Proposed at-sea training and testing activities are similar to those that have been occurring in the Study Area for decades

At Sea Training and Testing

The Proposed Action is to continue training and testing activities within the Study Area at sea and on Farallon de Medinilla (FDM). These activities include the use of active sonar and explosives while employing mitigation measures.

The purpose of the Proposed Action is to continue training and testing activities to ensure the Navy, other U.S. military services, and the U.S. Coast Guard meet their respective missions, which for the Navy is to maintain, train, and equip combat-ready forces capable of winning wars, deterring aggression, and maintaining freedom of the seas.

To achieve and maintain military readiness, the Navy proposes to: 

  • Continue at-sea training and testing activities at levels required to support military readiness requirements beyond 2020.
  • Incorporate evolving mission requirements, including those resulting from the development, testing, and introduction of new vessels, aircraft, and weapons systems into the fleet.

The type and level of activities included in the Proposed Action account for fluctuations in training and testing to be able to meet evolving or emergent requirements.

Importance of Realistic Training and Testing

Realistic training and testing are crucial for military readiness, personnel safety, and national defense

Military service members must be ready to respond to many different situations when called upon. The skills needed to achieve military readiness are challenging to master and require constant practice. Training activities must be diverse and as realistic as possible to prepare military personnel for what they will experience in real-world situations and ensure their success and survival.

Equipment and systems must be tested before use by military personnel during deployment. Systems are tested in varying marine environments, such as differing water depths, seafloor types, salinity levels, and other ocean conditions, as well as replicated warfighting environments, to ensure accuracy and safety.

While simulators provide early skill repetition at the basic operator level and enhance teamwork, there is no substitute for live training and testing in a realistic environment.

Importance of Training and Testing with Active Sonar and Explosives

Defense against enemy submarines is a top priority for the Navy. To detect potential hostile submarines, the Navy uses both passive and active sonar. Torpedoes, in-water mines, and quieter submarines are true threats to global commerce, national security, and the safety of military personnel. Active sonar is the most effective method of detecting these threats.

Sonar proficiency is complex and requires regular, hands-on training in realistic and diverse conditions. Lack of realistic training will jeopardize the lives of military personnel in real-life combat situations.


Submarines of the previous generation were noisy and could be detected with passive sonar before they came close enough to deploy short-range weapons against a vessel. Extremely quiet, difficult-to-detect, diesel-electric submarines can approach close enough to deploy long-range weapons before entering the passive sonar detection range of U.S. vessels. Active sonar has a longer detection range that is needed to allow Navy Sailors to detect, identify, and track quieter, modern submarines before they are close enough to attack.

Training and testing at sea with explosives significantly enhances the safety of U.S. forces in combat and improves readiness and equipment reliability. Training in a high-stress environment, including the use of and exposure to explosive ordnance, is necessary for military personnel to be fully prepared to respond to emergencies, national security threats, and to ensure their own safety.

For more information on the Proposed Action and types of training and testing activities, please see the project fact sheet booklet.

Alternatives Evaluated

Alternative 2 is the Navy’s Preferred Alternative because it allows for the greatest flexibility for the Navy to maintain future readiness

The National Environmental Policy Act (NEPA) requires federal agencies to evaluate a range of reasonable alternatives to achieve the purpose of and need for the Proposed Action. The Navy evaluated the potential environmental impacts of three alternatives, including a No Action Alternative. 

Alternative 1

  • Adjusts the types and levels of training and testing activities to meet current and future military readiness requirements.
  • Consists of activities and requirements associated with development, testing, and introduction of new vessels, aircraft, and weapons systems.
  • Reduces the amount of active sonar estimated to be necessary to meet training requirements.

Alternative 2 (Preferred Alternative)

  • Includes all activities under Alternative 1. 
  • Includes additional events should unanticipated emergent world events require increased readiness levels.

No Action Alternative

  • No authorizations or permits would be issued by the National Marine Fisheries Service.
  • Proposed at-sea and FDM training and testing activities would not be conducted.
  • Strike warfare (dropping of ordnance) on FDM would not be conducted.
  • Other military activities not associated with Proposed Action would continue.
  • Purpose and need would not be met.

For more information on the Proposed Action, alternatives, and types of training and testing activities, please see the Final Supplemental EIS/OEIS.

Key Updates Made in the Supplemental EIS/OEIS

Proposed training and testing activities are similar to activities conducted in the Mariana Islands for decades. In the Supplemental EIS/OEIS, the Navy:

  • Includes a No Action Alternative in which Marine Mammal Protection Act authorization would not be issued by the National Marine Fisheries Service (NMFS); therefore, proposed training and testing activities would not be conducted.
  • Refines the analysis of anti-submarine warfare activities, resulting in reduced levels of active sonar and fewer hours of underwater sound.
  • Includes analyses of training with new vessels, aircraft, weapons systems, and unmanned/autonomous systems, and decreases in other activities.
  • Includes analyses of testing new systems and technologies, such as radar, communication systems (or simulators), or high-energy lasers.
  • Includes an updated underwater sound effects model, criteria and thresholds, and marine mammal and sea turtle data.
  • Continues to use the most current and best available science and analytical methods.
  • Reviews procedural mitigation measures and considers geographic mitigation measures.