County profile · official public datasets

Snohomish County, WA

500 public highway bridges tracked in the FHWA National Bridge Inventory: 49% rated Good, 47% Fair, 4% Poor.

500
Public bridges
49%
Good condition
4%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Snohomish County pairs a better-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

Top 28%
lowest Poor share in state
4%
Poor-condition share
500
public highway bridges
1980
avg year built

Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.

Snohomish County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Snohomish County ranks #11 of 39 Washington counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 4%). Snohomish County, Washington contains 500 public highway bridges. Roughly 49% are rated “Good,” 47% “Fair,” and 4% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.

Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.

Source: FHWA National Bridge Inventory. See methodology for full definitions.

Total bridges

500

Public highway bridges in Snohomish County

Good condition

49%

245 of 500 rated 7-9

Fair condition

47%

235 of 500 rated 5-6

Poor condition

4%

20 of 500 rated 4 or below

In-state Poor-share rank

#11 of 39

Among Washington counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 500 NBI-tracked bridges by lowest applicable component rating.

Good
49% (245)
Fair
47% (235)
Poor
4% (20)

Snohomish County's Poor-condition bridges carry 152,948 vehicle crossings a day

That is 2% of the county's reported daily bridge traffic on 4% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 7,647 crossings a day against 13,761 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.

Computed over the 500 of 500 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

47.4% of Snohomish County's bridges have passed the 50-year mark

237 of the 500 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 49% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.

Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.

One structure carries 10.6% of the county's Poor-condition bridge traffic

SR 529 over STEAMBOAT SLOUGH, built 1927, carries 16,203 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 20-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 152,948 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Snohomish County's bridges were built

500 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1960s, when 131 of the county's bridges still in the inventory were built, which is 26.2% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year is 1980, 5 years newer than the Washington average of 1975.

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

How Snohomish County compares with Washington's closest counties by inventory size

The 5 Washington counties nearest Snohomish County in number of bridges, with their condition splits. Its 4% Poor share is the 2nd-lowest of these 6. Its average build year of 1980 against a peer-group mean of 1973 is 7 years newer.

Showing the 5 closest of 38 Washington counties eligible for comparison.

Bridge inventory size and condition shares for Snohomish County and the 5 Washington counties closest to it in inventory size
County Bridges Poor
Yakima County 558 5%
Snohomish County (this page) 500 4%
Pierce County 472 4.2%
Lewis County 419 3.8%
Grays Harbor County 363 9.4%
Whatcom County 354 5.4%

Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Snohomish County's. Source: FHWA National Bridge Inventory, 2024 release.

Nationwide counties with similar inventory size or average build year

Two NBI-derived peer sets for Snohomish County, both outside Washington so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside WA (500 bridges here).

Similar average build year

Nearest mean year-built outside WA (1980 here).

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 500 Good 245 Fair 235 Poor 20

Poor-condition bridges (20)

OLD 99

Poor

Over: PILCHUCK CREEK

2.0 N JCT SR 530, Snohomish, WA

Built 1933 Load: 7.3 t ADT: 428

MUKILTEO BLVD

Poor

Over: EDGEWATER CREEK

0.07 W JCT SHORE AVE, Snohomish, WA

Built 1946 Load: 8.7 t ADT: 4,883

MULIKLTEO BLVD

Poor

Over: MERRILL & RING CREEK

0.15 W JCT HARBOR LANE, Snohomish, WA

Built 1931 Load: 13.6 t ADT: 6,123

LOCUST WAY

Poor

Over: SWAMP CREEK

1.1 N KING CO LINE, Snohomish, WA

Built 1960 Load: 15.4 t ADT: 7,454

SR 529

Poor

Over: SNOHOMISH RIVER

4.6 N JCT SR 529 SPUR, Snohomish, WA

Built 1927 Load: 16.3 t ADT: 15,905

JORDAN RD

Poor

Over: JORDAN CREEK

5.9 NW JCT SR 92, Snohomish, WA

Built 1981 Load: 18.1 t ADT: 1,145

LOWELL-LARIMER RD

Poor

Over: CATTLE PASS

2.4 NW JCT SR 9, Snohomish, WA

Built 1972 Load: 19.0 t ADT: 5,643

SR 203

Poor

Over: DRAINAGE OVERFLOW

4.1 N KING CO, Snohomish, WA

Built 1954 Load: 22.7 t ADT: 11,836

44TH ST NE

Poor

Over: LITTLE PILCHUCK CREEK

0.2 W JCT SR 92, Snohomish, WA

Built 1961 Load: 22.7 t ADT: 953

SR 529

Poor

Over: UNION SL

5.9 N JCT SR 529 SPUR, Snohomish, WA

Built 1954 Load: 25.6 t ADT: 16,054

SR 529

Poor

Over: SNOHOMISH RIVER

4.7 N JCT SR 529 SPUR, Snohomish, WA

Built 1954 Load: 26.3 t ADT: 15,905

US 2

Poor

Over: S FK SKYKOMISH RIVER

20.3 E JCT SR 203, Snohomish, WA

Built 1933 Load: 27.2 t ADT: 6,051

SR 529

Poor

Over: UNION SL

5.9 N JCT SR 529 SPUR, Snohomish, WA

Built 1927 Load: 29.0 t ADT: 16,054

US 2

Poor

Over: BNRR

23.7 E JCT SR 203, Snohomish, WA

Built 1936 Load: 30.8 t ADT: 5,659

SR 529

Poor

Over: STEAMBOAT SLOUGH

6.2 N JCT SR 529 SPUR, Snohomish, WA

Built 1927 Load: 31.7 t ADT: 16,203

RD. NO. 49

Poor

Over: LOST CREEK

M.P. 4.5 RD. NO. 49, Snohomish, WA

Built 1959 Load: 31.8 t ADT: 37

US 2

Poor

Over: NO NAME CREEK

18.4 E JCT SR 203, Snohomish, WA

Built 1933 Load: 34.5 t ADT: 6,381

SR 203

Poor

Over: SKYKOMISH RIVER

5.2 N KING CO, Snohomish, WA

Built 1957 Load: 34.5 t ADT: 14,784

TUALCO LOOP RD

Poor

Over: RILEY SLOUGH

1.0 NW JCT SR 203, Snohomish, WA

Built 1970 Load: 34.5 t ADT: 200

12TH ST NE

Poor

Over: I-5

2.4 N JCT US 2, Snohomish, WA

Built 1967 Load: 35.4 t ADT: 1,250

Read our methodology - how this data is sourced, computed, and verified.

Related

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Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges

Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.