SB I-29 over Robinson Ditch

Good

Monona County, Iowa · 4.1 MI S of JCT Ia 141 · Structure no. 000000000037361

Built: 2009; 16 years old
Condition: Good; inspected April 2024
Type: Slab; Concrete Continuous
Length: 103 ft; 3 main spans
Daily traffic: 7,800; 2022 count
Owner: State; State Highway Agency

About this bridge

SB I-29 over Robinson Ditch is a concrete continuous slab carrying SB I-29 over Robinson Ditch in Monona County, Iowa. It was built in 2009, so it is 16 years old, younger than the Iowa average of 45.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 7,800 vehicles a day, roughly 31% of them trucks, projected to reach 7,800 by 2044. The structure is 103 ft (31.4 m) long and 44 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesSB I-29

CrossesRobinson Ditch

Location4.1 MI S of JCT Ia 141

RouteInterstate 29

CountyMonona County

StateIowa

Coordinates42.17126, -96.23002

Functional classRural Principal Arterial - Interstate

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

Component	Rating	Meaning
Deck	7 Good	Some minor problems.
Superstructure	7 Good	Some minor problems.
Substructure	8 Very Good	No problems noted.
Channel and channel protection	8 Very Good	No problems noted.

Last inspectionApril 2024

Inspection intervalevery 24 months

Operating statusOpen, no restriction

ScourFoundations stable; scour within limits of footing or piles

Structural evaluation7: Better than present minimum criteria

Deck geometry7: Better than present minimum criteria

Waterway adequacy8: Equal to present desirable criteria

Approach roadway alignment8: Equal to present desirable criteria

Operating rating82 US tons

Inventory rating49.2 US tons

Structure

Structure typeSlab

MaterialConcrete Continuous

DeckConcrete, cast-in-place

Main spans3

Design loadHL 93

Structure length103 ft (31.4 m)

Longest span39 ft (11.9 m)

Deck width44 ft (13.3 m)

Roadway width40 ft (12.3 m)

Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic7,800 (2022)

Projected traffic7,800 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—

NavigationNot applicable (no waterway)

Frequently asked questions

When was SB I-29 over Robinson Ditch built?

It was built in 2009, making it 16 years old in 2025.

What condition is SB I-29 over Robinson Ditch in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in April 2024.

How much traffic does SB I-29 over Robinson Ditch carry?

About 7,800 vehicles per day (2022 count), of which roughly 31% are trucks.

How long is SB I-29 over Robinson Ditch?

The structure is 103 ft (31.4 m) long with a longest span of 39 ft (11.9 m) and a deck 44 ft wide.

Who owns SB I-29 over Robinson Ditch?

It is owned by the State Highway Agency.