US Bridges

Mann RD over Big Muddy Creek

Fair

Sheridan County, Montana · SW Plentywood · Structure no. S00515001+00001

Built
1967
58 years old
Condition
Fair
inspected January 2024
Type
Tee Beam
Prestressed Concrete
Length
70 ft
1 main span
Daily traffic
163
2023 count
Owner
County
County Highway Agency

About this bridge

Mann RD over Big Muddy Creek is a prestressed concrete tee beam carrying Mann RD over Big Muddy Creek in Sheridan County, Montana. It was built in 1967, so it is 58 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 163 vehicles a day, roughly 2% of them trucks, projected to reach 171 by 2043. The structure is 70 ft (21.3 m) long and 24 ft wide. If it were closed, the detour would be 23 mi (37 km).

Location

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CarriesMann RD
CrossesBig Muddy Creek
LocationSW Plentywood
RouteCounty Highway 46629
CountySheridan County
StateMontana
Coordinates48.76575, -104.57916
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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionJanuary 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating31 US tons
Inventory rating23.9 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckConcrete, precast panels
Main spans1
Design loadUnknown
Structure length70 ft (21.3 m)
Longest span68 ft (20.7 m)
Deck width24 ft (7.3 m)
Roadway width24 ft (7.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic163 (2023)
Projected traffic171 by 2043
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed23 mi (37 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Mann RD over Big Muddy Creek built?

It was built in 1967, making it 58 years old in 2025.

What condition is Mann RD over Big Muddy Creek 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 January 2024.

How much traffic does Mann RD over Big Muddy Creek carry?

About 163 vehicles per day (2023 count), of which roughly 2% are trucks.

How long is Mann RD over Big Muddy Creek?

The structure is 70 ft (21.3 m) long with a longest span of 68 ft (20.7 m) and a deck 24 ft wide.

Who owns Mann RD over Big Muddy Creek?

It is owned by the County Highway Agency.