MARYSVILLE — Nearly all of State Avenue has undergone construction in the past couple of decades, except for one section.

Work is expected to begin early next year on that stretch, between 100th Street, near Fred Meyer, and 116th Street.

The main changes include adding sidewalks and widening the road from three to five lanes. Contractors are expected to be chosen in the fall. The plan is to complete the project in two phases.

The first part is between 100th and 104th streets, where a bridge would be built over Quilceda Creek. Fish swim through a culvert there now. The bridge would make it easier for them to get through, city project manager Pat Gruenhagen said.

That stage would take about a year and a half. The second half of the work would continue to 116th Street, and last nearly a year.

The drive has one lane heading each direction, north and south, and a center median. An extra lane will be added on each side to match the rest of State Avenue.

Railroad tracks are to the west, so most of the work is going to happen on the east side of the road, Gruenhagen said. The city is still working to reach an agreement with some of the property owners there.

Smaller adjustments also are happening during construction.

The traffic light at 100th Street and State Avenue is being moved to fit the new five-lane road. Pedestrian safety features will also be updated.

Wires on the power lines are expected to be moved underground, and a new drainage system is going to be installed.

“In a lot of places, there is no curb,” Gruenhagen said. “So when we have rain, essentially the water is running from the roadway into the ditches and finding its way into the body of water.”

The new channel would guide runoff through a series of pipes to be collected and treated before going back into the water source.

State Avenue is one of the main arterials through Marysville. The city hopes to find ways to minimize traffic disruptions during construction.

Design for the work is about 90 percent complete, Gruenhagen said. So far it’s estimated to cost about $19 million. Some of that has been covered by state grants.

Stephanie Davey: 425-339-3192; sdavey@heraldnet.com; Twitter: @stephrdavey.