US Bridges

I-405 over Damson RD

Good

Snohomish County, Washington · 2.2 N JCT SR 527 · Structure no. 0008417C0000000

Built
1968
57 years old, rebuilt 2001
Condition
Good
inspected August 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete Continuous
Length
212 ft
3 main spans
Daily traffic
61,143
2023 count
Owner
State
State Highway Agency

About this bridge

I-405 over Damson RD is a prestressed concrete continuous stringer/multi-beam or girder carrying I-405 over Damson RD in Snohomish County, Washington. It was built in 1968 and reconstructed in 2001, so it is 57 years old, older 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 61,143 vehicles a day, roughly 5% of them trucks, projected to reach 93,782 by 2039. The structure is 212 ft (64.6 m) long and 58 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

CarriesI-405
CrossesDamson RD
Location2.2 N JCT SR 527
RouteInterstate 405
Coordinates47.82008, -122.24206
Functional classUrban Principal Arterial - Interstate

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.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating66 US tons
Inventory rating39 US tons

Structure

MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length212 ft (64.6 m)
Longest span71 ft (21.6 m)
Deck width58 ft (17.8 m)
Roadway width55 ft (16.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic61,143 (2023)
Projected traffic93,782 by 2039
Trucks5%
Lanes on structure4
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

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$5.8 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-405 over Damson RD built?

It was built in 1968, making it 57 years old in 2025. It was reconstructed in 2001.

What condition is I-405 over Damson RD 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 August 2023.

How much traffic does I-405 over Damson RD carry?

About 61,143 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is I-405 over Damson RD?

The structure is 212 ft (64.6 m) long with a longest span of 71 ft (21.6 m) and a deck 58 ft wide.

Who owns I-405 over Damson RD?

It is owned by the State Highway Agency.