PROJECT DESIGN ENGINEER(S) & CONSTRUCTION MANAGEMENT:
Gottlieb, Barnett and Bridges, LLC
3600 Springhill Business Park, Suite 200
Mobile, AL 36608
David Volkert & Associates, Inc.
3809 Moffett Road
Mobile, Alabama 36670
Synergy Earth Systems, LLC
26240 Equity Drive
Daphne, AL 36526
Geotechnical Engineering Testing, Inc.
904 Butler Drive
Mobile, AL 36693
The Choctaw Point Terminal project is an expansion of the Alabama State Port Authority dock facilities in Mobile, Alabama. The project includes the development of a 120-acre two-berth deep-water container terminal at Choctaw Point and an 80-acre intermodal container transfer facility at Garrows Bend. The first phase of the expansion is the container terminal with construction of approximately 2000 feet of bulkhead construction and approximately 1000 feet of pile supported dock structure that includes all utility and interface requirements for future crane and container yard operation. This phase also includes the land reclamation and site stabilization of the 120 acres behind the bulkhead.
The Alabama State Port Authority retained the services of Gottlieb, Barnett and Bridges, LLC of Mobile to design the Stage 1 Wharf Structure. Volkert and Associates, Inc., also of Mobile, was retained to design the Land Reclamation and Site Stabilization portion of the Project. Both firms contracted with Synergy Earth Systems to provide the designs related to the soil modification and soil reinforcement that were required to overcome the difficult soil conditions that are present at the site.
The bulkhead alignment encapsulates about 30 acres of waterfront adjacent to the Mobile River waterfront. Water depths along the bulkhead range from 15 feet to 25 feet. This area is underlain with a layer of highly compressible, very soft marine clay that has an insitu shear strength range of 65 to 125 psf. This layer varied from about 17 feet to 33 feet in thickness. Settlement is estimated to range from 2 feet to as much as 10 feet across the site under final grade loading. The layer of soft soil created excessive bulkhead loadings and the initial concept included the dredge removal of this layer and cofferdam construction to develop the dock structure.
Synergy Earth Systems and Gottlieb, Barnett and Bridges developed an innovative concept to utilize wick drains, stone columns and a prism of lightweight fill reinforced with geosynthetics to significantly improve the insitu soil properties and allow the construction of the bulkhead and pile supported dock at a significant savings to the Alabama State Port Authority. The final design employed this concept in a 40-foot zone immediately behind the bulkhead. Wick drains and surcharging techniques were used to mitigate the settlement from the soft compressible soils behind the 40-foot zone.
The total cost of the Stage 1 Wharf Structure and the Land Reclamation and Site Stabilization is estimated to be approximately $43 million and the soil modification – soil reinforcement items are estimated at approximately $5 million. Bids will be received in March and construction of the facility is scheduled to begin in April and completed in 2007.