Citing evidence that sonar can disorient and harm marine mammals, conservation groups filed a lawsuit on Wednesday to block the Navy from using sonar in a military exercise off Hawaii.
The Navy received a federal permit on Tuesday, the first such permission granted by the National Oceanic and Atmospheric Administration.
The monthlong exercise, which includes anti-submarine training, involves naval forces from eight nations. It began Monday off the Hawaiian Islands. The sonar part of the exercise begins after July 4 and lasts three weeks.
NOAA gave the Navy a permit to use mid-frequency active sonar, which can affect marine mammals’ behavior. In documents released Tuesday, NOAA determined that the exercise would cause no significant environmental impact.
NOAA also concluded that the Navy’s use of the sonar was not likely to jeopardize the continued existence of threatened and endangered species — including the Hawaiian monk seal — in the exercise areas.
“The Navy and NOAA have worked hard these past several months to take the appropriate measures necessary to avoid harming marine life while also ensuring the realism of this vital multinational exercise,” said Navy Rear Adm. James Symonds, director of naval environmental programs.
But the Natural Resources Defense Council, one of the groups that sued, said using the sonar would be illegal, and runs counter to President Bush's designation earlier this month of a national monument around the Northwestern Hawaiian Islands.
“It is absurd to designate an area a marine national monument one week, and then authorize the Navy to blast it with high-intensity sonar the next,” said Joel Reynolds, a senior attorney at NRDC.
But the Navy said the ships using the sonar would not be inside the national monument area. Instead, according to the Navy, the sonar would be used in waters surrounding the main Hawaiian Islands.
Navy spokesman Lt. Ryan Perry said the exercise is critical to national security, and specific steps will be taken to avoid or minimize any effect on marine life.
The exercise is designed to train sailors to detect and hunt stealthy submarines — a top priority of the U.S. Pacific Fleet. Hawaiian waters provide the opportunity to realistically train for a variety of crises, Perry said.
Perry said the sonar operators will reduce active sonar power by 75 percent if a marine mammal is spotted within 1,094 yards of the ship, and drop it further if mammals are detected within 547 yards. They will turn off the sonar if the mammal is detected within 219 yards.
Earlier this year, NOAA said the sonar used during the Pacific Rim exercise in 2004 may have contributed to the mass stranding of more than 150 melon-headed whales in Hanalei Bay, Kauai. NOAA’s study concluded the whales — which usually inhabit only deep water — may have heard the signals and headed into the shallow water.
While there was no conclusive finding, NOAA asked the Navy to reduce its sonar’s power during this summer’s exercises, and also asked the Navy to turn off active sonar when the whales come within a set distance.