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Irr Bia Rte 73 over Rotten Grass Creek

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

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

Irr Bia Rte 73 over Rotten Grass Creek in Big Horn County, Montana, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the substructure, rated 6 (satisfactory condition) on the 0-9 scale.
It was built in 1980, making it 45 years old at the 2025 inventory.
It carries about 200 vehicles a day (traffic count year 2024).
It is one of 90 of the 133 inventoried bridges in Big Horn County rated fair (67.7%); 5 (3.8%) 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


Structure	Prestressed concrete stringer or multi-beam girder
Length	about 67 ft
Location	7.6 Km SE of St Xavier
NBI structure number	00000000000C217
Condition class	Fair

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	Good
Irr - I 90 over Bighorn River	1971	4,258	Fair