How do you blast bedrock for an underwater tunnel alignment without injuring or killing nearby fish? You use an electronic fish-startle system to rouse them into leaving the blast area, as Central Artery/Tunnel Project contractors did when they began constructing the alignment of the I-90 Ted Williams Tunnel across Boston's Inner Harbor. Minutes before each blast, they lowered transducers into the water at the blast site and used generators and amplifiers to send high frequency signals into the water through the transducers. The system temporarily rerouted 96% of the blast area's blueback herring and other migrating fish species. The fish stayed out of harm's way, returning to the area 20 minutes after the blasting was completed.
--Apr 25, 2003
|U.S. Fish and Wildlife Service photo|