US Bridges

M-21 over Alder Creek

Fair

Clinton County, Michigan · 1.2 MI W of Ovid · Structure no. 000000000001890

Built
1949
76 years old
Condition
Fair
inspected October 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
40 ft
1 main span
Daily traffic
7,103
2007 count
Owner
State
State Highway Agency

About this bridge

M-21 over Alder Creek is a steel stringer/multi-beam or girder carrying M-21 over Alder Creek in Clinton County, Michigan. It was built in 1949, so it is 76 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 7,103 vehicles a day, roughly 6% of them trucks, projected to reach 8,615 by 2018. The structure is 40 ft (12.2 m) long and 43 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesM-21
CrossesAlder Creek
Location1.2 MI W of Ovid
RouteState Highway 21
CountyClinton County
StateMichigan
Coordinates43.0013, -84.39572
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionOctober 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
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 rating97.6 US tons
Inventory rating58.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length40 ft (12.2 m)
Longest span40 ft (12.2 m)
Deck width43 ft (13.2 m)
Roadway width38 ft (11.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic7,103 (2007)
Projected traffic8,615 by 2018
Trucks6%
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 proposedDeck replacement with only incidental widening
Estimated improvement cost$34,000
NavigationNo navigation control on waterway

Frequently asked questions

When was M-21 over Alder Creek built?

It was built in 1949, making it 76 years old in 2025.

What condition is M-21 over Alder Creek 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 October 2024.

How much traffic does M-21 over Alder Creek carry?

About 7,103 vehicles per day (2007 count), of which roughly 6% are trucks.

How long is M-21 over Alder Creek?

The structure is 40 ft (12.2 m) long with a longest span of 40 ft (12.2 m) and a deck 43 ft wide.

Who owns M-21 over Alder Creek?

It is owned by the State Highway Agency.