Structure D-15-BE · Boulder County, CO
Carries US 36 Ml over Supply Ditch, In Lyons.
A culvert 23 ft across with 2 openings. Lengths are drawn to scale; at this length a semi-truck would be a speck. Each part is colored by its latest inspection rating. The inventory records lengths but not heights, so those are drawn as typical for a culvert.
| State | Colorado |
| County | Boulder |
| Location | In Lyons |
| Carries | US 36 Ml |
| Crosses | Supply Ditch |
| Coordinates | 40.21913, -105.26108 |
| Material | Concrete |
| Design | Culvert |
| Total Length | 22.6 ft (6.9 m) |
| Max Span | 10.8 ft (3.3 m) |
| Deck Width | 91.2 ft (27.8 m) |
| Deck Area | 191.8 sq m |
| Main Spans | 2 |
| Year Built | 1972 |
| Avg Daily Traffic | 15,000 (2020) |
| Truck Traffic | 3% |
| Lanes On Bridge | 4 |
| Last Inspection | March 2025 |
| Inspection Frequency | Every 24 months |
| Owner | State Highway Agency |
| Historical Significance | Bridge is not eligible for the National Register |
| Scour Critical | 8 — Stable, low risk |
| Structure Number | D-15-BE |
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.