US Bridges

420th Ave. over Mill Creek

Good

Clinton County, Iowa · 082E61602 · Structure no. 000000000124301

Built
2021
4 years old
Condition
Good
inspected December 2023
Type
Stringer/Multi-beam or Girder
Concrete
Length
25 ft
1 main span
Daily traffic
166
2022 count
Owner
County
County Highway Agency

About this bridge

420th Ave. over Mill Creek is a concrete stringer/multi-beam or girder carrying 420th Ave. over Mill Creek in Clinton County, Iowa. It was built in 2021, so it is 4 years old, younger than the Iowa average of 45.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 8 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 166 vehicles a day, projected to reach 166 by 2043. The structure is 25 ft (7.6 m) long and 32 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
Carries420th Ave.
CrossesMill Creek
Location082E61602
RouteCounty Highway 0
CountyClinton County
StateIowa
Coordinates41.91116, -90.27672
Functional classRural Local

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure8 Very GoodNo problems noted.
Substructure9 ExcellentNo problems noted.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionDecember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation8: Equal to present desirable criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating71.9 US tons
Inventory rating43.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete
DeckConcrete, precast panels
Main spans1
Design loadHS 20
Structure length25 ft (7.6 m)
Longest span22 ft (6.7 m)
Deck width32 ft (9.8 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic166 (2022)
Projected traffic166 by 2043
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.7 mi (6 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$122,000
NavigationNot applicable (no waterway)

Frequently asked questions

When was 420th Ave. over Mill Creek built?

It was built in 2021, making it 4 years old in 2025.

What condition is 420th Ave. over Mill Creek in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in December 2023.

How much traffic does 420th Ave. over Mill Creek carry?

About 166 vehicles per day (2022 count).

How long is 420th Ave. over Mill Creek?

The structure is 25 ft (7.6 m) long with a longest span of 22 ft (6.7 m) and a deck 32 ft wide.

Who owns 420th Ave. over Mill Creek?

It is owned by the County Highway Agency.