US Bridges

M-46 M-66 over Flat River

Fair

Montcalm County, Michigan · 0.5 MI SE of W JCT M-66 · Structure no. 000000000007445

Built
1937
88 years old
Condition
Fair
inspected October 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
45 ft
1 main span
Daily traffic
6,822
2007 count
Owner
State
State Highway Agency

About this bridge

M-46 M-66 over Flat River is a steel stringer/multi-beam or girder carrying M-46 M-66 over Flat River in Montcalm County, Michigan. It was built in 1937, so it is 88 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 6,822 vehicles a day, roughly 10% of them trucks, projected to reach 10,677 by 2018. The structure is 45 ft (13.7 m) long and 39 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesM-46 M-66
CrossesFlat River
Location0.5 MI SE of W JCT M-66
RouteState Highway 46
CountyMontcalm County
StateMichigan
Coordinates43.42453, -85.14424
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionOctober 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
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 alignment8: Equal to present desirable criteria
Operating rating62.8 US tons
Inventory rating32.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadH 20
Structure length45 ft (13.7 m)
Longest span45 ft (13.7 m)
Deck width39 ft (11.8 m)
Roadway width33 ft (10.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,822 (2007)
Projected traffic10,677 by 2018
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 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 proposedDeck replacement with only incidental widening
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was M-46 M-66 over Flat River built?

It was built in 1937, making it 88 years old in 2025.

What condition is M-46 M-66 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-46 M-66 over Flat River carry?

About 6,822 vehicles per day (2007 count), of which roughly 10% are trucks.

How long is M-46 M-66 over Flat River?

The structure is 45 ft (13.7 m) long with a longest span of 45 ft (13.7 m) and a deck 39 ft wide.

Who owns M-46 M-66 over Flat River?

It is owned by the State Highway Agency.