US Bridges

Route 284 over Canyon Ferry Spillway

Fair

Lewis and Clark County, Montana · 14 MI E-Ne of Helena Mt · Structure no. MTA-CF-001

Built
1950
75 years old
Condition
Fair
inspected April 2024
Type
Girder and Floorbeam System
Steel
Length
230 ft
4 main spans
Daily traffic
600
2015 count
Owner
Federal
Bureau of Reclamation

About this bridge

Route 284 over Canyon Ferry Spillway is a steel girder and floorbeam system carrying Route 284 over Canyon Ferry Spillway in Lewis and Clark County, Montana. It was built in 1950, so it is 75 years old, older than the Montana average of 47 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 600 vehicles a day, projected to reach 660 by 2042. The structure is 230 ft (70.2 m) long and 27 ft wide. If it were closed, the detour would be 67.7 mi (109 km).

Location

Open in Google Maps
CarriesRoute 284
CrossesCanyon Ferry Spillway
Location14 MI E-Ne of Helena Mt
RouteCounty Highway 284
CountyLewis and Clark County
StateMontana
Coordinates46.64828, -111.72829
Functional classRural Major Collector

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating70.4 US tons
Inventory rating47.6 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20 + Mod
Structure length230 ft (70.2 m)
Longest span57 ft (17.4 m)
Deck width27 ft (8.3 m)
Roadway width21 ft (6.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic600 (2015)
Projected traffic660 by 2042
Trucks—
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed67.7 mi (109 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerBureau of Reclamation
Maintained byBureau of Reclamation
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Route 284 over Canyon Ferry Spillway built?

It was built in 1950, making it 75 years old in 2025.

What condition is Route 284 over Canyon Ferry Spillway in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in April 2024.

How much traffic does Route 284 over Canyon Ferry Spillway carry?

About 600 vehicles per day (2015 count).

How long is Route 284 over Canyon Ferry Spillway?

The structure is 230 ft (70.2 m) long with a longest span of 57 ft (17.4 m) and a deck 27 ft wide.

Who owns Route 284 over Canyon Ferry Spillway?

It is owned by the Bureau of Reclamation.