US Bridges

Csah 18 over Maple River

Fair

Blue Earth County, Minnesota · 0.4 MI E of JCT Csah 1 · Structure no. 07507

Built
1963
62 years old
Condition
Fair
inspected November 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
136 ft
3 main spans
Daily traffic
328
2021 count
Owner
County
County Highway Agency

About this bridge

Csah 18 over Maple River is a steel continuous stringer/multi-beam or girder carrying Csah 18 over Maple River in Blue Earth County, Minnesota. It was built in 1963, so it is 62 years old, older than the Minnesota average of 38.5 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 328 vehicles a day, projected to reach 305 by 2041. The structure is 136 ft (41.5 m) long and 30 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesCsah 18
CrossesMaple River
Location0.4 MI E of JCT Csah 1
RouteCounty Highway 18
CountyBlue Earth County
StateMinnesota
Coordinates43.93497, -94.07076
Functional classRural Minor 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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionNovember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating46.4 US tons
Inventory rating27.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadH 20
Structure length136 ft (41.5 m)
Longest span50 ft (15.3 m)
Deck width30 ft (9.1 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic328 (2021)
Projected traffic305 by 2041
Trucks—
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.8 mi (11 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$243 million
NavigationNo navigation control on waterway

Frequently asked questions

When was Csah 18 over Maple River built?

It was built in 1963, making it 62 years old in 2025.

What condition is Csah 18 over Maple River 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 November 2024.

How much traffic does Csah 18 over Maple River carry?

About 328 vehicles per day (2021 count).

How long is Csah 18 over Maple River?

The structure is 136 ft (41.5 m) long with a longest span of 50 ft (15.3 m) and a deck 30 ft wide.

Who owns Csah 18 over Maple River?

It is owned by the County Highway Agency.