US Bridges

I-5 over Cowlitz River

Fair

Lewis County, Washington · 2.0 N Cowlitz CO · Structure no. 0004367A0000000

Built
1953
72 years old
Condition
Fair
inspected September 2024
Type
Truss - Thru
Steel
Length
760 ft
2 main spans
Daily traffic
21,828
2023 count
Owner
State
State Highway Agency

About this bridge

I-5 over Cowlitz River is a steel truss - thru carrying I-5 over Cowlitz River in Lewis County, Washington. It was built in 1953, so it is 72 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 21,828 vehicles a day, roughly 21% of them trucks, projected to reach 29,461 by 2039. The structure is 760 ft (231.6 m) long and 35 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI-5
CrossesCowlitz River
Location2.0 N Cowlitz CO
RouteInterstate 5
CountyLewis County
StateWashington
Coordinates46.41288, -122.88985
Functional classRural 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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionSeptember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
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 rating46 US tons
Inventory rating27 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans2 (+5 approach)
Design loadHS 20
Structure length760 ft (231.6 m)
Longest span240 ft (73.2 m)
Deck width35 ft (10.6 m)
Roadway width32 ft (9.7 m)
Vertical clearance over deck16 ft (4.8 m)

Traffic and service

Average daily traffic21,828 (2023)
Projected traffic29,461 by 2039
Trucks21%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway and waterway
Detour if closed1.2 mi (2 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$13.4 million (2022 estimate)
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was I-5 over Cowlitz River built?

It was built in 1953, making it 72 years old in 2025.

What condition is I-5 over Cowlitz 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 September 2024.

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

About 21,828 vehicles per day (2023 count), of which roughly 21% are trucks.

How long is I-5 over Cowlitz River?

The structure is 760 ft (231.6 m) long with a longest span of 240 ft (73.2 m) and a deck 35 ft wide.

Who owns I-5 over Cowlitz River?

It is owned by the State Highway Agency.