US Bridges

256th ST over SR 18

Fair

King County, Washington · 1.5 E JCT SR 516 · Structure no. 0016008B0000000

Built
2002
23 years old
Condition
Fair
inspected March 2024
Type
Box Beam or Girders - Multiple
Prestressed Concrete Continuous
Length
304 ft
2 main spans
Daily traffic
3,706
2010 count
Owner
State
State Highway Agency

About this bridge

256th ST over SR 18 is a prestressed concrete continuous box beam or girders - multiple carrying 256th ST over SR 18 in King County, Washington. It was built in 2002, so it is 23 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 3,706 vehicles a day, roughly 16% of them trucks, projected to reach 5,826 by 2036. The structure is 304 ft (92.7 m) long and 54 ft wide. If it were closed, the detour would be 11.8 mi (19 km).

Location

Open in Google Maps
Carries256th ST
CrossesSR 18
Location1.5 E JCT SR 516
RouteCounty Highway 0
CountyKing County
StateWashington
Coordinates47.37258, -122.09153
Functional classUrban Minor 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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating99 US tons
Inventory rating68 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHL 93
Structure length304 ft (92.7 m)
Longest span175 ft (53.3 m)
Deck width54 ft (16.4 m)
Roadway width39 ft (11.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,706 (2010)
Projected traffic5,826 by 2036
Trucks16%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesHighway
Detour if closed11.8 mi (19 km)
TollOn a free road
National Highway SystemNo

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$5.9 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was 256th ST over SR 18 built?

It was built in 2002, making it 23 years old in 2025.

What condition is 256th ST over SR 18 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 256th ST over SR 18 carry?

About 3,706 vehicles per day (2010 count), of which roughly 16% are trucks.

How long is 256th ST over SR 18?

The structure is 304 ft (92.7 m) long with a longest span of 175 ft (53.3 m) and a deck 54 ft wide.

Who owns 256th ST over SR 18?

It is owned by the State Highway Agency.