US Bridges

170th ST over Drainage Ditch 36

Fair

Story County, Iowa · 084221201 · Structure no. 000000000315130

Built
1969
56 years old, rebuilt 1974
Condition
Fair
inspected December 2022
Type
Channel Beam
Concrete
Length
27 ft
1 main span
Daily traffic
34
2022 count
Owner
County
County Highway Agency

About this bridge

170th ST over Drainage Ditch 36 is a concrete channel beam carrying 170th ST over Drainage Ditch 36 in Story County, Iowa. It was built in 1969 and reconstructed in 1974, so it is 56 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 34 vehicles a day, projected to reach 34 by 2043. The structure is 27 ft (8.2 m) long and 27 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries170th ST
CrossesDrainage Ditch 36
Location084221201
RouteCounty Highway 0
CountyStory County
StateIowa
Coordinates42.10671, -93.35091
Functional classRural Minor 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
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 2022
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 geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment5: Somewhat better than minimum adequacy to tolerate being left in place as is
Operating rating40.1 US tons
Inventory rating24.6 US tons

Structure

Structure typeChannel Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadH 20
Structure length27 ft (8.2 m)
Longest span24 ft (7.3 m)
Deck width27 ft (8.2 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic34 (2022)
Projected traffic34 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 proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was 170th ST over Drainage Ditch 36 built?

It was built in 1969, making it 56 years old in 2025. It was reconstructed in 1974.

What condition is 170th ST over Drainage Ditch 36 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 Drainage Ditch 36 carry?

About 34 vehicles per day (2022 count).

How long is 170th ST over Drainage Ditch 36?

The structure is 27 ft (8.2 m) long with a longest span of 24 ft (7.3 m) and a deck 27 ft wide.

Who owns 170th ST over Drainage Ditch 36?

It is owned by the County Highway Agency.