Structure 5677B0000000 · Thurston County, WA

US 101 over Mud Bay

Carries US 101 over Mud Bay, 1.3 S Jct SR 8.

Overall conditionFair

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

How ratings work
Decksets the rating6/9 · Satisfactory
Superstructure7/9 · Good
Substructure7/9 · Good
Channelnot part of overall8/9 · Very Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT290 FT OVERALL50 FT0ELEVATION · LENGTHS TO SCALE
Deck 6/9 · sets the ratingSuperstructure 7/9Substructure 7/9

290 ft end to end, longest span 40 ft: about 4 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 slab bridge.

Built195868 years old
Length290.0 ft88.4 m
Daily traffic21,984counted 2023
Last inspectedApril 2024every 24 months

Location

StateWashington
CountyThurston
Location1.3 S Jct SR 8
CarriesUS 101
CrossesMud Bay
Coordinates47.04519, -122.99075

Physical Characteristics

MaterialConcrete Continuous
DesignSlab
Total Length290.0 ft (88.4 m)
Max Span40.0 ft (12.2 m)
Deck Width33.5 ft (10.2 m)
Deck Area901.7 sq m
Main Spans8
Year Built1958

Traffic

Avg Daily Traffic21,984 (2023)
Truck Traffic6%
Lanes On Bridge2

Inspection & Ownership

Last InspectionApril 2024
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour Critical8 — Stable, low risk
Structure Number0005677B0000000

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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