The Sky Harbor Airport Runway in Duluth, Minnesota, is in the process of being realigned to increase safety with the runway approach. In 2007, the Duluth Airport Authority identified several obstructions to the Runway 32 approach surface. As a result, the Authority completed a multi-year federal Environmental Assessment and a state Environmental Assessment Worksheet to evaluate alternative solutions with respect to the runway approach. The obstructions consisted of old growth trees, the majority of which were located within a scientific and natural area (SNA) protected by the Minnesota Department of Natural Resources. The selected solution consisted of shortening the runway from 3,050 feet to 2,600 feet and rotating it 5 degrees into Superior Bay. The geotechnical design of the runway considered slope stability and settlement of the embankment fill. Staged preloading of the site was completed using surcharge fill with a geotextile reinforcement base layer to improve stability of the fill. In addition to monitoring settlement with settlement gauges, drone surveys were completed of the surcharge fill embankment. Underwater surveys, using a multi-beam echo-sounder (MBES) to provide depth measurements, detailed surface model, and point cloud, were completed to verify the riprap embankment protection dimensions placed in Superior Bay. This case study presents the geotechnical investigation and design of the runway relocation along with results of construction monitoring of fill placement and settlement.
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