US Bridges

SR 99 over N 50th ST

Fair

King County, Washington · 9.2 N JCT SR 509 · Structure no. 0001684A0000000

Built
1933
92 years old
Condition
Fair
inspected March 2024
Type
Tee Beam
Concrete
Length
44 ft
1 main span
Daily traffic
37,273
2023 count
Owner
State
State Highway Agency

About this bridge

SR 99 over N 50th ST is a concrete tee beam carrying SR 99 over N 50th ST in King County, Washington. It was built in 1933, so it is 92 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 5 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 37,273 vehicles a day, roughly 3% of them trucks, projected to reach 57,886 by 2039. The structure is 44 ft (13.4 m) long and 81 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesSR 99
CrossesN 50th ST
Location9.2 N JCT SR 509
RouteState Highway 99
CountyKing County
StateWashington
Coordinates47.66502, -122.34731
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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Approach roadway alignment8: Equal to present desirable criteria
Operating rating27.1 US tons
Inventory rating20.7 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length44 ft (13.4 m)
Longest span40 ft (12.2 m)
Deck width81 ft (24.8 m)
Roadway width65 ft (19.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic37,273 (2023)
Projected traffic57,886 by 2039
Trucks3%
Lanes on structure5
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
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$1.8 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was SR 99 over N 50th ST built?

It was built in 1933, making it 92 years old in 2025.

What condition is SR 99 over N 50th ST 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 March 2024.

How much traffic does SR 99 over N 50th ST carry?

About 37,273 vehicles per day (2023 count), of which roughly 3% are trucks.

How long is SR 99 over N 50th ST?

The structure is 44 ft (13.4 m) long with a longest span of 40 ft (12.2 m) and a deck 81 ft wide.

Who owns SR 99 over N 50th ST?

It is owned by the State Highway Agency.