# Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to the U.S. Navy Training and Testing Activities in the Northwest Training and Testing (NWTT) Study Area > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2020-08533 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** June 2, 2020 - **Citation:** 85 FR 33914 ## Text DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 218 [200417-0114] RIN 0648-BJ30 Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to the U.S. Navy Training and Testing Activities in the Northwest Training and Testing (NWTT) Study Area AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Proposed rule; request for comments and information. SUMMARY: NMFS has received a request from the U.S. Navy (Navy) to take marine mammals incidental to training and testing activities conducted in the Northwest Training and Testing (NWTT) Study Area. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue regulations and subsequent Letters of Authorization (LOAs) to the Navy to incidentally take marine mammals during the specified activities. NMFS will consider public comments prior to issuing any final rule and making final decisions on the issuance of the requested LOAs. Agency responses to public comments will be provided in the notice of the final decision. The Navy's activities qualify as military readiness activities pursuant to the MMPA, as amended by the National Defense Authorization Act for Fiscal Year 2004 (2004 NDAA). DATES: Comments and information must be received no later than July 17, 2020. ADDRESSES: You may submit comments on this document, identified by NOAA-NMFS-2020-0055, by any of the following methods: • Electronic submission: Submit all electronic public comments via the Federal e-Rulemaking Portal. Go to www.regulations.gov/#!docketDetail;D=NOAA-NMFS-2020-0055, click the “Comment Now!” icon, complete the required fields, and enter or attach your comments. • Mail: Submit written comments to Jolie Harrison, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910. Instructions: Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing on www.regulations.gov without change. All personal identifying information ( e.g., name, address), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible. NMFS will accept anonymous comments (enter “N/A” in the required fields if you wish to remain anonymous). Attachments to electronic comments will be accepted in Microsoft Word, Excel, or Adobe PDF file formats only. A copy of the Navy's application and other supporting documents and documents cited herein may be obtained online at: www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities. In case of problems accessing these documents, please use the contact listed here (see FOR FURTHER INFORMATION CONTACT ). FOR FURTHER INFORMATION CONTACT: Wendy Piniak, Office of Protected Resources, NMFS, (301) 427-8401. SUPPLEMENTARY INFORMATION: Purpose of Regulatory Action These proposed regulations, issued under the authority of the MMPA (16 U.S.C. 1361 et seq. ), would provide the framework for authorizing the take of marine mammals incidental to the Navy's training and testing activities (which qualify as military readiness activities) from the use of sonar and other transducers, in-water detonations, and potential vessel strikes based on Navy movement in the NWTT Study Area. The Study Area includes air and water space off the coast of Washington, Oregon, and northern California; in the Western Behm Canal, Alaska; and portions of waters of the Strait of Juan de Fuca and Puget Sound, including Navy pierside and harbor locations in Puget Sound (see Figure 1-1 of the Navy's rulemaking/LOA application). NMFS received an application from the Navy requesting seven-year regulations and authorizations to incidentally take individuals of multiple species of marine mammals (“Navy's rulemaking/LOA application” or “Navy's application”). Take is anticipated to occur by Level A harassment and Level B harassment as well as a very small number of serious injuries or mortalities incidental to the Navy's training and testing activities. Background The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, the public is provided with notice of the proposed incidental take authorization and provided the opportunity to review and submit comments. An authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stocks and will not have an unmitigable adverse impact on the availability of the species or stocks for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of such species or stocks for taking for certain subsistence uses (referred to in this rule as “mitigation measures”); and requirements pertaining to the monitoring and reporting of such takings. The MMPA defines “take” to mean to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal. The Preliminary Analysis and Negligible Impact Determination section below discusses the definition of “negligible impact.” The NDAA for Fiscal Year 2004 (2004 NDAA) (Pub. L. 108-136) amended section 101(a)(5) of the MMPA to remove the “small numbers” and “specified geographical