US Bridges

Big Mound RD over I-39 & US 51

Good

Ogle County, Illinois · 1.5 MI S of Ill 72 · Structure no. 071005000000000

Built
1980
45 years old
Condition
Good
inspected November 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
256 ft
2 main spans
Daily traffic
225
2022 count
Owner
State
State Highway Agency

About this bridge

Big Mound RD over I-39 & US 51 is a steel continuous stringer/multi-beam or girder carrying Big Mound RD over I-39 & US 51 in Ogle County, Illinois. It was built in 1980, so it is 45 years old, younger than the Illinois average of 45.3 years.

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

It carries about 225 vehicles a day, roughly 32% of them trucks, projected to reach 156 by 2046. The structure is 256 ft (78.1 m) long and 30 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesBig Mound RD
CrossesI-39 & US 51
Location1.5 MI S of Ill 72
RouteCounty Highway 0
CountyOgle County
StateIllinois
Coordinates42.07885, -89.02237
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionNovember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating69.7 US tons
Inventory rating41.4 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans2 (+2 approach)
Design loadHS 20 + Mod
Structure length256 ft (78.1 m)
Longest span104 ft (31.7 m)
Deck width30 ft (9.1 m)
Roadway width27 ft (8.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic225 (2022)
Projected traffic156 by 2046
Trucks32%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway
Detour if closed6.8 mi (11 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—
NavigationNot applicable (no waterway)

Frequently asked questions

When was Big Mound RD over I-39 & US 51 built?

It was built in 1980, making it 45 years old in 2025.

What condition is Big Mound RD over I-39 & US 51 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 November 2023.

How much traffic does Big Mound RD over I-39 & US 51 carry?

About 225 vehicles per day (2022 count), of which roughly 32% are trucks.

How long is Big Mound RD over I-39 & US 51?

The structure is 256 ft (78.1 m) long with a longest span of 104 ft (31.7 m) and a deck 30 ft wide.

Who owns Big Mound RD over I-39 & US 51?

It is owned by the State Highway Agency.