US Bridges

US 12 over Cowlitz R

Fair

Lewis County, Washington · 0.8 E JCT SR 122 · Structure no. 0008154A0000000

Built
1968
57 years old
Condition
Fair
inspected March 2024
Type
Arch - Deck
Concrete
Length
1,136 ft
1 main span
Daily traffic
4,771
2023 count
Owner
State
State Highway Agency

About this bridge

US 12 over Cowlitz R is a concrete arch - deck carrying US 12 over Cowlitz R in Lewis County, Washington. It was built in 1968, so it is 57 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 6 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 4,771 vehicles a day, roughly 22% of them trucks, projected to reach 5,801 by 2039. The structure is 1,136 ft (346.3 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 R
Location0.8 E JCT SR 122
RouteU.S. Route 12
CountyLewis County
StateWashington
Coordinates46.53863, -122.46898
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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations on dry land well above flood water elevations
Structural evaluation6: Equal to present minimum criteria
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 rating58 US tons
Inventory rating34 US tons

Structure

Structure typeArch - Deck
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1 (+8 approach)
Design loadHS 20
Structure length1,136 ft (346.3 m)
Longest span520 ft (158.5 m)
Deck width33 ft (10 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,771 (2023)
Projected traffic5,801 by 2039
Trucks22%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
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 statusPossibly eligible for the National Register; requires further investigation
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$21.6 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was US 12 over Cowlitz R built?

It was built in 1968, making it 57 years old in 2025.

What condition is US 12 over Cowlitz R 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 R carry?

About 4,771 vehicles per day (2023 count), of which roughly 22% are trucks.

How long is US 12 over Cowlitz R?

The structure is 1,136 ft (346.3 m) long with a longest span of 520 ft (158.5 m) and a deck 33 ft wide.

Who owns US 12 over Cowlitz R?

It is owned by the State Highway Agency.