Northern Edge

The U.S.S. Shoup at the Port of Anchorage on June 24, 2015. The Navy destroyer has participated in Exercise Northern Edge in recent years.

The U.S. Navy is seeking public review for an environmental impact statement for its Northern Edge training exercise. The upcoming training exercise is likely to be held in 2021 in the Gulf of Alaska. 

The 2020 Draft Supplemental Environmental Impact Statement and Overseas Environmental Impact Statement, released Dec. 11, outlines the potential impacts that could occur while the Navy conducts its military readiness activities. 

The exercises are typically held every other year in conjunction with the U.S. Coast Guard, Army and Air Force with the goal of maintaining fleet readiness. They have been held in Kodiak in 2011, 2016 and 2019. 

Activities include air, surface and underwater warfare, with the use of missiles, sonar, guns and explosives. 

The exercise will be conducted in international waters 45 nautical miles east of Kodiak Island. The rectangular training area measures 42,146 square nautical miles. According to the impact statement document, the boundaries were developed to avoid Steller sea lion critical habitat. 

Since the release of the 2011 and 2016 environmental impact statements, the Navy has updated information and data in cooperation with the National Marine Fisheries Service.

The changes include marine species density estimates, new auditory effects criteria and the impacts of the activities on different species. The changes in science and data include new surveys, updated oceanographic data and recently published marine mammal behavioral response studies. 

The revised density estimates, acoustic impact criteria, and impact assessment methods are publicly available at the Gulf of Alaska EIS website under Supporting Technical Documents.

“The updates to the Navy’s behavioral response criteria reflect a better understanding of how some marine mammals react to sonar and other sound sources,” said Julianne Stanford, a spokesperson for the Navy.

“Incorporation of behavioral data obtained from recent studies of both wild and captive animals improves the ability to assess susceptibility to disturbance by different types of marine mammals.”

The Navy also noted that about 99.6% of the modeled exposures from the Northern Edge training included in the document would cause reactions and temporarily reduced hearing sensitivity for marine mammals. 

According to the document, the use of explosives, sonar, vessel noise, aircraft noise and weapon noise may affect salmon species — Chinook, coho, chum and sockeye — as well as green sturgeon listed on the endangered species list. 

Explosive detonations and non-impulsive sources such as sonar also have the potential to disturb or injure marine mammals. However, the Navy said in its impact statement that “there are very few injuries and no mortalities expected or predicted by the modeling.” 

The Navy maintains that the activities do not compromise productivity of fishes or impact their habitats, but added that exposure to explosions could result in temporary hearing loss in nearby fishes. Certain types of fishes may be more susceptible to temporary hearing loss, among other changes from sonar. 

The Navy also plans to use both passive and active sonar at mid-level frequencies.

According to Stanford, passive sonar is used to listen for objects underwater, such as submarines, while active sonar sends out an acoustic signal that bounces off underwater objects to determine their precise locations.  

“The Navy will continue to implement mitigation measures to avoid or reduce potential impacts on marine species during sonar training activities,” Stanford said. 

She noted that mitigation measures include the use of trained lookouts and additional sensor systems to determine the presence of marine mammals, and then powering down or shutting down sonar systems if animals are within a designated range from the event.

The environmental impact statement is available online, and public comment will be open through Feb. 16. The Navy will also hold virtual meetings on Jan. 19 and Feb. 3 to answer questions. The public can review the documents and comment by visiting the website

The original story misreported the date that the activities will be held. The activities are likely to be scheduled in 2021. 

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