US Bridges

NB I-29 over Boyer River

Fair

Harrison County, Iowa · 3.0 Mi. S of Jct. U.S. 30 · Structure no. 000000000028060

Built
1958
67 years old, rebuilt 2009
Condition
Fair
inspected August 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
414 ft
3 main spans
Daily traffic
10,050
2022 count
Owner
State
State Highway Agency

About this bridge

NB I-29 over Boyer River is a steel continuous stringer/multi-beam or girder carrying NB I-29 over Boyer River in Harrison County, Iowa. It was built in 1958 and reconstructed in 2009, so it is 67 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 10,050 vehicles a day, roughly 28% of them trucks, projected to reach 10,050 by 2043. The structure is 414 ft (126.2 m) long and 45 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesNB I-29
CrossesBoyer River
Location3.0 Mi. S of Jct. U.S. 30
RouteInterstate 29
CountyHarrison County
StateIowa
Coordinates41.5083, -95.90536
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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating87.1 US tons
Inventory rating52.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length414 ft (126.2 m)
Longest span160 ft (48.8 m)
Deck width45 ft (13.6 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic10,050 (2022)
Projected traffic10,050 by 2043
Trucks28%
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 Boyer River built?

It was built in 1958, making it 67 years old in 2025. It was reconstructed in 2009.

What condition is NB I-29 over Boyer 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 August 2023.

How much traffic does NB I-29 over Boyer River carry?

About 10,050 vehicles per day (2022 count), of which roughly 28% are trucks.

How long is NB I-29 over Boyer River?

The structure is 414 ft (126.2 m) long with a longest span of 160 ft (48.8 m) and a deck 45 ft wide.

Who owns NB I-29 over Boyer River?

It is owned by the State Highway Agency.