US Bridges

SR 520 over 120th Ave NE

Fair

King County, Washington · 0.3 E JCT I-405 · Structure no. 0009086B0000000

Built
1971
54 years old, rebuilt 1993
Condition
Fair
inspected June 2024
Type
Box Beam or Girders - Multiple
Concrete Continuous
Length
392 ft
3 main spans
Daily traffic
45,466
2023 count
Owner
State
State Highway Agency

About this bridge

SR 520 over 120th Ave NE is a concrete continuous box beam or girders - multiple carrying SR 520 over 120th Ave NE in King County, Washington. It was built in 1971 and reconstructed in 1993, 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 45,466 vehicles a day, roughly 3% of them trucks, projected to reach 74,202 by 2039. The structure is 392 ft (119.5 m) long and 53 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesSR 520
Crosses120th Ave NE
Location0.3 E JCT I-405
RouteState Highway 520
CountyKing County
StateWashington
Coordinates47.63192, -122.18136
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Last inspectionJune 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to 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 rating99 US tons
Inventory rating90.9 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length392 ft (119.5 m)
Longest span168 ft (51.2 m)
Deck width53 ft (16.2 m)
Roadway width50 ft (15.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic45,466 (2023)
Projected traffic74,202 by 2039
Trucks3%
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$9.7 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was SR 520 over 120th Ave NE built?

It was built in 1971, making it 54 years old in 2025. It was reconstructed in 1993.

What condition is SR 520 over 120th Ave NE 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 2024.

How much traffic does SR 520 over 120th Ave NE carry?

About 45,466 vehicles per day (2023 count), of which roughly 3% are trucks.

How long is SR 520 over 120th Ave NE?

The structure is 392 ft (119.5 m) long with a longest span of 168 ft (51.2 m) and a deck 53 ft wide.

Who owns SR 520 over 120th Ave NE?

It is owned by the State Highway Agency.