US Bridges

US 12 over Cowlitz River

Fair

Lewis County, Washington · 7.8 E JCT SR 131 · Structure no. 0003348A0000000

Built
1948
77 years old
Condition
Fair
inspected March 2024
Type
Truss - Thru
Steel
Length
554 ft
1 main span
Daily traffic
2,712
2023 count
Owner
State
State Highway Agency

About this bridge

US 12 over Cowlitz River is a steel truss - thru carrying US 12 over Cowlitz River in Lewis County, Washington. It was built in 1948, so it is 77 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 2,712 vehicles a day, roughly 19% of them trucks, projected to reach 4,281 by 2039. The structure is 554 ft (168.9 m) long and 33 ft wide. If it were closed, the detour would be 18 mi (29 km).

Location

Open in Google Maps
CarriesUS 12
CrossesCowlitz River
Location7.8 E JCT SR 131
RouteU.S. Route 12
CountyLewis County
StateWashington
Coordinates46.53508, -121.79522
Functional classRural Principal Arterial - Other

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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionMarch 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 geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating69 US tons
Inventory rating41 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+5 approach)
Design loadHS 20
Structure length554 ft (168.9 m)
Longest span240 ft (73.2 m)
Deck width33 ft (10.1 m)
Roadway width26 ft (7.9 m)
Vertical clearance over deck15 ft (4.5 m)

Traffic and service

Average daily traffic2,712 (2023)
Projected traffic4,281 by 2039
Trucks19%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed18 mi (29 km)
TollOn a free road
National Highway SystemYes

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$10.5 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was US 12 over Cowlitz River built?

It was built in 1948, making it 77 years old in 2025.

What condition is US 12 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 March 2024.

How much traffic does US 12 over Cowlitz River carry?

About 2,712 vehicles per day (2023 count), of which roughly 19% are trucks.

How long is US 12 over Cowlitz River?

The structure is 554 ft (168.9 m) long with a longest span of 240 ft (73.2 m) and a deck 33 ft wide.

Who owns US 12 over Cowlitz River?

It is owned by the State Highway Agency.