US Bridges

Il 78 over Coon Creek

Fair

Whiteside County, Illinois · 2 MI S Prophetstown · Structure no. 098010300000000

Built
1996
29 years old
Condition
Fair
inspected September 2022
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
55 ft
1 main span
Daily traffic
1,050
2023 count
Owner
State
State Highway Agency

About this bridge

Il 78 over Coon Creek is a prestressed concrete stringer/multi-beam or girder carrying Il 78 over Coon Creek in Whiteside County, Illinois. It was built in 1996, so it is 29 years old, younger than the Illinois average of 45.3 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 1,050 vehicles a day, roughly 15% of them trucks, projected to reach 1,162 by 2046. The structure is 55 ft (16.9 m) long and 35 ft wide. If it were closed, the detour would be 28 mi (45 km).

Location

Open in Google Maps
CarriesIl 78
CrossesCoon Creek
Location2 MI S Prophetstown
RouteState Highway 78
CountyWhiteside County
StateIllinois
Coordinates41.63672, -89.93994
Functional classRural Minor 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.
Superstructure8 Very GoodNo problems noted.
Substructure8 Very GoodNo problems noted.
Channel and channel protection9 ExcellentNo problems noted.
Last inspectionSeptember 2022
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation8: Equal to present desirable 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 rating73.2 US tons
Inventory rating45.3 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20 + Mod
Structure length55 ft (16.9 m)
Longest span53 ft (16.2 m)
Deck width35 ft (10.7 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,050 (2023)
Projected traffic1,162 by 2046
Trucks15%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed28 mi (45 km)
TollOn a free road
National Highway SystemNo

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 Il 78 over Coon Creek built?

It was built in 1996, making it 29 years old in 2025.

What condition is Il 78 over Coon Creek 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 September 2022.

How much traffic does Il 78 over Coon Creek carry?

About 1,050 vehicles per day (2023 count), of which roughly 15% are trucks.

How long is Il 78 over Coon Creek?

The structure is 55 ft (16.9 m) long with a longest span of 53 ft (16.2 m) and a deck 35 ft wide.

Who owns Il 78 over Coon Creek?

It is owned by the State Highway Agency.