The Barrier incorporates a sealable cavity at the interlocking joint between piles that can be flushed clean, inspected, and then sealed after the piles have been driven into the ground. The system allows for documentable quality assurance and a high degree of quality control. Bulk wall hydraulic conductivities of 10-8 to 10-10 cm/sec have typically been achieved in testing conducted by the University, the Air Force, and others.