The Navy and the Natural Resources Defense Council (NRDC) have reached an out-of-court agreement on the issue of whale safety that will allow the Navy to use active sonar during a multinational exercise underway off Hawaii.

The Navy agreed to add whale spotters during sonar drills and to expand a buffer zone where it would not conduct the active sonar drills. In exchange, the NRDC withdrew its lawsuit. The compromise was ratified by a US judge in Los Angeles.

The Navy insisted that the active sonar exercises were needed to train sailors to detect stealthy submarines such as those in the naval forces of Iran, North Korea and China. But environmentalists say the sound waves produced by the sonar could injure or possibly kill whales and other marine mammals. Rear Adm. James Symonds, the Navy's director of environmental readiness, in announcing the settlement, said it was "critically important that we have been able to turn active sonar on" for the rest of the RIMPAC exercise, set to run through July 28.

Among other things, the settlement specifically:

* Prevents the Navy from using sonar within the newly established Northwestern Hawaiian Islands Marine National Monument or within a
25-nautical-mile sonar buffer zone around it

* Requires all Navy personnel listening through underwater detection
microphones to monitor for marine mammals and report the detection of any marine mammal to the appropriate watch station for action

* Requires aerial surveillance for marine mammals during sonar drills and reporting of sightings to a marine mammal response officer

* Requires the Navy to have at least one dedicated and three non-dedicated marine mammal observers on every surface sonar vessel during all sonar drills, and to add an additional dedicated marine mammal observer during the three exercises occurring in channels between the islands

* Requires the Navy to publicise in the local Hawaii press a hotline for reporting marine mammal incidents

During the last RIMPAC exercise in 2004, there was a mass stranding of more than 150 melon-headed whales in Kauai. A US government investigation concluded that the Navy's sonar use was the "plausible, if not likely" cause of the stranding.

The issue of sonar's impact on marine life has flared for several years as whales have beached in several areas around the globe after Navy ships have used active sonar. Whales exposed to high intensity mid-frequency sonar have repeatedly stranded themselves and died on beaches around the world (including in Hawaii, Washington State, North Carolina and the Bahamas), some bleeding around the brain and in the ears, with severe lesions in their organ tissue. At lower intensities, sonar can interfere with the ability of marine mammals to navigate, avoid predators, find food, care for their young, and, ultimately, to survive.

One of the best-documented incidents took place in the Bahamas, in 2000, when 16 whales of three species stranded along 150 miles of shoreline as ships blasted the area with sonar. The U.S. Navy later acknowledged in an official report that its use of sonar was the likely cause of the stranding.