US Bridges

Old HWY 21 over Rock CR

FairPosted for load

Jefferson County, Missouri · S 1974 T 43 N R 5 E · Structure no. 31217

Built
2006
19 years old
Condition
Fair
inspected February 2025
Type
Stringer/Multi-beam or Girder
Steel
Length
122 ft
1 main span
Daily traffic
5,438
2023 count
Owner
County
County Highway Agency

About this bridge

Old HWY 21 over Rock CR is a steel stringer/multi-beam or girder carrying Old HWY 21 over Rock CR in Jefferson County, Missouri. It was built in 2006, so it is 19 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. Its operating status is: posted for load restriction.

It carries about 5,438 vehicles a day, roughly 5% of them trucks, projected to reach 9,245 by 2043. The structure is 122 ft (37.2 m) long and 43 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

Open in Google Maps
CarriesOld HWY 21
CrossesRock CR
LocationS 1974 T 43 N R 5 E
RouteCounty Highway 39
CountyJefferson County
StateMissouri
Coordinates38.4267, -90.47428
Functional classUrban 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
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 inspectionFebruary 2025
Inspection intervalevery 24 months
Operating statusPosted for load 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 rating90.3 US tons
Inventory rating42.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length122 ft (37.2 m)
Longest span114 ft (34.7 m)
Deck width43 ft (13 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic5,438 (2023)
Projected traffic9,245 by 2043
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed5 mi (8 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 Old HWY 21 over Rock CR built?

It was built in 2006, making it 19 years old in 2025.

What condition is Old HWY 21 over Rock 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 Old HWY 21 over Rock CR carry?

About 5,438 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is Old HWY 21 over Rock CR?

The structure is 122 ft (37.2 m) long with a longest span of 114 ft (34.7 m) and a deck 43 ft wide.

Who owns Old HWY 21 over Rock CR?

It is owned by the County Highway Agency.