US Bridges

M-91 over Flat River

Fair

Montcalm County, Michigan · In Greenville · Structure no. 000000000007439

Built
1994
31 years old
Condition
Fair
inspected October 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
176 ft
3 main spans
Daily traffic
11,433
2007 count
Owner
State
State Highway Agency

About this bridge

M-91 over Flat River is a prestressed concrete stringer/multi-beam or girder carrying M-91 over Flat River in Montcalm County, Michigan. It was built in 1994, so it is 31 years old, younger 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 11,433 vehicles a day, roughly 1% of them trucks, projected to reach 17,268 by 2018. The structure is 176 ft (53.6 m) long and 63 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
CarriesM-91
CrossesFlat River
LocationIn Greenville
RouteState Highway 91
CountyMontcalm County
StateMichigan
Coordinates43.18336, -85.2531
Functional classUrban 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 protection8 Very GoodNo problems noted.
Last inspectionOctober 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourCountermeasures installed to correct a previously existing problem
Structural evaluation6: Equal to present minimum criteria
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating80.7 US tons
Inventory rating48.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 25 or greater
Structure length176 ft (53.6 m)
Longest span59 ft (17.9 m)
Deck width63 ft (19.1 m)
Roadway width48 ft (14.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11,433 (2007)
Projected traffic17,268 by 2018
Trucks1%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed3.7 mi (6 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for 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-91 over Flat River built?

It was built in 1994, making it 31 years old in 2025.

What condition is M-91 over Flat 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 October 2023.

How much traffic does M-91 over Flat River carry?

About 11,433 vehicles per day (2007 count), of which roughly 1% are trucks.

How long is M-91 over Flat River?

The structure is 176 ft (53.6 m) long with a longest span of 59 ft (17.9 m) and a deck 63 ft wide.

Who owns M-91 over Flat River?

It is owned by the State Highway Agency.