US Bridges

SR 520 over Lake Washington

Good

King County, Washington · 2.9 E JCT SR 513 · Structure no. 0018066C0000000

Built
2016
9 years old
Condition
Good
inspected August 2023
Type
Segmental Box Girder
Concrete Continuous
Length
820 ft
2 main spans
Daily traffic
28,957
2023 count
Owner
State
State Highway Agency

About this bridge

SR 520 over Lake Washington is a concrete continuous segmental box girder carrying SR 520 over Lake Washington in King County, Washington. It was built in 2016, so it is 9 years old, younger than the Washington average of 49.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 28,957 vehicles a day, roughly 3% of them trucks, projected to reach 52,332 by 2039. The structure is 820 ft (249.9 m) long and 52 ft wide. If it were closed, the detour would be 18 mi (29 km).

Location

Open in Google Maps
CarriesSR 520
CrossesLake Washington
Location2.9 E JCT SR 513
RouteState Highway 520
CountyKing County
StateWashington
Coordinates47.63836, -122.24369
Functional classUrban Principal Arterial - Other Freeway or Expressway

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure8 Very GoodNo problems noted.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating63.2 US tons
Inventory rating48.6 US tons

Structure

Structure typeSegmental Box Girder
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans2 (+1 approach)
Design loadUnknown
Structure length820 ft (249.9 m)
Longest span321 ft (97.8 m)
Deck width52 ft (15.8 m)
Roadway width48 ft (14.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic28,957 (2023)
Projected traffic52,332 by 2039
Trucks3%
Lanes on structure4
Traffic directionOne-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed18 mi (29 km)
TollToll bridge
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedWidening of existing bridge without deck rehabilitation
Estimated improvement cost$19.5 million (2022 estimate)
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was SR 520 over Lake Washington built?

It was built in 2016, making it 9 years old in 2025.

What condition is SR 520 over Lake Washington in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in August 2023.

How much traffic does SR 520 over Lake Washington carry?

About 28,957 vehicles per day (2023 count), of which roughly 3% are trucks.

How long is SR 520 over Lake Washington?

The structure is 820 ft (249.9 m) long with a longest span of 321 ft (97.8 m) and a deck 52 ft wide.

Who owns SR 520 over Lake Washington?

It is owned by the State Highway Agency.