US Bridges

Duffy Road over Somonauk Creek

Fair

DeKalb County, Illinois · 1000N 1075E · Structure no. 019531800000000

Built
1983
42 years old
Condition
Fair
inspected April 2023
Type
Box Beam or Girders - Multiple
Prestressed Concrete
Length
59 ft
1 main span
Daily traffic
25
2021 count
Owner
Town / Township
Town or Township Highway Agency

About this bridge

Duffy Road over Somonauk Creek is a prestressed concrete box beam or girders - multiple carrying Duffy Road over Somonauk Creek in DeKalb County, Illinois. It was built in 1983, so it is 42 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 25 vehicles a day, projected to reach 28 by 2046. The structure is 59 ft (18 m) long and 28 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesDuffy Road
CrossesSomonauk Creek
Location1000N 1075E
RouteCounty Highway 0
CountyDeKalb County
StateIllinois
Coordinates41.77614, -88.73949
Functional classRural Local

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 protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionApril 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 geometry7: Better than present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating48.9 US tons
Inventory rating35.7 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialPrestressed Concrete
DeckConcrete, precast panels
Main spans1
Design loadHS 20
Structure length59 ft (18 m)
Longest span57 ft (17.4 m)
Deck width28 ft (8.5 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic25 (2021)
Projected traffic28 by 2046
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerTown or Township Highway Agency
Maintained byTown or Township 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 Duffy Road over Somonauk Creek built?

It was built in 1983, making it 42 years old in 2025.

What condition is Duffy Road over Somonauk 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 April 2023.

How much traffic does Duffy Road over Somonauk Creek carry?

About 25 vehicles per day (2021 count).

How long is Duffy Road over Somonauk Creek?

The structure is 59 ft (18 m) long with a longest span of 57 ft (17.4 m) and a deck 28 ft wide.

Who owns Duffy Road over Somonauk Creek?

It is owned by the Town or Township Highway Agency.