County profile · official public datasets

Thurston County, WA

205 public highway bridges tracked in the FHWA National Bridge Inventory: 59.5% rated Good, 39.5% Fair, 1% Poor.

205
Public bridges: 59.5%
Good condition: 1%
Poor condition

The verdict

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

Thurston County posts a top-10% lowest Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 10%
lowest Poor share in state: 1%
Poor-condition share: 205
public highway bridges: 1979
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.

Thurston County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Thurston County ranks #4 of 39 Washington counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 1%). Thurston County, Washington contains 205 public highway bridges. Roughly 59.5% are rated “Good,” 39.5% “Fair,” and 1% “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

205

Public highway bridges in Thurston County

Good condition

59.5%

122 of 205 rated 7-9

Fair condition

39.5%

81 of 205 rated 5-6

Poor condition

2 of 205 rated 4 or below

In-state Poor-share rank

#4 of 39

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

Condition distribution

Share of 205 NBI-tracked bridges by lowest applicable component rating.

Good

59.5% (122)

Fair

39.5% (81)

Poor

1% (2)

Thurston County's Poor-condition bridges carry 20,568 vehicle crossings a day

That is 0.8% of the county's reported daily bridge traffic on 1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 10,284 crossings a day against 10,482 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 205 of 205 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

41% of Thurston County's bridges have passed the 50-year mark

84 of the 205 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 59.5% 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 66.9% of the county's Poor-condition bridge traffic

CAPITOL BLVD over I-5 RAMP, built 1956, carries 13,767 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 2-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 20,568 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

1
1920s

7
1930s

5
1940s

3
1950s

34
1960s

24
1970s

20
1980s

42
1990s

28
2000s

18
2010s

17
2020s

6

What this shows Construction peaked in the 1980s, when 42 of the county's bridges still in the inventory were built, which is 20.5% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year (1979) matches the Washington average (1975).

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

The 5 Washington counties nearest Thurston County in number of bridges, with their condition splits. Its 1% Poor share is the 1st-lowest of these 6. Its average build year of 1979 against a peer-group mean of 1972 is 7 years newer.

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

Bridge inventory size and condition shares for Thurston County and the 5 Washington counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Clark County	218	55%	40.8%	4.1%	1979
Thurston County (this page)	205	59.5%	39.5%	1%	1979
Walla Walla County	195	64.1%	27.2%	8.7%	1980
Adams County	187	35.3%	54.5%	10.2%	1961
Lincoln County	180	56.7%	37.2%	6.1%	1965
Benton County	167	58.7%	35.9%	5.4%	1977

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 Thurston 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 Thurston County, both outside Washington so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside WA (205 bridges here).

Geneva County, AL · 205 bridges
Russell County, AL · 205 bridges
Wilson County, KS · 205 bridges
Bell County, KY · 205 bridges

Similar average build year

Nearest mean year-built outside WA (1979 here).

Pima County, AZ · avg 1979 · 1,150 bridges
Jefferson County, KY · avg 1979 · 662 bridges
Spartanburg County, SC · avg 1979 · 638 bridges
McPherson County, KS · avg 1979 · 586 bridges

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

All 205 Good 122 Fair 81 Poor 2

Fair-condition bridges (81)

Sort:

Thurston County Bridge Snapshot

Condition distribution

Thurston County's Poor-condition bridges carry 20,568 vehicle crossings a day

41% of Thurston County's bridges have passed the 50-year mark

One structure carries 66.9% of the county's Poor-condition bridge traffic

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

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Fair-condition bridges (81)

CUSTER WAY

W 5TH AVENUE

I-5

I-5

I-5

I-5 S-W RAMP

I-5

CARPENTER RD

HOLMES ISD RD

I-5

YELM HWY S.E.

CAPITOL BOULEVARD

I-5

DELPHI RD

5TH AVE

113TH AVE SW

DELPHI ROAD SW

STEAMBOAT IS. RD.

US 12

US 12

I-5

SR 121 / 93RD AVE

I-5

BOULEVARD RD

SR 507

TONO ROAD

NISQUALLY CUTOFF

OLD HWY NO. 9

WOODARD BAY ROAD

MOON ROAD

VAIL CUTOFF RD

I-5

I-5

JOHNSON CREEK ROAD

I-5

US 101

LEITNER ST.

COOPER POINT ROAD

I-5

US 101

HENDERSON BLVD

Madrona Beach Road

STEILACOOM ROAD

US 101

188 SW

SCH. LND. RD. CULV

ENDICOTT ROAD

US 12

SR 507

BOSTON STREET

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