US Bridges

I 15 over Int Apex-Birch CR RD

Fair

Beaverhead County, Montana · 11.2M N Dillon · Structure no. I00015074+09742

Built
1973
52 years old
Condition
Fair
inspected February 2025
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
170 ft
3 main spans
Daily traffic
1,926
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Int Apex-Birch CR RD is a prestressed concrete stringer/multi-beam or girder carrying I 15 over Int Apex-Birch CR RD 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 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 1,926 vehicles a day, roughly 24% of them trucks, projected to reach 2,080 by 2043. The structure is 170 ft (51.8 m) long and 44 ft wide.

Location

Open in Google Maps
CarriesI 15
CrossesInt Apex-Birch CR RD
Location11.2M N Dillon
RouteInterstate 15
CountyBeaverhead County
StateMontana
Coordinates45.37849, -112.70879
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.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionFebruary 2025
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating57 US tons
Inventory rating33 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length170 ft (51.8 m)
Longest span75 ft (22.9 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
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 Apex-Birch CR RD built?

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

What condition is I 15 over Int Apex-Birch CR RD 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 February 2025.

How much traffic does I 15 over Int Apex-Birch CR RD carry?

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

How long is I 15 over Int Apex-Birch CR RD?

The structure is 170 ft (51.8 m) long with a longest span of 75 ft (22.9 m) and a deck 44 ft wide.

Who owns I 15 over Int Apex-Birch CR RD?

It is owned by the State Highway Agency.