Boston Avenue Bridge Replacement

This project will replace the Boston Avenue Bridge over St. Vrain Creek just east of the South Francis Street intersection. The bridge is being replaced in part so that it will safely pass 100-year flood flows. The project is part of the Resilient St. Vrain Project (RSVP) which is a multi-year, multi-phase flood recovery project to restore the St. Vrain Greenway and protect people and property from future flood risks. The City has partnered with the United States Army Corps of Engineers (USACE) for the next phase of channel improvements on the RSVP Izaak Walton Reach 2 (S. Sunset Street to Boston Avenue).

The new Boston Avenue Bridge will be longer and the channel underneath the bridge will be wider and deeper. This will result in a bridge that is better able to withstand larger flood events. There also will be several multi-modal improvements made while the bridge is being replaced. The surface sidewalks will be widened, the bike lanes will be redesigned to meet current standards and the pedestrian underpass will be upgraded so there is less likelihood of having to close the underpass due to flooding.

Updated November 15, 2024

• The bridge is now fully open to all lanes of traffic and will remain open through the end of the project in the spring of 2025.
• Remaining work includes; rebuilding the Greenway trail and connections to Boston Avenue, completing the decorative metal caps and architectural coating on the bridge, installing landscaping and irrigation, and adding new fencing and lighting.
• NOTE: There is heavy trucking activity on and around the bridge. Flagging operations may occasionally reduce traffic to one lane only to allow trucks to move through the area. Delays at all times should be expected.
• The underpass and Greenway trail are closed for the duration of the project. Bicyclists and pedestrians are allowed to cross over the bridge until the Greenway trail is complete.
• Normal construction hours are Monday–Friday, 7 am–7 pm. Some work may be necessary on Saturdays and in the evenings due to weather delays.

Project hotline: 720-819-7544
Project email: bostonavebridge@gmail.com

The goal of this project is to provide safe and efficient transportation along Boston Avenue, while furthering the goals of the adjacent USACE and RSVP channel improvements. The new, larger bridge structure will improve flood conveyance and provide increased flood protection for surrounding areas.

The RSVP Izaak Walton Reach 2 improvements include replacement of the Boston Avenue Bridge over St. Vrain Creek and channel improvements from Boston Avenue to S. Sunset Street including a new levee between Izaak Walton Pond and the creek. The City has partnered with the USACE for this phase of the RSVP improvements. Total project costs for this phase of improvements are estimated to be approximately $15 million. The City of Longmont’s local funding match is estimated to be approximately $8.5 million for construction of the bridge. Funding for the bridge project comes primarily from the Street Fund Sales and Use Tax.

• Design Complete – November 2022
• Bid Advertisement – December 2022
• Construction Award –July 2023
• Construction Start – August 2023
• Construction Period – Anticipated 24 months

There will be some traffic impacts during phased construction that will close half of the bridge at a time. During the first phase, one half of the bridge will be demolished and reconstructed, while traffic is allowed on the other half. In the second phase, the remaining half of the bridge will be demolished and reconstructed. This will allow traffic on Boston to cross the creek throughout construction while the old bridge is removed and the new bridge is constructed.

A public meeting was held on September 18, 2019 at the Longmont Museum to discuss projects associated with the RSVP.

This project was also included in a public meeting held on June 6, 2022 at the Longmont Senior Center to discuss upcoming projects in the Central Longmont Area.