The Navy acknowledges that its proposed test and training plan for sonar and explosives in Hawaii and California waters might unintentionally cause more than 1,600 instances of hearing loss and other injuries to marine mammals yearly.

But, it says, the numbers can be reduced significantly with mitigative measures.

"These are worst-case numbers and very conservative mathematical models and do not take into account any of the mitigation measures," spokesman Mark Matsunaga said as the Navy prepares to hold public meetings on its latest draft environmental impact statement on its use of sonar.

Meetings are scheduled starting Tuesday on Kauai to allow the public to comment on the draft EIS for the proposed Hawaii-Southern California Training and Testing plan, which covers the north-central Pacific area where the Navy testing and training would take place through 2019.

The environmental group National Resources Defense Council says the Navy’s new plan fails to adequately identify and assess alternatives, including ways to reduce the effects of explosives and sonar on marine mammals.

But Navy officials say their approach is based on the best recommendations by researchers and that some risks are necessary to protect the U.S. at a time when more than 40 nations as well as drug traffickers and terrorists are developing submarine technology.

Matsunaga said the Navy has been training and testing in the ocean around Hawaii for decades.

"The fact is that sonar has not been linked to marine mammal deaths in Hawaii in the past and we don’t expect any in the future."

Matsunaga said the Navy will take a variety of measures to prevent harm to animals, including turning off sonar when a marine mammal is seen nearby.

Matsunaga said with help from the National Marine Fisheries Service, Navy personnel have been undergoing marine species awareness training and posting lookouts on ships to conduct surveillance before and during the use of sonar.

He said safety zones have been established to allow a reduction in sonar power in the event of a marine mammal sighting.

Zak Smith, a staff attorney with the National Resources Defense Council, said even in the best conditions, only a small percentage of marine mammals are spotted in the water because most are below the surface.

Smith said the Navy could minimize harm by identifying and avoiding areas dense with marine life — a move that would be the "most effective means of reducing harmful impacts from training and testing."

The Navy said some of the proposed training activities include testing with sonar, explosives and weapons, which it has been doing for decades, as well as new systems such as unmanned aerial and underwater vehicles.

The draft study estimates that without mitigation measures, explosives training and testing might result in the inadvertent death of 200 marine mammals a year. But that again is a worst-case scenario, Navy officials said.

The draft study estimated as many as two beaked whales a year could be subjected to sonar at levels that might cause permanent injury.

The Navy said it invests about $20 million each year on marine mammal research, including $5 million in the Hawaii-Southern California area.

It said its Hawaii monitoring program has been collecting information on marine mammals, including monk seals and humpback whales, during training events, and that scientific surveys have not shown any stranded or distressed animals.

Matsunaga said the Navy acknowledges that sonar could have been a factor in the 2001 stranding of beaked whales in the Bahamas.

"The Navy has changed its protective measures based on lessons learned in that incident," he said.

Matsunaga said research shows that most strandings of marine mammals appear to be caused by factors other than Navy sonar, including disease and other environmental factors.

A previous Navy analysis — covering 2009-2013 — estimated the service might unintentionally cause injury or death to about 100 marine mammals in Hawaii and California, although no deaths have been reported.

The Navy uses sonar to track enemy submarines, torpedoes, mines and other potential threats underwater. Sonar operators send pulses of sound through the ocean and then listen for echoes from objects hit by the sound waves.

Scientists say the sound may disrupt the feeding patterns of marine mammals. The sound may also startle some species of whales, causing them to surface rapidly.

While public meetings on the study in Hawaii begin this week, meetings will be held in Southern California beginning June 20.

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The Associated Press contributed to this report.