US Bridges

M-32 over Thunder Bay River

Fair

Montmorency County, Michigan · 2.8 MI NE of M-33 · Structure no. 000000000007541

Built
1927
98 years old, rebuilt 1991
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
100 ft
2 main spans
Daily traffic
4,572
2007 count
Owner
State
State Highway Agency

About this bridge

M-32 over Thunder Bay River is a steel stringer/multi-beam or girder carrying M-32 over Thunder Bay River in Montmorency County, Michigan. It was built in 1927 and reconstructed in 1991, so it is 98 years old, older than the Michigan average of 48.3 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 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 4,572 vehicles a day, roughly 8% of them trucks, projected to reach 5,600 by 2018. The structure is 100 ft (30.5 m) long and 47 ft wide. If it were closed, the detour would be 24.9 mi (40 km).

Location

Open in Google Maps
CarriesM-32
CrossesThunder Bay River
Location2.8 MI NE of M-33
RouteState Highway 32
CountyMontmorency County
StateMichigan
Coordinates45.00863, -83.9725
Functional classRural Principal Arterial - Other

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry7: Better than present minimum criteria
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating58.5 US tons
Inventory rating35.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length100 ft (30.5 m)
Longest span48 ft (14.6 m)
Deck width47 ft (14.4 m)
Roadway width44 ft (13.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,572 (2007)
Projected traffic5,600 by 2018
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed24.9 mi (40 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedDeck replacement with only incidental widening
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was M-32 over Thunder Bay River built?

It was built in 1927, making it 98 years old in 2025. It was reconstructed in 1991.

What condition is M-32 over Thunder Bay River 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 July 2024.

How much traffic does M-32 over Thunder Bay River carry?

About 4,572 vehicles per day (2007 count), of which roughly 8% are trucks.

How long is M-32 over Thunder Bay River?

The structure is 100 ft (30.5 m) long with a longest span of 48 ft (14.6 m) and a deck 47 ft wide.

Who owns M-32 over Thunder Bay River?

It is owned by the State Highway Agency.