170TH St over Skunk River
Story County, Iowa · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- 170TH St over Skunk River in Story County, Iowa, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the deck, rated 5 (fair condition) on the 0-9 scale.
- It was built in 1939, making it 86 years old at the 2025 inventory.
- It carries about 139 vehicles a day (traffic count year 2022).
- Its listed owner is the county highway agency.
- It is one of 160 of the 302 inventoried bridges in Story County rated fair (53.0%); 40 (13.2%) are rated poor.
- Its traffic status in the 2025 inventory is posted for another load-capacity restriction (speed, number of vehicles on the bridge, etc.) (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated December 2022, on a 24-month routine inspection cycle.
- It has fracture-critical members (NBI item 92A): steel tension members without a redundant load path, which get their own scheduled inspections.
- 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 → (42.10619, -93.57086)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 5 | 5 | Fair condition |
| Superstructure | 5 | 5 | Fair condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Steel through truss |
| Length | about 151 ft |
| Location | 084230703 |
| NBI structure number | 000000000315280 |
| Condition class | Fair |
| Traffic status (item 41) | Posted for another load-capacity restriction (speed, number of vehicles on the bridge, etc.) |
| Last inspection (item 90) | December 2022 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 8: foundations stable, scour above the top of the footing |
| Fracture critical (item 92A) | Yes |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Iowa department of transportation.
Busiest bridges in Story County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I-35 over Ballard Creek | 1964 | 48,300 | Fair |
| I-35 over Walnut Creek | 1964 | 48,300 | Fair |
| I 35 over South Skunk Rvr Overflow | 2017 | 48,300 | Good |
| I-35 over Drainage Ditch | 1967 | 28,300 | Good |
| US 69 over Ioway Creek | 1924 | 24,600 | Good |
| NB I-35 over Bike Path | 1964 | 24,150 | Fair |
All bridges nearby: Story County, IA bridge conditions · every bridge in Story County · Iowa bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.