US Bridges

I-5 SB over Terrain

Fair

King County, Washington · 5.6 N JCT SR 900 · Structure no. 0007741D0000000

Built
1967
58 years old, rebuilt 1992
Condition
Fair
inspected August 2023
Type
Slab
Concrete Continuous
Length
6,584 ft
157 main spans
Daily traffic
96,609
2023 count
Owner
State
State Highway Agency

About this bridge

I-5 SB over Terrain is a concrete continuous slab carrying I-5 SB 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 6,584 ft (2,006.8 m) long and 66 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI-5 SB
CrossesTerrain
Location5.6 N JCT SR 900
RouteInterstate 5
CountyKing County
StateWashington
Coordinates47.5728, -122.32011
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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating35.7 US tons
Inventory rating27.4 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans157
Design loadHS 20 + Mod
Structure length6,584 ft (2,006.8 m)
Longest span46 ft (14 m)
Deck width66 ft (20.1 m)
Roadway width49 ft (15 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic96,609 (2023)
Projected traffic139,501 by 2039
Trucks7%
Lanes on structure3
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$159.5 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-5 SB 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 SB 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 2023.

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

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

How long is I-5 SB over Terrain?

The structure is 6,584 ft (2,006.8 m) long with a longest span of 46 ft (14 m) and a deck 66 ft wide.

Who owns I-5 SB over Terrain?

It is owned by the State Highway Agency.