region” provisions indicated above and amended the definition of “harassment” as applied to a “military readiness activity.” The definition of harassment for military readiness activities (Section 3(18)(B) of the MMPA) is (i) Any act that injures or has the significant potential to injure a marine mammal or marine mammal stock in the wild (Level A Harassment); or (ii) Any act that disturbs or is likely to disturb a marine mammal or marine mammal stock in the wild by causing disruption of natural behavioral patterns, including, but not limited to, migration, surfacing, nursing, breeding, feeding, or sheltering, to a point where such behavioral patterns are abandoned or significantly altered (Level B harassment). In addition, the 2004 NDAA amended the MMPA as it relates to military readiness activities such that the least practicable adverse impact analysis shall include consideration of personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity. More recently, Section 316 of the NDAA for Fiscal Year 2019 (2019 NDAA) (Pub. L. 115-232), signed on August 13, 2018, amended the MMPA to allow incidental take rules for military readiness activities under section 101(a)(5)(A) to be issued for up to seven years. Prior to this amendment, all incidental take rules under section 101(a)(5)(A) were limited to five years. Summary and Background of Request On March 11, 2019, NMFS received an application from the Navy for authorization to take marine mammals by Level A harassment and Level B harassment incidental to training and testing activities (which qualify as military readiness activities) from the use of sonar and other transducers and in-water detonations in the NWTT Study Area over a seven-year period beginning when the current authorization expires. In addition, the Navy requested incidental take authorization by serious injury or mortality for up to three takes of large whales from vessel strikes over the seven-year period. We received revised applications on June 6, 2019 and June 21, 2019 which provided revisions in the take number estimates and vessel strike analysis and Navy's rulemaking/LOA application was found to be adequate and complete. On August 6, 2019 (84 FR 38225), we published a notice of receipt (NOR) of application in the Federal Register , requesting comments and information related to the Navy's request for 30 days. We reviewed and considered all comments and information received on the NOR in development of this proposed rule. On October 4, 2019, the Navy submitted an amendment to its application which incorporated new Southern Resident killer whale offshore density information, and on December 19, 2019, the Navy submitted an amendment to its application which incorporated revised testing activity numbers. The following types of training and testing, which are classified as military readiness activities pursuant to the MMPA, as amended by the 2004 NDAA, would be covered under the regulations and LOAs (if authorized): Anti-submarine warfare (sonar and other transducers, underwater detonations), mine warfare (sonar and other transducers, underwater detonations), surface warfare (underwater detonations), and other testing and training (sonar and other transducers). The activities would not include pile driving/removal or use of air guns. This would be the third time NMFS has promulgated incidental take regulations pursuant to the MMPA relating to similar military readiness activities in the NWTT Study Area, following those effective from November 9, 2010 through November 8, 2015 ( 75 FR 69275; November 10, 2010) and from November 9, 2015 through November 8, 2020 ( 80 FR 73555; November 24, 2015). The Navy's mission is to organize, train, equip, and maintain combat-ready naval forces capable of winning wars, deterring aggression, and maintaining freedom of the seas. This mission is mandated by Federal law (10 U.S.C. 8062), which requires the readiness of the naval forces of the United States. The Navy executes this responsibility in part by training and testing at sea, often in designated operating areas (OPAREA) and testing and training ranges. The Navy must be able to access and utilize these areas and associated sea space and air space in order to develop and maintain skills for conducting naval operations. The Navy's testing activities ensure naval forces are equipped with well-maintained systems that take advantage of the latest technological advances. The Navy's research and acquisition community conducts military readiness activities that involve testing. The Navy tests ships, aircraft, weapons, combat systems, sensors, and related equipment, and conducts scientific research activities to achieve and maintain military readiness. The Navy has been conducting training and testing activities in the NWTT Study Area for decades, with some activities dating back to at least the early 1900s. The tempo and types of training and testing activities have fluctuated because of the introduction of new technologies, the evolving nature of international events, advances in warfighting doctrine and procedures, and changes in force structure ( e.g., organization of ships, submarines, aircraft, weapons, and personnel). Such developments influence the frequency, duration, intensity, and location of required training and testing activities, however the Navy's proposed activities for the period of this proposed rule would be largely a continuation of ongoing activities. In addition to ongoing activities, the Navy is proposing some new training activities such as torpedo exercise—submarine training and unmanned underwater vehicle training. 