US Bridges

Auburn ST over Rock River

Fair

Winnebago County, Illinois · 0.4 MI W of Ill 251 · Structure no. 101011500000000

Built
1938
87 years old, rebuilt 1986
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
642 ft
8 main spans
Daily traffic
22,600
2022 count
Owner
City
City or Municipal Highway Agency

About this bridge

Auburn ST over Rock River is a steel stringer/multi-beam or girder carrying Auburn ST over Rock River in Winnebago County, Illinois. It was built in 1938 and reconstructed in 1986, so it is 87 years old, older 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 22,600 vehicles a day, roughly 3% of them trucks, projected to reach 22,321 by 2046. The structure is 642 ft (195.7 m) long and 77 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

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CarriesAuburn ST
CrossesRock River
Location0.4 MI W of Ill 251
CountyWinnebago County
StateIllinois
Coordinates42.28869, -89.06548
Functional classUrban 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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 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 rating65 US tons
Inventory rating38.9 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans8
Design loadHS 20
Structure length642 ft (195.7 m)
Longest span81 ft (24.7 m)
Deck width77 ft (23.4 m)
Roadway width56 ft (17.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic22,600 (2022)
Projected traffic22,321 by 2046
Trucks3%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal 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 Auburn ST over Rock River built?

It was built in 1938, making it 87 years old in 2025. It was reconstructed in 1986.

What condition is Auburn ST over Rock 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 July 2023.

How much traffic does Auburn ST over Rock River carry?

About 22,600 vehicles per day (2022 count), of which roughly 3% are trucks.

How long is Auburn ST over Rock River?

The structure is 642 ft (195.7 m) long with a longest span of 81 ft (24.7 m) and a deck 77 ft wide.

Who owns Auburn ST over Rock River?

It is owned by the City or Municipal Highway Agency.