Structure 7541 · Montmorency County, MI

M-32 over Thunder Bay River

Carries M-32 over Thunder Bay River, 2.8 Mi NE Of M-33.

Overall conditionFair

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

How ratings work
Decksets the rating5/9 · Fair
Superstructuresets the rating5/9 · Fair
Substructuresets the rating5/9 · Fair
Channelnot part of overall5/9 · Fair
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
CAR · 15 FT100 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 5/9Superstructure 5/9Substructure 5/9

100 ft end to end, longest span 48 ft. Lengths and the car 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.

Built1927rebuilt 1991
Length100.1 ft30.5 m
Daily traffic4,572counted 2007
Last inspectedJuly 2024every 24 months

Location

StateMichigan
CountyMontmorency
Location2.8 Mi NE Of M-33
CarriesM-32
CrossesThunder Bay River
Coordinates45.00863, -83.97250

Physical Characteristics

MaterialSteel
DesignStringer/Multi-beam
Total Length100.1 ft (30.5 m)
Max Span47.9 ft (14.6 m)
Deck Width47.2 ft (14.4 m)
Deck Area439.2 sq m
Main Spans2
Year Built1927 (reconstructed 1991)

Traffic

Avg Daily Traffic4,572 (2007)
Truck Traffic8%
Lanes On Bridge2

Inspection & Ownership

Last InspectionJuly 2024
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is on the National Register of Historic Places
Scour Critical3 — Scour critical
Structure Number000000000007541

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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