M-21 over Maple River
PoorIonia County, Michigan · 1.0 MI E of Muir · Structure no. 000000000004011
- Built
- 1929
- 96 years old, rebuilt 2005
- Condition
- Poor
- inspected October 2024
- Type
- Stringer/Multi-beam or Girder
- Steel
- Length
- 220 ft
- 4 main spans
- Daily traffic
- 2,533
- 2007 count
- Owner
- State
- State Highway Agency
About this bridge
M-21 over Maple River is a steel stringer/multi-beam or girder carrying M-21 over Maple River in Ionia County, Michigan. It was built in 1929 and reconstructed in 2005, 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 poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.
It carries about 2,533 vehicles a day, roughly 13% of them trucks, projected to reach 3,388 by 2018. The structure is 220 ft (67.1 m) long and 46 ft wide. If it were closed, the detour would be 3.7 mi (6 km).
Location
Open in Google MapsCondition and inspection
The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 6 Satisfactory | Structural elements show some minor deterioration. |
| Superstructure | 5 Fair | All primary structural elements are sound but may have minor section loss, cracking, spalling or scour. |
| Substructure | 4 Poor | Advanced section loss, deterioration, spalling or scour. |
| Channel and channel protection | 6 Satisfactory | Structural elements show some minor deterioration. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was M-21 over Maple River built?
It was built in 1929, making it 96 years old in 2025. It was reconstructed in 2005.
What condition is M-21 over Maple River in?
The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in October 2024.
How much traffic does M-21 over Maple River carry?
About 2,533 vehicles per day (2007 count), of which roughly 13% are trucks.
How long is M-21 over Maple River?
The structure is 220 ft (67.1 m) long with a longest span of 54 ft (16.4 m) and a deck 46 ft wide.
Who owns M-21 over Maple River?
It is owned by the State Highway Agency.