US Bridges

M-66 over Clam River

Fair

Missaukee County, Michigan · 3.6 MI N of Mcbain · Structure no. 000000000007025

Built
1929
96 years old
Condition
Fair
inspected August 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
44 ft
1 main span
Daily traffic
2,696
2007 count
Owner
State
State Highway Agency

About this bridge

M-66 over Clam River is a steel stringer/multi-beam or girder carrying M-66 over Clam River in Missaukee County, Michigan. It was built in 1929, so it is 96 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 2,696 vehicles a day, roughly 5% of them trucks, projected to reach 4,141 by 2018. The structure is 44 ft (13.4 m) long and 39 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesM-66
CrossesClam River
Location3.6 MI N of Mcbain
RouteState Highway 66
CountyMissaukee County
StateMichigan
Coordinates44.24294, -85.21509
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 protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating61.1 US tons
Inventory rating32.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadH 15
Structure length44 ft (13.4 m)
Longest span43 ft (13.2 m)
Deck width39 ft (11.8 m)
Roadway width36 ft (11 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,696 (2007)
Projected traffic4,141 by 2018
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
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 proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$39,000
NavigationNo navigation control on waterway

Frequently asked questions

When was M-66 over Clam River built?

It was built in 1929, making it 96 years old in 2025.

What condition is M-66 over Clam 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 August 2024.

How much traffic does M-66 over Clam River carry?

About 2,696 vehicles per day (2007 count), of which roughly 5% are trucks.

How long is M-66 over Clam River?

The structure is 44 ft (13.4 m) long with a longest span of 43 ft (13.2 m) and a deck 39 ft wide.

Who owns M-66 over Clam River?

It is owned by the State Highway Agency.