US Bridges

I-90 over Issaquah Creek

Good

King County, Washington · 0.9 E JCT SR 900 · Structure no. 0008573A0000000

Built
1970
55 years old
Condition
Good
inspected October 2022
Type
Slab
Concrete Continuous
Length
126 ft
3 main spans
Daily traffic
46,269
2023 count
Owner
State
State Highway Agency

About this bridge

I-90 over Issaquah Creek is a concrete continuous slab carrying I-90 over Issaquah Creek in King County, Washington. It was built in 1970, so it is 55 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 46,269 vehicles a day, roughly 7% of them trucks, projected to reach 70,446 by 2039. The structure is 126 ft (38.4 m) long and 55 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI-90
CrossesIssaquah Creek
Location0.9 E JCT SR 900
RouteInterstate 90
CountyKing County
StateWashington
Coordinates47.54447, -122.04495
Functional classUrban Principal Arterial - Interstate

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.
Substructure8 Very GoodNo problems noted.
Channel and channel protection7 GoodSome minor problems.
Last inspectionOctober 2022
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
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 rating86 US tons
Inventory rating51 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length126 ft (38.4 m)
Longest span52 ft (15.8 m)
Deck width55 ft (16.9 m)
Roadway width52 ft (15.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic46,269 (2023)
Projected traffic70,446 by 2039
Trucks7%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

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$3.2 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was I-90 over Issaquah Creek built?

It was built in 1970, making it 55 years old in 2025.

What condition is I-90 over Issaquah 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 October 2022.

How much traffic does I-90 over Issaquah Creek carry?

About 46,269 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is I-90 over Issaquah Creek?

The structure is 126 ft (38.4 m) long with a longest span of 52 ft (15.8 m) and a deck 55 ft wide.

Who owns I-90 over Issaquah Creek?

It is owned by the State Highway Agency.