Mann Rd and Ben Howard Rd

March 2018 Update

The timeline for the proposed project on Mann Rd and Ben Howard Rd has been updated due to some unforeseen complexities, including additional time spent to obtain temporary construction easements, delays in topographical survey and preliminary environmental field work, and schedule adjustments needed to mitigate extended permitting timelines. Construction is expected to occur in 2021.


Mann Road is the only access point for hundreds of homes south of the City of Sultan. During the fall and winter, flooding in the area is caused by the Skykomish River, the South Slough, and streams draining the hills to the south. Multiple points along Mann Road, Ben Howard Road, and 311th Avenue SE are susceptible to flooding during these events. Road closures due to flooding disrupt residents from accessing their homes and impacts school bus routes, emergency services, and more.

In February 2015, Snohomish County committed to performing a hydraulic analysis of the area to understand where the roads flood, to what extent, and how the levels of the Skykomish River correlate with the flooding.

The results of the study identified four locations susceptible to flooding at or less than a two-year recurrence interval: two along Ben Howard Road, one on Mann Road at Devil's Elbow, and a long-stretch of 311th Avenue SE.

Project Plans

Two locations on Ben Howard Road and one on Mann Road at Devil's Elbow have been identified to potentially raise the road elevation. Culverts would be installed on Ben Howard Road at the two locations. At Devil's Elbow, the existing culvert would be replaced with a 12-foot wide concrete box culvert and two smaller culverts.

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

If 311th Avenue SE is flooded, residents can access their property via Ben Howard Road from Monroe.


*This schedule is contingent upon approval of permits and funding availability.

  • January 19, 2017: Snohomish County hosts a public meeting to present findings of feasibility study
  • 2017: Began topography survey and preliminary environmental review
  • 2018: Complete topography survey and preliminary environmental review; begin design and environmental permitting process
  • 2019 - 2020: Develop final design, complete right-of-way acquisitions (if needed) and complete permitting process
  • 2021: Construction


This project is estimated to cost $1.9 million. Snohomish County Public Works has applied for a grant to cover some of the cost.

Public Meeting

Snohomish County Public Works held a public meeting on January 19, 2017 from 5:30 p.m. to 7:30 p.m. The gathering was at Mountainview Christian Fellowship, 211 6th Street, Sultan, WA. Snohomish County Public Works presented the findings of a feasibility study and potential project plans. The public had the opportunity to provide comment on the project.

Meeting Displays and Reports

Additional Resources