US Bridges

Diablo Dam Access over Skagit River

Fair

King County, Washington · Diablo Dam · Structure no. 087473000000000

Built
1930
95 years old
Condition
Fair
inspected August 2022
Type
Slab
Concrete
Length
300 ft
11 main spans
Daily traffic
220
2022 count
Owner
Local
Other Local Agency

About this bridge

Diablo Dam Access over Skagit River is a concrete slab 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 5 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: open, posting recommended but not legally implemented.

It carries about 220 vehicles a day, roughly 10% of them trucks, projected to reach 300 by 2042. The structure is 300 ft (91.4 m) long and 19 ft wide.

Location

Open in Google Maps
CarriesDiablo Dam Access
CrossesSkagit River
LocationDiablo Dam
CountyKing County
StateWashington
Coordinates48.71457, -121.13207
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
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, posting recommended but not legally implemented
ScourFoundations on dry land well above flood water elevations
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating27 US tons
Inventory rating16 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, cast-in-place
Main spans11
Design loadUnknown
Structure length300 ft (91.4 m)
Longest span22 ft (6.7 m)
Deck width19 ft (5.8 m)
Roadway width17 ft (5.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic220 (2022)
Projected traffic300 by 2042
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesRelief for waterway
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$2.7 million (2022 estimate)
NavigationNo navigation control on 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 220 vehicles per day (2022 count), of which roughly 10% are trucks.

How long is Diablo Dam Access over Skagit River?

The structure is 300 ft (91.4 m) long with a longest span of 22 ft (6.7 m) and a deck 19 ft wide.

Who owns Diablo Dam Access over Skagit River?

It is owned by the Other Local Agency.