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
- Old 99W over Glenn Valley Slough Oflo in Colusa County, California, is rated in good condition in the 2025 National Bridge Inventory (as of ).
- 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.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated July 2023, on a 24-month routine inspection cycle.
- 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.
View this bridge on a map → (39.21065, -122.18246)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Culvert | 7 | 7 | Good condition |
Bridge details
| Structure | Continuous concrete culvert |
| Length | about 24 ft |
| Location | 1.9 Mi North of Haas Rd |
| NBI structure number | 15C0088 |
| Condition class | Good |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | July 2023 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 8: foundations stable, scour above the top of the footing |
Source: FHWA National Bridge Inventory, 2025 data as reported by the California department of transportation.
Busiest bridges in Colusa County
| 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 |
All bridges nearby: Colusa County, CA bridge conditions · every bridge in Colusa County · California bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.