1 The Navy is also proposing some new testing activities, including: At-sea sonar testing, mine countermeasure and neutralization testing, mine detection and classification testing, kinetic energy weapon testing, propulsion testing, undersea warfare testing, vessel signature evaluation, acoustic and oceanographic research, radar and other system testing, and simulant testing. 2 1 Some of the activities included here are new to the 2019 NWTT DSEIS/OEIS, but are not new to the Study Area. TORPEX—SUB activity was previously analyzed in 2010 as part of the Sinking Exercise. The Sinking Exercise is no longer conducted in the NWTT Study Area and the TORPEX—SUB activity is now a separate activity included in the NWTT DSEIS/OEIS. Unmanned underwater vehicle activity was analyzed in 2010 as a testing activity, but is now being included as a training activity. 2 Mine detection and classification testing was analyzed in 2010 in the Inland waters, but was not previously analyzed in the Offshore waters. Vessel signature evaluation testing was analyzed in 2010 as a component to other activities, but is included in the list of new activities because it was not previously identified as an independent activity. The Navy's rulemaking/LOA application reflects the most up-to-date compilation of training and testing activities deemed necessary by senior Navy leadership to accomplish military readiness requirements. The types and numbers of activities included in the proposed rule account for fluctuations in training and testing in order to meet evolving or emergent military readiness requirements. These proposed regulations would cover training and testing activities that would occur for a seven-year period following the expiration of the current MMPA authorization for the NWTT Study Area, which expires on November 8, 2020. Description of the Specified Activity The Navy requests authorization to take marine mammals incidental to conducting training and testing activities. The Navy has determined that acoustic and explosives stressors are most likely to result in impacts on marine mammals that could rise to the level of harassment, and NMFS concurs with this determination. Detailed descriptions of these activities are provided in Chapter 2 of the 2019 NWTT Draft Supplemental Environmental Impact Statement (SEIS)/Overseas EIS (OEIS) (2019 NWTT DSEIS/OEIS) ( https://www.nwtteis.com ) and in the Navy's rulemaking/LOA application ( https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities ) and are summarized here. Dates and Duration The specified activities would occur at any time during the seven-year period of validity of the regulations. The proposed number of training and testing activities are described in the Detailed Description of the Specified Activities section (Tables 3 through 4). Geographical Region The NWTT Study Area is composed of established maritime operating and warning areas in the eastern North Pacific Ocean region, including areas of the Strait of Juan de Fuca, Puget Sound, and Western Behm Canal in southeastern Alaska. The Study Area includes air and water space within and outside Washington state waters, within Alaska state waters, and outside state waters of Oregon and Northern California (Figure 1). The eastern boundary of the Offshore Area portion of the Study Area is 12 nautical miles (nmi) off the coastline for most of the Study Area, including southern Washington, Oregon, and Northern California. The Offshore Area includes the ocean all the way to the coastline only along that part of the Washington coast that lies beneath the airspace of W-237 and the Olympic Military Operating Area (MOA) and the Washington coastline north of the Olympic MOA. The Study Area includes four existing range complexes and facilities: The Northwest Training Range Complex, the Keyport Range Complex, Carr Inlet Operations Area, and the Southeast Alaska Acoustic Measurement Facility (Western Behm Canal, Alaska). In addition to these range complexes, the Study Area also includes Navy pierside locations where sonar maintenance and testing occurs as part of overhaul, modernization, maintenance, and repair activities at Naval Base Kitsap, Bremerton; Naval Base Kitsap, Bangor; and Naval Station Everett. Additional detail can be found in Chapter 2 of the Navy's rulemaking/LOA application. BILLING CODE 3510-22-P EP02JN20.002 BILLING CODE 3510-22-C Primary Mission Areas The Navy categorizes many of its training and testing activities into functional warfare areas called primary mission areas. The Navy's