This is a Transportation Authority of Marin (TAM) project. At the request of TAM, the County of Marin is managing the construction effort of the project.
Overview
The Transportation Authority of Marin (TAM) project includes adding a second lane to the off-ramp of Bellam Boulevard from US 101, separating the traffic turning left onto Bellam Boulevard from the traffic turning right or continuing straight across the intersection to the eastbound I-580 on-ramp, widening the I-580 on-ramp in order to receive the shifted through lane. Additional improvements generally include concrete barrier, traffic signal modification, storm drain improvements, pavement markings/striping and a new retaining wall. The County of Marin Department of Public Works is managing the construction effort of the TAM project.
This project is intended to mitigate the traffic congestion on northbound US-101 and eastbound I-580 at the Bellam Boulevard off-ramp in San Rafael.
Funding
Construction project cost is estimated at $8.1 million, funded by Transportation Sales Tax (Measures A and AA) and California Transportation Commission. There was a separate project for tree removal was completed for an estimated $200,000 to make room for the ramp improvement project. Additionally, TAM's project development costs are estimated at $1.7 million.
Traffic impacts
There will be construction activities on the ramps but it will be separated from the traffic lanes by "K-rail" barriers. At this time, it is not anticipated that lane closures will be required. There will be intermittent nighttime ramp closures to accommodate construction work. While no daytime lane/ramp closures are planned at this time, drivers should expect for some traffic slowdown on the ramps due to the nature of a construction zone and we appreciate drivers being patient. All lane/ramp closures will need to be approved by Caltrans (the property owner) and public notifications with detour instructions will be made in advance. Please see the Timeline section of this webpage for specific closure date announcements.
Timeline
May 2024
- County of Marin Board of Supervisors authorized a Cooperative Agreement with TAM for the County to advertise, award, and administer the construction contract on behalf of TAM.
Early-January 2025
- Preparations at construction site expected to begin. This may include activities such as clearing, grubbing and tree removal.
- Crews will first conduct tree removal along the right side of the off-ramp from US 101 to Bellam Boulevard and then move to working along the right side of the on-ramp to I-580 from Bellam Boulevard.
- Tree removal is required to provide space for the off-ramp widening and associated retaining walls.
End of January
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- Preparations at construction site expected to be completed.
March 10, 2025
- Start of construction phase
March 17 through March 20
- NIGHTTIME (midnight to 5:00 AM) RAMP CLOSURES for US-101 and I-580
March 24 through March 28
- NIGHTTIME (midnight to 5:00 AM) RAMP CLOSURES for US-101 and I-580
Late Fall 2025
- Anticipated completion of the construction phase
