M-29 over Marine City Drain
St. Clair County, Michigan · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- M-29 over Marine City Drain in St. Clair County, Michigan, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the deck, rated 6 (satisfactory condition) on the 0-9 scale.
- It was built in 1942 and reconstructed in 1997, making it 83 years old at the 2025 inventory.
- It carries about 3,717 vehicles a day (traffic count year 2007).
- Its listed owner is the state highway agency.
- It is one of 165 of the 326 inventoried bridges in St. Clair County rated fair (50.6%); 31 (9.5%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated March 2023, on a 24-month routine inspection cycle.
- A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.
View this bridge on a map → (42.63056, -82.51722)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 6 | 6 | Satisfactory condition |
| Superstructure | 7 | 7 | Good condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Prestressed concrete single box beam |
| Length | about 35 ft |
| Location | In Algonac |
| NBI structure number | 000000000009971 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | March 2023 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 5: foundations stable, scour within the limits of the footing or piles |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Michigan department of transportation.
Busiest bridges in St. Clair County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I-94 over Stocks Creek Drain | 2011 | 50,660 | Good |
| I-94 & I-69 over M-25 Pine Grove Ave | 1993 | 43,238 | Good |
| M-25 over Black River Spillway | 2000 | 40,250 | Fair |
| I-94 over Stocks Creek | 1964 | 29,650 | Fair |
| M-25 over Howe Drain | 1981 | 28,550 | Fair |
| I-94 & I-69 WB over Black River & Scott Ave | 2011 | 26,010 | Fair |
All bridges nearby: St. Clair County, MI bridge conditions · every bridge in St. Clair County · Michigan bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.