Route 284 over Canyon Ferry Spillway
Lewis and Clark County, Montana · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Route 284 over Canyon Ferry Spillway in Lewis and Clark County, Montana, 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 1950, making it 75 years old at the 2025 inventory.
- It carries about 600 vehicles a day (traffic count year 2015).
- It is one of 75 of the 204 inventoried bridges in Lewis and Clark County rated fair (36.8%); 11 (5.4%) 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 2024, 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 → (46.64828, -111.72829)
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 girder and floorbeam |
| Length | about 230 ft |
| Location | 14 mi E-NE of Helena MT |
| NBI structure number | MTA-CF-001 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | April 2024 |
| 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 Montana department of transportation.
Busiest bridges in Lewis and Clark County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Lyndale Ave-us 12 over Great Northern Area | 2003 | 20,397 | Good |
| US 12 over RR | 1978 | 19,327 | Good |
| N Last Chance Gulc over RR | 2003 | 18,569 | Good |
| E Custer Ave over Int Custer Ave-i 15 | 2012 | 16,988 | Good |
| US 12 over Prickly Pear Creek | 1978 | 15,333 | Good |
| I 15 over Sep Boulder Ave-rr | 2016 | 14,810 | Fair |
All bridges nearby: Lewis and Clark County, MT bridge conditions · every bridge in Lewis and Clark County · Montana bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.