US Bridges

320th ST over Skunk River

FairPosted for load

Story County, Iowa · 082232703 · Structure no. 000000000314210

Built
1949
76 years old
Condition
Fair
inspected January 2023
Type
Truss - Thru
Steel
Length
184 ft
2 main spans
Daily traffic
80
2022 count
Owner
County
County Highway Agency

About this bridge

320th ST over Skunk River is a steel truss - thru carrying 320th ST over Skunk River in Story County, Iowa. It was built in 1949, so it is 76 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 80 vehicles a day, roughly 11% of them trucks, projected to reach 80 by 2043. The structure is 184 ft (56.1 m) long and 17 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries320th ST
CrossesSkunk River
Location082232703
RouteCounty Highway 0
CountyStory County
StateIowa
Coordinates41.89196, -93.51643
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.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection4 PoorAdvanced section loss, deterioration, spalling or scour.
Last inspectionJanuary 2023
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourUnknown foundation; not evaluated for scour
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment2: Basically intolerable, requiring high priority of replacement
Operating rating20 US tons
Inventory rating13 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckWood or timber
Main spans2
Design loadH 10
Structure length184 ft (56.1 m)
Longest span90 ft (27.4 m)
Deck width17 ft (5.2 m)
Roadway width16 ft (4.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic80 (2022)
Projected traffic80 by 2043
Trucks11%
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 320th ST over Skunk River built?

It was built in 1949, making it 76 years old in 2025.

What condition is 320th ST over Skunk River 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 January 2023.

How much traffic does 320th ST over Skunk River carry?

About 80 vehicles per day (2022 count), of which roughly 11% are trucks.

How long is 320th ST over Skunk River?

The structure is 184 ft (56.1 m) long with a longest span of 90 ft (27.4 m) and a deck 17 ft wide.

Who owns 320th ST over Skunk River?

It is owned by the County Highway Agency.