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Irr - I 90 over Bighorn River

Big Horn County, Montana · rated Good in the 2025 National Bridge Inventory

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

Irr - I 90 over Bighorn River in Big Horn County, Montana, 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 1971, making it 54 years old at the 2025 inventory.
It carries about 4,258 vehicles a day (traffic count year 2023).
Its listed owner is the state highway agency.
It is one of 38 of the 133 inventoried bridges in Big Horn County rated good (28.6%); 5 (3.8%) 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.

Component ratings


Structure	Continuous steel stringer or multi-beam girder
Length	about 593 ft
Location	Hardin
NBI structure number	I00090498+01011
Condition class	Good

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

Bridge	Built	Vehicles/day	Condition
I 90 over Irrigation Canal	1971	8,516	Fair
Irr-s 47 over Int W Hardin I 90	1970	5,396	Fair
Irr - I 90 over Int Dunmore	1959	4,473	Fair
Irr - I 90 over Int Dunmore	1959	4,473	Fair
Irr - I 90 over Bighorn River	1971	4,258	Fair
Irr - I 90 over Sarpy Road-s 384	1971	4,258	Fair