US Bridges

I-405 over SR 900 / N Park DR

Fair

King County, Washington · JCT SR 900 · Structure no. 0007828B0000000

Built
1966
59 years old
Condition
Fair
inspected June 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
215 ft
3 main spans
Daily traffic
65,721
2023 count
Owner
State
State Highway Agency

About this bridge

I-405 over SR 900 / N Park DR is a prestressed concrete stringer/multi-beam or girder carrying I-405 over SR 900 / N Park DR in King County, Washington. It was built in 1966, 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 65,721 vehicles a day, roughly 6% of them trucks, projected to reach 95,644 by 2039. The structure is 215 ft (65.5 m) long and 40 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-405
CrossesSR 900 / N Park DR
LocationJCT SR 900
RouteInterstate 405
CountyKing County
StateWashington
Coordinates47.50239, -122.19676
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 inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation3: Basically intolerable, requiring high priority of corrective action
Deck geometry2: Basically intolerable, requiring high priority of replacement
Approach roadway alignment8: Equal to present desirable criteria
Operating rating21.8 US tons
Inventory rating16.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length215 ft (65.5 m)
Longest span105 ft (32 m)
Deck width40 ft (12.3 m)
Roadway width37 ft (11.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic65,721 (2023)
Projected traffic95,644 by 2039
Trucks6%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
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$4.7 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-405 over SR 900 / N Park DR built?

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

What condition is I-405 over SR 900 / N Park DR 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 June 2023.

How much traffic does I-405 over SR 900 / N Park DR carry?

About 65,721 vehicles per day (2023 count), of which roughly 6% are trucks.

How long is I-405 over SR 900 / N Park DR?

The structure is 215 ft (65.5 m) long with a longest span of 105 ft (32 m) and a deck 40 ft wide.

Who owns I-405 over SR 900 / N Park DR?

It is owned by the State Highway Agency.