US Bridges

SR 508 over Alder Creek

Fair

Lewis County, Washington · 22.7 E JCT I-5 · Structure no. 000000CQ0000000

Built
1937
88 years old
Condition
Fair
inspected February 2024
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
88 ft
3 main spans
Daily traffic
1,200
2023 count
Owner
State
State Highway Agency

About this bridge

SR 508 over Alder Creek is a wood or timber stringer/multi-beam or girder carrying SR 508 over Alder Creek in Lewis County, Washington. It was built in 1937, so it is 88 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 1,200 vehicles a day, roughly 11% of them trucks, projected to reach 1,517 by 2039. The structure is 88 ft (26.8 m) long and 21 ft wide. If it were closed, the detour would be 34.8 mi (56 km).

Location

Open in Google Maps
CarriesSR 508
CrossesAlder Creek
Location22.7 E JCT I-5
RouteState Highway 508
CountyLewis County
StateWashington
Coordinates46.60428, -122.45108
Functional classRural Major 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
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 protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionFebruary 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
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 rating46 US tons
Inventory rating33 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckWood or timber
Main spans3
Design loadUnknown
Structure length88 ft (26.8 m)
Longest span29 ft (8.8 m)
Deck width21 ft (6.4 m)
Roadway width20 ft (6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,200 (2023)
Projected traffic1,517 by 2039
Trucks11%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed34.8 mi (56 km)
TollOn a free road
National Highway SystemNo

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$961,000 (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 508 over Alder Creek built?

It was built in 1937, making it 88 years old in 2025.

What condition is SR 508 over Alder 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 February 2024.

How much traffic does SR 508 over Alder Creek carry?

About 1,200 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is SR 508 over Alder Creek?

The structure is 88 ft (26.8 m) long with a longest span of 29 ft (8.8 m) and a deck 21 ft wide.

Who owns SR 508 over Alder Creek?

It is owned by the State Highway Agency.