US Bridges

Mason RD S over Is 64

Fair

St. Louis County, Missouri · S 17 T 45 N R 5 E · Structure no. 3549

Built
1987
38 years old
Condition
Fair
inspected October 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
252 ft
2 main spans
Daily traffic
6,288
2024 count
Owner
State
State Highway Agency

About this bridge

Mason RD S over Is 64 is a steel continuous stringer/multi-beam or girder carrying Mason RD S over Is 64 in St. Louis County, Missouri. It was built in 1987, so it is 38 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 6,288 vehicles a day, roughly 1% of them trucks, projected to reach 9,432 by 2044. The structure is 252 ft (76.8 m) long and 85 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesMason RD S
CrossesIs 64
LocationS 17 T 45 N R 5 E
RouteCity Street 0
CountySt. Louis County
StateMissouri
Coordinates38.6386, -90.48082
Functional classUrban Collector

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 inspectionOctober 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating49.6 US tons
Inventory rating35.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length252 ft (76.8 m)
Longest span102 ft (31 m)
Deck width85 ft (25.8 m)
Roadway width78 ft (23.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,288 (2024)
Projected traffic9,432 by 2044
Trucks1%
Lanes on structure6
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesHighway
Detour if closed1.9 mi (3 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 Mason RD S over Is 64 built?

It was built in 1987, making it 38 years old in 2025.

What condition is Mason RD S over Is 64 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 October 2024.

How much traffic does Mason RD S over Is 64 carry?

About 6,288 vehicles per day (2024 count), of which roughly 1% are trucks.

How long is Mason RD S over Is 64?

The structure is 252 ft (76.8 m) long with a longest span of 102 ft (31 m) and a deck 85 ft wide.

Who owns Mason RD S over Is 64?

It is owned by the State Highway Agency.