US Bridges

120th ST over Hamilton-Story 1 Open Dd

FairPosted for load

Story County, Iowa · 085241501 · Structure no. 000000000316350

Built
1940
85 years old, rebuilt 1970
Condition
Fair
inspected November 2022
Type
Stringer/Multi-beam or Girder
Steel
Length
34 ft
1 main span
Daily traffic
50
2022 count
Owner
County
County Highway Agency

About this bridge

120th ST over Hamilton-Story 1 Open Dd is a steel stringer/multi-beam or girder carrying 120th ST over Hamilton-Story 1 Open Dd in Story County, Iowa. It was built in 1940 and reconstructed in 1970, so it is 85 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 5 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 34 ft (10.4 m) long and 24 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries120th ST
CrossesHamilton-Story 1 Open Dd
Location085241501
RouteCounty Highway 0
CountyStory County
StateIowa
Coordinates42.18077, -93.63511
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
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 geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating32.7 US tons
Inventory rating19.6 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckWood or timber
Main spans1
Design loadUnknown
Structure length34 ft (10.4 m)
Longest span33 ft (10.1 m)
Deck width24 ft (7.3 m)
Roadway width24 ft (7.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic50 (2022)
Projected traffic50 by 2043
Trucks0%
Lanes on structure1
Traffic directionOne-lane bridge for two-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 Hamilton-Story 1 Open Dd built?

It was built in 1940, making it 85 years old in 2025. It was reconstructed in 1970.

What condition is 120th ST over Hamilton-Story 1 Open Dd 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 Hamilton-Story 1 Open Dd carry?

About 50 vehicles per day (2022 count).

How long is 120th ST over Hamilton-Story 1 Open Dd?

The structure is 34 ft (10.4 m) long with a longest span of 33 ft (10.1 m) and a deck 24 ft wide.

Who owns 120th ST over Hamilton-Story 1 Open Dd?

It is owned by the County Highway Agency.