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Auto Tour Route over Main Drain

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

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

Auto Tour Route over Main Drain in Colusa County, California, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the superstructure, rated 5 (fair condition) on the 0-9 scale.
It was built in 1976, making it 49 years old at the 2025 inventory.
It carries about 25 vehicles a day (traffic count year 2024).
It is one of 100 of the 213 inventoried bridges in Colusa County rated fair (46.9%); 12 (5.6%) 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 tee beam
Length	about 143 ft
Location	W .8 Mi on Refuge Road
NBI structure number	000011621-00159
Condition class	Fair

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