US Bridges

170th ST over Rock CR

Fair

Cedar County, Iowa · 081031101 · Structure no. 000000000103881

Built
1975
50 years old, rebuilt 2001
Condition
Fair
inspected May 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
24 ft
1 main span
Daily traffic
11
2022 count
Owner
County
County Highway Agency

About this bridge

170th ST over Rock CR is a steel stringer/multi-beam or girder carrying 170th ST over Rock CR in Cedar County, Iowa. It was built in 1975 and reconstructed in 2001, so it is 50 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 6 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 11 vehicles a day, projected to reach 11 by 2044. The structure is 24 ft (7.3 m) long and 24 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries170th ST
CrossesRock CR
Location081031101
RouteCounty Highway 0
CountyCedar County
StateIowa
Coordinates41.84469, -91.16464
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating35.4 US tons
Inventory rating29.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckWood or timber
Main spans1
Design loadUnknown
Structure length24 ft (7.3 m)
Longest span23 ft (7 m)
Deck width24 ft (7.4 m)
Roadway width24 ft (7.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11 (2022)
Projected traffic11 by 2044
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 170th ST over Rock CR built?

It was built in 1975, making it 50 years old in 2025. It was reconstructed in 2001.

What condition is 170th ST over Rock CR 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 May 2024.

How much traffic does 170th ST over Rock CR carry?

About 11 vehicles per day (2022 count).

How long is 170th ST over Rock CR?

The structure is 24 ft (7.3 m) long with a longest span of 23 ft (7 m) and a deck 24 ft wide.

Who owns 170th ST over Rock CR?

It is owned by the County Highway Agency.