US Bridges

SR 181 over Mill Creek

Good

King County, Washington · 3.0 N JCT SR 516 · Structure no. 0008509B0000000

Built
1922
103 years old, rebuilt 1990
Condition
Good
inspected September 2023
Type
Tee Beam
Concrete
Length
38 ft
1 main span
Daily traffic
30,762
2023 count
Owner
State
State Highway Agency

About this bridge

SR 181 over Mill Creek is a concrete tee beam carrying SR 181 over Mill Creek in King County, Washington. It was built in 1922 and reconstructed in 1990, so it is 103 years old, older 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 30,762 vehicles a day, roughly 9% of them trucks, projected to reach 44,069 by 2039. The structure is 38 ft (11.6 m) long and 102 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

CarriesSR 181
CrossesMill Creek
Location3.0 N JCT SR 516
RouteState Highway 181
Coordinates47.4205, -122.24925
Functional classUrban Other Principal Arterial

Condition and inspection

Good

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

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating33 US tons
Inventory rating20 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length38 ft (11.6 m)
Longest span37 ft (11.3 m)
Deck width102 ft (31.1 m)
Roadway width84 ft (25.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic30,762 (2023)
Projected traffic44,069 by 2039
Trucks9%
Lanes on structure6
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 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$1.6 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 181 over Mill Creek built?

It was built in 1922, making it 103 years old in 2025. It was reconstructed in 1990.

What condition is SR 181 over Mill Creek 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 September 2023.

How much traffic does SR 181 over Mill Creek carry?

About 30,762 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is SR 181 over Mill Creek?

The structure is 38 ft (11.6 m) long with a longest span of 37 ft (11.3 m) and a deck 102 ft wide.

Who owns SR 181 over Mill Creek?

It is owned by the State Highway Agency.