US Bridges

M-81 over N Branch Cass River

Fair

Tuscola County, Michigan · 1.1 MI W of Sanilac Col · Structure no. 000000000010436

Built
1977
48 years old
Condition
Fair
inspected September 2023
Type
Box Beam or Girders - Multiple
Prestressed Concrete
Length
75 ft
1 main span
Daily traffic
2,500
2010 count
Owner
State
State Highway Agency

About this bridge

M-81 over N Branch Cass River is a prestressed concrete box beam or girders - multiple carrying M-81 over N Branch Cass River in Tuscola County, Michigan. It was built in 1977, so it is 48 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 2,500 vehicles a day, roughly 7% of them trucks, projected to reach 3,800 by 2030. The structure is 75 ft (22.8 m) long and 49 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

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CarriesM-81
CrossesN Branch Cass River
Location1.1 MI W of Sanilac Col
RouteState Highway 81
CountyTuscola County
StateMichigan
Coordinates43.60183, -83.13662
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 2023
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 adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating76.1 US tons
Inventory rating42.9 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length75 ft (22.8 m)
Longest span75 ft (22.8 m)
Deck width49 ft (15 m)
Roadway width47 ft (14.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,500 (2010)
Projected traffic3,800 by 2030
Trucks7%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was M-81 over N Branch Cass River built?

It was built in 1977, making it 48 years old in 2025.

What condition is M-81 over N Branch Cass 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 2023.

How much traffic does M-81 over N Branch Cass River carry?

About 2,500 vehicles per day (2010 count), of which roughly 7% are trucks.

How long is M-81 over N Branch Cass River?

The structure is 75 ft (22.8 m) long with a longest span of 75 ft (22.8 m) and a deck 49 ft wide.

Who owns M-81 over N Branch Cass River?

It is owned by the State Highway Agency.