US Bridges

20th Ave. over Lake Sacajawea

FairPosted for load

Cowlitz County, Washington · JCT 20th Ave. & Lake Saca · Structure no. 085584000000000

Built
1940
85 years old
Condition
Fair
inspected March 2023
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
163 ft
9 main spans
Daily traffic
3,133
2019 count
Owner
City
City or Municipal Highway Agency

About this bridge

20th Ave. over Lake Sacajawea is a wood or timber stringer/multi-beam or girder carrying 20th Ave. over Lake Sacajawea in Cowlitz County, Washington. It was built in 1940, so it is 85 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. Its operating status is: posted for load restriction.

It carries about 3,133 vehicles a day, roughly 5% of them trucks, projected to reach 3,846 by 2032. The structure is 163 ft (49.7 m) long and 36 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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Carries20th Ave.
CrossesLake Sacajawea
LocationJCT 20th Ave. & Lake Saca
RouteCity Street 20
CountyCowlitz County
StateWashington
Coordinates46.13025, -122.947
Functional classUrban Collector

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.
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 statusPosted for load restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating30.3 US tons
Inventory rating23.3 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckConcrete, cast-in-place
Main spans9
Design loadH 15
Structure length163 ft (49.7 m)
Longest span32 ft (9.8 m)
Deck width36 ft (11 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,133 (2019)
Projected traffic3,846 by 2032
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$6.2 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was 20th Ave. over Lake Sacajawea built?

It was built in 1940, making it 85 years old in 2025.

What condition is 20th Ave. over Lake Sacajawea 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 20th Ave. over Lake Sacajawea carry?

About 3,133 vehicles per day (2019 count), of which roughly 5% are trucks.

How long is 20th Ave. over Lake Sacajawea?

The structure is 163 ft (49.7 m) long with a longest span of 32 ft (9.8 m) and a deck 36 ft wide.

Who owns 20th Ave. over Lake Sacajawea?

It is owned by the City or Municipal Highway Agency.