Integrated Site Investigation for Craney Island Eastward Expansion, Portsmouth, Virginia

The proposed 210-hectare Craney Island Eastward Expansion (and its subsequent development as a container terminal) in Portsmouth, Virginia is the largest port- development land reclamation ever proposed along the eastern U.S. coast. The shallow-water site is underlain by substantial (25- to 40-meter-thick) deposits of highly compressible, weak clay that is predicted to settle 7 to 10 meters under the weight of the land reclamation fill and terminal loads. Due to difficult site conditions and long-term design requirements for the project, the site investigation approach was not "business as usual." Rather, the 2007 investigation included the application of offshore-based geophysics, borings, in situ soundings and laboratory testing methods. Extensive exploration on the adjacent Craney Island Dredged Material Management Area supplemented the marine exploration. The integrated site investigation provided an understanding of the subsurface conditions and their engineering properties within a geological context, and an understanding of the affects of biogenic gas within the sediments. It also provided enhanced definition of the in situ strength and compressibility characteristics of the subsurface sediments.