Many Road Warrior readers have lots of questions about the Highway 101 construction underway south of Petaluma. We’ve gotten answers (read them here) as well as a progress report from Jit Pandher of the Transportation Authority of Marin. We’ll have an update on the northern half of the project in coming weeks.

Work began in April on the first phase of the Marin-Sonoma Narrows widening project, which covers the 16-mile stretch between Petaluma Boulevard North (Old Redwood Highway) and Highway 37 in Novato. Pandher discussed the southern half of the project that falls within Marin County.

The first phase of the $745 million Narrows project involves widening the highway to make room for HOV lanes, rebuilding bridges that cross 101 and creating one central interchange between Petaluma and Novato, eliminating access from small farm roads and San Antonio Road.

At the end of phase 1, however, the highway will still have just two lanes of traffic in each direction. Although it will have been widened to accommodate six lanes of traffic, the middle two lanes will remain undeveloped until funding is available to create HOV lanes.

“This whole project is setting (Highway 101) up for future HOV lanes,” said Pandher. That includes acquiring right-of-ways, doing environmental impact studies, relocating utilities and reconfiguring the highway for six lanes of traffic. When funding for the HOV lanes is available, Pandher said, “then it will be simple to add them.”

Both Marin and Sonoma counties have been chipping away at HOV lanes, adding one segment at a time, with Sonoma working south from Windsor and Marin working north from the Golden Gate Bridge. “Some day they will meet at the county line,” Pandher said.

Here are the details he provided:

–By the end of October, a half-mile of new southbound HOV lane will open on the north end of Novato between Franklin the existing HOV lane at Novato Creek bridge. It was part of a state-funded project that widened the Novato Creek Bridge.

–Another northbound HOV lane will open in spring 2014, starting at Atherton Avenue in Novato and contining 1.6 miles north toward Olompali State Historic Park.

–A new highway interchange has been under construction since April 1 at the Redwood Landfill north of Olompali. It will become the only place between Novato and Petaluma for motorists to enter or exit the highway. Local traffic that has been entering from San Antonio Road, Kastania Road and other driveways will use new frontage roads on either side of the highway. The existing overhead bridge used by southbound traffic to access the landfill will be widened. The interchange will be done by the end of 2014 or early 2015, depending on weather delays.

–Frontage roads have been under construction on both sides of the highway since spring. On the west side of the road, the existing frontage road from Novato will be extended to Olompali and will include a class I bike path. On the east side of the road, a short frontage road is being built between the Redwood Landfill interchange and a private marina to the south.

–The freeway will be relocated slightly at San Antonio Road, correcting the curve to make it safer and to ease the highway’s impact on San Antonio Creek.

The Sonoma County Transportation Authority is responsible for construction from San Antonio Road north to the Old Redwood Highway/Petaluma Blvd. North interchange. This SCTA map gives a rough view of the entire project and its phases. Access it yourself HERE or click on the map to enlarge it.


Marin-Sonoma Narrows project. (SCTA)


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  1. Maggie Rufo

    Too bad Caltrans is DESTROYING the environment every step of the way.

    September 26th, 2013 8:47 am

  2. Jennifer Pitts

    What is going on with the HWY 12 and HWY 101 interchange in Santa Rosa? It is a traffic nightmare in all directions. Why don’t they use the metering lights? Do they plan to add another lane? Doesn’t look like there is room with the sound walls?

    September 26th, 2013 11:32 am

  3. Monster Joe

    Since most Sonoma drivers drive solo, how can anyone justify NOT improving traffic flow by mandating HOV lanes? HOV lanes will do very little to decrease congestion, but maybe ticket revenue from HOV violators is the ultimate goal?

    We need six lanes of regular traffic, add 2 HOV lanes if someone can find a way to justify their needless expense.

    September 26th, 2013 12:24 pm

  4. Z

    Anybody know what those long antennas on stop lights are at the corner of Mendocino and College? Also seen at Marlow and Guerneville.

    September 26th, 2013 1:10 pm

  5. Steve

    Jennifer Pitts:

    The plan is to add 6,000 residents in Railroad Square and call it a transit village.

    October 1st, 2013 12:50 pm

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