US Bridges

170th ST over Des Moines River

Fair

Webster County, Iowa · 089291205 · Structure no. 000000000343345

Built
1979
46 years old
Condition
Fair
inspected November 2022
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
585 ft
6 main spans
Daily traffic
3,132
2022 count
Owner
County
County Highway Agency

About this bridge

170th ST over Des Moines River is a prestressed concrete stringer/multi-beam or girder carrying 170th ST over Des Moines River in Webster County, Iowa. It was built in 1979, so it is 46 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 3,132 vehicles a day, roughly 13% of them trucks, projected to reach 3,132 by 2042. The structure is 585 ft (178.3 m) long and 35 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

Open in Google Maps
Carries170th ST
CrossesDes Moines River
Location089291205
RouteCounty Highway 0
CountyWebster County
StateIowa
Coordinates42.54354, -94.21745
Functional classUrban 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.
Superstructure8 Very GoodNo problems noted.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionNovember 2022
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating75.3 US tons
Inventory rating45.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans6
Design loadHS 20
Structure length585 ft (178.3 m)
Longest span96 ft (29.3 m)
Deck width35 ft (10.7 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,132 (2022)
Projected traffic3,132 by 2042
Trucks13%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 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 proposedOther structural work, including hydraulic replacements
Estimated improvement cost$5.8 million (2023 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was 170th ST over Des Moines River built?

It was built in 1979, making it 46 years old in 2025.

What condition is 170th ST over Des Moines River 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 November 2022.

How much traffic does 170th ST over Des Moines River carry?

About 3,132 vehicles per day (2022 count), of which roughly 13% are trucks.

How long is 170th ST over Des Moines River?

The structure is 585 ft (178.3 m) long with a longest span of 96 ft (29.3 m) and a deck 35 ft wide.

Who owns 170th ST over Des Moines River?

It is owned by the County Highway Agency.