INDEX — In some places around soggy Snohomish County, it’s still a giant log that gets you over a rushing stream of water.

Log girders that form the foundation for a 61-foot span over Howard Creek near Index are starting to fail, however. Bridge 496, on Index Galena Road, is one of two bridges in line for replacement in 2017 for Snohomish County. The second rebuild project is May Creek Bridge 559, east of Gold Bar, where winter flows in the creek have devoured the earth beneath a bridge pier.

The county recently released an annual bridge report. After a relatively quiet 2015, major bridge construction projects are wrapping up in 2016 on Pilchuck River Bridge 581 near Granite Falls and Swamp Creek Bridge 504 near Bothell.

And near Monroe last week, Snohomish County road maintenance crews closed Tualco Road to drill soil borings, part of the design work that continues for a future replacement of Riley Slough Bridge 155. Construction is slated for 2019.

“Usually we try to get one to two (bridge construction projects) out a year, but it’s also dependent on our funding and also how design goes and our permitting required for those projects,” said Max Phan, county engineering manager.

“Our challenges have been the environmental permits. The rules and regulations are constantly changing, so we need to adapt our design and permits to those new regulations,” he said.

Most bridges span a body of water, which carries specific environmental concerns for fish passage and water health. There also are criss-crossing jurisdictions, including areas where local, state, federal and tribal approval all must be secured. For some permits, it can take six months to a year to hear back from the permitting agency.

The wait for dollars can add to a project’s time, too.

Federal grants often cover about 80 percent of project costs. Money is secured for the $4.5 million Riley Slough, $2.4 million Howard Creek, and $3.1 million May Creek bridge replacements.

Bigger projects continue to wait.

Planners apply each year for a federal grant to move forward on a $22 million rebuild of Granite Falls Bridge 102. The Mountain Loop Highway bridge spans the Stillaguamish River and is considered a “lifeline route” for nearby communities. The steel and concrete Bridge 102 was built in 1934. Plans call for building a new bridge just downstream that is double the current bridge’s width.

The county’s request for federal funds failed again in 2016.

“We will keep trying,” Phan said.

In the meantime, bridge inspections continue on an every-other-year schedule. Crews also perform inspections for several cities which don’t have the manpower to inspect their own bridges.

Snohomish County owns and maintains 201 bridges, mostly in sodden hinterlands. Much of the county’s bridge work is focused on maintenance and repairs.

Rain, rivers and birds combine with simple age to wear down bridge parts. So workers are busy throughout the year cleaning, painting and replacing components, such as footings or deck boards, to prolong the useful lives of bridges.

“In Snohomish County, it was lots of old-growth forest here. We built lots of timber bridges. Timber in the wet western part of Washington tends to deteriorate over time. Now my job, for the last 30 years, has been replacing timber bridges with concrete or steel bridges,” county bridge engineer Darrell Ash said.

But it’s the water that flows below the bridge, rather than the water that falls from above, that poses the largest concern.

“Scouring is the leading cause of bridge failures. It’s the biggest thing that I worry about,” Ash said.

And that carries additional steps for inspections.

With funding in hand for May Creek, the county’s main scouring worry turns to Red Bridge 537 on the Mountain Loop Highway. The bridge spans the South Fork of the Stillaguamish River east of Verlot.

Divers from the Washington State Department of Transportation are set to visit the bridge again in summer 2017 to measure how much the river has eaten away since the last inspection.

County planners don’t have an estimate yet for pier repairs there, but they’ve started applying for federal dollars.

Meanwhile, scour repairs also are planned for the state-owned Highway 529 Union Slough and the U.S. 2 South Fork Skykomish River bridges. WSDOT is working on design for the projects, with construction slated for 2018.

There are nearly 9,800 bridges in Washington. The state owns and maintains about 4 in 10 of them.

Not all bridges carry cars. In Everett, work is slated to begin in 2017 on a pedestrian bridge, linking Grand Avenue Park to the waterfront.

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

On deck

Snohomish County plans to replace two of its bridges in 2017:

May Creek Bridge 559 east of Gold Bar is classified as “scour critical” and will be replaced with a 100-foot span. Work on the $3.1 million project is slated to begin in May.

Winter flows in the creek are devouring the foundation of the single-lane concrete and timber bridge, dropping the streambed by about 5 feet. Several efforts have been made over the years to shore things up. Still, local residents have been notified that the bridge can be closed at a moment’s notice for safety reasons.

Howard Creek Bridge 496 on Index Galena Road, near Index, also will be replaced. The log girders that were placed in 1976 for this 61-foot span have begun to fail. Traffic is restricted to one lane, and a 5-ton weight limit has been in effect since August 2008.

The new Howard Creek bridge will be longer, wide enough for two lanes of traffic, and made of steel and concrete. Construction on the $2.4 million project also is set to begin in the spring.