Csah 21 over Rock River

Fair

Rock County, Minnesota · 0.3 MI W of JCT Csah 2 · Structure no. 67510

Built: 1979; 46 years old
Condition: Fair; inspected October 2023
Type: Slab; Wood or Timber
Length: 178 ft; 6 main spans
Daily traffic: 44; 2022 count
Owner: County; County Highway Agency

About this bridge

Csah 21 over Rock River is a wood or timber slab carrying Csah 21 over Rock River in Rock County, Minnesota. It was built in 1979, so it is 46 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 44 vehicles a day, projected to reach 40 by 2042. The structure is 178 ft (54.4 m) long and 34 ft wide. If it were closed, the detour would be 9.9 mi (16 km).

Location

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CarriesCsah 21

CrossesRock River

Location0.3 MI W of JCT Csah 2

RouteCounty Highway 21

CountyRock County

StateMinnesota

Coordinates43.80466, -96.12111

Functional classRural Local

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

Component	Rating	Meaning
Deck	6 Satisfactory	Structural elements show some minor deterioration.
Superstructure	6 Satisfactory	Structural elements show some minor deterioration.
Substructure	7 Good	Some minor problems.
Channel and channel protection	7 Good	Some minor problems.

Last inspectionOctober 2023

Inspection intervalevery 24 months

Operating statusOpen, no restriction

ScourFoundations stable; scour above top of footing

Structural evaluation6: Equal to present minimum criteria

Deck geometry8: Equal to present desirable criteria

Waterway adequacy6: Equal to present minimum criteria

Approach roadway alignment8: Equal to present desirable criteria

Operating rating59 US tons

Inventory rating41.4 US tons

Structure

Structure typeSlab

MaterialWood or Timber

DeckWood or timber

Main spans6

Design loadHS 20

Structure length178 ft (54.4 m)

Longest span32 ft (9.7 m)

Deck width34 ft (10.4 m)

Roadway width32 ft (9.8 m)

Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic44 (2022)

Projected traffic40 by 2042

Trucks—

Lanes on structure2

Traffic directionTwo-way traffic

CarriesHighway

CrossesWaterway

Detour if closed9.9 mi (16 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 21 over Rock River built?

It was built in 1979, making it 46 years old in 2025.

What condition is Csah 21 over Rock 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 21 over Rock River carry?

About 44 vehicles per day (2022 count).

How long is Csah 21 over Rock River?

The structure is 178 ft (54.4 m) long with a longest span of 32 ft (9.7 m) and a deck 34 ft wide.

Who owns Csah 21 over Rock River?

It is owned by the County Highway Agency.