On April 29 2011, Houston-based Griffin Dewatering Corp. began pumping 15 million gallons of water from the site. It also used 42 10-in.-dia, 75-ft-deep wells outside the dam perimeter to lower the groundwater table and relieve external hydraulic pressure.
Griffin is working on several Corps projects in New Orleans, but Michael Lippard, Griffin senior project manager, says Seabrook is 'extraordinary' because of the depth of the wells, the size of the cofferdam, the amount of water moved, and the dewatering of a backfilled, vibrocompacted area. “Normally, when we are dewatering, it's virgin ground,” Lippard says. “The soils in here are more permeable than natural soils.”
Once the excavation is dry and ready, the next step will be a six-week, around-the-clock operation to drive foundation piles for the permanent complex. We're driving 414 74- to 86-ft-long, 32-in.-dia pipe piles through consolidated sand on 7-ft centers.