In 2001, a liquefied natural gas (LNG) terminal and ship off-loading facility was re-commissioned in Savannah Harbor, Georgia. A turning basin and ship slip were constructed in support of off-loading LNG. The turning basin and ship slip are maintained through periodic dredging events. Long-term management of the sediments dredged from these areas is critical to the continued operation of the LNG facility. The dredged material is disposed in two on-site confined disposal facilities (CDFs) which are referred to as dredged material containment areas (DMCAs) 1 and 2. The DMCAs have a total footprint of approximately 101 hectares (250 acres), separated by an interior dike, and were specifically designed and constructed to support the facility's operations. The perimeter dikes of the DMCAs were initially constructed to elevation 11.6 meters [m] (38 feet [ft]), Mean Low Water (MLW).
The results of modeling, using a software program developed by the U.S. Army Corps of Engineers (USACE), indicated that the storage capacity of the two DMCAs would be exhausted by approximately 2027, assuming the perimeter dikes are raised in 1.8-m (6-ft) increments to a maximum elevation of 18.9 m (62 ft), MLW. The facility was therefore faced with the challenges of being able to dredge any time of the year as well as having a long-term disposal volume available in the DMCAs in order to meet its contractual obligations.
To address the long-term management problems, the authors developed a comprehensive approach to evaluate dredging and disposal options for the facility in 2010. One of the disposal options consisted of intensive management of the dredged material within the DMCAs to maximize storage capacity. This option has been implemented in DMCA 2 while DMCA 1 is used for disposal since 2011. Geotechnical parameters, especially void ratio and specific gravity, of the sediments and dredged material were estimated from laboratory tests to help support the approach presented herein.
This paper presents the results of more than four years of intensive management of dredged material to increase the disposal life of the DMCAs for the LNG facility in Savannah Harbor, Georgia.