US Bridges

I-5 over Terrain

Fair

King County, Washington · 4.5 N JCT SR 516 · Structure no. 0007401B0000000

Built
1966
59 years old, rebuilt 1994
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
515 ft
5 main spans
Daily traffic
106,282
2023 count
Owner
State
State Highway Agency

About this bridge

I-5 over Terrain is a prestressed concrete stringer/multi-beam or girder carrying I-5 over Terrain in King County, Washington. It was built in 1966 and reconstructed in 1994, so it is 59 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 106,282 vehicles a day, roughly 7% of them trucks, projected to reach 173,197 by 2039. The structure is 515 ft (157 m) long and 80 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

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CarriesI-5
CrossesTerrain
Location4.5 N JCT SR 516
RouteInterstate 5
CountyKing County
StateWashington
Coordinates47.45072, -122.26528
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 inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating23.6 US tons
Inventory rating18.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans5
Design loadHS 20 + Mod
Structure length515 ft (157 m)
Longest span104 ft (31.7 m)
Deck width80 ft (24.3 m)
Roadway width77 ft (23.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic106,282 (2023)
Projected traffic173,197 by 2039
Trucks7%
Lanes on structure5
Traffic directionOne-way traffic
CarriesHighway
CrossesOther
Detour if closed3.7 mi (6 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$19.1 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-5 over Terrain built?

It was built in 1966, making it 59 years old in 2025. It was reconstructed in 1994.

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 July 2023.

How much traffic does I-5 over Terrain carry?

About 106,282 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is I-5 over Terrain?

The structure is 515 ft (157 m) long with a longest span of 104 ft (31.7 m) and a deck 80 ft wide.

Who owns I-5 over Terrain?

It is owned by the State Highway Agency.