Fixing flood-prone roadways delayed

Homeowners living on rural roads just south of Sultan will wait a few more years before their route out is guaranteed during a flooding event.

Snohomish County Public Works announced construction is scheduled to start in 2021. Three spots will be raised along Ben Howard and Mann roads and drains will be installed to keep water off the winding two-way streets.

“The timeline for the proposed project on Mann Rd and Ben Howard Rd has been updated due to some unforeseen complexities,” according to a news release, “including additional time spent to obtain temporary construction easements.”

The agency’s topographical survey and preliminary environmental studies were held up, and adjustments were made to account for how long permits will be needed, according to the county. The survey and environmental work should be finished this year. Next year permits and right-of-ways should be secured, and a final design will be developed.

Hundreds of people live in the valley community that sits in the Skykomish River floodplain. Neighbors communicate on social media when heavy rains are expected. Group members post photos of brown, cold water covering the roads. They guess together when the route has become impassable. 

311th Avenue Southeast extends south from U.S. Highway 2 and downtown Sultan, and intersects Ben Howard and Mann roads, which cut west and east from the junction.

The route is the quickest way for people to get into town. Mann Road is the only access point for hundreds of people, according to the county. 

“These roads are the sole access to the local community,” according to the Mann Road Hydraulic Analysis prepared by the county surface water management department, “and the frequent closures significantly impact commuters, school bus service, maintenance of public infrastructure and utilities, and emergency services.”

Homeowners expect about two significant floods each year. In the 2014-15 season, the frequency tripled.

The county’s plan should prepare the area for a “5-year flood” event. On average, floods affect the area for 28 hours annually.

The National Flood Insurance Program has recently altered similar terminology from a 100-year flood event to a 1 percent annual chance, eliminating the expectation that such an event will only occur every 100 years.

A 2015 study found four locations on 311th Avenue Southeast, Ben Howard and Mann roads see the worst flooding. Three of those will be raised. Stretches that were identified along 311th Avenue Southeast will not.

“Due to the widespread flooding on 311th Avenue SE, it is not feasible to raise the entire one-mile stretch of road,” according to the county. “This would likely block the water flow and potentially have unintentional consequences to the surrounding area.”

The three sections are along the edge of the floodplain. Changing water flow by reshaping roadways does hold the risk of diverting water flow in such a way that other problems could result. Raising 311th Avenue Southeast a few feet would have a much bigger impact.

“It could effectively make a dam out of the road, and that’s not what we want to do,” county surface water management engineer Zach Brown said during an open house in January 2017.

A stretch of roadway just after the intersection with Mann Road, and one further west on a sharp turn will be raised on Ben Howard Road. A corner, notoriously called Devil’s Elbow, is to be fixed on Mann Road.

Building a bridge east of the one that crosses the Skykomish River on 311th Avenue Southeast is not possible, according to the county. The shoreline, riverbeds, small channels and islands are too unstable for construction.

The price of the project is estimated at $1.9 million. The county is in the process of applying for a grant to offset some of the costs. Once finished, Ben Howard Road will serve as the way in and out for the community during a flood.

The plan is considered a lasting solution, but unknown environmental factors always have the potential to change that, Brown said during the open house.

“Long-term is a hard thing to discuss with a very dynamic river like that,” he said, referring to the Skykomish.