US Bridges

I 15 over Int Monida S 509

Fair

Beaverhead County, Montana · Monida · Structure no. I00015000+05202

Built
1981
44 years old
Condition
Fair
inspected October 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
118 ft
3 main spans
Daily traffic
1,771
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Int Monida S 509 is a prestressed concrete stringer/multi-beam or girder carrying I 15 over Int Monida S 509 in Beaverhead County, Montana. It was built in 1981, so it is 44 years old, younger 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 1,771 vehicles a day, roughly 30% of them trucks, projected to reach 1,894 by 2043. The structure is 118 ft (36 m) long and 44 ft wide.

Location

Open in Google Maps
CarriesI 15
CrossesInt Monida S 509
LocationMonida
RouteInterstate 15
CountyBeaverhead County
StateMontana
Coordinates44.559, -112.31828
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 inspectionOctober 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 rating53 US tons
Inventory rating41 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length118 ft (36 m)
Longest span47 ft (14.2 m)
Deck width44 ft (13.4 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,771 (2023)
Projected traffic1,894 by 2043
Trucks30%
Lanes on structure2
Traffic directionOne-way traffic
CarriesOverpass structure at an interchange
CrossesHighway
Detour if closed—
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 Int Monida S 509 built?

It was built in 1981, making it 44 years old in 2025.

What condition is I 15 over Int Monida S 509 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 October 2024.

How much traffic does I 15 over Int Monida S 509 carry?

About 1,771 vehicles per day (2023 count), of which roughly 30% are trucks.

How long is I 15 over Int Monida S 509?

The structure is 118 ft (36 m) long with a longest span of 47 ft (14.2 m) and a deck 44 ft wide.

Who owns I 15 over Int Monida S 509?

It is owned by the State Highway Agency.