US Bridges

I 15 over Sep Gosman Lane

Fair

Beaverhead County, Montana · 3.7M S Dell · Structure no. I00015019+08072

Built
1971
54 years old
Condition
Fair
inspected September 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
108 ft
3 main spans
Daily traffic
1,863
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Sep Gosman Lane is a prestressed concrete stringer/multi-beam or girder carrying I 15 over Sep Gosman Lane in Beaverhead County, Montana. It was built in 1971, so it is 54 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 1,863 vehicles a day, roughly 29% of them trucks, projected to reach 1,993 by 2043. The structure is 108 ft (32.9 m) long and 44 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI 15
CrossesSep Gosman Lane
Location3.7M S Dell
RouteInterstate 15
CountyBeaverhead County
StateMontana
Coordinates44.68306, -112.64868
Functional classRural Principal Arterial - Interstate

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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating57 US tons
Inventory rating43 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length108 ft (32.9 m)
Longest span47 ft (14.2 m)
Deck width44 ft (13.5 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,863 (2023)
Projected traffic1,993 by 2043
Trucks29%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

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—
NavigationNot applicable (no waterway)

Frequently asked questions

When was I 15 over Sep Gosman Lane built?

It was built in 1971, making it 54 years old in 2025.

What condition is I 15 over Sep Gosman Lane 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 September 2023.

How much traffic does I 15 over Sep Gosman Lane carry?

About 1,863 vehicles per day (2023 count), of which roughly 29% are trucks.

How long is I 15 over Sep Gosman Lane?

The structure is 108 ft (32.9 m) long with a longest span of 47 ft (14.2 m) and a deck 44 ft wide.

Who owns I 15 over Sep Gosman Lane?

It is owned by the State Highway Agency.