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 September 13, 2024
- From September 18 – 27, River Rd. will be closed to through traffic from S. Francis St. to Barnard Ct.
- S. Francis St. will remain open to Boston Ave.
- Local access to adjacent residences on River Rd. will remain open.
- Detour routes will be set up on S. Francis St. and Center Place.
- Additional work is currently occurring on the north side of the bridge and two lanes of traffic are open on the south half of the bridge.
- 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 must merge with vehicle traffic across the bridge. Pedestrians are prohibited from crossing the bridge.
- 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.
- Slow for the Cone Zone! The speed limit has been reduced to 25 mph on Boston Avenue across the bridge.
Project hotline: 720-819-7544
Project email:Â 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.
Frequently Asked Questions
No. Two lanes of traffic will remain open for vehicles. However, travel delays should be expected.
Yes. The trail and underpass will be closed. Bicyclists and pedestrians are encouraged to use alternate routes.
Travelers may use S. Pratt Parkway or S. Sunset Street as alternate routes across the St. Vrain.
The sidewalks on the bridge will be 8 feet wide and the on-street bike lanes will be 5 feet wide with an additional 1.5 feet of width where there is no curb and gutter on the bridge. This is similar to the S. Pratt Parkway Bridge over the St Vrain.
No the center lane will remain. The new bridge is wider than the existing bridge. There will be two 12-foot wide travel lanes and a 12-foot wide center turn lane.
No. The current design and width of the bike lanes will ensure the safety of bicyclists.
Yes. Because the channel is being widened and the bottom of the channel lowered, the design grade for the new St. Vrain Greenway underpass should reduce the frequency of trail closures due to high creek flows that typically occur during spring runoff.
There are several design standards that were used to inform the project design. These include the Longmont Municipal Code, the City of Longmont Design Standards and Construction Specifications and approved material lists, the St. Vrain Greenway Signage System and Graphic Standards, and the Longmont St. Vrain Greenway Master Plan. For the bridge structure, the Colorado Department of Transportation (CDOT) Bridge Design Manual, the CDOT Construction Specifications and a few CDOT M-Standards Details were used. In addition, the design of the creek channel was informed by the CDOT Drainage Design Manual and the Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual. The low flow channel design, wetlands plantings, flood bench seeding, wall margin plantings, and upland seeding and trees were developed through previous phases of the City’s overall Resilient St. Vrain Project (RSVP).