US Bridges

M-46 over Pine River

Fair

Gratiot County, Michigan · In ST Louis · Structure no. 000000000003112

Built
1930
95 years old, rebuilt 1984
Condition
Fair
inspected May 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
90 ft
2 main spans
Daily traffic
9,548
2007 count
Owner
State
State Highway Agency

About this bridge

M-46 over Pine River is a steel stringer/multi-beam or girder carrying M-46 over Pine River in Gratiot County, Michigan. It was built in 1930 and reconstructed in 1984, so it is 95 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 9,548 vehicles a day, roughly 6% of them trucks, projected to reach 12,851 by 2018. The structure is 90 ft (27.4 m) long and 36 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesM-46
CrossesPine River
LocationIn ST Louis
RouteState Highway 46
CountyGratiot County
StateMichigan
Coordinates43.40783, -84.61874
Functional classUrban Other Principal 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
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 protection7 GoodSome minor problems.
Last inspectionMay 2023
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 geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating60 US tons
Inventory rating35.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans2
Design loadHS 15
Structure length90 ft (27.4 m)
Longest span45 ft (13.7 m)
Deck width36 ft (11.1 m)
Roadway width33 ft (10.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic9,548 (2007)
Projected traffic12,851 by 2018
Trucks6%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.1 mi (5 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-46 over Pine River built?

It was built in 1930, making it 95 years old in 2025. It was reconstructed in 1984.

What condition is M-46 over Pine 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 May 2023.

How much traffic does M-46 over Pine River carry?

About 9,548 vehicles per day (2007 count), of which roughly 6% are trucks.

How long is M-46 over Pine River?

The structure is 90 ft (27.4 m) long with a longest span of 45 ft (13.7 m) and a deck 36 ft wide.

Who owns M-46 over Pine River?

It is owned by the State Highway Agency.