US Bridges

183rd SW over Overflow Channel

Fair

Thurston County, Washington · 0.65 M E of Moon RD · Structure no. 079733000000000

Built
1924
101 years old
Condition
Fair
inspected March 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
26 ft
1 main span
Daily traffic
301
2020 count
Owner
County
County Highway Agency

About this bridge

183rd SW over Overflow Channel is a steel stringer/multi-beam or girder carrying 183rd SW over Overflow Channel in Thurston County, Washington. It was built in 1924, so it is 101 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 301 vehicles a day, roughly 10% of them trucks, projected to reach 484 by 2042. The structure is 26 ft (7.9 m) long and 22 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries183rd SW
CrossesOverflow Channel
Location0.65 M E of Moon RD
RouteCounty Highway 16125
CountyThurston County
StateWashington
Coordinates46.82178, -123.12603
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMarch 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating99 US tons
Inventory rating51 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length26 ft (7.9 m)
Longest span25 ft (7.6 m)
Deck width22 ft (6.7 m)
Roadway width21 ft (6.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic301 (2020)
Projected traffic484 by 2042
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty 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$1.3 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was 183rd SW over Overflow Channel built?

It was built in 1924, making it 101 years old in 2025.

What condition is 183rd SW over Overflow Channel 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 2024.

How much traffic does 183rd SW over Overflow Channel carry?

About 301 vehicles per day (2020 count), of which roughly 10% are trucks.

How long is 183rd SW over Overflow Channel?

The structure is 26 ft (7.9 m) long with a longest span of 25 ft (7.6 m) and a deck 22 ft wide.

Who owns 183rd SW over Overflow Channel?

It is owned by the County Highway Agency.