US Bridges

NB I-35 over 324th Street

Fair

Decatur County, Iowa · At Missouri State Line · Structure no. 000000000022810

Built
1970
55 years old
Condition
Fair
inspected August 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
198 ft
3 main spans
Daily traffic
6,900
2022 count
Owner
State
State Highway Agency

About this bridge

NB I-35 over 324th Street is a steel continuous stringer/multi-beam or girder carrying NB I-35 over 324th Street in Decatur County, Iowa. It was built in 1970, so it is 55 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 6,900 vehicles a day, roughly 39% of them trucks, projected to reach 6,900 by 2044. The structure is 198 ft (60.4 m) long and 43 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesNB I-35
Crosses324th Street
LocationAt Missouri State Line
RouteInterstate 35
CountyDecatur County
StateIowa
Coordinates40.57523, -93.93715
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
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.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating53.4 US tons
Inventory rating32.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length198 ft (60.4 m)
Longest span75 ft (22.9 m)
Deck width43 ft (13.2 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,900 (2022)
Projected traffic6,900 by 2044
Trucks39%
Lanes on structure2
Traffic directionOne-way traffic
CarriesOverpass structure at an interchange
CrossesHighway
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—
NavigationNot applicable (no waterway)

Frequently asked questions

When was NB I-35 over 324th Street built?

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

What condition is NB I-35 over 324th Street 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 August 2024.

How much traffic does NB I-35 over 324th Street carry?

About 6,900 vehicles per day (2022 count), of which roughly 39% are trucks.

How long is NB I-35 over 324th Street?

The structure is 198 ft (60.4 m) long with a longest span of 75 ft (22.9 m) and a deck 43 ft wide.

Who owns NB I-35 over 324th Street?

It is owned by the State Highway Agency.