US Bridges

US 18 over Mississippi River Ia 76

Fair

Clayton County, Iowa · In Marquette · Structure no. 000000000020515

Built
1974
51 years old
Condition
Fair
inspected August 2023
Type
Arch - Thru
Steel
Length
2,561 ft
1 main span
Daily traffic
10,100
2022 count
Owner
State
State Highway Agency

About this bridge

US 18 over Mississippi River Ia 76 is a steel arch - thru carrying US 18 over Mississippi River Ia 76 in Clayton County, Iowa. It was built in 1974, so it is 51 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 10,100 vehicles a day, roughly 12% of them trucks, projected to reach 10,100 by 2043. The structure is 2,561 ft (780.6 m) long and 44 ft wide. If it were closed, the detour would be 62.8 mi (101 km).

Location

Open in Google Maps
CarriesUS 18
CrossesMississippi River Ia 76
LocationIn Marquette
RouteU.S. Route 18
CountyClayton County
StateIowa
Coordinates43.04387, -91.17836
Functional classUrban Other Principal Arterial

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 protection8 Very GoodNo problems noted.
Last inspectionAugust 2023
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 geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating50.4 US tons
Inventory rating30.6 US tons

Structure

Structure typeArch - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+12 approach)
Design loadHS 20
Structure length2,561 ft (780.6 m)
Longest span462 ft (140.8 m)
Deck width44 ft (13.4 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deck23 ft (7.1 m)

Traffic and service

Average daily traffic10,100 (2022)
Projected traffic10,100 by 2043
Trucks12%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway, waterway and railroad
Detour if closed62.8 mi (101 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—
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was US 18 over Mississippi River Ia 76 built?

It was built in 1974, making it 51 years old in 2025.

What condition is US 18 over Mississippi River Ia 76 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 2023.

How much traffic does US 18 over Mississippi River Ia 76 carry?

About 10,100 vehicles per day (2022 count), of which roughly 12% are trucks.

How long is US 18 over Mississippi River Ia 76?

The structure is 2,561 ft (780.6 m) long with a longest span of 462 ft (140.8 m) and a deck 44 ft wide.

Who owns US 18 over Mississippi River Ia 76?

It is owned by the State Highway Agency.