US Bridges

148th Ave over SR 520

Fair

King County, Washington · 2.3 E JCT I-405 · Structure no. 0011764A0000000

Built
1981
44 years old
Condition
Fair
inspected September 2023
Type
Box Beam or Girders - Multiple
Prestressed Concrete Continuous
Length
325 ft
2 main spans
Daily traffic
46,948
2020 count
Owner
State
State Highway Agency

About this bridge

148th Ave over SR 520 is a prestressed concrete continuous box beam or girders - multiple carrying 148th Ave over SR 520 in King County, Washington. It was built in 1981, so it is 44 years old, younger 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 46,948 vehicles a day, roughly 5% of them trucks, projected to reach 76,930 by 2040. The structure is 325 ft (99.1 m) long and 61 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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Carries148th Ave
CrossesSR 520
Location2.3 E JCT I-405
RouteCity Street 0
CountyKing County
StateWashington
Coordinates47.634, -122.14308
Functional classUrban Other Principal Arterial

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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionSeptember 2023
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 rating46 US tons
Inventory rating27 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20 + Mod
Structure length325 ft (99.1 m)
Longest span168 ft (51.2 m)
Deck width61 ft (18.7 m)
Roadway width52 ft (16 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic46,948 (2020)
Projected traffic76,930 by 2040
Trucks5%
Lanes on structure4
Traffic directionTwo-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 148th Ave over SR 520 built?

It was built in 1981, making it 44 years old in 2025.

What condition is 148th Ave over SR 520 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 148th Ave over SR 520 carry?

About 46,948 vehicles per day (2020 count), of which roughly 5% are trucks.

How long is 148th Ave over SR 520?

The structure is 325 ft (99.1 m) long with a longest span of 168 ft (51.2 m) and a deck 61 ft wide.

Who owns 148th Ave over SR 520?

It is owned by the State Highway Agency.