US Bridges

Ia 31 over Little Sioux River

Fair

Woodbury County, Iowa · 0.8 MI S of JCT US 20 · Structure no. 000000000053181

Built
1973
52 years old
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
425 ft
5 main spans
Daily traffic
1,120
2022 count
Owner
State
State Highway Agency

About this bridge

Ia 31 over Little Sioux River is a prestressed concrete stringer/multi-beam or girder carrying Ia 31 over Little Sioux River in Woodbury County, Iowa. It was built in 1973, so it is 52 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 5 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 1,120 vehicles a day, roughly 19% of them trucks, projected to reach 1,120 by 2044. The structure is 425 ft (129.5 m) long and 35 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesIa 31
CrossesLittle Sioux River
Location0.8 MI S of JCT US 20
RouteState Highway 31
CountyWoodbury County
StateIowa
Coordinates42.47029, -95.79716
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating58 US tons
Inventory rating39.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans5
Design loadHS 20
Structure length425 ft (129.5 m)
Longest span92 ft (28 m)
Deck width35 ft (10.8 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,120 (2022)
Projected traffic1,120 by 2044
Trucks19%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.8 mi (11 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 Ia 31 over Little Sioux River built?

It was built in 1973, making it 52 years old in 2025.

What condition is Ia 31 over Little Sioux 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 July 2024.

How much traffic does Ia 31 over Little Sioux River carry?

About 1,120 vehicles per day (2022 count), of which roughly 19% are trucks.

How long is Ia 31 over Little Sioux River?

The structure is 425 ft (129.5 m) long with a longest span of 92 ft (28 m) and a deck 35 ft wide.

Who owns Ia 31 over Little Sioux River?

It is owned by the State Highway Agency.