US Bridges

SR 99 over SR 518 Riverton Hts

Fair

King County, Washington · 4.9 N JCT SR 516 · Structure no. 0007046A0000000

Built
1962
63 years old, rebuilt 2011
Condition
Fair
inspected March 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
324 ft
4 main spans
Daily traffic
33,632
2023 count
Owner
State
State Highway Agency

About this bridge

SR 99 over SR 518 Riverton Hts is a prestressed concrete stringer/multi-beam or girder carrying SR 99 over SR 518 Riverton Hts in King County, Washington. It was built in 1962 and reconstructed in 2011, so it is 63 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 33,632 vehicles a day, roughly 9% of them trucks, projected to reach 50,281 by 2039. The structure is 324 ft (98.8 m) long and 91 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

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CarriesSR 99
CrossesSR 518 Riverton Hts
Location4.9 N JCT SR 516
RouteState Highway 99
CountyKing County
StateWashington
Coordinates47.46303, -122.29011
Functional classUrban Other Principal Arterial

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation3: Basically intolerable, requiring high priority of corrective action
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating16.4 US tons
Inventory rating12.9 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20 + Mod
Structure length324 ft (98.8 m)
Longest span97 ft (29.6 m)
Deck width91 ft (27.6 m)
Roadway width77 ft (23.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic33,632 (2023)
Projected traffic50,281 by 2039
Trucks9%
Lanes on structure6
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesHighway
Detour if closed1.9 mi (3 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$12.2 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was SR 99 over SR 518 Riverton Hts built?

It was built in 1962, making it 63 years old in 2025. It was reconstructed in 2011.

What condition is SR 99 over SR 518 Riverton Hts 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 99 over SR 518 Riverton Hts carry?

About 33,632 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is SR 99 over SR 518 Riverton Hts?

The structure is 324 ft (98.8 m) long with a longest span of 97 ft (29.6 m) and a deck 91 ft wide.

Who owns SR 99 over SR 518 Riverton Hts?

It is owned by the State Highway Agency.