US Bridges

NB Airport Expy over Nae Aoa Tunnel

Good

King County, Washington · 0.1 Mile N of S 170th ST · Structure no. 088544000000000

Built
2010
15 years old
Condition
Good
inspected May 2023
Type
Slab
Concrete Continuous
Length
58 ft
2 main spans
Daily traffic
34,200
2016 count
Owner
Local
Other Local Agency

About this bridge

NB Airport Expy over Nae Aoa Tunnel is a concrete continuous slab carrying NB Airport Expy over Nae Aoa Tunnel in King County, Washington. It was built in 2010, so it is 15 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 34,200 vehicles a day, roughly 2% of them trucks, projected to reach 25,000 by 2036. The structure is 58 ft (17.7 m) long and 122 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesNB Airport Expy
CrossesNae Aoa Tunnel
Location0.1 Mile N of S 170th ST
CountyKing County
StateWashington
Coordinates47.45197, -122.30002
Functional classUrban Other Principal Arterial

Condition and inspection

Good

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

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure8 Very GoodNo problems noted.
Substructure7 GoodSome minor problems.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating60.7 US tons
Inventory rating46.4 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 25 or greater
Structure length58 ft (17.7 m)
Longest span37 ft (11.3 m)
Deck width122 ft (37.2 m)
Roadway width73 ft (22.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic34,200 (2016)
Projected traffic25,000 by 2036
Trucks2%
Lanes on structure5
Traffic directionOne-way traffic
CarriesHighway and railroad
CrossesOther
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerOther Local Agency
Maintained byOther Local Agency
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was NB Airport Expy over Nae Aoa Tunnel built?

It was built in 2010, making it 15 years old in 2025.

What condition is NB Airport Expy over Nae Aoa Tunnel 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 May 2023.

How much traffic does NB Airport Expy over Nae Aoa Tunnel carry?

About 34,200 vehicles per day (2016 count), of which roughly 2% are trucks.

How long is NB Airport Expy over Nae Aoa Tunnel?

The structure is 58 ft (17.7 m) long with a longest span of 37 ft (11.3 m) and a deck 122 ft wide.

Who owns NB Airport Expy over Nae Aoa Tunnel?

It is owned by the Other Local Agency.