US Bridges

Ia 175 over Missouri River

FairPosted for load

Monona County, Iowa · E.Of Decatur NE · Structure no. 000000000036810

Built
1950
75 years old
Condition
Fair
inspected September 2022
Type
Truss - Thru
Steel Continuous
Length
1,956 ft
2 main spans
Daily traffic
1,790
2022 count
Owner
State
State Highway Agency

About this bridge

Ia 175 over Missouri River is a steel continuous truss - thru carrying Ia 175 over Missouri River in Monona County, Iowa. It was built in 1950, so it is 75 years old, older than the Iowa average of 45.5 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. Its operating status is: posted for load restriction.

It carries about 1,790 vehicles a day, roughly 27% of them trucks, projected to reach 1,790 by 2042. The structure is 1,956 ft (596.2 m) long and 24 ft wide. If it were closed, the detour would be 67.7 mi (109 km).

Location

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CarriesIa 175
CrossesMissouri River
LocationE.Of Decatur NE
RouteState Highway 175
CountyMonona County
StateIowa
Coordinates42.00662, -96.24137
Functional classRural Minor Arterial

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.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionSeptember 2022
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourFoundations stable; action required to protect exposed foundations
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating27 US tons
Inventory rating16 US tons

Structure

Structure typeTruss - Thru
MaterialSteel Continuous
DeckOpen grating
Main spans2 (+9 approach)
Design loadH 15
Structure length1,956 ft (596.2 m)
Longest span421 ft (128.3 m)
Deck width24 ft (7.3 m)
Roadway width23 ft (6.9 m)
Vertical clearance over deck18 ft (5.5 m)

Traffic and service

Average daily traffic1,790 (2022)
Projected traffic1,790 by 2042
Trucks27%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway and waterway
Detour if closed67.7 mi (109 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusEligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was Ia 175 over Missouri River built?

It was built in 1950, making it 75 years old in 2025.

What condition is Ia 175 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 September 2022.

How much traffic does Ia 175 over Missouri River carry?

About 1,790 vehicles per day (2022 count), of which roughly 27% are trucks.

How long is Ia 175 over Missouri River?

The structure is 1,956 ft (596.2 m) long with a longest span of 421 ft (128.3 m) and a deck 24 ft wide.

Who owns Ia 175 over Missouri River?

It is owned by the State Highway Agency.