US Bridges

SR-143 over I-15 (SR-15) Nbl and Sbl

Fair

Iron County, Utah · So.Parowan Interchange · Structure no. 0C 537

Built
1973
52 years old
Condition
Fair
inspected March 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
291 ft
2 main spans
Daily traffic
4,347
2017 count
Owner
State
State Highway Agency

About this bridge

SR-143 over I-15 (SR-15) Nbl and Sbl is a steel continuous stringer/multi-beam or girder carrying SR-143 over I-15 (SR-15) Nbl and Sbl in Iron County, Utah. It was built in 1973, so it is 52 years old, older than the Utah average of 40.1 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 4,347 vehicles a day, roughly 19% of them trucks, projected to reach 5,216 by 2037. The structure is 291 ft (88.8 m) long and 34 ft wide. If it were closed, the detour would be 9.9 mi (16 km).

Location

Open in Google Maps
CarriesSR-143
CrossesI-15 (SR-15) Nbl and Sbl
LocationSo.Parowan Interchange
RouteState Highway 143
CountyIron County
StateUtah
Coordinates37.83906, -112.86886
Functional classRural 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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment6: Equal to present minimum criteria
Operating rating107.1 US tons
Inventory rating46.4 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20 + Mod
Structure length291 ft (88.8 m)
Longest span143 ft (43.6 m)
Deck width34 ft (10.4 m)
Roadway width31 ft (9.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,347 (2017)
Projected traffic5,216 by 2037
Trucks19%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway
Detour if closed9.9 mi (16 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 SR-143 over I-15 (SR-15) Nbl and Sbl built?

It was built in 1973, making it 52 years old in 2025.

What condition is SR-143 over I-15 (SR-15) Nbl and Sbl 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 2023.

How much traffic does SR-143 over I-15 (SR-15) Nbl and Sbl carry?

About 4,347 vehicles per day (2017 count), of which roughly 19% are trucks.

How long is SR-143 over I-15 (SR-15) Nbl and Sbl?

The structure is 291 ft (88.8 m) long with a longest span of 143 ft (43.6 m) and a deck 34 ft wide.

Who owns SR-143 over I-15 (SR-15) Nbl and Sbl?

It is owned by the State Highway Agency.