US Bridges

Mo 79 S over Is 70

Fair

St. Charles County, Missouri · S 731 T 47 N R 3 E · Structure no. 3511

Built
1985
40 years old
Condition
Fair
inspected September 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
272 ft
2 main spans
Daily traffic
17,228
2024 count
Owner
State
State Highway Agency

About this bridge

Mo 79 S over Is 70 is a steel continuous stringer/multi-beam or girder carrying Mo 79 S over Is 70 in St. Charles County, Missouri. It was built in 1985, so it is 40 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 17,228 vehicles a day, roughly 5% of them trucks, projected to reach 31,010 by 2044. The structure is 272 ft (82.9 m) long and 81 ft wide. If it were closed, the detour would be 8.7 mi (14 km).

Location

Open in Google Maps
CarriesMo 79 S
CrossesIs 70
LocationS 731 T 47 N R 3 E
RouteState Highway 79
CountySt. Charles County
StateMissouri
Coordinates38.80174, -90.65171
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating71.4 US tons
Inventory rating42.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20 + Mod
Structure length272 ft (82.9 m)
Longest span112 ft (34.2 m)
Deck width81 ft (24.8 m)
Roadway width79 ft (24 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic17,228 (2024)
Projected traffic31,010 by 2044
Trucks5%
Lanes on structure5
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway
Detour if closed8.7 mi (14 km)
TollOn a free road
National Highway SystemYes

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 Mo 79 S over Is 70 built?

It was built in 1985, making it 40 years old in 2025.

What condition is Mo 79 S over Is 70 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 September 2023.

How much traffic does Mo 79 S over Is 70 carry?

About 17,228 vehicles per day (2024 count), of which roughly 5% are trucks.

How long is Mo 79 S over Is 70?

The structure is 272 ft (82.9 m) long with a longest span of 112 ft (34.2 m) and a deck 81 ft wide.

Who owns Mo 79 S over Is 70?

It is owned by the State Highway Agency.