SR 529 over Steamboat Slough

Snohomish County, Washington · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

• SR 529 over Steamboat Slough in Snohomish County, Washington, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
• Its lowest-rated component is the superstructure, rated 5 (fair condition) on the 0-9 scale.
• It was built in 1954, making it 71 years old at the 2025 inventory.
• It carries about 16,592 vehicles a day (traffic count year 2023).
• Its listed owner is the state highway agency.
• It is one of 232 of the 500 inventoried bridges in Snohomish County rated fair (46.4%); 20 (4.0%) are rated poor.
• Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
• Its class is unchanged from 2024 (fair), but component ratings moved: deck 6 to 7.
• Its most recent inspection on record is dated July 2024, on a 24-month routine inspection cycle.
• It is coded scour critical (NBI item 113 = 3): scour critical: foundations unstable for the assessed or calculated scour.
• It has fracture-critical members (NBI item 92A): steel tension members without a redundant load path, which get their own scheduled inspections.
• A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

View this bridge on a map → (48.03489, -122.1815)

Component ratings

Bridge details

Source: FHWA National Bridge Inventory, 2025 data as reported by the Washington department of transportation.

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Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.