US Bridges

SR 509 over Thames Creek/Ped Trail

Fair

King County, Washington · 11.0 N JCT I-705 · Structure no. 000000HX0000000

Built
1929
96 years old, rebuilt 1996
Condition
Fair
inspected July 2024
Type
Girder and Floorbeam System
Steel
Length
557 ft
11 main spans
Daily traffic
3,869
2023 count
Owner
State
State Highway Agency

About this bridge

SR 509 over Thames Creek/Ped Trail is a steel girder and floorbeam system carrying SR 509 over Thames Creek/Ped Trail in King County, Washington. It was built in 1929 and reconstructed in 1996, so it is 96 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 3,869 vehicles a day, roughly 3% of them trucks, projected to reach 5,683 by 2039. The structure is 557 ft (169.8 m) long and 35 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

Location

Open in Google Maps
CarriesSR 509
CrossesThames Creek/Ped Trail
Location11.0 N JCT I-705
RouteState Highway 509
CountyKing County
StateWashington
Coordinates47.31797, -122.41444
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
Deck7 GoodSome minor problems.
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 protection8 Very GoodNo problems noted.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations on dry land well above flood water elevations
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
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 rating39 US tons
Inventory rating23 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel
DeckConcrete, cast-in-place
Main spans11
Design loadUnknown
Structure length557 ft (169.8 m)
Longest span72 ft (21.9 m)
Deck width35 ft (10.7 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,869 (2023)
Projected traffic5,683 by 2039
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed6.2 mi (10 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$8.5 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 509 over Thames Creek/Ped Trail built?

It was built in 1929, making it 96 years old in 2025. It was reconstructed in 1996.

What condition is SR 509 over Thames Creek/Ped Trail 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 July 2024.

How much traffic does SR 509 over Thames Creek/Ped Trail carry?

About 3,869 vehicles per day (2023 count), of which roughly 3% are trucks.

How long is SR 509 over Thames Creek/Ped Trail?

The structure is 557 ft (169.8 m) long with a longest span of 72 ft (21.9 m) and a deck 35 ft wide.

Who owns SR 509 over Thames Creek/Ped Trail?

It is owned by the State Highway Agency.