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MSN Petaluma Project Map
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MSN 101 Petaluma Blvd South Interchange and Petaluma Bridge Project Interstate 116 Interchange Project

Lane Configuration and Speed Limit
In November 2014, just south of the Petaluma River on U.S. 101, Caltrans switched northbound traffic to new lanes in the median. This traffic switch was necessary to begin demolition of the old northbound bridge. For the current traffic configuration, be aware that maximum speed limits have been reduced:

  • The northbound speed limit is 45 MPH
  • The southbound speed limit is 55 MPH
  • In the interests of public safety, the California Highway Patrol has been requested to increase traffic enforcement in the project area.
  • In addition, if your vehicle is disabled in the construction zone, please remain inside your vehicle until emergency services arrive to assist you. Do not exit the vehicle while parked in live traffic.
Opening of the Northbound On-Ramp from Petaluma Blvd. South
When northbound traffic was shifted to the median, the northbound on-ramp from Petaluma Boulevard South was closed to allow for construction of new northbound lanes a new northbound on-ramp from Petaluma Blvd. south.
  • Due to current weather conditions, there is no firm date for opening the new northbound on-ramp from Petaluma Boulevard South. Construction will require approximately one month of dry weather to build the new on-ramp. We anticipate that the new ramp will open in early 2015, but a precise date for opening is uncertain at this time.
The Petaluma Blvd South Interchange project will construct a new interchange at Petaluma Blvd South, frontage roads and replace the Petaluma River bridge. The existing Petaluma River bridge is an 866 feet long, twin reinforced concrete box girder (with pre-cast I girder span over the river) bridge that was built in 1955. The existing bridge has two lanes of traffic in each direction and no shoulders The new bridge will be 907 feet long with three lanes of traffic in each direction and standard shoulders. This will be one of the longest precast, post-tensioned spliced concrete girder bridges in the U.S. Constructing the new bridge over the Petaluma River, which is a navigation channel, will be very challenging. The bridge will be constructed in three stages and require erection of 99 girders up to 130 feet in length and weighing up to 60 tons each.

The project will also replace the existing South Petaluma Blvd On/Off Ramps constructed underneath Highway 101 in the mid 1950's with a new "diamond" interchange with a decorative gateway structure (overcrossing).

Construction is anticipated to be complete by the end of in 2016.

The Route 116 (Lakeville) interchange project will replace the northbound U.S 101/116 separation bridge and widen southbound U.S 101/116 Separation Bridge to accommodate future HOV lanes in both directions from the Petaluma River Bridge to State Route 116.

The existing bridges have 2 lanes with no shoulder and were built in 1955. The new and widened bridges will have three lanes in each direction with standard shoulders

The project will also install sound walls along the on-ramp from Route 116 to northbound Highway 101 just beyond the Caufield Lane Overcrossing.

Challenges for this project will be working adjacent to and over the SMART Railroad tracks and Highway 116

Construction is anticipated to be complete by mid 2015.
Thank you,

Allyn Amsk
Public Information Officer
Caltrans, District 4, Office of Public Affairs
Office (510) 286-5445

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