Verification of Design and Construction Techniques for Gaillard Island Dredged Material Disposal Area, Mobile, Alabama

摘要

A 1,700-acre, triangular-shaped dredged material island was constructed by both barge haul and hydraulic placement of the dredged material excavated from the Theodore Ship channel. Approximately 6 miles of perimeter dikes were constructed on very soft bay bottom soils at the northwest junction of the Mobile and Theodore ship channels. The dike area exposed above mean low water(m1w) was approximately 320 acres. In addition, an area exposed of about 350 acres inside the containment area was exposed at m1w. The new work dredging consisted of the removal of about 33.5 million cu yd of material. The material dredged was either hydraulically pumped or barged to the disposal area for use in constructing the dikes. The project consisted of dredging a deep draft ship channel about 5.2 miles long, 400 ft wide, and 40 ft deep linking the mobile Ship Channel with the Middle Fork Deer River shoreline at Theodore, Alabama. An inland ship channel about 1.9 miles long, 300 ft wide, and 40 ft deep was also dredged to join a 42-acre ship turning basin with a 6,500-ft-long barge channel. About 95 percent of the material dredged from the bay cut and about 52 percent of the material from the land cut was clay that readily formed clay balls. The remaining channel material was primarily sand with small amounts of shell and gravel.