US Bridges

520th Ave over Keigley Branch

Poor

Story County, Iowa · 085240902 · Structure no. 000000000316340

Built
1949
76 years old
Condition
Poor
inspected November 2022
Type
Stringer/Multi-beam or Girder
Steel
Length
43 ft
1 main span
Daily traffic
34
2022 count
Owner
County
County Highway Agency

About this bridge

520th Ave over Keigley Branch is a steel stringer/multi-beam or girder carrying 520th Ave over Keigley Branch in Story County, Iowa. It was built in 1949, so it is 76 years old, older than the Iowa average of 45.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 34 vehicles a day, projected to reach 34 by 2043. The structure is 43 ft (13.1 m) long and 20 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries520th Ave
CrossesKeigley Branch
Location085240902
RouteCounty Highway 0
CountyStory County
StateIowa
Coordinates42.19396, -93.65939
Functional classRural Minor Collector

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionNovember 2022
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating34.9 US tons
Inventory rating20.9 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckWood or timber
Main spans1
Design loadUnknown
Structure length43 ft (13.1 m)
Longest span41 ft (12.5 m)
Deck width20 ft (6.1 m)
Roadway width19 ft (5.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic34 (2022)
Projected traffic34 by 2043
Trucks0%
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 Keigley Branch built?

It was built in 1949, making it 76 years old in 2025.

What condition is 520th Ave over Keigley Branch in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in November 2022.

How much traffic does 520th Ave over Keigley Branch carry?

About 34 vehicles per day (2022 count).

How long is 520th Ave over Keigley Branch?

The structure is 43 ft (13.1 m) long with a longest span of 41 ft (12.5 m) and a deck 20 ft wide.

Who owns 520th Ave over Keigley Branch?

It is owned by the County Highway Agency.