The historically congested stretch of Highway 101 south of Petaluma is primed for work that eventually will widen the corridor and provide relief for what is known as the Novato Narrows bottleneck.
But don't get too excited, drivers.
The $120 million project, which really is two projects at once, will take three years and include temporary lane closures that at times will squeeze traffic to one lane in each direction.
And even when construction is done, the carpool lanes won't exist. Funding for them isn't yet available.
Still, at a groundbreaking ceremony Monday in Petaluma, local officials and transportation experts said starting work on the two projects is a huge step forward in the long-term widening of 101 from Windsor to Novato.
"What a momentous occasion," said Sonoma County Supervisor David Rabbitt, who represents the Petaluma area. The projects mean a safer highway, better transportation infrastructure and jobs, he said.
Overall, work on the 17-mile Marin-Sonoma Narrows, which Caltrans defines as Cotati to Highway 37 in Novato, is expected to cost $700 million, Caltrans estimates. Thus far, the northernmost and southernmost sections have been completed, leaving the thorny center stretch to be dealt with.
"It may be April Fools', but it's no joke that the project is commencing," said Sonoma County Transportation Authority Executive Director Suzanne Smith. "This has been more than a decade in the making."
This two-projects-in-one segment includes a $77 million contract for a new Petaluma Boulevard South interchange, new frontage roads and replacement of the dual Petaluma River bridges with one, six-lane bridge to accommodate future carpool lanes.
The nine-mile section between Novato and Petaluma, commonly referred to as the narrows, will be converted from expressway to freeway status by closing uncontrolled access. Wider frontage roads will feature bicycle access.
A $28 million contract will provide for the replacement of the northbound 101 overpass of Lakeville Highway/Highway 116 and widening the southbound span. The construction contracts do not include the previous land acquisition, design and engineering costs.
Construction of the 116 sections is expected to finish in the winter of 2014, with the Petaluma Boulevard South work to be done in the winter of 2015. Ghilloti Brothers and Myers JV won the bids for the projects.
Rabbitt, who serves on the Sonoma County Transportation Authority, called for patience from drivers who are certain to face frustration. "It's going to be a little trying for the next two, three years and beyond as we work through the construction," he said.
Petaluma City Councilman Mike Harris stressed that the upcoming work is foundational for eventual carpool, or high-occupancy-vehicle, lanes.
"When these jobs are done, there will be no HOV lanes, but the structures will all be wide enough to accommodate the third lane when the money comes forward," he said.
"This is definitely exciting . . . These are the first baby steps towards a fix for the Novato Narrows and will eventually give commuters some relief."
Motorists will notice changes in the next couple of weeks, said Darren Kirby construction superintendent for both projects.
K-rails, the concrete center-line dividers, will be placed soon in the Petaluma Boulevard South interchange area. In a few months, the northbound onramp will be closed. The entire interchange will be moved farther south and redesigned into a "tight diamond configuration."