US Bridges

170th ST over Small

Fair

Story County, Iowa · 084240701 · Structure no. 000000000365110

Built
2006
19 years old
Condition
Fair
inspected December 2022
Type
Channel Beam
Concrete
Length
37 ft
1 main span
Daily traffic
1,137
2022 count
Owner
County
County Highway Agency

About this bridge

170th ST over Small is a concrete channel beam carrying 170th ST over Small in Story County, Iowa. It was built in 2006, so it is 19 years old, younger 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 1,137 vehicles a day, roughly 8% of them trucks, projected to reach 1,137 by 2043. The structure is 37 ft (11.3 m) long and 31 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
Carries170th ST
CrossesSmall
Location084240701
RouteCounty Highway 0
CountyStory County
StateIowa
Coordinates42.10696, -93.69778
Functional classRural Major Collector

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.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionDecember 2022
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 alignment8: Equal to present desirable criteria
Operating rating62.4 US tons
Inventory rating37.4 US tons

Structure

Structure typeChannel Beam
MaterialConcrete
DeckConcrete, precast panels
Main spans1
Design loadHS 20
Structure length37 ft (11.3 m)
Longest span36 ft (11 m)
Deck width31 ft (9.5 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,137 (2022)
Projected traffic1,137 by 2043
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.8 mi (11 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 170th ST over Small built?

It was built in 2006, making it 19 years old in 2025.

What condition is 170th ST over Small 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 2022.

How much traffic does 170th ST over Small carry?

About 1,137 vehicles per day (2022 count), of which roughly 8% are trucks.

How long is 170th ST over Small?

The structure is 37 ft (11.3 m) long with a longest span of 36 ft (11 m) and a deck 31 ft wide.

Who owns 170th ST over Small?

It is owned by the County Highway Agency.