US Bridges

320th Ave over Small

Fair

Clinton County, Iowa · 083E42604 · Structure no. 000000000125331

Built
1978
47 years old
Condition
Fair
inspected December 2024
Type
Tee Beam
Prestressed Concrete
Length
41 ft
1 main span
Daily traffic
350
2022 count
Owner
County
County Highway Agency

About this bridge

320th Ave over Small is a prestressed concrete tee beam carrying 320th Ave over Small in Clinton County, Iowa. It was built in 1978, so it is 47 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.

It carries about 350 vehicles a day, projected to reach 350 by 2044. The structure is 41 ft (12.5 m) long and 24 ft wide.

Location

Open in Google Maps
Carries320th Ave
CrossesSmall
Location083E42604
RouteCounty Highway 0
CountyClinton County
StateIowa
Coordinates41.97024, -90.46715
Functional classRural Minor Collector

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 inspectionDecember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating59.7 US tons
Inventory rating35.8 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckConcrete, precast panels
Main spans1
Design loadHS 20
Structure length41 ft (12.5 m)
Longest span40 ft (12.2 m)
Deck width24 ft (7.3 m)
Roadway width22 ft (6.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic350 (2022)
Projected traffic350 by 2044
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed—
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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was 320th Ave over Small built?

It was built in 1978, making it 47 years old in 2025.

What condition is 320th Ave over Small 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 December 2024.

How much traffic does 320th Ave over Small carry?

About 350 vehicles per day (2022 count).

How long is 320th Ave over Small?

The structure is 41 ft (12.5 m) long with a longest span of 40 ft (12.2 m) and a deck 24 ft wide.

Who owns 320th Ave over Small?

It is owned by the County Highway Agency.