US Bridges

SR 18 over Green River

Fair

King County, Washington · 2.5 E JCT SR 164 · Structure no. 0006066B0000000

Built
1959
66 years old
Condition
Fair
inspected April 2024
Type
Truss - Thru
Steel
Length
371 ft
1 main span
Daily traffic
28,147
2023 count
Owner
State
State Highway Agency

About this bridge

SR 18 over Green River is a steel truss - thru carrying SR 18 over Green River in King County, Washington. It was built in 1959, so it is 66 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 28,147 vehicles a day, roughly 11% of them trucks, projected to reach 40,870 by 2039. The structure is 371 ft (113.1 m) long and 33 ft wide. If it were closed, the detour would be 9.9 mi (16 km).

Location

Open in Google Maps
CarriesSR 18
CrossesGreen River
Location2.5 E JCT SR 164
RouteState Highway 18
CountyKing County
StateWashington
Coordinates47.30246, -122.17746
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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating56 US tons
Inventory rating34 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+4 approach)
Design loadHS 20
Structure length371 ft (113.1 m)
Longest span200 ft (61 m)
Deck width33 ft (10 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deck15 ft (4.5 m)

Traffic and service

Average daily traffic28,147 (2023)
Projected traffic40,870 by 2039
Trucks11%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed9.9 mi (16 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$6 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 18 over Green River built?

It was built in 1959, making it 66 years old in 2025.

What condition is SR 18 over Green River 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 April 2024.

How much traffic does SR 18 over Green River carry?

About 28,147 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is SR 18 over Green River?

The structure is 371 ft (113.1 m) long with a longest span of 200 ft (61 m) and a deck 33 ft wide.

Who owns SR 18 over Green River?

It is owned by the State Highway Agency.