US Bridges

720th Ave over Hardin-Story Dd 1

PoorPosted for load

Story County, Iowa · 085211104 · Structure no. 000000000315730

Built
1900
125 years old, rebuilt 1974
Condition
Poor
inspected November 2022
Type
Truss - Thru
Steel
Length
42 ft
1 main span
Daily traffic
15
2022 count
Owner
County
County Highway Agency

About this bridge

720th Ave over Hardin-Story Dd 1 is a steel truss - thru carrying 720th Ave over Hardin-Story Dd 1 in Story County, Iowa. It was built in 1900 and reconstructed in 1974, 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 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. Its operating status is: posted for load restriction.

It carries about 15 vehicles a day, projected to reach 15 by 2043. The structure is 42 ft (12.8 m) long and 24 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries720th Ave
CrossesHardin-Story Dd 1
Location085211104
RouteCounty Highway 0
CountyStory County
StateIowa
Coordinates42.18767, -93.27059
Functional classRural Local

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
Deck7 GoodSome minor problems.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
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 statusPosted for load restriction
ScourFoundations stable; scour above top of footing
Structural evaluation2: Basically intolerable, requiring high priority of replacement
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating14 US tons
Inventory rating5 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length42 ft (12.8 m)
Longest span40 ft (12.2 m)
Deck width24 ft (7.3 m)
Roadway width23 ft (7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic15 (2022)
Projected traffic15 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 720th Ave over Hardin-Story Dd 1 built?

It was built in 1900, making it 125 years old in 2025. It was reconstructed in 1974.

What condition is 720th Ave over Hardin-Story Dd 1 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 720th Ave over Hardin-Story Dd 1 carry?

About 15 vehicles per day (2022 count).

How long is 720th Ave over Hardin-Story Dd 1?

The structure is 42 ft (12.8 m) long with a longest span of 40 ft (12.2 m) and a deck 24 ft wide.

Who owns 720th Ave over Hardin-Story Dd 1?

It is owned by the County Highway Agency.