NB I-35 over 310TH St
Decatur County, Iowa · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- NB I-35 over 310TH St in Decatur County, Iowa, 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 1970, making it 55 years old at the 2025 inventory.
- It carries about 7,100 vehicles a day (traffic count year 2022).
- Its listed owner is the state highway agency.
- It is one of 84 of the 199 inventoried bridges in Decatur County rated fair (42.2%); 78 (39.2%) 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 July 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 → (40.59444, -93.91602)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 6 | 6 | Satisfactory condition |
| Superstructure | 6 | 6 | Satisfactory condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Continuous steel stringer or multi-beam girder |
| Length | about 177 ft |
| Location | 2.5 mi. S of US 69 |
| NBI structure number | 000000000022830 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | July 2023 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | N: not over a waterway |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Iowa department of transportation.
Busiest bridges in Decatur County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Rest Area Road over Rest Area Road | 1994 | 13,800 | Fair |
| SB I-35 over Grand River | 1970 | 7,700 | Fair |
| NB I-35 over Grand River | 1970 | 7,550 | Fair |
| SB I-35 over 310TH Street | 1970 | 7,250 | Fair |
| SB I-35 over Stream | 1970 | 7,250 | Good |
| NB I-35 over Stream | 1970 | 7,100 | Fair |
All bridges nearby: Decatur County, IA bridge conditions · every bridge in Decatur County · Iowa bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.