US Bridges

I-405 over SR 522 Sammamish R

Fair

King County, Washington · 8.7 N JCT SR 520 · Structure no. 0008382A0000000

Built
1968
57 years old, rebuilt 1997
Condition
Fair
inspected November 2024
Type
Box Beam or Girders - Multiple
Concrete Continuous
Length
1,352 ft
12 main spans
Daily traffic
56,311
2023 count
Owner
State
State Highway Agency

About this bridge

I-405 over SR 522 Sammamish R is a concrete continuous box beam or girders - multiple carrying I-405 over SR 522 Sammamish R in King County, Washington. It was built in 1968 and reconstructed in 1997, 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 56,311 vehicles a day, roughly 6% of them trucks, projected to reach 86,175 by 2039. The structure is 1,352 ft (412.1 m) long and 43 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-405
CrossesSR 522 Sammamish R
Location8.7 N JCT SR 520
RouteInterstate 405
CountyKing County
StateWashington
Coordinates47.75578, -122.18532
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.
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 geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating59 US tons
Inventory rating34.9 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans12
Design loadHS 20 + Mod
Structure length1,352 ft (412.1 m)
Longest span122 ft (37.2 m)
Deck width43 ft (13.1 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deck17 ft (5.1 m)

Traffic and service

Average daily traffic56,311 (2023)
Projected traffic86,175 by 2039
Trucks6%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway and waterway
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$27 million (2022 estimate)
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was I-405 over SR 522 Sammamish R built?

It was built in 1968, making it 57 years old in 2025. It was reconstructed in 1997.

What condition is I-405 over SR 522 Sammamish R 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 over SR 522 Sammamish R carry?

About 56,311 vehicles per day (2023 count), of which roughly 6% are trucks.

How long is I-405 over SR 522 Sammamish R?

The structure is 1,352 ft (412.1 m) long with a longest span of 122 ft (37.2 m) and a deck 43 ft wide.

Who owns I-405 over SR 522 Sammamish R?

It is owned by the State Highway Agency.