US Bridges

County Road 1090 over Twisp River

Fair

Okanogan County, Washington · 10.9 W.SR20 @ Twisp · Structure no. 081831000000000

Built
1959
66 years old
Condition
Fair
inspected September 2024
Type
Stringer/Multi-beam or Girder
Concrete Continuous
Length
102 ft
2 main spans
Daily traffic
52
2021 count
Owner
County
County Highway Agency

About this bridge

County Road 1090 over Twisp River is a concrete continuous stringer/multi-beam or girder carrying County Road 1090 over Twisp River in Okanogan County, Washington. It was built in 1959, so it is 66 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 52 vehicles a day, roughly 17% of them trucks, projected to reach 88 by 2042. The structure is 102 ft (31.2 m) long and 16 ft wide. If it were closed, the detour would be 14.3 mi (23 km).

Location

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CarriesCounty Road 1090
CrossesTwisp River
Location10.9 W.SR20 @ Twisp
RouteCounty Highway 10900
CountyOkanogan County
StateWashington
Coordinates48.36389, -120.33694
Functional classRural Local

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionSeptember 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourUnknown foundation; not evaluated for scour
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating43 US tons
Inventory rating24 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 15
Structure length102 ft (31.2 m)
Longest span59 ft (18.1 m)
Deck width16 ft (4.9 m)
Roadway width14 ft (4.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic52 (2021)
Projected traffic88 by 2042
Trucks17%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed14.3 mi (23 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$1.1 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was County Road 1090 over Twisp River built?

It was built in 1959, making it 66 years old in 2025.

What condition is County Road 1090 over Twisp River 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 September 2024.

How much traffic does County Road 1090 over Twisp River carry?

About 52 vehicles per day (2021 count), of which roughly 17% are trucks.

How long is County Road 1090 over Twisp River?

The structure is 102 ft (31.2 m) long with a longest span of 59 ft (18.1 m) and a deck 16 ft wide.

Who owns County Road 1090 over Twisp River?

It is owned by the County Highway Agency.