US Bridges

I-90 over Cascade Canal Overflow

Fair

Kittitas County, Washington · 17.3 E JCT SR 970 · Structure no. 0008036A0000000

Built
1967
58 years old
Condition
Fair
inspected July 2023
Type
Slab
Concrete Continuous
Length
321 ft
8 main spans
Daily traffic
15,974
2023 count
Owner
State
State Highway Agency

About this bridge

I-90 over Cascade Canal Overflow is a concrete continuous slab carrying I-90 over Cascade Canal Overflow in Kittitas County, Washington. It was built in 1967, so it is 58 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 15,974 vehicles a day, roughly 23% of them trucks, projected to reach 20,086 by 2039. The structure is 321 ft (97.8 m) long and 35 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-90
CrossesCascade Canal Overflow
Location17.3 E JCT SR 970
RouteInterstate 90
CountyKittitas County
StateWashington
Coordinates47.03853, -120.62792
Functional classRural Principal Arterial - Interstate

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.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
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 rating74 US tons
Inventory rating44 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans8
Design loadHS 20 + Mod
Structure length321 ft (97.8 m)
Longest span45 ft (13.7 m)
Deck width35 ft (10.7 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic15,974 (2023)
Projected traffic20,086 by 2039
Trucks23%
Lanes on structure2
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$6.3 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was I-90 over Cascade Canal Overflow built?

It was built in 1967, making it 58 years old in 2025.

What condition is I-90 over Cascade Canal Overflow 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 2023.

How much traffic does I-90 over Cascade Canal Overflow carry?

About 15,974 vehicles per day (2023 count), of which roughly 23% are trucks.

How long is I-90 over Cascade Canal Overflow?

The structure is 321 ft (97.8 m) long with a longest span of 45 ft (13.7 m) and a deck 35 ft wide.

Who owns I-90 over Cascade Canal Overflow?

It is owned by the State Highway Agency.