US Bridges

I 90 over St. Regis River

Good

Mineral County, Montana · 3.1M W St. Regis · Structure no. I00090030+05492

Built
1981
44 years old
Condition
Good
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
376 ft
4 main spans
Daily traffic
4,056
2023 count
Owner
State
State Highway Agency

About this bridge

I 90 over St. Regis River is a steel stringer/multi-beam or girder carrying I 90 over St. Regis River in Mineral 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 good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 4,056 vehicles a day, roughly 24% of them trucks, projected to reach 4,258 by 2043. The structure is 376 ft (114.6 m) long and 43 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI 90
CrossesSt. Regis River
Location3.1M W St. Regis
RouteInterstate 90
CountyMineral County
StateMontana
Coordinates47.29433, -115.15725
Functional classRural Principal Arterial - Interstate

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation7: Better than present minimum criteria
Deck geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating65 US tons
Inventory rating39 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length376 ft (114.6 m)
Longest span101 ft (30.8 m)
Deck width43 ft (13.1 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,056 (2023)
Projected traffic4,258 by 2043
Trucks24%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
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—
NavigationNo navigation control on waterway

Frequently asked questions

When was I 90 over St. Regis River built?

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

What condition is I 90 over St. Regis River in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in July 2023.

How much traffic does I 90 over St. Regis River carry?

About 4,056 vehicles per day (2023 count), of which roughly 24% are trucks.

How long is I 90 over St. Regis River?

The structure is 376 ft (114.6 m) long with a longest span of 101 ft (30.8 m) and a deck 43 ft wide.

Who owns I 90 over St. Regis River?

It is owned by the State Highway Agency.