US Bridges

M-66 over ST Joseph River

Fair

St. Joseph County, Michigan · 0.3 MI S of M-60 · Structure no. 000000000010278

Built
1965
60 years old
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
350 ft
5 main spans
Daily traffic
3,375
2018 count
Owner
State
State Highway Agency

About this bridge

M-66 over ST Joseph River is a steel stringer/multi-beam or girder carrying M-66 over ST Joseph River in St. Joseph County, Michigan. It was built in 1965, so it is 60 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 3,375 vehicles a day, roughly 10% of them trucks, projected to reach 3,750 by 2038. The structure is 350 ft (106.7 m) long and 36 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
CarriesM-66
CrossesST Joseph River
Location0.3 MI S of M-60
RouteState Highway 66
CountySt. Joseph County
StateMichigan
Coordinates42.00716, -85.41122
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.
Substructure7 GoodSome minor problems.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
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 alignment6: Equal to present minimum criteria
Operating rating75 US tons
Inventory rating44.6 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans5
Design loadHS 20
Structure length350 ft (106.7 m)
Longest span72 ft (21.9 m)
Deck width36 ft (11.1 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,375 (2018)
Projected traffic3,750 by 2038
Trucks10%
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 proposedDeck replacement with only incidental widening
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was M-66 over ST Joseph River built?

It was built in 1965, making it 60 years old in 2025.

What condition is M-66 over ST Joseph 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-66 over ST Joseph River carry?

About 3,375 vehicles per day (2018 count), of which roughly 10% are trucks.

How long is M-66 over ST Joseph River?

The structure is 350 ft (106.7 m) long with a longest span of 72 ft (21.9 m) and a deck 36 ft wide.

Who owns M-66 over ST Joseph River?

It is owned by the State Highway Agency.