US Bridges

FM 520th ST over Iowa River

Poor

Johnson County, Iowa · 078062301 · Structure no. 000000000203355

Built
1971
54 years old
Condition
Poor
inspected April 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
348 ft
4 main spans
Daily traffic
2,060
2021 count
Owner
County
County Highway Agency

About this bridge

FM 520th ST over Iowa River is a steel continuous stringer/multi-beam or girder carrying FM 520th ST over Iowa River in Johnson County, Iowa. It was built in 1971, so it is 54 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 2,060 vehicles a day, roughly 7% of them trucks, projected to reach 2,060 by 2043. The structure is 348 ft (106.1 m) long and 31 ft wide. If it were closed, the detour would be 8.7 mi (14 km).

Location

Open in Google Maps
CarriesFM 520th ST
CrossesIowa River
Location078062301
RouteCounty Highway 0
CountyJohnson County
StateIowa
Coordinates41.55481, -91.51921
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionApril 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating43.3 US tons
Inventory rating30 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length348 ft (106.1 m)
Longest span98 ft (29.9 m)
Deck width31 ft (9.3 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,060 (2021)
Projected traffic2,060 by 2043
Trucks7%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.7 mi (14 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 FM 520th ST over Iowa River built?

It was built in 1971, making it 54 years old in 2025.

What condition is FM 520th ST over Iowa 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 April 2023.

How much traffic does FM 520th ST over Iowa River carry?

About 2,060 vehicles per day (2021 count), of which roughly 7% are trucks.

How long is FM 520th ST over Iowa River?

The structure is 348 ft (106.1 m) long with a longest span of 98 ft (29.9 m) and a deck 31 ft wide.

Who owns FM 520th ST over Iowa River?

It is owned by the County Highway Agency.