US Bridges

NB I-35 over 310th ST

Fair

Decatur County, Iowa · 2.5 Mi. S of US 69 · Structure no. 000000000022830

Built
1970
55 years old
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
177 ft
3 main spans
Daily traffic
7,100
2022 count
Owner
State
State Highway Agency

About this bridge

NB I-35 over 310th ST is a steel continuous stringer/multi-beam or girder carrying NB I-35 over 310th ST 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 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 7,100 vehicles a day, roughly 39% of them trucks, projected to reach 7,100 by 2043. The structure is 177 ft (54 m) long and 44 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesNB I-35
Crosses310th ST
Location2.5 Mi. S of US 69
RouteInterstate 35
CountyDecatur County
StateIowa
Coordinates40.59444, -93.91602
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating56 US tons
Inventory rating36 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length177 ft (54 m)
Longest span66 ft (20.1 m)
Deck width44 ft (13.4 m)
Roadway width40 ft (12.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic7,100 (2022)
Projected traffic7,100 by 2043
Trucks39%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
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 310th ST built?

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

What condition is NB I-35 over 310th ST 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 NB I-35 over 310th ST carry?

About 7,100 vehicles per day (2022 count), of which roughly 39% are trucks.

How long is NB I-35 over 310th ST?

The structure is 177 ft (54 m) long with a longest span of 66 ft (20.1 m) and a deck 44 ft wide.

Who owns NB I-35 over 310th ST?

It is owned by the State Highway Agency.