before. >> volume of water was so fast. the spillway itself had some structural issues and it undermined and ripped out the bottom half of the spillway. if >> if the loose soil erodes that the bottom of the dam, it could cause catastrophic flooding below. u.s. marines are working with navy pilots to ch-53 naval helicopters. >> it's a pretty cool experienc experience. glad to be out here to help. >> in the end, it's not a sophisticated solution. they are turning those into a big pile of rocks. but the problem is so big, they've got more than 200 areas in the pile and it's not enough. they need to keep adding to the pile before it rains again. >> this continues to erode back, these concrete pieces you will see behind us will fall away. and it could lead to failure of the dam behind there. >> remote towns in the island are still unreachable by truck. tactical helicopter unit of the fbi's only hostage rescue team