Mann Rd and Ben Howard Rd

Description - Completed

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 has been 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 impact 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 (Locations A and B on the map in the right hand column), one on Mann Road at Devil’s Elbow (Location C), 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 were identified to potentially raise the road elevation. Culverts were installed on Ben Howard Road at the two locations. At Devil’s Elbow, the existing culvert was replaced with a larger concrete box culvert.

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

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


  • 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 design and continue permitting process
  • February 2020: Right of Way plan approved by County Council
  • 2021-2022: Complete final design, right-of-way acquisitions and permitting process
  • 2023: Construction completed

Environmental Review

On February 8, 2019, Snohomish County Public Works determined that this project does not have a probable, significant adverse impact on the environment and has issued a Determination of Non-Significance (DNS). An Environmental Impact Statement (EIS), under RCW 43.21C.030(2)C, is not required. This decision was made after review of SEPA documents and other information on file with this agency. 

There is no opportunity for appeal at this time. Pursuant to SCC 30.61.300(10), SEPA appeals related to a shoreline substantial development permit shall be submitted to the state shorelines hearings board together with appeal of the underlying permit.


This project cost $5.1 million. 

2020 Public Meeting

Snohomish County Public Works hosted a virtual public meeting to update residents on changes to the project including the construction timeline on October 20, 2020. 

2017 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

Other Projects in the Area