477TH Avenue over Six Mile Ck

Brookings County, South Dakota · rated Good in the 2025 National Bridge Inventory

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

• 477TH Avenue over Six Mile Ck in Brookings County, South Dakota, is rated in good condition in the 2025 National Bridge Inventory (as of August 20, 2026).
• Its lowest-rated component is the deck, rated 7 (good condition) on the 0-9 scale.
• It was built in 1999, making it 26 years old at the 2025 inventory.
• It carries about 92 vehicles a day (traffic count year 2022).
• Its listed owner is the county highway agency.
• It is one of 64 of the 232 inventoried bridges in Brookings County rated good (27.6%); 53 (22.8%) are rated poor.
• Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
• Its condition class and component ratings are unchanged from the 2024 inventory.
• Its most recent inspection on record is dated September 2023, on a 24-month routine inspection cycle.
• A good rating means every major component - deck, superstructure, substructure, or culvert - is rated 7 or higher on FHWA's 0-9 scale: no more than minor problems.

View this bridge on a map → (44.43812, -96.66626)

Component ratings

Bridge details

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

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Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.