One of 4 remaining deficient county bridges to be replaced

MONROE — A rural bridge in a Tualco Valley farming area is on track to be replaced.

The 1930-built Riley Slough Bridge 155, on Tualco Road, is supported by timber piles that are in various stages of decay. Temporary repairs have been made over the years, but the bridge now has a sufficiency rating of 19.25 out of 100.

The $4.4 million project will construct a new concrete bridge. Federal grants will cover 80 percent of those costs.

Snohomish County will seek construction bids in fall 2018, with construction slated for 2019.

Once the Monroe-area bridge is replaced, the county will be down to three remaining bridges in its inventory of more than 200 that are considered structurally deficient — which means the bridges are in need of replacement and are eligible for federal funds.

Grant applications are submitted already for Trout Creek Bridge 494 on Index Galena Road and Swamp Creek Bridge 503 on Locust Way. The county also will apply in 2018 for a grant to replace Black Creek Bridge 547 on the Mountain Loop Highway.

Howard Creek Bridge 496, on Index Galena Road, had been on the structurally deficient list until it was replaced in 2017.

Grants are key

The county’s bridge team plans to put some dollars into design work in 2018 in an effort to be more competitive in landing federal dollars for the other structurally deficient bridges, said Bruce Duvall, engineering services bridge group supervisor.

“We’re going to spend a little bit of the county road fund money … so that we have a sharper pencil to use in our grant applications — so we have a more exact amount of money we need for them,” Duvall said.

Other bridges are eligible for different federal grants aimed at rehabilitation.

Among them is the Red Bridge 537 on the Mountain Loop Highway. The bridge spans the South Fork of the Stillaguamish River east of Verlot. Dive teams were out again this past summer to check the river’s scouring effects.

The county’s grant application for rehab work on Red Bridge, though, was turned down in 2017.

“It’s continuing to erode a bit but it’s not in any dire need for repair. But it is eligible … so we’ll continue in the future to make grant applications,” Duvall said.

The county is waiting to hear on its latest application to a much larger federal grant program to help with a planned $22 million rebuild of Granite Falls Bridge 102 on the Mountain Loop Highway. The steel and concrete bridge was built in 1934 and is considered functionally obsolete and fracture critical. They hope to hear in early 2018 if their request was successful. Design of the bridge project is about a third of the way done.

In the meantime, regular inspections and maintenance continues on a scheduled basis for all the county’s bridges, said Charlie Green, engineering design manager.

“That’s just our common practice to make sure they’re safe and functioning for our public as we compete for this funding,” Green said.

Tualco work affects buildings

Nearly 600 vehicles use the Riley Slough Bridge each day.

In the wet season, the ground around the timber piles fills with water. The boggy conditions have slowly eaten away at the wood. The bridge has had load limits since 2011.

The replacement bridge will be the same length, at 206 feet, and remain a two-lane road. It will be 32.5 feet wide to accommodate shoulders.

Construction might require the removal of some portions of nearby outbuildings, planners said. They are in right-of-way discussions with the property owner.

A rental house very near the bridge will remain, but the driveway likely will be relocated to accommodate the new bridge approach.

More information is at https://tinyurl.com/Bridge155.

Melissa Slager: streetsmarts@heraldnet.com; 425-339-3432.