US Bridges

Millegan RD over Missouri River

Fair

Cascade County, Montana · Ulm · Structure no. S00330000+04061

Built
1983
42 years old
Condition
Fair
inspected May 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
530 ft
3 main spans
Daily traffic
553
2023 count
Owner
State
State Highway Agency

About this bridge

Millegan RD over Missouri River is a steel continuous stringer/multi-beam or girder carrying Millegan RD over Missouri River in Cascade County, Montana. It was built in 1983, so it is 42 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 553 vehicles a day, roughly 2% of them trucks, projected to reach 581 by 2043. The structure is 530 ft (161.6 m) long and 36 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

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CarriesMillegan RD
CrossesMissouri River
LocationUlm
RouteState Highway 330
CountyCascade County
StateMontana
Coordinates47.43048, -111.50257
Functional classRural Major Collector

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.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating35.7 US tons
Inventory rating27.6 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length530 ft (161.6 m)
Longest span203 ft (62 m)
Deck width36 ft (11.1 m)
Roadway width33 ft (10.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic553 (2023)
Projected traffic581 by 2043
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 km)
TollOn a free road
National Highway SystemNo

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 Millegan RD over Missouri River built?

It was built in 1983, making it 42 years old in 2025.

What condition is Millegan RD over Missouri River 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 May 2023.

How much traffic does Millegan RD over Missouri River carry?

About 553 vehicles per day (2023 count), of which roughly 2% are trucks.

How long is Millegan RD over Missouri River?

The structure is 530 ft (161.6 m) long with a longest span of 203 ft (62 m) and a deck 36 ft wide.

Who owns Millegan RD over Missouri River?

It is owned by the State Highway Agency.