US Bridges

SR 520 Ramp over Portage Bay

Fair

King County, Washington · 0.8 E JCT I-5 · Structure no. 0006819B0000000

Built
1963
62 years old
Condition
Fair
inspected March 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
375 ft
5 main spans
Daily traffic
11,169
2022 count
Owner
State
State Highway Agency

About this bridge

SR 520 Ramp over Portage Bay is a prestressed concrete stringer/multi-beam or girder carrying SR 520 Ramp over Portage Bay in King County, Washington. It was built in 1963, so it is 62 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 11,169 vehicles a day, roughly 5% of them trucks, projected to reach 23,512 by 2039. The structure is 375 ft (114.3 m) long and 23 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesSR 520 Ramp
CrossesPortage Bay
Location0.8 E JCT I-5
RouteState Highway 520
CountyKing County
StateWashington
Coordinates47.64356, -122.30466
Functional classUrban Principal Arterial - Other Freeway or Expressway

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.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating47.8 US tons
Inventory rating36.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans5
Design loadHS 20
Structure length375 ft (114.3 m)
Longest span75 ft (22.9 m)
Deck width23 ft (6.9 m)
Roadway width18 ft (5.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11,169 (2022)
Projected traffic23,512 by 2039
Trucks5%
Lanes on structure1
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes

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$3.6 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 520 Ramp over Portage Bay built?

It was built in 1963, making it 62 years old in 2025.

What condition is SR 520 Ramp over Portage Bay 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 March 2024.

How much traffic does SR 520 Ramp over Portage Bay carry?

About 11,169 vehicles per day (2022 count), of which roughly 5% are trucks.

How long is SR 520 Ramp over Portage Bay?

The structure is 375 ft (114.3 m) long with a longest span of 75 ft (22.9 m) and a deck 23 ft wide.

Who owns SR 520 Ramp over Portage Bay?

It is owned by the State Highway Agency.