US Bridges

NB I-29 over Allen Creek

Fair

Harrison County, Iowa · 1.9 Mi. N of Jct. US 30 · Structure no. 000000000028150

Built
1967
58 years old
Condition
Fair
inspected June 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
160 ft
3 main spans
Daily traffic
7,750
2022 count
Owner
State
State Highway Agency

About this bridge

NB I-29 over Allen Creek is a steel continuous stringer/multi-beam or girder carrying NB I-29 over Allen Creek in Harrison County, Iowa. It was built in 1967, so it is 58 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 7,750 vehicles a day, roughly 31% of them trucks, projected to reach 7,750 by 2044. The structure is 160 ft (48.8 m) long and 42 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesNB I-29
CrossesAllen Creek
Location1.9 Mi. N of Jct. US 30
RouteInterstate 29
CountyHarrison County
StateIowa
Coordinates41.57403, -95.92809
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.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJune 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 geometry6: Equal to present minimum criteria
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating69 US tons
Inventory rating41 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length160 ft (48.8 m)
Longest span61 ft (18.6 m)
Deck width42 ft (12.9 m)
Roadway width39 ft (11.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic7,750 (2022)
Projected traffic7,750 by 2044
Trucks31%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
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—
NavigationNo navigation control on waterway

Frequently asked questions

When was NB I-29 over Allen Creek built?

It was built in 1967, making it 58 years old in 2025.

What condition is NB I-29 over Allen Creek 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 June 2024.

How much traffic does NB I-29 over Allen Creek carry?

About 7,750 vehicles per day (2022 count), of which roughly 31% are trucks.

How long is NB I-29 over Allen Creek?

The structure is 160 ft (48.8 m) long with a longest span of 61 ft (18.6 m) and a deck 42 ft wide.

Who owns NB I-29 over Allen Creek?

It is owned by the State Highway Agency.