US Bridges

S 261 over O`brien Creek

Fair

Richland County, Montana · 9M S Sidney · Structure no. S00261047+09001

Built
1977
48 years old
Condition
Fair
inspected May 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
102 ft
2 main spans
Daily traffic
95
2023 count
Owner
State
State Highway Agency

About this bridge

S 261 over O`brien Creek is a prestressed concrete stringer/multi-beam or girder carrying S 261 over O`brien Creek in Richland County, Montana. It was built in 1977, so it is 48 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 95 vehicles a day, roughly 17% of them trucks, projected to reach 100 by 2043. The structure is 102 ft (31.1 m) long and 34 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

Open in Google Maps
CarriesS 261
CrossesO`brien Creek
Location9M S Sidney
RouteState Highway 261
CountyRichland County
StateMontana
Coordinates47.60378, -104.14222
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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 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 geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating44 US tons
Inventory rating22 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length102 ft (31.1 m)
Longest span51 ft (15.5 m)
Deck width34 ft (10.3 m)
Roadway width31 ft (9.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic95 (2023)
Projected traffic100 by 2043
Trucks17%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState 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 S 261 over O`brien Creek built?

It was built in 1977, making it 48 years old in 2025.

What condition is S 261 over O`brien 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 May 2024.

How much traffic does S 261 over O`brien Creek carry?

About 95 vehicles per day (2023 count), of which roughly 17% are trucks.

How long is S 261 over O`brien Creek?

The structure is 102 ft (31.1 m) long with a longest span of 51 ft (15.5 m) and a deck 34 ft wide.

Who owns S 261 over O`brien Creek?

It is owned by the State Highway Agency.