Airport fish ladder wins engineering award

Middleton, Wis. — Mead & Hunt and ESA Vigil-Agrimis accepted the Engineering Excellence Award for the Roseburg Airport Fish Ladder Project from American Council of Engineering Companies of Oregon. The award-winning project helped solve a safety issue while addressing environmental concerns for a local airport, the Roseburg Regional Airport. Mead & Hunt and ESA Vigil-Agrimis lead the project team that included Land Mark Surveying, Pinnacle Western and Wildish Construction Co.

The EEA is an annual design competition that recognizes engineering achievements that demonstrate the highest degree of merit and ingenuity. The competition spotlights outstanding work performed by Oregon and southwest Washington engineering and land surveying firms. A panel of judges selects the best engineering projects based on criteria such as original or innovative application of new or existing design techniques; social, economic and sustainable design considerations; and complexity.

The Roseburg Regional Airport faced the challenge of balancing the need to improve airfield safety while providing fish passage and maintaining floodplain function.

Newton Creek crosses under the airport through a 550-foot-long box culvert that drains to the South Umpqua River. Airfield safety requirements called for a taxiway relocation and box culvert extension. The culvert outlet dropped 4 feet vertically, which created a fish passage barrier. The extension required improvements to connect downstream to the upstream habitat areas.

Engineered enhancements included a pool and chute fishway, a roughened downstream channel, and structures interspersed within the culvert to simulate a natural streambed condition. Because the culvert extension was within a FEMA-designated mapped floodway, fish passage improvements were designed to maintain hydraulic capacity to convey flood flows without increasing flood stages. The design considered flow rates, velocities and storage. Although natural channels are often preferred for restoration and fish passage, permitting agencies favored this concrete step-pool structure because of peak scour flows and concerns for stability.

The team’s analysis enabled the city’s Certified Floodplain Manager to properly document that there was not an effective rise in the floodway or loss of storage or conveyance capacity that would increase flood risk to the airport or adjacent properties. Construction occurred during the summer 2013 in-water work period and now provides access to upstream habitat while maintaining suitable floodplain function.