US Bridges

I-5 over Terrain

Fair

King County, Washington · 5.2 N JCT SR 900 · Structure no. 0007741B0000000

Built
1967
58 years old, rebuilt 1992
Condition
Fair
inspected August 2024
Type
Slab
Concrete Continuous
Length
746 ft
18 main spans
Daily traffic
96,609
2023 count
Owner
State
State Highway Agency

About this bridge

I-5 over Terrain is a concrete continuous slab carrying I-5 over Terrain in King County, Washington. It was built in 1967 and reconstructed in 1992, 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 96,609 vehicles a day, roughly 7% of them trucks, projected to reach 139,501 by 2039. The structure is 746 ft (227.4 m) long and 54 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

CarriesI-5
CrossesTerrain
Location5.2 N JCT SR 900
RouteInterstate 5
Coordinates47.57086, -122.32024
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
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 geometry3: Basically intolerable, requiring high priority of corrective action
Approach roadway alignment8: Equal to present desirable criteria
Operating rating36.8 US tons
Inventory rating28.2 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans18
Design loadHS 20 + Mod
Structure length746 ft (227.4 m)
Longest span42 ft (12.8 m)
Deck width54 ft (16.4 m)
Roadway width51 ft (15.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic96,609 (2023)
Projected traffic139,501 by 2039
Trucks7%
Lanes on structure4
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 statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$18.8 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-5 over Terrain built?

It was built in 1967, making it 58 years old in 2025. It was reconstructed in 1992.

What condition is I-5 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 over Terrain carry?

About 96,609 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is I-5 over Terrain?

The structure is 746 ft (227.4 m) long with a longest span of 42 ft (12.8 m) and a deck 54 ft wide.

Who owns I-5 over Terrain?

It is owned by the State Highway Agency.