US Bridges

305th ST over Allen Creek

Fair

Harrison County, Iowa · 078441701 · Structure no. 000000000177711

Built
1974
51 years old
Condition
Fair
inspected December 2023
Type
Girder and Floorbeam System
Steel
Length
66 ft
1 main span
Daily traffic
139
2022 count
Owner
County
County Highway Agency

About this bridge

305th ST over Allen Creek is a steel girder and floorbeam system carrying 305th ST over Allen Creek in Harrison County, Iowa. It was built in 1974, so it is 51 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.

It carries about 139 vehicles a day, projected to reach 139 by 2043. The structure is 66 ft (20.1 m) long and 24 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries305th ST
CrossesAllen Creek
Location078441701
RouteCounty Highway 0
CountyHarrison County
StateIowa
Coordinates41.56469, -95.92874
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
Deck7 GoodSome minor problems.
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 protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionDecember 2023
Inspection intervalevery 24 months
Operating statusOpen, no 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 alignment5: Somewhat better than minimum adequacy to tolerate being left in place as is
Operating rating39.6 US tons
Inventory rating28.5 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel
DeckCorrugated steel
Main spans1
Design loadHS 20
Structure length66 ft (20.1 m)
Longest span65 ft (19.8 m)
Deck width24 ft (7.3 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic139 (2022)
Projected traffic139 by 2043
Trucks0%
Lanes on structure2
Traffic directionTwo-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 proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was 305th ST over Allen Creek built?

It was built in 1974, making it 51 years old in 2025.

What condition is 305th ST over Allen 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 December 2023.

How much traffic does 305th ST over Allen Creek carry?

About 139 vehicles per day (2022 count).

How long is 305th ST over Allen Creek?

The structure is 66 ft (20.1 m) long with a longest span of 65 ft (19.8 m) and a deck 24 ft wide.

Who owns 305th ST over Allen Creek?

It is owned by the County Highway Agency.