US Bridges

SR 203 over Slough

Good

King County, Washington · 16.4 N JCT SR 202 · Structure no. 0012644A0000000

Built
1984
41 years old
Condition
Good
inspected July 2021
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
64 ft
1 main span
Daily traffic
10,445
2023 count
Owner
State
State Highway Agency

About this bridge

SR 203 over Slough is a prestressed concrete stringer/multi-beam or girder carrying SR 203 over Slough in King County, Washington. It was built in 1984, so it is 41 years old, younger than the Washington average of 49.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 10,445 vehicles a day, roughly 9% of them trucks, projected to reach 14,690 by 2039. The structure is 64 ft (19.5 m) long and 35 ft wide. If it were closed, the detour would be 14.3 mi (23 km).

Location

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CarriesSR 203
CrossesSlough
Location16.4 N JCT SR 202
RouteState Highway 203
CountyKing County
StateWashington
Coordinates47.75833, -121.97167
Functional classRural Minor Arterial

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJuly 2021
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating67 US tons
Inventory rating39 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckOther
Main spans1
Design loadHS 20 + Mod
Structure length64 ft (19.5 m)
Longest span58 ft (17.7 m)
Deck width35 ft (10.7 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic10,445 (2023)
Projected traffic14,690 by 2039
Trucks9%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed14.3 mi (23 km)
TollOn a free road
National Highway SystemNo

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 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 203 over Slough built?

It was built in 1984, making it 41 years old in 2025.

What condition is SR 203 over Slough in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in July 2021.

How much traffic does SR 203 over Slough carry?

About 10,445 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is SR 203 over Slough?

The structure is 64 ft (19.5 m) long with a longest span of 58 ft (17.7 m) and a deck 35 ft wide.

Who owns SR 203 over Slough?

It is owned by the State Highway Agency.