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Old 99W over Glenn Valley Slough Oflo

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

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

Old 99W over Glenn Valley Slough Oflo 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 culvert, rated 7 (good condition) on the 0-9 scale.
It was built in 1914 and reconstructed in 1930, making it 111 years old at the 2025 inventory.
It carries about 1,298 vehicles a day (traffic count year 2014).
Its listed owner is the county highway agency.
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

Component	Rating (2025)	FHWA scale meaning
Culvert	7	Good condition


Structure	Continuous concrete culvert
Length	about 24 ft
Location	1.9 Mi North of Haas Rd
NBI structure number	15C0088
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