US Bridges

I 15 over Sep County RD 203

Fair

Beaverhead County, Montana · 11.2M S Melrose · Structure no. I00015079+00121

Built
1973
52 years old
Condition
Fair
inspected January 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
119 ft
3 main spans
Daily traffic
1,926
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Sep County RD 203 is a prestressed concrete stringer/multi-beam or girder carrying I 15 over Sep County RD 203 in Beaverhead County, Montana. It was built in 1973, so it is 52 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 1,926 vehicles a day, roughly 24% of them trucks, projected to reach 2,080 by 2043. The structure is 119 ft (36.3 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 County RD 203
Location11.2M S Melrose
RouteInterstate 15
CountyBeaverhead County
StateMontana
Coordinates45.43679, -112.7063
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJanuary 2024
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 rating58 US tons
Inventory rating45 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length119 ft (36.3 m)
Longest span50 ft (15.2 m)
Deck width44 ft (13.4 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,926 (2023)
Projected traffic2,080 by 2043
Trucks24%
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 County RD 203 built?

It was built in 1973, making it 52 years old in 2025.

What condition is I 15 over Sep County RD 203 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 I 15 over Sep County RD 203 carry?

About 1,926 vehicles per day (2023 count), of which roughly 24% are trucks.

How long is I 15 over Sep County RD 203?

The structure is 119 ft (36.3 m) long with a longest span of 50 ft (15.2 m) and a deck 44 ft wide.

Who owns I 15 over Sep County RD 203?

It is owned by the State Highway Agency.