US Bridges

310th ST over Porter Creek

FairPosted for load

Crawford County, Iowa · 085380301 · Structure no. 000000000365850

Built
1940
85 years old
Condition
Fair
inspected March 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
41 ft
1 main span
Daily traffic
5
2022 count
Owner
County
County Highway Agency

About this bridge

310th ST over Porter Creek is a steel stringer/multi-beam or girder carrying 310th ST over Porter Creek in Crawford County, Iowa. It was built in 1940, so it is 85 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 other load-capacity restriction.

It carries about 5 vehicles a day, projected to reach 5 by 2044. The structure is 41 ft (12.5 m) long and 24 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
Carries310th ST
CrossesPorter Creek
Location085380301
RouteCounty Highway 0
CountyCrawford County
StateIowa
Coordinates42.21078, -95.24626
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
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 inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusPosted for other load-capacity restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating36.4 US tons
Inventory rating21.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length41 ft (12.5 m)
Longest span40 ft (12.2 m)
Deck width24 ft (7.3 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic5 (2022)
Projected traffic5 by 2044
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 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 310th ST over Porter Creek built?

It was built in 1940, making it 85 years old in 2025.

What condition is 310th ST over Porter 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 March 2024.

How much traffic does 310th ST over Porter Creek carry?

About 5 vehicles per day (2022 count).

How long is 310th ST over Porter Creek?

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 310th ST over Porter Creek?

It is owned by the County Highway Agency.