 104th Avenue Bridge was slated to be the second longest bridge on the project, but the changes in design shortened the bridge from 2,616 ft. to 401 ft., which results in substantial cost savings.
Building a bridge is one of the marvels of engineering involving many parts, specific terminology as well as high technology. Want to learn the process of building a bridge? Read it here!
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