US Bridges

120th ST over Keigley Branch

FairPosted for load

Story County, Iowa · 085241601 · Structure no. 000000000316360

Built
1968
57 years old
Condition
Fair
inspected November 2022
Type
Stringer/Multi-beam or Girder
Steel
Length
44 ft
1 main span
Daily traffic
50
2022 count
Owner
County
County Highway Agency

About this bridge

120th ST over Keigley Branch is a steel stringer/multi-beam or girder carrying 120th ST over Keigley Branch in Story County, Iowa. It was built in 1968, so it is 57 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 50 vehicles a day, projected to reach 50 by 2043. The structure is 44 ft (13.4 m) long and 26 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries120th ST
CrossesKeigley Branch
Location085241601
RouteCounty Highway 0
CountyStory County
StateIowa
Coordinates42.1808, -93.65736
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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionNovember 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 adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating32 US tons
Inventory rating18 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadH 15
Structure length44 ft (13.4 m)
Longest span43 ft (13.1 m)
Deck width26 ft (7.9 m)
Roadway width24 ft (7.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic50 (2022)
Projected traffic50 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 120th ST over Keigley Branch built?

It was built in 1968, making it 57 years old in 2025.

What condition is 120th ST over Keigley Branch 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 November 2022.

How much traffic does 120th ST over Keigley Branch carry?

About 50 vehicles per day (2022 count).

How long is 120th ST over Keigley Branch?

The structure is 44 ft (13.4 m) long with a longest span of 43 ft (13.1 m) and a deck 26 ft wide.

Who owns 120th ST over Keigley Branch?

It is owned by the County Highway Agency.