US Bridges

I-5 over Skookumchuck River

Fair

Lewis County, Washington · 0.7 N JCT SR 507 · Structure no. 0011757A0000000

Built
1951
74 years old
Condition
Fair
inspected June 2024
Type
Truss - Thru
Steel
Length
252 ft
1 main span
Daily traffic
24,769
2023 count
Owner
State
State Highway Agency

About this bridge

I-5 over Skookumchuck River is a steel truss - thru carrying I-5 over Skookumchuck River in Lewis County, Washington. It was built in 1951, so it is 74 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 24,769 vehicles a day, roughly 17% of them trucks, projected to reach 33,066 by 2039. The structure is 252 ft (76.8 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
CrossesSkookumchuck River
Location0.7 N JCT SR 507
RouteInterstate 5
CountyLewis County
StateWashington
Coordinates46.72076, -122.9765
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
Deck7 GoodSome minor problems.
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 protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 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 rating40.7 US tons
Inventory rating31.1 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadHS 20
Structure length252 ft (76.8 m)
Longest span160 ft (48.8 m)
Deck width35 ft (10.6 m)
Roadway width31 ft (9.4 m)
Vertical clearance over deck16 ft (5 m)

Traffic and service

Average daily traffic24,769 (2023)
Projected traffic33,066 by 2039
Trucks17%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
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$5 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was I-5 over Skookumchuck River built?

It was built in 1951, making it 74 years old in 2025.

What condition is I-5 over Skookumchuck 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 June 2024.

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

About 24,769 vehicles per day (2023 count), of which roughly 17% are trucks.

How long is I-5 over Skookumchuck River?

The structure is 252 ft (76.8 m) long with a longest span of 160 ft (48.8 m) and a deck 35 ft wide.

Who owns I-5 over Skookumchuck River?

It is owned by the State Highway Agency.