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The project included earthwork, drainage, and erosion control for a new 10,000-foot parallel runway designed to CAT III standards with a full parallel taxiway. It included the design of four modified high-speed exit taxiways and a 6,000-foot connector taxiway.
The project site, like most of the Memphis area, is relatively flat, which made the drainage design for Runway 18-36 East particularly difficult. Further complicating the drainage design is the site’s light, silty soil, which is highly susceptible to erosion. For this runway project, storm water modeling was performed in addition to using the FAA required calculations. The additional analysis provided more refined data for retention basin design, as well as a higher level of confidence that paved surfaces would be protected during a 100-year storm event. The additional analysis also allowed for better sizing of major trunk lines, optimizing overall project costs, and maximizing the use of retention and sedimentation basins.
One unusual facet of this assignment was managing a difficult geotechnical issue located on the project site. On old ravine had filled with loess over time, leaving layers of loose compressible materials deep within the ravine. The firm hired by the airport to perform the geotechnical investigation and preliminary design recommended surcharging the ravine and installing wick drains to reduce the effects of settlement of the highly compressible fills.