Structure 6966B0000000 · King County, WA

I-90 over SR 18

Carries I-90 over SR 18, 9.7 E Jct SR 900.

Overall conditionFair

Set by its lowest-rated component: Deck and Superstructure at 6 of 9.

How ratings work
Decksets the rating6/9 · Satisfactory
Superstructuresets the rating6/9 · Satisfactory
Substructure7/9 · Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT158 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 6/9 · sets the ratingSuperstructure 6/9 · sets the ratingSubstructure 7/9

158 ft end to end, longest span 72 ft: about 2 semi-trucks nose to tail. Lengths and the semi-truck on the deck are drawn to the same scale. Each part is colored by its latest inspection rating. The inventory records lengths but not heights or the layout of the shorter spans, so those are drawn as typical for a multi-beam bridge.

Built1963rebuilt 1978
Length158.1 ft48.2 m
Daily traffic22,901counted 2023
Last inspectedJune 2023every 24 months

Location

StateWashington
CountyKing
Location9.7 E Jct SR 900
CarriesI-90
CrossesSR 18
Coordinates47.50900, -121.88392

Physical Characteristics

MaterialPrestressed Concrete
DesignStringer/Multi-beam
Total Length158.1 ft (48.2 m)
Max Span71.9 ft (21.9 m)
Deck Width75.5 ft (23 m)
Deck Area1108.6 sq m
Main Spans3
Year Built1963 (reconstructed 1978)

Traffic

Avg Daily Traffic22,901 (2023)
Truck Traffic7%
Lanes On Bridge3
Lanes Under Bridge5

Inspection & Ownership

Last InspectionJune 2023
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour CriticalNot applicable
Structure Number0006966B0000000

How Bridge Ratings Work

Inspectors rate each major part of a bridge (the deck you drive on, the superstructure of beams that holds it up, and the substructure of piers and abutments beneath) on a 0–9 scale. A bridge's overall condition is its lowest of those ratings, so one deteriorated component makes the whole bridge "poor."

0Failed
1Imminent failure
2Critical
3Serious
4Poor
5Fair
6Satisfactory
7Good
8Very good
9Excellent
Good · lowest component 7–9
Fair · lowest component 5–6
Poor · lowest component 0–4

A poor rating is not a closure. It means the bridge is flagged for priority repair or replacement; bridges judged unsafe are closed or posted with weight limits. The waterway (channel) rating is reported, but it does not count toward the overall classification.

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