US Bridges

M-33 over Thunder Bay River

Fair

Montmorency County, Michigan · 1.5 MI S of M-32 · Structure no. 000000000007536

Built
1968
57 years old
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
65 ft
1 main span
Daily traffic
1,647
2007 count
Owner
State
State Highway Agency

About this bridge

M-33 over Thunder Bay River is a steel stringer/multi-beam or girder carrying M-33 over Thunder Bay River in Montmorency County, Michigan. It was built in 1968, so it is 57 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 6 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 1,647 vehicles a day, roughly 18% of them trucks, projected to reach 1,948 by 2018. The structure is 65 ft (19.9 m) long and 48 ft wide. If it were closed, the detour would be 29.2 mi (47 km).

Location

Open in Google Maps
CarriesM-33
CrossesThunder Bay River
Location1.5 MI S of M-32
RouteState Highway 33
CountyMontmorency County
StateMichigan
Coordinates44.97197, -84.03212
Functional classRural Minor Arterial

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating70.3 US tons
Inventory rating42.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadH 20
Structure length65 ft (19.9 m)
Longest span64 ft (19.4 m)
Deck width48 ft (14.5 m)
Roadway width45 ft (13.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,647 (2007)
Projected traffic1,948 by 2018
Trucks18%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed29.2 mi (47 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was M-33 over Thunder Bay River built?

It was built in 1968, making it 57 years old in 2025.

What condition is M-33 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-33 over Thunder Bay River carry?

About 1,647 vehicles per day (2007 count), of which roughly 18% are trucks.

How long is M-33 over Thunder Bay River?

The structure is 65 ft (19.9 m) long with a longest span of 64 ft (19.4 m) and a deck 48 ft wide.

Who owns M-33 over Thunder Bay River?

It is owned by the State Highway Agency.