US Bridges

I-5 over Nisqually River

Fair

Thurston County, Washington · 2.9 N JCT SR 510 · Structure no. 0002069A0000000

Built
1937
88 years old, rebuilt 1982
Condition
Fair
inspected April 2023
Type
Truss - Thru
Steel
Length
447 ft
1 main span
Daily traffic
62,815
2023 count
Owner
State
State Highway Agency

About this bridge

I-5 over Nisqually River is a steel truss - thru carrying I-5 over Nisqually River in Thurston County, Washington. It was built in 1937 and reconstructed in 1982, so it is 88 years old, older than the Washington average of 49.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 62,815 vehicles a day, roughly 12% of them trucks, projected to reach 90,182 by 2039. The structure is 447 ft (136.2 m) long and 46 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

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CarriesI-5
CrossesNisqually River
Location2.9 N JCT SR 510
RouteInterstate 5
CountyThurston County
StateWashington
Coordinates47.07129, -122.70486
Functional classUrban Principal Arterial - Interstate

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection4 PoorAdvanced section loss, deterioration, spalling or scour.
Last inspectionApril 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating61 US tons
Inventory rating37 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadH 15
Structure length447 ft (136.2 m)
Longest span323 ft (98.5 m)
Deck width46 ft (14 m)
Roadway width43 ft (13 m)
Vertical clearance over deck15 ft (4.6 m)

Traffic and service

Average daily traffic62,815 (2023)
Projected traffic90,182 by 2039
Trucks12%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.7 mi (6 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$11.5 million (2022 estimate)
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was I-5 over Nisqually River built?

It was built in 1937, making it 88 years old in 2025. It was reconstructed in 1982.

What condition is I-5 over Nisqually River in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in April 2023.

How much traffic does I-5 over Nisqually River carry?

About 62,815 vehicles per day (2023 count), of which roughly 12% are trucks.

How long is I-5 over Nisqually River?

The structure is 447 ft (136.2 m) long with a longest span of 323 ft (98.5 m) and a deck 46 ft wide.

Who owns I-5 over Nisqually River?

It is owned by the State Highway Agency.