US Bridges

I-90 over Highline Canal

Fair

Kittitas County, Washington · 4.8 E JCT SR 970 · Structure no. 0007574C0000000

Built
1965
60 years old
Condition
Fair
inspected February 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
178 ft
2 main spans
Daily traffic
14,717
2023 count
Owner
State
State Highway Agency

About this bridge

I-90 over Highline Canal is a prestressed concrete stringer/multi-beam or girder carrying I-90 over Highline Canal in Kittitas County, Washington. It was built in 1965, so it is 60 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 14,717 vehicles a day, roughly 23% of them trucks, projected to reach 18,248 by 2039. The structure is 178 ft (54.3 m) long and 40 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-90
CrossesHighline Canal
Location4.8 E JCT SR 970
RouteInterstate 90
CountyKittitas County
StateWashington
Coordinates47.15068, -120.81893
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionFebruary 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being 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 rating30.8 US tons
Inventory rating23.6 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20 + Mod
Structure length178 ft (54.3 m)
Longest span104 ft (31.7 m)
Deck width40 ft (12.2 m)
Roadway width36 ft (11.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic14,717 (2023)
Projected traffic18,248 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$3.7 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was I-90 over Highline Canal built?

It was built in 1965, making it 60 years old in 2025.

What condition is I-90 over Highline Canal 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 February 2024.

How much traffic does I-90 over Highline Canal carry?

About 14,717 vehicles per day (2023 count), of which roughly 23% are trucks.

How long is I-90 over Highline Canal?

The structure is 178 ft (54.3 m) long with a longest span of 104 ft (31.7 m) and a deck 40 ft wide.

Who owns I-90 over Highline Canal?

It is owned by the State Highway Agency.