US Bridges

Dunn Road over Portage River

Fair

Jackson County, Michigan · 3.5 MI SE of Munith · Structure no. 000000000004511

Built
1978
47 years old
Condition
Fair
inspected May 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
100 ft
1 main span
Daily traffic
250
1994 count
Owner
County
County Highway Agency

About this bridge

Dunn Road over Portage River is a steel stringer/multi-beam or girder carrying Dunn Road over Portage River in Jackson County, Michigan. It was built in 1978, so it is 47 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 250 vehicles a day, projected to reach 250 by 2014. The structure is 100 ft (30.4 m) long and 34 ft wide. If it were closed, the detour would be 9.9 mi (16 km).

Location

Open in Google Maps
CarriesDunn Road
CrossesPortage River
Location3.5 MI SE of Munith
RouteCounty Highway 0
CountyJackson County
StateMichigan
Coordinates42.34983, -84.26347
Functional classRural Local

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.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating110.1 US tons
Inventory rating66.4 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length100 ft (30.4 m)
Longest span97 ft (29.5 m)
Deck width34 ft (10.4 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic250 (1994)
Projected traffic250 by 2014
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed9.9 mi (16 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty 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 Dunn Road over Portage River built?

It was built in 1978, making it 47 years old in 2025.

What condition is Dunn Road over Portage 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 May 2023.

How much traffic does Dunn Road over Portage River carry?

About 250 vehicles per day (1994 count).

How long is Dunn Road over Portage River?

The structure is 100 ft (30.4 m) long with a longest span of 97 ft (29.5 m) and a deck 34 ft wide.

Who owns Dunn Road over Portage River?

It is owned by the County Highway Agency.