US Bridges

720th Ave over Middle Minerva Creek

FairPosted for load

Story County, Iowa · 085212302 · Structure no. 000000000315840

Built
1930
95 years old, rebuilt 1974
Condition
Fair
inspected November 2022
Type
Stringer/Multi-beam or Girder
Steel
Length
65 ft
1 main span
Daily traffic
11
2022 count
Owner
County
County Highway Agency

About this bridge

720th Ave over Middle Minerva Creek is a steel stringer/multi-beam or girder carrying 720th Ave over Middle Minerva Creek in Story County, Iowa. It was built in 1930 and reconstructed in 1974, so it is 95 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 11 vehicles a day, projected to reach 11 by 2043. The structure is 65 ft (19.8 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
CrossesMiddle Minerva Creek
Location085212302
RouteCounty Highway 0
CountyStory County
StateIowa
Coordinates42.15844, -93.27041
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, 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 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 adequacy7: Better than present minimum criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating28 US tons
Inventory rating19 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckWood or timber
Main spans1 (+2 approach)
Design loadUnknown
Structure length65 ft (19.8 m)
Longest span31 ft (9.4 m)
Deck width24 ft (7.3 m)
Roadway width23 ft (7.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11 (2022)
Projected traffic11 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 Middle Minerva Creek built?

It was built in 1930, making it 95 years old in 2025. It was reconstructed in 1974.

What condition is 720th Ave over Middle Minerva 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 November 2022.

How much traffic does 720th Ave over Middle Minerva Creek carry?

About 11 vehicles per day (2022 count).

How long is 720th Ave over Middle Minerva Creek?

The structure is 65 ft (19.8 m) long with a longest span of 31 ft (9.4 m) and a deck 24 ft wide.

Who owns 720th Ave over Middle Minerva Creek?

It is owned by the County Highway Agency.