US Bridges

FAU 9175 over Rock Spring Branch

Fair

St. Clair County, Illinois · 0.5M N US 50 · Structure no. 082300700000000

Built
1972
53 years old
Condition
Fair
inspected March 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
143 ft
3 main spans
Daily traffic
11,400
2023 count
Owner
County
County Highway Agency

About this bridge

FAU 9175 over Rock Spring Branch is a steel continuous stringer/multi-beam or girder carrying FAU 9175 over Rock Spring Branch in St. Clair County, Illinois. It was built in 1972, so it is 53 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 11,400 vehicles a day, roughly 8% of them trucks, projected to reach 11,110 by 2046. The structure is 143 ft (43.5 m) long and 46 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

Open in Google Maps
CarriesFAU 9175
CrossesRock Spring Branch
Location0.5M N US 50
CountySt. Clair County
StateIllinois
Coordinates38.58853, -89.87408
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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating61.4 US tons
Inventory rating36.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length143 ft (43.5 m)
Longest span51 ft (15.5 m)
Deck width46 ft (14 m)
Roadway width43 ft (13 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11,400 (2023)
Projected traffic11,110 by 2046
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty 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 FAU 9175 over Rock Spring Branch built?

It was built in 1972, making it 53 years old in 2025.

What condition is FAU 9175 over Rock Spring Branch 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 March 2024.

How much traffic does FAU 9175 over Rock Spring Branch carry?

About 11,400 vehicles per day (2023 count), of which roughly 8% are trucks.

How long is FAU 9175 over Rock Spring Branch?

The structure is 143 ft (43.5 m) long with a longest span of 51 ft (15.5 m) and a deck 46 ft wide.

Who owns FAU 9175 over Rock Spring Branch?

It is owned by the County Highway Agency.