US Bridges

M-66 over Middle Branch River

Fair

Osceola County, Michigan · 4.5 MI N of M-61 · Structure no. 000000000008595

Built
1939
86 years old
Condition
Fair
inspected September 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
45 ft
1 main span
Daily traffic
1,485
2007 count
Owner
State
State Highway Agency

About this bridge

M-66 over Middle Branch River is a steel stringer/multi-beam or girder carrying M-66 over Middle Branch River in Osceola County, Michigan. It was built in 1939, so it is 86 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 1,485 vehicles a day, roughly 8% of them trucks, projected to reach 3,410 by 2018. The structure is 45 ft (13.7 m) long and 50 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesM-66
CrossesMiddle Branch River
Location4.5 MI N of M-61
RouteState Highway 66
CountyOsceola County
StateMichigan
Coordinates44.11106, -85.14752
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
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 inspectionSeptember 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 adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating56.8 US tons
Inventory rating34 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 width50 ft (15.3 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,485 (2007)
Projected traffic3,410 by 2018
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed3.1 mi (5 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$26,000
NavigationNo navigation control on waterway

Frequently asked questions

When was M-66 over Middle Branch River built?

It was built in 1939, making it 86 years old in 2025.

What condition is M-66 over Middle Branch 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 September 2024.

How much traffic does M-66 over Middle Branch River carry?

About 1,485 vehicles per day (2007 count), of which roughly 8% are trucks.

How long is M-66 over Middle Branch River?

The structure is 45 ft (13.7 m) long with a longest span of 45 ft (13.7 m) and a deck 50 ft wide.

Who owns M-66 over Middle Branch River?

It is owned by the State Highway Agency.