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S 431 over Greenfield Main Canal

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

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

S 431 over Greenfield Main Canal in Teton 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 5 (fair condition) on the 0-9 scale.
It was built in 1959, making it 66 years old at the 2025 inventory.
It carries about 285 vehicles a day (traffic count year 2023).
Its listed owner is the state highway agency.
It is one of 45 of the 82 inventoried bridges in Teton County rated fair (54.9%); 3 (3.7%) 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	Timber stringer or multi-beam girder
Length	about 59 ft
Location	8M NE Fairfield
NBI structure number	S00431004+08001
Condition class	Fair

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

Bridge	Built	Vehicles/day	Condition
I 15 over Sep 9TH Rd NE	1972	1,969	Good
I 15 over Sep 9TH Rd NE	1972	1,969	Good
US 89 over Greenfields South Canal	1983	1,798	Good
US 89 over Greenfields Main Canal	1983	1,798	Good
I 15 over Int Main St	1976	1,703	Fair
I 15 over Int Main St	1976	1,703	Fair