December 25, 2013 — "Bubble curtains are designed to protect the fish in the area from the noise generated by the hammer impact below the water level," said Walter Reichert, project manager for Tappan Zee Constructors. "This divides the water into basically two sections. It greatly reduces the sound waves."
Tappan Zee Constructors is the consortium designing and building the $3.9 billion replacement crossing over the Hudson River. The state required the consortium to somehow reduce underwater noise generated by pile driving.
Sound, or pressure, waves produced by the hammering can be a threat to fish, damaging their hearing, harming organs and possibly even killing them, scientists say. The bubbles absorb some of the energy from the sound waves, and also are thought to persuade fish to swim away from the construction area.
"Pile driving is probably one of the most obvious problems with sounds and fishes," said Rodney Rountree, who studies how fish and sound interact and is an adjunct professor at the University of Massachusetts. "The air in the bubbles creates an acoustic barrier. A lot of the sound gets reflected back (and away from the surrounding water)."
Most pile driving takes place in environmentally sensitive areas — estuaries like the Hudson or marshes, he noted. Fish and other aquatic organisms depend on such places for food and shelter.
Bubble curtains were used in California for the new, $6.4 billion east span of the San Francisco-Oakland Bay Bridge, which opened in September.
Read the full story at USA Today