US Bridges

IRR SD1806 over Oak Ck

Fair

Corson County, South Dakota · 5.7 N JCT US 12 · Structure no. 000000016720217

Built
1963
62 years old
Condition
Fair
inspected October 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
232 ft
3 main spans
Daily traffic
368
2024 count
Owner
State
State Highway Agency

About this bridge

IRR SD1806 over Oak Ck is a steel continuous stringer/multi-beam or girder carrying IRR SD1806 over Oak Ck in Corson County, South Dakota. It was built in 1963, so it is 62 years old, older than the South Dakota average of 48.9 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 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 368 vehicles a day, roughly 6% of them trucks, projected to reach 481 by 2044. The structure is 232 ft (70.7 m) long and 26 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

Open in Google Maps
CarriesIRR SD1806
CrossesOak Ck
Location5.7 N JCT US 12
RouteState Highway 1806
CountyCorson County
StateSouth Dakota
Coordinates45.63778, -100.52472
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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionOctober 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourCountermeasures installed to correct a previously existing problem
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating47 US tons
Inventory rating28.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length232 ft (70.7 m)
Longest span90 ft (27.4 m)
Deck width26 ft (8 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic368 (2024)
Projected traffic481 by 2044
Trucks6%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed5 mi (8 km)
TollOn a free road
National Highway SystemNo

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—
NavigationNo navigation control on waterway

Frequently asked questions

When was IRR SD1806 over Oak Ck built?

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

What condition is IRR SD1806 over Oak Ck 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 IRR SD1806 over Oak Ck carry?

About 368 vehicles per day (2024 count), of which roughly 6% are trucks.

How long is IRR SD1806 over Oak Ck?

The structure is 232 ft (70.7 m) long with a longest span of 90 ft (27.4 m) and a deck 26 ft wide.

Who owns IRR SD1806 over Oak Ck?

It is owned by the State Highway Agency.