Haystack Creek flows from the hills south of Mann Road and crosses the roadway in three locations. The easternmost crossing consists of two corrugated metal culverts that are undersized causing debris blockages. Although Snohomish County Road Maintenance removes the debris on a routine basis, the blockages tends to cause road flooding during storm events several times a year. These culverts are also partially crushed and deteriorating. Haystack Creek is a fish bearing stream that drains to a slough of the Skykomish River.
To limit ongoing maintenance, reduce road flooding, and prevent road damage and possible traffic impacts due to culvert failure, the culverts must be replaced.
The project will replace the twin culverts with one 20-foot span by 6-foot rise, concrete box culvert. To accommodate the new culvert and improve sight distance, the road elevation will be raised for approximately 1,400 lineal feet. Ditches and driveway culverts will be installed on the south side of the roadway. Guardrail will be installed adjacent to the stream culvert. The new culvert will be designed to accommodate fish passage.
Schedule is contingent on permit approvals and funding availability. The project is currently in design. Construction is projected to begin in 2021.
During construction, Mann Road between milepost 1.7 and milepost 2.0 will have a single-lane closure controlled by a temporary traffic signal. More information will be shared as the project progresses.
Construction is estimated at $1.2 million and will be paid for by SWM Utility Fees.