Irr Bia Rte 4178 over Drainage Canal
San Juan County, New Mexico · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Irr Bia Rte 4178 over Drainage Canal in San Juan County, New Mexico, 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 1980, making it 45 years old at the 2025 inventory.
- It carries about 100 vehicles a day (traffic count year 2023).
- It is one of 104 of the 174 inventoried bridges in San Juan County rated fair (59.8%); 10 (5.7%) 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 April 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 → (36.54608, -108.15531)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 6 | 6 | Satisfactory condition |
| Superstructure | 8 | 8 | Very good condition |
| Substructure | 8 | 8 | Very good condition |
Bridge details
| Structure | Prestressed concrete stringer or multi-beam girder |
| Length | about 54 ft |
| Location | 8KM East of Nm Rte 371 |
| NBI structure number | 0000N48796B0821 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | April 2023 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 8: foundations stable, scour above the top of the footing |
Source: FHWA National Bridge Inventory, 2025 data as reported by the New Mexico department of transportation.
Busiest bridges in San Juan County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Nm-516 over Unnamed Waterway | 1937 | 37,626 | Fair |
| Nm-516 over Unnamed Waterway | 1937 | 29,593 | Fair |
| Nm-516 over Unnamed Waterway | 1937 | 22,275 | Fair |
| Nm-516 over Unnamed Waterway | 1937 | 22,275 | Fair |
| Nm-516 over Unnamed Waterway | 1937 | 22,275 | Fair |
| US-64 Ebl/wbl over Unnamed Waterway | 1964 | 21,685 | Good |
All bridges nearby: San Juan County, NM bridge conditions · every bridge in San Juan County · New Mexico bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.