Structure 3700 · Polk County, IA
Carries Walnut ST over Des Moines River, 078240400.
Set by its lowest-rated component: Deck and Superstructure at 3 of 9.
How ratings work503 ft end to end, longest span 75 ft: about 7 semi-trucks nose to tail. Lengths and the semi-truck 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 deck arch.
| State | Iowa |
| County | Polk |
| Location | 078240400 |
| Carries | Walnut ST |
| Crosses | Des Moines River |
| Coordinates | 41.58724, -93.61828 |
| Material | Concrete Continuous |
| Design | Arch - Deck |
| Total Length | 503.0 ft (153.3 m) |
| Max Span | 75.1 ft (22.9 m) |
| Deck Width | 85.0 ft (25.9 m) |
| Deck Area | 3970.5 sq m |
| Main Spans | 6 |
| Year Built | 1911 (reconstructed 1966) |
| Avg Daily Traffic | 3,844 (2022) |
| Lanes On Bridge | 4 |
| Last Inspection | August 2023 |
| Inspection Frequency | Every 24 months |
| Owner | City/Municipal Highway Agency |
| Historical Significance | Bridge is possibly eligible (requires evaluation) |
| Scour Critical | 5 — Stable for scour |
| Structure Number | 000000000003700 |
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.