US Bridges

SR 518 over N-W Ramp SR 518

Fair

King County, Washington · 1.9 E JCT SR 509 · Structure no. 0008902A0000000

Built
1971
54 years old
Condition
Fair
inspected September 2023
Type
Box Beam or Girders - Multiple
Concrete Continuous
Length
609 ft
7 main spans
Daily traffic
4,108
2022 count
Owner
State
State Highway Agency

About this bridge

SR 518 over N-W Ramp SR 518 is a concrete continuous box beam or girders - multiple carrying SR 518 over N-W Ramp SR 518 in King County, Washington. It was built in 1971, so it is 54 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 4,108 vehicles a day, roughly 5% of them trucks, projected to reach 6,742 by 2039. The structure is 609 ft (185.6 m) long and 41 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesSR 518
CrossesN-W Ramp SR 518
Location1.9 E JCT SR 509
RouteState Highway 518
CountyKing County
StateWashington
Coordinates47.46258, -122.29433
Functional classUrban Principal Arterial - Other Freeway or Expressway

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.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating91.9 US tons
Inventory rating54 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans7
Design loadHS 20
Structure length609 ft (185.6 m)
Longest span111 ft (33.8 m)
Deck width41 ft (12.6 m)
Roadway width38 ft (11.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,108 (2022)
Projected traffic6,742 by 2039
Trucks5%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
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$12.7 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was SR 518 over N-W Ramp SR 518 built?

It was built in 1971, making it 54 years old in 2025.

What condition is SR 518 over N-W Ramp SR 518 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 September 2023.

How much traffic does SR 518 over N-W Ramp SR 518 carry?

About 4,108 vehicles per day (2022 count), of which roughly 5% are trucks.

How long is SR 518 over N-W Ramp SR 518?

The structure is 609 ft (185.6 m) long with a longest span of 111 ft (33.8 m) and a deck 41 ft wide.

Who owns SR 518 over N-W Ramp SR 518?

It is owned by the State Highway Agency.