Stabilization of Dredge Spoil Basin and Filled Marsh for Container Terminal Development at the Former Charleston Naval Base

The Charleston Naval Base Container Terminal is planned for a 2007 construction groundbreaking. The 113-hectare site is primarily an inactive dredge spoil basin and filled tidal marsh. Soft soil thicknesses in the dredge spoil basin average 13.7 m and local maxima exceed 21 m. Since the container terminal site elevation must be raised by an average of about 3 m, the primary site stabilization challenges are large settlements and control of post-construction settlement. This paper presents the site characterization using cone penetration testing supplemented with soil test borings and also presents site stabilization evaluations. Site stabilization evaluation focuses on the use of prefabricated vertical drains with soil surcharge to control post-construction settlement from the anticipated pavement loadings. Predicted total settlements of up to 2.5 m result from raising the site grades and placing up to a 150% soil surcharge. This paper provides an overview of successful exploration techniques for these difficult sites and design considerations for post construction settlement control.