The Navy and opponents of high-volume, low-frequency active sonar remain at opposite poles on the impact of the submarine-detecting technology on marine mammals and other ocean life.

Joe Johnson, Navy program manager for the sonar environmental impact statement process, said the system has adequate safeguards for marine life, and that fleet commanders find it invaluable. He said a high-frequency marine mammal detection system alerts ship captains when the animals are within a mile or so of their vessels, so they can avoid using the sonar.

The Navy held the third of three national public hearings on its supplemental EIS for the system Monday night at the University of Hawai'i. The new study is aimed at establishing a National Marine Fisheries Service rule allowing its use aboard four ships. The Navy's original request for multiocean use of the technology was blocked in federal court, following a lawsuit by the Natural Resources Defense Council. The only two operational SURTASS LFA ships are based in Japan.

The system has two parts: a loudspeaker and a microphone. The speaker is the Low Frequency Active or LFA sonar emitter, which is suspended under a vessel. The microphone is called a Surveillance Towed Array Sensor System, or SURTASS, which is towed by the vessel. The LFA speaker emits a big noise, which bounces off a distant enemy submarine, and the echo is caught on the SURTASS.

With SURTASS, enemy subs can show up on detection equipment even if they're more than 100 miles away, Johnson said. The actual operational range of the system is classified, he said.

"The fleet commanders not only like SURTASS, they love it," Johnson said.

At Monday's hearing, several speakers said they felt that nothing they could say would affect the outcome of the Navy's environmental study.

Big Island attorney Lanny Sinkin, who was at the hearing and has filed lawsuits against high-power sonar systems, said he doubts the Navy is approaching the environmental impact process fairly.

"We have no confidence in the work that they are doing. This technology can do harm in numerous ways to marine life, everything from annoy them (marine mammals) to kill them, depending on the level of exposure," Sinkin told The Advertiser yesterday.

Also testifying was Kat Brady, assistant executive director of Life of the Land. She said the Navy has invested too much in the sonar system to abandon it, regardless of its impacts on marine life. She said there have been incidents of whales beaching themselves while sonar tests were conducted.

Johnson said opponents often cited cases that involved other kinds of Navy sonar, or were presenting anecdotal evidence that was not scientifically useful.

The Green Party's Ira Rohter, who attended the hearing, said yesterday that he thinks the outcome of the EIS process is pre-determined. "According to them, this has no impact, but they ignored things that didn't suit their selected outcome," he said.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.