Service Life of Craney Island Dredged Material Management Area Under Proposed Restricted Use Program

This study investigates the service life of the Craney Island Dredged Material Management Area (CIDMMA) under the proposed Restricted Use Program. The Restricted Use Program involves ocean dumping of suitable material and the other material being placed in the CIDMMA. The projected filling rates of the CIDMMA under the Restricted Use Program were estimated using a mathematical model that considers both consolidation and desiccation of the dredged material. Mathematical model simulations of past filling history between 1956 and 1992 show excellent agreement with field data. This simulation served to calibrate the model and input parameters for future projection of fill rates under the proposed Restricted Use Program. Based on projections of fill rates under the Restricted Use Program, the service life of the CIDMMA will be extended significantly by reducing the quantity of dredged material placed in the CIDMMA. It is estimated that the CIDMMA will reach capacity near the year 2130 under the Baseline Maintenance Dredging Case and around the year 2080 under the Worst Case Dredging Scenario. These service life estimates are for planning level purposes and should only be used to determine if the proposed Restricted Use Program deserves further consideration. Implementation of the Restricted Use Program will require a substantial amount of suitable material to be ocean dumped. Since ocean dumping is significantly more expensive than confmed disposal, it is recommended that the life of the CIDMMA be extended. One technique being investigated to extend the service life is the installation of vertical strip drains. Strip drains will accelerate consolidation of the dredged fill and foundation clay at the CIDMMA. Consolidation of these materials will result in substantial settlement and increase in storage capacity.