US Bridges

ST Marys RD over Knob CR

Fair

Iron County, Missouri · S 32 T 34 N R 4 E · Structure no. 13451

Built
1988
37 years old
Condition
Fair
inspected February 2025
Type
Tee Beam
Prestressed Concrete
Length
81 ft
3 main spans
Daily traffic
750
2023 count
Owner
County
County Highway Agency

About this bridge

ST Marys RD over Knob CR is a prestressed concrete tee beam carrying ST Marys RD over Knob CR in Iron County, Missouri. It was built in 1988, so it is 37 years old, younger than the Missouri average of 45.1 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 750 vehicles a day, roughly 10% of them trucks, projected to reach 900 by 2043. The structure is 81 ft (24.7 m) long and 27 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

Open in Google Maps
CarriesST Marys RD
CrossesKnob CR
LocationS 32 T 34 N R 4 E
RouteCounty Highway 39
CountyIron County
StateMissouri
Coordinates37.6021, -90.6184
Functional classRural Local

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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionFebruary 2025
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourCountermeasures installed to correct a previously existing problem
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating54.6 US tons
Inventory rating35.7 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadOther
Structure length81 ft (24.7 m)
Longest span37 ft (11.3 m)
Deck width27 ft (8.1 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic750 (2023)
Projected traffic900 by 2043
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 km)
TollOn a free road
National Highway SystemNo

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 ST Marys RD over Knob CR built?

It was built in 1988, making it 37 years old in 2025.

What condition is ST Marys RD over Knob CR 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 February 2025.

How much traffic does ST Marys RD over Knob CR carry?

About 750 vehicles per day (2023 count), of which roughly 10% are trucks.

How long is ST Marys RD over Knob CR?

The structure is 81 ft (24.7 m) long with a longest span of 37 ft (11.3 m) and a deck 27 ft wide.

Who owns ST Marys RD over Knob CR?

It is owned by the County Highway Agency.