US Bridges

I 90 over Sep Coal Mine Road

Fair

Missoula County, Montana · Missoula · Structure no. I00090103+01642

Built
1966
59 years old
Condition
Fair
inspected January 2025
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
138 ft
3 main spans
Daily traffic
13,664
2023 count
Owner
State
State Highway Agency

About this bridge

I 90 over Sep Coal Mine Road is a prestressed concrete stringer/multi-beam or girder carrying I 90 over Sep Coal Mine Road in Missoula County, Montana. It was built in 1966, so it is 59 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 13,664 vehicles a day, roughly 9% of them trucks, projected to reach 14,552 by 2042. The structure is 138 ft (42.1 m) long and 40 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI 90
CrossesSep Coal Mine Road
LocationMissoula
RouteInterstate 90
CountyMissoula County
StateMontana
Coordinates46.89779, -114.01348
Functional classUrban 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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Last inspectionJanuary 2025
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating59 US tons
Inventory rating36 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length138 ft (42.1 m)
Longest span52 ft (15.7 m)
Deck width40 ft (12.3 m)
Roadway width37 ft (11.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic13,664 (2023)
Projected traffic14,552 by 2042
Trucks9%
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 90 over Sep Coal Mine Road built?

It was built in 1966, making it 59 years old in 2025.

What condition is I 90 over Sep Coal Mine Road 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 2025.

How much traffic does I 90 over Sep Coal Mine Road carry?

About 13,664 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is I 90 over Sep Coal Mine Road?

The structure is 138 ft (42.1 m) long with a longest span of 52 ft (15.7 m) and a deck 40 ft wide.

Who owns I 90 over Sep Coal Mine Road?

It is owned by the State Highway Agency.