US Bridges

Csah 20 over Watonwan River

Fair

Blue Earth County, Minnesota · 1.4 MI N of JCT Csah 31 · Structure no. 07538

Built
1977
48 years old
Condition
Fair
inspected October 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
178 ft
3 main spans
Daily traffic
1,160
2021 count
Owner
County
County Highway Agency

About this bridge

Csah 20 over Watonwan River is a steel continuous stringer/multi-beam or girder carrying Csah 20 over Watonwan River in Blue Earth County, Minnesota. It was built in 1977, so it is 48 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 1,160 vehicles a day, projected to reach 1,000 by 2041. The structure is 178 ft (54.4 m) long and 48 ft wide. If it were closed, the detour would be 11.2 mi (18 km).

Location

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CarriesCsah 20
CrossesWatonwan River
Location1.4 MI N of JCT Csah 31
RouteCounty Highway 20
CountyBlue Earth County
StateMinnesota
Coordinates44.02558, -94.22934
Functional classRural Major 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.
Superstructure8 Very GoodNo problems noted.
Substructure8 Very GoodNo problems noted.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionOctober 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation7: Better than present minimum criteria
Deck geometry8: Equal to present desirable criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating53.2 US tons
Inventory rating31.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length178 ft (54.4 m)
Longest span68 ft (20.7 m)
Deck width48 ft (14.6 m)
Roadway width44 ft (13.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,160 (2021)
Projected traffic1,000 by 2041
Trucks—
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed11.2 mi (18 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 Csah 20 over Watonwan River built?

It was built in 1977, making it 48 years old in 2025.

What condition is Csah 20 over Watonwan 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 October 2023.

How much traffic does Csah 20 over Watonwan River carry?

About 1,160 vehicles per day (2021 count).

How long is Csah 20 over Watonwan River?

The structure is 178 ft (54.4 m) long with a longest span of 68 ft (20.7 m) and a deck 48 ft wide.

Who owns Csah 20 over Watonwan River?

It is owned by the County Highway Agency.