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Irr US018 over Trib to Oak Ck

Todd County, South Dakota · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

Irr US018 over Trib to Oak Ck in Todd County, South Dakota, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the culvert, rated 6 (satisfactory condition) on the 0-9 scale.
It was built in 2005, making it 20 years old at the 2025 inventory.
It carries about 1,303 vehicles a day (traffic count year 2024).
Its listed owner is the state highway agency.
It is one of 8 of the 27 inventoried bridges in Todd County rated fair (29.6%); 7 (25.9%) are rated poor.
A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

Component ratings

Component	Rating (2025)	FHWA scale meaning
Culvert	6	Satisfactory condition


Structure	Continuous concrete culvert
Length	about 23 ft
Location	9.4 W Tripp Co Line
NBI structure number	000000061431020
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the South Dakota department of transportation.

Bridge	Built	Vehicles/day	Condition
Irr US083 over Antelope Ck	1981	2,544	Fair
Irr Bia Rte 7 over Little White River	1972	1,851	Poor
Main Street over Antelope Ck	1978	1,400	Fair
Irr US018 over Little White Rv	1989	1,340	Fair
Irr US018 over White Horse Ck	2016	1,303	Fair
Irr Bia Rte 5 over Little White River	2016	1,096	Good