US Bridges

FM over Rock River

Poor

Lyon County, Iowa · 098462402 · Structure no. 000000000228870

Built
1966
59 years old
Condition
Poor
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
278 ft
4 main spans
Daily traffic
977
2022 count
Owner
County
County Highway Agency

About this bridge

FM over Rock River is a steel continuous stringer/multi-beam or girder carrying FM over Rock River in Lyon County, Iowa. It was built in 1966, so it is 59 years old, older than the Iowa average of 45.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 977 vehicles a day, projected to reach 977 by 2043. The structure is 278 ft (84.7 m) long and 30 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

Open in Google Maps
CarriesFM
CrossesRock River
Location098462402
RouteCounty Highway 0
CountyLyon County
StateIowa
Coordinates43.29465, -96.23558
Functional classRural Major Collector

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck4 PoorAdvanced section loss, deterioration, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2023
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 adequacy7: Better than present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating43.2 US tons
Inventory rating29.9 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadH 20
Structure length278 ft (84.7 m)
Longest span78 ft (23.8 m)
Deck width30 ft (9.1 m)
Roadway width29 ft (8.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic977 (2022)
Projected traffic977 by 2043
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed5 mi (8 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 FM over Rock River built?

It was built in 1966, making it 59 years old in 2025.

What condition is FM over Rock River in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in July 2023.

How much traffic does FM over Rock River carry?

About 977 vehicles per day (2022 count).

How long is FM over Rock River?

The structure is 278 ft (84.7 m) long with a longest span of 78 ft (23.8 m) and a deck 30 ft wide.

Who owns FM over Rock River?

It is owned by the County Highway Agency.