US Bridges

US 18 over Boone River

Fair

Hancock County, Iowa · 4.7 Mi. W of Jct. SR R35 · Structure no. 000000000026770

Built
1959
66 years old
Condition
Fair
inspected August 2024
Type
Slab
Concrete Continuous
Length
92 ft
3 main spans
Daily traffic
2,980
2022 count
Owner
State
State Highway Agency

About this bridge

US 18 over Boone River is a concrete continuous slab carrying US 18 over Boone River in Hancock County, Iowa. It was built in 1959, so it is 66 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 2,980 vehicles a day, roughly 20% of them trucks, projected to reach 2,980 by 2044. The structure is 92 ft (28 m) long and 36 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesUS 18
CrossesBoone River
Location4.7 Mi. W of Jct. SR R35
RouteU.S. Route 18
CountyHancock County
StateIowa
Coordinates43.09739, -93.89413
Functional classRural Principal Arterial - Other

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 protection7 GoodSome minor problems.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
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 rating47.5 US tons
Inventory rating26.7 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length92 ft (28 m)
Longest span35 ft (10.7 m)
Deck width36 ft (11 m)
Roadway width30 ft (9.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,980 (2022)
Projected traffic2,980 by 2044
Trucks20%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState 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 US 18 over Boone River built?

It was built in 1959, making it 66 years old in 2025.

What condition is US 18 over Boone 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 August 2024.

How much traffic does US 18 over Boone River carry?

About 2,980 vehicles per day (2022 count), of which roughly 20% are trucks.

How long is US 18 over Boone River?

The structure is 92 ft (28 m) long with a longest span of 35 ft (10.7 m) and a deck 36 ft wide.

Who owns US 18 over Boone River?

It is owned by the State Highway Agency.