US Bridges

320th ST over Unnamed Stream

Good

Adair County, Iowa · 0.1 MI E of Lewis on 320 · Structure no. 000000000366140

Built
2015
10 years old
Condition
Good
inspected April 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
31 ft
1 main span
Daily traffic
21
2022 count
Owner
County
County Highway Agency

About this bridge

320th ST over Unnamed Stream is a steel stringer/multi-beam or girder carrying 320th ST over Unnamed Stream in Adair County, Iowa. It was built in 2015, so it is 10 years old, younger than the Iowa average of 45.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 21 vehicles a day, projected to reach 21 by 2043. The structure is 31 ft (9.4 m) long and 25 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
Carries320th ST
CrossesUnnamed Stream
Location0.1 MI E of Lewis on 320
RouteCounty Highway 0
CountyAdair County
StateIowa
Coordinates41.1865, -94.48736
Functional classRural Local

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionApril 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating91.6 US tons
Inventory rating54.9 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length31 ft (9.4 m)
Longest span29 ft (8.7 m)
Deck width25 ft (7.7 m)
Roadway width25 ft (7.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic21 (2022)
Projected traffic21 by 2043
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was 320th ST over Unnamed Stream built?

It was built in 2015, making it 10 years old in 2025.

What condition is 320th ST over Unnamed Stream in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in April 2023.

How much traffic does 320th ST over Unnamed Stream carry?

About 21 vehicles per day (2022 count).

How long is 320th ST over Unnamed Stream?

The structure is 31 ft (9.4 m) long with a longest span of 29 ft (8.7 m) and a deck 25 ft wide.

Who owns 320th ST over Unnamed Stream?

It is owned by the County Highway Agency.