US Bridges

120th ST over Roberts Creek

Fair

Clayton County, Iowa · 095061601 · Structure no. 000000000121400

Built
1900
125 years old, rebuilt 1988
Condition
Fair
inspected September 2024
Type
Tee Beam
Prestressed Concrete
Length
37 ft
1 main span
Daily traffic
98
2022 count
Owner
County
County Highway Agency

About this bridge

120th ST over Roberts Creek is a prestressed concrete tee beam carrying 120th ST over Roberts Creek in Clayton County, Iowa. It was built in 1900 and reconstructed in 1988, so it is 125 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 98 vehicles a day, projected to reach 98 by 2044. The structure is 37 ft (11.3 m) long and 24 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
Carries120th ST
CrossesRoberts Creek
Location095061601
RouteCounty Highway 0
CountyClayton County
StateIowa
Coordinates43.05114, -91.55578
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 inspectionSeptember 2024
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 alignment8: Equal to present desirable criteria
Operating rating32.5 US tons
Inventory rating25 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length37 ft (11.3 m)
Longest span36 ft (11 m)
Deck width24 ft (7.3 m)
Roadway width24 ft (7.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic98 (2022)
Projected traffic98 by 2044
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.7 mi (6 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was 120th ST over Roberts Creek built?

It was built in 1900, making it 125 years old in 2025. It was reconstructed in 1988.

What condition is 120th ST over Roberts 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 September 2024.

How much traffic does 120th ST over Roberts Creek carry?

About 98 vehicles per day (2022 count).

How long is 120th ST over Roberts Creek?

The structure is 37 ft (11.3 m) long with a longest span of 36 ft (11 m) and a deck 24 ft wide.

Who owns 120th ST over Roberts Creek?

It is owned by the County Highway Agency.