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Sunset Street Corridor

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Sunset Street Bridge long side view
Sunset Street Bridge side view with pillar

Boulder County Transportation in partnership with the City of Longmont is planning to reconstruct both Sunset Street and Boston Street in a section of unincorporated Boulder County located within Longmont. Learn more about the Boston-Sunset Project >

Project Overview


The new Sunset Street Bridge opened to all traffic—vehicular, cyclist and pedestrian—on May 19, 2016.

Timeline of Work

The project removed and replaced the Sunset Street Bridge, which was destroyed by the September 2013 flood event. The new structure was lengthened and widened to accommodate pedestrians and cyclists as well as designed to pass a 100-year storm event. (For comparison, the original bridge was 90 feet long and 24 feet wide; the new bridge is approximately 220 feet long and 50 feet wide.)  

Bridge design work began in early September 2014. Efforts included determining the overall footprint of the bridge and its effect on creek hydrology. The bridge design, including all environmental clearances, was completed as of July 2015.

Get a detailed look at the bridge design >

The final step, prior to construction, was to complete right-of-way agreements; the wider and longer structure required additional easements adjacent to the bridge. This step was completed in the third quarter of 2015. Boulder County was the lead agency responsible for this process.

Construction began November 30, 2015. The bridge and surrounding work area was closed throughout construction, and all traffic was routed around the construction zone. The bridge opened to traffic on May 19, 2016.

This improvement is part of the City's larger effort known as Resilient St. Vrain, an extensive, multi-year undertaking to make the community more resilient for future floods by reducing the size of the floodplain through Longmont, while also restoring the valuable community asset of the St. Vrain Greenway.

Look back on how we built a bigger, better bridge for Sunset Street! The Bridge Blog told the story through monthly progress updates and photos.


Sunset Street from Boston Avenue to the Burlington Northern and Santa Fe Railroad (BNSF RR) serves as a primary connection from residential neighborhoods to Ken Pratt Boulevard and surrounding commercial businesses. The Sunset Street Bridge at St. Vrain Creek also provides access and serves as a pedestrian underpass for the City’s St. Vrain Greenway system. Sunset Street is classified as a neighborhood collector on the City’s Comprehensive Plan and is a multi-modal corridor in the Multi-Modal Transportation Plan. Sunset Street from just north of Boston Avenue to the BNSF RR and the bridge at the St. Vrain Creek are currently owned and maintained by Boulder County. Portions of Sunset Street and the Sunset Street Bridge were destroyed by the September 2013 flood event.


The Sunset Street Bridge Replacement Project is a joint project between Boulder County and the City with significant involvement from the Colorado Department of Transportation and the Federal Highway Administration (FHWA).


Funding for this project will be contributed by FHWA at about 83% of total eligible project costs. The remaining project costs will be funded between the State of Colorado, Boulder County and the City of Longmont. The total cost of the bridge is $3,428,657.


Tom Caprarella, Project Manager

Stay Informed

Open Houses

An open house was held on June 11, 2014 to present initial designs and plans.

An open house was held on March 4, 2015 to present final designs and plans. 

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