US Bridges

I 90 over Big Ditch

Fair

Stillwater County, Montana · 5.6M W Park City · Structure no. I00090420+05442

Built
1970
55 years old
Condition
Fair
inspected November 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
73 ft
1 main span
Daily traffic
6,161
2023 count
Owner
State
State Highway Agency

About this bridge

I 90 over Big Ditch is a prestressed concrete stringer/multi-beam or girder carrying I 90 over Big Ditch in Stillwater County, Montana. It was built in 1970, so it is 55 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 6,161 vehicles a day, roughly 20% of them trucks, projected to reach 6,715 by 2043. The structure is 73 ft (22.3 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 90
CrossesBig Ditch
Location5.6M W Park City
RouteInterstate 90
CountyStillwater County
StateMontana
Coordinates45.60571, -109.03151
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionNovember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry7: Better than present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating43 US tons
Inventory rating28 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length73 ft (22.3 m)
Longest span73 ft (22.3 m)
Deck width44 ft (13.4 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,161 (2023)
Projected traffic6,715 by 2043
Trucks20%
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 Big Ditch built?

It was built in 1970, making it 55 years old in 2025.

What condition is I 90 over Big Ditch 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 November 2024.

How much traffic does I 90 over Big Ditch carry?

About 6,161 vehicles per day (2023 count), of which roughly 20% are trucks.

How long is I 90 over Big Ditch?

The structure is 73 ft (22.3 m) long with a longest span of 73 ft (22.3 m) and a deck 44 ft wide.

Who owns I 90 over Big Ditch?

It is owned by the State Highway Agency.