Structure D-15-B · Boulder County, CO
Carries US 36 Ml over Four Mile Canyon Creek, 28th ST In Boulder.
Set by its lowest-rated component: Deck and Superstructure and Substructure at 6 of 9.
How ratings work93 ft end to end, longest span 30 ft. Lengths and the car on the deck are drawn to the same scale. Each part is colored by its latest inspection rating. The inventory records lengths but not heights or the layout of the shorter spans, so those are drawn as typical for a tee-beam bridge.
| State | Colorado |
| County | Boulder |
| Location | 28th ST In Boulder |
| Carries | US 36 Ml |
| Crosses | Four Mile Canyon Creek |
| Coordinates | 40.04659, -105.25860 |
| Material | Concrete |
| Design | Tee Beam |
| Total Length | 92.8 ft (28.3 m) |
| Max Span | 29.9 ft (9.1 m) |
| Deck Width | 43.0 ft (13.1 m) |
| Deck Area | 370.7 sq m |
| Main Spans | 3 |
| Year Built | 1957 (reconstructed 2016) |
| Avg Daily Traffic | 16,000 (2020) |
| Truck Traffic | 2% |
| Lanes On Bridge | 2 |
| Last Inspection | August 2023 |
| Inspection Frequency | Every 24 months |
| Owner | State Highway Agency |
| Historical Significance | Bridge is not eligible for the National Register |
| Scour Critical | 3 — Scour critical |
| Structure Number | D-15-B |
Inspectors rate each major part of a bridge (the deck you drive on, the superstructure of beams that holds it up, and the substructure of piers and abutments beneath) on a 0–9 scale. A bridge's overall condition is its lowest of those ratings, so one deteriorated component makes the whole bridge "poor."
A poor rating is not a closure. It means the bridge is flagged for priority repair or replacement; bridges judged unsafe are closed or posted with weight limits. The waterway (channel) rating is reported, but it does not count toward the overall classification.