US Bridges

SR 508 over Tilton River

Good

Lewis County, Washington · 28.5 E JCT I-5 · Structure no. 0014208A0000000

Built
1994
31 years old
Condition
Good
inspected November 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete Continuous
Length
352 ft
4 main spans
Daily traffic
1,200
2023 count
Owner
State
State Highway Agency

About this bridge

SR 508 over Tilton River is a prestressed concrete continuous stringer/multi-beam or girder carrying SR 508 over Tilton River in Lewis County, Washington. It was built in 1994, so it is 31 years old, younger than the Washington average of 49.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 1,200 vehicles a day, roughly 11% of them trucks, projected to reach 1,517 by 2039. The structure is 352 ft (107.3 m) long and 31 ft wide. If it were closed, the detour would be 39.8 mi (64 km).

CarriesSR 508
CrossesTilton River
Location28.5 E JCT I-5
RouteState Highway 508
Coordinates46.58472, -122.34908
Functional classRural Major Collector

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure8 Very GoodNo problems noted.
Substructure8 Very GoodNo problems noted.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionNovember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation8: Equal to present desirable criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating86 US tons
Inventory rating52 US tons

Structure

MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 25 or greater
Structure length352 ft (107.3 m)
Longest span110 ft (33.5 m)
Deck width31 ft (9.4 m)
Roadway width28 ft (8.5 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 closed39.8 mi (64 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$5 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 508 over Tilton River built?

It was built in 1994, making it 31 years old in 2025.

What condition is SR 508 over Tilton River in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in November 2024.

How much traffic does SR 508 over Tilton River carry?

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

How long is SR 508 over Tilton River?

The structure is 352 ft (107.3 m) long with a longest span of 110 ft (33.5 m) and a deck 31 ft wide.

Who owns SR 508 over Tilton River?

It is owned by the State Highway Agency.