US Bridges

SR 518 over 42nd Ave S

Good

King County, Washington · 0.4 E JCT SR 99 · Structure no. 0007956A0000000

Built
1966
59 years old, rebuilt 2007
Condition
Good
inspected August 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
207 ft
3 main spans
Daily traffic
59,545
2023 count
Owner
State
State Highway Agency

About this bridge

SR 518 over 42nd Ave S is a prestressed concrete stringer/multi-beam or girder carrying SR 518 over 42nd Ave S in King County, Washington. It was built in 1966 and reconstructed in 2007, 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 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 59,545 vehicles a day, roughly 2% of them trucks, projected to reach 93,890 by 2039. The structure is 207 ft (63.1 m) long and 54 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

CarriesSR 518
Crosses42nd Ave S
Location0.4 E JCT SR 99
RouteState Highway 518
Coordinates47.4639, -122.28148
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.
Substructure7 GoodSome minor problems.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating86 US tons
Inventory rating51 US tons

Structure

MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length207 ft (63.1 m)
Longest span70 ft (21.3 m)
Deck width54 ft (16.4 m)
Roadway width49 ft (14.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic59,545 (2023)
Projected traffic93,890 by 2039
Trucks2%
Lanes on structure3
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$5 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was SR 518 over 42nd Ave S built?

It was built in 1966, making it 59 years old in 2025. It was reconstructed in 2007.

What condition is SR 518 over 42nd Ave S 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 518 over 42nd Ave S carry?

About 59,545 vehicles per day (2023 count), of which roughly 2% are trucks.

How long is SR 518 over 42nd Ave S?

The structure is 207 ft (63.1 m) long with a longest span of 70 ft (21.3 m) and a deck 54 ft wide.

Who owns SR 518 over 42nd Ave S?

It is owned by the State Highway Agency.