US Bridges

I-405 N-E Ramp over Sammamish River

Fair

King County, Washington · 8.7 N JCT SR 520 · Structure no. 0008382C0000000

Built
1968
57 years old
Condition
Fair
inspected November 2024
Type
Box Beam or Girders - Multiple
Concrete Continuous
Length
709 ft
7 main spans
Daily traffic
23,617
2023 count
Owner
State
State Highway Agency

About this bridge

I-405 N-E Ramp over Sammamish River is a concrete continuous box beam or girders - multiple carrying I-405 N-E Ramp over Sammamish River in King County, Washington. It was built in 1968, so it is 57 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 23,617 vehicles a day, roughly 5% of them trucks, projected to reach 36,759 by 2038. The structure is 709 ft (216.1 m) long and 27 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-405 N-E Ramp
CrossesSammamish River
Location8.7 N JCT SR 520
RouteInterstate 405
CountyKing County
StateWashington
Coordinates47.75606, -122.18486
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionNovember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating53 US tons
Inventory rating31 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans7
Design loadHS 20
Structure length709 ft (216.1 m)
Longest span109 ft (33.2 m)
Deck width27 ft (8.1 m)
Roadway width23 ft (7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic23,617 (2023)
Projected traffic36,759 by 2038
Trucks5%
Lanes on structure1
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway and waterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes

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$10.4 million (2022 estimate)
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was I-405 N-E Ramp over Sammamish River built?

It was built in 1968, making it 57 years old in 2025.

What condition is I-405 N-E Ramp over Sammamish 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 November 2024.

How much traffic does I-405 N-E Ramp over Sammamish River carry?

About 23,617 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is I-405 N-E Ramp over Sammamish River?

The structure is 709 ft (216.1 m) long with a longest span of 109 ft (33.2 m) and a deck 27 ft wide.

Who owns I-405 N-E Ramp over Sammamish River?

It is owned by the State Highway Agency.