US Bridges

0427: Mcnamara Roa over Blackfoot River

Fair

Missoula County, Montana · 21 MI E of Missoula Mt · Structure no. 000000000L59190

Built
1964
61 years old, rebuilt 2014
Condition
Fair
inspected August 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
196 ft
2 main spans
Daily traffic
25
2022 count
Owner
Federal
Bureau of Land Management

About this bridge

0427: Mcnamara Roa over Blackfoot River is a steel stringer/multi-beam or girder carrying 0427: Mcnamara Roa over Blackfoot River in Missoula County, Montana. It was built in 1964 and reconstructed in 2014, so it is 61 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 6 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 25 vehicles a day, projected to reach 35 by 2040. The structure is 196 ft (59.6 m) long and 14 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

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Carries0427: Mcnamara Roa
CrossesBlackfoot River
Location21 MI E of Missoula Mt
RouteFederal Lands Road 0
CountyMissoula County
StateMontana
Coordinates46.94278, -113.60194
Functional classRural Local

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating51.8 US tons
Inventory rating40 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckWood or timber
Main spans2
Design loadUnknown
Structure length196 ft (59.6 m)
Longest span95 ft (29.1 m)
Deck width14 ft (4.3 m)
Roadway width13 ft (3.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic25 (2022)
Projected traffic35 by 2040
Trucks—
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

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

Frequently asked questions

When was 0427: Mcnamara Roa over Blackfoot River built?

It was built in 1964, making it 61 years old in 2025. It was reconstructed in 2014.

What condition is 0427: Mcnamara Roa over Blackfoot River 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 August 2024.

How much traffic does 0427: Mcnamara Roa over Blackfoot River carry?

About 25 vehicles per day (2022 count).

How long is 0427: Mcnamara Roa over Blackfoot River?

The structure is 196 ft (59.6 m) long with a longest span of 95 ft (29.1 m) and a deck 14 ft wide.

Who owns 0427: Mcnamara Roa over Blackfoot River?

It is owned by the Bureau of Land Management.