US Bridges

SR 20 over Bonaparte Creek

Fair

Okanogan County, Washington · 0.9 E JCT US 97 · Structure no. 0001738A0000000

Built
1933
92 years old
Condition
Fair
inspected March 2023
Type
Arch - Deck
Concrete
Length
118 ft
1 main span
Daily traffic
1,755
2023 count
Owner
State
State Highway Agency

About this bridge

SR 20 over Bonaparte Creek is a concrete arch - deck carrying SR 20 over Bonaparte Creek in Okanogan County, Washington. It was built in 1933, so it is 92 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 6 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 1,755 vehicles a day, roughly 11% of them trucks, projected to reach 2,004 by 2039. The structure is 118 ft (36 m) long and 27 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesSR 20
CrossesBonaparte Creek
Location0.9 E JCT US 97
RouteState Highway 20
CountyOkanogan County
StateWashington
Coordinates48.69456, -119.42808
Functional classRural 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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations on dry land well above flood water elevations
Structural evaluation4: Meets minimum tolerable limits to be 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 rating25.7 US tons
Inventory rating19.6 US tons

Structure

Structure typeArch - Deck
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1 (+3 approach)
Design loadH 15
Structure length118 ft (36 m)
Longest span88 ft (26.8 m)
Deck width27 ft (8.2 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,755 (2023)
Projected traffic2,004 by 2039
Trucks11%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$1.6 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 20 over Bonaparte Creek built?

It was built in 1933, making it 92 years old in 2025.

What condition is SR 20 over Bonaparte Creek 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 March 2023.

How much traffic does SR 20 over Bonaparte Creek carry?

About 1,755 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is SR 20 over Bonaparte Creek?

The structure is 118 ft (36 m) long with a longest span of 88 ft (26.8 m) and a deck 27 ft wide.

Who owns SR 20 over Bonaparte Creek?

It is owned by the State Highway Agency.