SR-21 over Tunnel Spring Mtns. Wash

Millard County, Utah · rated Good in the 2025 National Bridge Inventory

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

• SR-21 over Tunnel Spring Mtns. Wash in Millard County, Utah, is rated in good condition in the 2025 National Bridge Inventory (as of August 20, 2026).
• Its lowest-rated component is the culvert, rated 7 (good condition) on the 0-9 scale.
• It was built in 1975, making it 50 years old at the 2025 inventory.
• It carries about 231 vehicles a day (traffic count year 2021).
• Its listed owner is the state highway agency.
• It is one of 8 of the 72 inventoried bridges in Millard County rated good (11.1%); 2 (2.8%) are rated poor.
• 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 → (38.58897, -113.81773)

Component ratings

Bridge details

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

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