US Bridges

Diablo Dam Access over Skagit River

Fair

King County, Washington · Diablo Dam · Structure no. 087472000000000

Built
1930
95 years old
Condition
Fair
inspected August 2022
Type
Arch - Deck
Concrete
Length
512 ft
14 main spans
Daily traffic
250
2022 count
Owner
Local
Other Local Agency

About this bridge

Diablo Dam Access over Skagit River is a concrete arch - deck carrying Diablo Dam Access over Skagit River in King County, Washington. It was built in 1930, so it is 95 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 250 vehicles a day, projected to reach 300 by 2042. The structure is 512 ft (156.1 m) long and 19 ft wide.

Location

Open in Google Maps
CarriesDiablo Dam Access
CrossesSkagit River
LocationDiablo Dam
CountyKing County
StateWashington
Coordinates48.71294, -121.13187
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionAugust 2022
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations on dry land well above flood water elevations
Structural evaluation6: Equal to present minimum criteria
Deck geometry2: Basically intolerable, requiring high priority of replacement
Approach roadway alignment8: Equal to present desirable criteria
Operating rating89.9 US tons
Inventory rating54 US tons

Structure

Structure typeArch - Deck
MaterialConcrete
DeckWood or timber
Main spans14
Design loadUnknown
Structure length512 ft (156.1 m)
Longest span32 ft (9.8 m)
Deck width19 ft (5.8 m)
Roadway width17 ft (5.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic250 (2022)
Projected traffic300 by 2042
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesOther
Detour if closed—
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerOther Local Agency
Maintained byOther Local Agency
Historic statusHistorical significance not determinable at this time
Work proposedDeck rehabilitation with only incidental widening
Estimated improvement cost$4.6 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was Diablo Dam Access over Skagit River built?

It was built in 1930, making it 95 years old in 2025.

What condition is Diablo Dam Access over Skagit River 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 August 2022.

How much traffic does Diablo Dam Access over Skagit River carry?

About 250 vehicles per day (2022 count).

How long is Diablo Dam Access over Skagit River?

The structure is 512 ft (156.1 m) long with a longest span of 32 ft (9.8 m) and a deck 19 ft wide.

Who owns Diablo Dam Access over Skagit River?

It is owned by the Other Local Agency.