US Bridges

520th Ave over Walnut Creek

FairPosted for load

Story County, Iowa · 083242802 · Structure no. 000000000314940

Built
1900
125 years old, rebuilt 1949
Condition
Fair
inspected December 2022
Type
Stringer/Multi-beam or Girder
Steel
Length
33 ft
1 main span
Daily traffic
80
2022 count
Owner
County
County Highway Agency

About this bridge

520th Ave over Walnut Creek is a steel stringer/multi-beam or girder carrying 520th Ave over Walnut Creek in Story County, Iowa. It was built in 1900 and reconstructed in 1949, so it is 125 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. Its operating status is: posted for load restriction.

It carries about 80 vehicles a day, roughly 15% of them trucks, projected to reach 80 by 2043. The structure is 33 ft (10.1 m) long and 25 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

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Carries520th Ave
CrossesWalnut Creek
Location083242802
RouteCounty Highway 0
CountyStory County
StateIowa
Coordinates41.96566, -93.65844
Functional classRural Local

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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionDecember 2022
Inspection intervalevery 24 months
Operating statusPosted for load 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 adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating33 US tons
Inventory rating20.9 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckWood or timber
Main spans1
Design loadUnknown
Structure length33 ft (10.1 m)
Longest span31 ft (9.4 m)
Deck width25 ft (7.6 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic80 (2022)
Projected traffic80 by 2043
Trucks15%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was 520th Ave over Walnut Creek built?

It was built in 1900, making it 125 years old in 2025. It was reconstructed in 1949.

What condition is 520th Ave over Walnut 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 December 2022.

How much traffic does 520th Ave over Walnut Creek carry?

About 80 vehicles per day (2022 count), of which roughly 15% are trucks.

How long is 520th Ave over Walnut Creek?

The structure is 33 ft (10.1 m) long with a longest span of 31 ft (9.4 m) and a deck 25 ft wide.

Who owns 520th Ave over Walnut Creek?

It is owned by the County Highway Agency.