6) Marin/Sonoma Narrows (MSN) (Highway 37 in Novato to Old Redwood Highway in Petaluma)

6) Marin/Sonoma Narrows (MSN) (Highway 37 in Novato to Old Redwood Highway in Petaluma)

This project will add approximately 17 miles of HOV lanes in each direction. The project also includes new structures; structure improvements; intelligent transportation systems, including ramp metering; and soundwalls. The project would also upgrade the 9-mile long “Novato Narrows” section from expressway to freeway. It would provide interchanges and frontage roads to replace eighty (80) at grade intersections and driveways, and would replace the San Antonio Creek Bridge, which is prone to flooding and major highway closures. It would also improve horizontal and vertical alignment, in order to bring the facility to freeway standards. This project will be constructed in phases. The following initial phases have been identified:

Phase I Projects: The following four fully funded projects are considered the MSN Phase I projects.

Phase A1 will construct a northbound HOV lane from State Route 37 to just north of Atherton Avenue and a southbound HOV lane from SR 37 to Rowland Boulevard in Marin County. It will also construct soundwalls, and intelligent transportation systems, including ramp metering. Phase A-1 is fully funded. This project started construction in 2011 and was completed in 2012.

Phase A2 will construct a southbound HOV lane from Novato Creek to Franklin Overhead in Novato and was completed in 2013.

Phase A3 will extend the northbound HOV lane from Atherton Avenue to 1.5 miles south of the new Redwood Landfill Interchange. Construction on Phase A3 began in 2012 and was substantially completed by end of 2014.

Phase B1 will convert the Redwood Landfill overcrossing into a full interchange and add frontage roads. The new frontage roads will eliminate existing direct access from San Antonio Road and driveways and include Class I & II bicycle facility. By implementing access control within the contract limits, the facility will ultimately be converted from expressway to freeway. Construction started on Phase B-1 in 2012 and is expected to be completed in 2015.

Phase B2 will construct a new Petaluma Boulevard South interchange and overcrossing, south of the existing interchange. Kastania Road will be lengthened to the north and the south and will connect to the new interchange location. Petaluma Boulevard South will be re-aligned, lengthened, and widened for a Class II bike lane. The frontage Roads will allow implementation of access control within the contract limits, so the facility can ultimately be converted from expressway to freeway. Phase B-2 also replaces the existing two Highway 101 bridges over Petaluma River with a new 6-lane bridge. The highway profile is corrected to improve site distance and widened between the Petaluma River Bridge and the new interchange location. Phase B-2 is started construction in 2012 and is expected to be completed by 2016. http://www.dot.ca.gov/dist4/101petalumablvd/

Phase B3 will realign Highway 101 to the west, in the vicinity of the San Antonio Creek at the Sonoma – Marin County Line. The project will construct a new 6-lane Highway 101 bridge over San Antonio Creek and improve sight distance and resolve flooding issues at this location. This project will extend the Petaluma Boulevard South frontage road to the County Line, including Class II bike lanes. A new Class I bike lane will be constructed along San Antonito Creek to connect facilities on the west and east side of the highway. Phase B-3 is expected to start construction in 2015 and be completed by 2017.

Phase C1 Considered a part of the Marin/Sonoma Narrows (MSN) project, Phase C1 has been environmental cleared as part of a separate document to advance delivery. The project will improve ramps at the East Washington interchange in Petaluma. It will correct the ramp geometry of the southbound on-ramp and will provide a new on-ramp from westbound East Washington Street to northbound Highway 101 in order to help local circulation in Petaluma. The East Washington project started construction in 2011 and was completed in 2014.

Phase C2 will construct HOV lanes in both directions from just north of Route 116 (East) to Old Redwood Highway (Petaluma Boulevard North) in Petaluma. This project will widen bridges, replace the North Petaluma Overhead Bridge, construct soundwalls in Petaluma, and provide intelligent transportation systems, including ramp metering. This project has been completed to 95% design in 2014. The challenges for future years will include obtaining funds to complete remaining MSN HOV lanes and landscaping the entire corridor.

Phase C3 will replace the existing southbound bridge over Route 116 (East) with a 3-lane bridge and widen the existing northbound bridge to accommodate future HOV lanes. This project will also improve the northbound ramps at the Route 116 (East) separation, including a HOV bypass lane and ramp metering. A soundwall is included in Petaluma on the NB on-ramp from Route 116 (East). Phase C3 construction began in 2012 and is expected to be completed by 2015.

Future Phase Projects: Future phases of the MSN project are under-development. SCTA is advancing the design of the following two future phase projects. Additional phases to complete the overall MSN project are also being considered.

Sonoma Phase 2 – Median Widening This project will widen Highway 101 for HOV between the Marin County Line and the new Petaluma Boulevard South Interchange. This project is funded through design and a schedule is being developed to ready the project for construction funding opportunities.

Other Phases The Transportation Authority of Marin (TAM) is working with Caltrans to develop the remaining phases to complete the Highway 101 HOV lanes between Novato and the Sonoma County Line. There is also a follow-up landscaping project scheduled for 2015.

The Caltrans website for the MSN project is located at: http://www.dot.ca.gov/dist4/msn/

The draft environmental document for the MSN Corridor project can be found at: http://www.dot.ca.gov/dist4/envdocs.htm#msnhov

The separate environmental document for the East Washington project can be found at: http://www.dot.ca.gov/dist4/envdocs.htm#101ew

Some documents on this web site are saved in Portable Document Format (PDF). We recommend you download AdobeĀ® ReaderĀ®, a free software that lets you view and print PDF files.

About the Author