Structure 6262A0000000 · King County, WA

S 320th ST over I-5

Carries S 320th ST over I-5, 1.8 N Jct SR 18.

Overall conditionFair

Set by its lowest-rated component: Superstructure at 5 of 9.

How ratings work
Deck6/9 · Satisfactory
Superstructuresets the rating5/9 · Fair
Substructure7/9 · Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT332 FT OVERALL50 FT0ELEVATION · LENGTHS TO SCALE
Deck 6/9Superstructure 5/9 · sets the ratingSubstructure 7/9

332 ft end to end, longest span 100 ft: about 5 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.

Built196066 years old
Length332.0 ft101.2 m
Daily traffic49,879counted 2021
Last inspectedOctober 2024every 24 months

Location

StateWashington
CountyKing
Location1.8 N Jct SR 18
CarriesS 320th ST
CrossesI-5
Coordinates47.31514, -122.29819

Physical Characteristics

MaterialPrestressed Concrete
DesignStringer/Multi-beam
Total Length332.0 ft (101.2 m)
Max Span100.1 ft (30.5 m)
Deck Width76.1 ft (23.2 m)
Deck Area2347.8 sq m
Main Spans4
Year Built1960

Traffic

Avg Daily Traffic49,879 (2021)
Truck Traffic6%
Lanes On Bridge5
Lanes Under Bridge14

Inspection & Ownership

Last InspectionOctober 2024
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour CriticalNot applicable
Structure Number0006262A0000000

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.

Nearby Bridges