US Bridges

US 51 SB (fap 710) over Lake Decatur

Fair

Macon County, Illinois · In Decatur · Structure no. 058004900000000

Built
1971
54 years old
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
476 ft
3 main spans
Daily traffic
22,400
2023 count
Owner
State
State Highway Agency

About this bridge

US 51 SB (fap 710) over Lake Decatur is a steel continuous stringer/multi-beam or girder carrying US 51 SB (fap 710) over Lake Decatur in Macon County, Illinois. It was built in 1971, so it is 54 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 22,400 vehicles a day, roughly 5% of them trucks, projected to reach 11,413 by 2046. The structure is 476 ft (145.2 m) long and 35 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesUS 51 SB (fap 710)
CrossesLake Decatur
LocationIn Decatur
RouteState Highway 105
CountyMacon County
StateIllinois
Coordinates39.82588, -88.95527
Functional classUrban Other Principal 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 protection8 Very GoodNo problems noted.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating62.5 US tons
Inventory rating37.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+2 approach)
Design loadHS 20
Structure length476 ft (145.2 m)
Longest span188 ft (57.3 m)
Deck width35 ft (10.7 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic22,400 (2023)
Projected traffic11,413 by 2046
Trucks5%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes

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 US 51 SB (fap 710) over Lake Decatur built?

It was built in 1971, making it 54 years old in 2025.

What condition is US 51 SB (fap 710) over Lake Decatur 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 2024.

How much traffic does US 51 SB (fap 710) over Lake Decatur carry?

About 22,400 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is US 51 SB (fap 710) over Lake Decatur?

The structure is 476 ft (145.2 m) long with a longest span of 188 ft (57.3 m) and a deck 35 ft wide.

Who owns US 51 SB (fap 710) over Lake Decatur?

It is owned by the State Highway Agency.