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Auto Tour Route over Powell Slough

Colusa County, California · rated Good in the 2025 National Bridge Inventory

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

Auto Tour Route over Powell Slough in Colusa County, California, 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 1991 and reconstructed in 2008, making it 34 years old at the 2025 inventory.
It carries about 25 vehicles a day (traffic count year 2022).
It is one of 101 of the 213 inventoried bridges in Colusa County rated good (47.4%); 12 (5.6%) 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	Prestressed concrete multiple box beam
Length	about 64 ft
Location	W .2 Mi on Refuge Road
NBI structure number	000011621-00055
Condition class	Good

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

Bridge	Built	Vehicles/day	Condition
Interstate 5 over Hillgate Road	1957	35,000	Good
Interstate 5 over Brush Creek	1967	35,000	Good
Interstate 5 over Cortina Creek Overflow	1946	33,000	Good
Interstate 5 over Farm Land Drain	1968	30,000	Fair
Interstate 5 over South Branch Sand Creek	1967	29,500	Good
Interstate 5 over Petroleum Creek	1967	18,000	Fair