US Bridges

Csah 4 over Big Cobb River

PoorPosted for load

Blue Earth County, Minnesota · 0.1 MI N of JCT CR 164 · Structure no. 07509

Built
1963
62 years old
Condition
Poor
inspected October 2024
Type
Channel Beam
Prestressed Concrete
Length
94 ft
3 main spans
Daily traffic
253
2021 count
Owner
County
County Highway Agency

About this bridge

Csah 4 over Big Cobb River is a prestressed concrete channel beam carrying Csah 4 over Big Cobb 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 poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. Its operating status is: posted for load restriction.

It carries about 253 vehicles a day, projected to reach 205 by 2041. The structure is 94 ft (28.6 m) long and 32 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesCsah 4
CrossesBig Cobb River
Location0.1 MI N of JCT CR 164
RouteCounty Highway 4
CountyBlue Earth County
StateMinnesota
Coordinates43.96709, -93.91836
Functional classRural Minor Collector

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionOctober 2024
Inspection intervalevery 12 months
Operating statusPosted for load restriction
ScourFoundations stable; action required to protect exposed foundations
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating30.3 US tons
Inventory rating20.4 US tons

Structure

Structure typeChannel Beam
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadH 20
Structure length94 ft (28.6 m)
Longest span31 ft (9.5 m)
Deck width32 ft (9.8 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic253 (2021)
Projected traffic205 by 2041
Trucks—
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.1 mi (5 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 4 over Big Cobb River built?

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

What condition is Csah 4 over Big Cobb River in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in October 2024.

How much traffic does Csah 4 over Big Cobb River carry?

About 253 vehicles per day (2021 count).

How long is Csah 4 over Big Cobb River?

The structure is 94 ft (28.6 m) long with a longest span of 31 ft (9.5 m) and a deck 32 ft wide.

Who owns Csah 4 over Big Cobb River?

It is owned by the County Highway Agency.