US Bridges

M-25 over Pinnebog River

Fair

Huron County, Michigan · 6.0 MI SW of Port Austin · Structure no. 000000000003450

Built
1976
49 years old
Condition
Fair
inspected July 2023
Type
Box Beam or Girders - Multiple
Prestressed Concrete
Length
120 ft
2 main spans
Daily traffic
1,500
2011 count
Owner
State
State Highway Agency

About this bridge

M-25 over Pinnebog River is a prestressed concrete box beam or girders - multiple carrying M-25 over Pinnebog River in Huron County, Michigan. It was built in 1976, so it is 49 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 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 1,500 vehicles a day, roughly 4% of them trucks, projected to reach 1,910 by 2018. The structure is 120 ft (36.6 m) long and 52 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

Open in Google Maps
CarriesM-25
CrossesPinnebog River
Location6.0 MI SW of Port Austin
RouteState Highway 25
CountyHuron County
StateMichigan
Coordinates43.99341, -83.07562
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.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 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 adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating76.4 US tons
Inventory rating46.7 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length120 ft (36.6 m)
Longest span60 ft (18.3 m)
Deck width52 ft (15.8 m)
Roadway width48 ft (14.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,500 (2011)
Projected traffic1,910 by 2018
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 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-25 over Pinnebog River built?

It was built in 1976, making it 49 years old in 2025.

What condition is M-25 over Pinnebog 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 July 2023.

How much traffic does M-25 over Pinnebog River carry?

About 1,500 vehicles per day (2011 count), of which roughly 4% are trucks.

How long is M-25 over Pinnebog River?

The structure is 120 ft (36.6 m) long with a longest span of 60 ft (18.3 m) and a deck 52 ft wide.

Who owns M-25 over Pinnebog River?

It is owned by the State Highway Agency.