US Bridges

A50 (bridge St) over Big Sioux River

Fair

Lyon County, Iowa · 098492519 · Structure no. 000000000229541

Built
1971
54 years old
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
348 ft
4 main spans
Daily traffic
888
2022 count
Owner
County
County Highway Agency

About this bridge

A50 (bridge St) over Big Sioux River is a steel continuous stringer/multi-beam or girder carrying A50 (bridge St) over Big Sioux River in Lyon County, Iowa. It was built in 1971, so it is 54 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 888 vehicles a day, roughly 12% of them trucks, projected to reach 888 by 2043. The structure is 348 ft (106.1 m) long and 32 ft wide. If it were closed, the detour would be 11.2 mi (18 km).

Location

Open in Google Maps
CarriesA50 (bridge St)
CrossesBig Sioux River
Location098492519
RouteCounty Highway 0
CountyLyon County
StateIowa
Coordinates43.28146, -96.57835
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2023
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 geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating51 US tons
Inventory rating32.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadH 20
Structure length348 ft (106.1 m)
Longest span98 ft (29.9 m)
Deck width32 ft (9.8 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic888 (2022)
Projected traffic888 by 2043
Trucks12%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed11.2 mi (18 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedOther structural work, including hydraulic replacements
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was A50 (bridge St) over Big Sioux River built?

It was built in 1971, making it 54 years old in 2025.

What condition is A50 (bridge St) over Big 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 2023.

How much traffic does A50 (bridge St) over Big Sioux River carry?

About 888 vehicles per day (2022 count), of which roughly 12% are trucks.

How long is A50 (bridge St) over Big Sioux River?

The structure is 348 ft (106.1 m) long with a longest span of 98 ft (29.9 m) and a deck 32 ft wide.

Who owns A50 (bridge St) over Big Sioux River?

It is owned by the County Highway Agency.