US Bridges

I-5 Southbound over Terrain

Fair

King County, Washington · 2.6 N JCT SR 900 · Structure no. 0007990A0000000

Built
1967
58 years old, rebuilt 1995
Condition
Fair
inspected August 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
529 ft
4 main spans
Daily traffic
103,312
2023 count
Owner
State
State Highway Agency

About this bridge

I-5 Southbound over Terrain is a steel continuous stringer/multi-beam or girder carrying I-5 Southbound over Terrain in King County, Washington. It was built in 1967 and reconstructed in 1995, so it is 58 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 103,312 vehicles a day, roughly 7% of them trucks, projected to reach 154,285 by 2039. The structure is 529 ft (161.2 m) long and 78 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-5 Southbound
CrossesTerrain
Location2.6 N JCT SR 900
RouteInterstate 5
CountyKing County
StateWashington
Coordinates47.53528, -122.29725
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.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating44 US tons
Inventory rating27 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length529 ft (161.2 m)
Longest span150 ft (45.7 m)
Deck width78 ft (23.8 m)
Roadway width77 ft (23.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic103,312 (2023)
Projected traffic154,285 by 2039
Trucks7%
Lanes on structure5
Traffic directionOne-way traffic
CarriesHighway
CrossesOther
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 statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$21.1 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-5 Southbound over Terrain built?

It was built in 1967, making it 58 years old in 2025. It was reconstructed in 1995.

What condition is I-5 Southbound over Terrain 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 August 2024.

How much traffic does I-5 Southbound over Terrain carry?

About 103,312 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is I-5 Southbound over Terrain?

The structure is 529 ft (161.2 m) long with a longest span of 150 ft (45.7 m) and a deck 78 ft wide.

Who owns I-5 Southbound over Terrain?

It is owned by the State Highway Agency.