CAMANO ISLAND — Crews are driving piles into the tideflats to build a new bridge and laying down gravel to widen and raise the highway between Stanwood and Camano Island.

The $29.3 million project, funded by gas tax dollars, is scheduled to wrap up in fall 2015.

Highway 532 over the Stillaguamish River and Davis Slough is the only road access onto the island of about 15,000 people, and the state Department of Transportation says it’s too vulnerable to the forces of harsh weather and floodwaters.

Bridges spanning the gap from the mainland to Camano Island were built in 1949. The Camano Gateway Bridge — formerly the Mark Clark Bridge — over the Stillaguamish River was rebuilt in 2010. Replacing the Davis Slough Bridge, on the other hand, is overdue.

The 65-year-old structure is too low and too narrow, according to the Department of Transportation. Logs and debris washed in by tides and river currents have accumulated below the bridge, and a strong storm or flood could damage or destroy the span of road.

“We’ve occasionally had issues, and we want to keep on top of those,” WSDOT spokesman Tom Pearce said. “We’re trying to be very sensitive to the folks out there on Camano Island because we know they’re very concerned about their access.”

Work started in August on a project to elevate the road, stabilize the bridge and widen the lanes and shoulders. Crews plan to raise the highway five feet on land and the new bridge will be about 10 feet higher than the current bridge. The roadway also will be widened by 24 feet, adding space along the shoulder for pedestrians, bicyclists or emergencies.

The shoulder space is critical, Pearce said. It will provide a way to route traffic around any crashes or stalled vehicles.

“One of the reasons for making it wider, one of the big reasons, is that if there is a collision on or near the bridge, it shuts down the whole road,” he said. “ And that’s the only road onto Camano, so there’s no way around it until the collision is cleared.”

The work area stretches less than a mile from Eide Road to Smith Road, and the intersection of Eide Road and Highway 532 is being reworked to be safer and easier to navigate, according to WSDOT.

The project is planned in two stages. The first focuses on the south half of the bridge and highway, leaving the north lanes open for traffic. Vehicles can then use the new south lanes while the north lanes are completed, Pearce said.

The project is just getting started, he said. For the next few weeks, crews are expected to lay down gravel for elevating the road and drive in pilings for the new bridge.

Nighttime lane closures are scheduled this week, continuing into Friday morning. Additional lane closures may be needed, Pearce said.

Kari Bray: kbray@heraldnet.com; 425-339-3439.