US Bridges

SR 520 W-N Ramp over Sammamish Pkwy/River

Good

King County, Washington · 4.9 E JCT I-405 · Structure no. 0017637A0000000

Built
2010
15 years old
Condition
Good
inspected August 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete Continuous
Length
400 ft
4 main spans
Daily traffic
3,902
2012 count
Owner
State
State Highway Agency

About this bridge

SR 520 W-N Ramp over Sammamish Pkwy/River is a prestressed concrete continuous stringer/multi-beam or girder carrying SR 520 W-N Ramp over Sammamish Pkwy/River in King County, Washington. It was built in 2010, so it is 15 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 8 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 3,902 vehicles a day, roughly 3% of them trucks. The structure is 400 ft (121.9 m) long and 29 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesSR 520 W-N Ramp
CrossesSammamish Pkwy/River
Location4.9 E JCT I-405
RouteState Highway 520
CountyKing County
StateWashington
Coordinates47.66736, -122.12744
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
Deck8 Very GoodNo problems noted.
Superstructure8 Very GoodNo problems noted.
Substructure8 Very GoodNo problems noted.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation8: Equal to present desirable criteria
Deck geometry9: Superior to present desirable criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating99 US tons
Inventory rating66 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHL 93
Structure length400 ft (121.9 m)
Longest span132 ft (40.2 m)
Deck width29 ft (8.8 m)
Roadway width27 ft (8.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,902 (2012)
Projected traffic—
Trucks3%
Lanes on structure1
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway and waterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$5.5 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 520 W-N Ramp over Sammamish Pkwy/River built?

It was built in 2010, making it 15 years old in 2025.

What condition is SR 520 W-N Ramp over Sammamish Pkwy/River 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 2024.

How much traffic does SR 520 W-N Ramp over Sammamish Pkwy/River carry?

About 3,902 vehicles per day (2012 count), of which roughly 3% are trucks.

How long is SR 520 W-N Ramp over Sammamish Pkwy/River?

The structure is 400 ft (121.9 m) long with a longest span of 132 ft (40.2 m) and a deck 29 ft wide.

Who owns SR 520 W-N Ramp over Sammamish Pkwy/River?

It is owned by the State Highway Agency.