proposed activities for NWTT generally fall into the following six primary mission areas: Air warfare; anti-submarine warfare; electronic warfare; expeditionary warfare; mine warfare; and surface warfare. Most activities conducted in NWTT are categorized under one of these primary mission areas; activities that do not fall within one of these areas are listed as “other activities.” Each warfare community (surface, subsurface, aviation, and expeditionary warfare) may train in some or all of these primary mission areas. The research and acquisition community also categorizes most, but not all, of its testing activities under these primary mission areas. A description of the sonar, munitions, targets, systems, and other material used during training and testing activities within these primary mission areas is provided in Appendix A ( Navy Activities Descriptions ) of the 2019 NWTT DSEIS/OEIS. The Navy describes and analyzes the effects of its activities within the 2019 NWTT DSEIS/OEIS. In its assessment, the Navy concluded that sonar and other transducers and underwater detonations were the stressors most likely to result in impacts on marine mammals that could rise to the level of harassment as defined under the MMPA. Therefore, the Navy's rulemaking/LOA application provides the Navy's assessment of potential effects from these stressors in terms of the various warfare mission areas in which they would be conducted. Those mission areas include the following: • Anti-submarine warfare (sonar and other transducers, underwater detonations); • expeditionary warfare; • mine warfare (sonar and other transducers, underwater detonations); • surface warfare (underwater detonations); and • other (sonar and other transducers). The Navy's training and testing activities in air warfare and electronic warfare do not involve sonar and other transducers, underwater detonations, or any other stressors that could result in harassment, serious injury, or mortality of marine mammals. Therefore, the activities in air warfare and electronic warfare are not discussed further in this proposed rule, but are analyzed fully in the 2019 NWTT DSEIS/OEIS. Anti-Submarine Warfare The mission of anti-submarine warfare is to locate, neutralize, and defeat hostile submarine forces that threaten Navy surface forces. Anti-submarine warfare can involve various assets such as aircraft, ships, and submarines which all search for hostile submarines. These forces operate together or independently to gain early warning and detection, and to localize, track, target, and attack submarine threats. Anti-submarine warfare training addresses basic skills such as detecting and classifying submarines, as well as evaluating sounds to distinguish between enemy submarines and friendly submarines, ships, and marine life. More advanced training integrates the full spectrum of anti-submarine warfare, from detecting and tracking a submarine to attacking a target using either exercise torpedoes ( i.e., torpedoes that do not contain a warhead), or simulated weapons. These integrated anti-submarine warfare training exercises are conducted in coordinated, at-sea training events involving submarines, ships, and aircraft. Testing of anti-submarine warfare systems is conducted to develop new technologies and assess weapon performance and operability with new systems and platforms, such as unmanned systems. Testing uses ships, submarines, and aircraft to demonstrate capabilities of torpedoes (exercise and explosive), missiles, countermeasure systems, and underwater surveillance and communications systems. Tests may be conducted as part of a large-scale training event involving submarines, ships, fixed-wing aircraft, and helicopters. These integrated training events offer opportunities to conduct research and acquisition activities and to train aircrew in the use of new or newly enhanced systems during a large-scale, complex exercise. Expeditionary Warfare The mission of expeditionary warfare is to provide security and surveillance in the littoral (at the shoreline), riparian (along a river), or coastal environments. Expeditionary warfare is wide ranging and includes defense of harbors, operation of remotely operated vehicles, defense against swimmers, and boarding/seizure operations. Expeditionary warfare training activities include underwater construction team training, dive and salvage operations, and insertion/extraction via air, surface, and subsurface platforms. Mine Warfare The mission of mine warfare is to detect, classify, and avoid or neutralize (disable) mines to protect Navy ships and submarines and to maintain free access to ports and shipping lanes. Mine warfare also includes training and testing in offensive mine laying to gain control of or deny the enemy access to sea space. Naval mines can be laid by ships, submarines, or aircraft. Mine warfare training includes exercises in which ships, aircraft, submarines, underwater vehicles, unmanned vehicles, or marine mammal detection systems search for mine shapes. Personnel train to destroy or disable mines by attaching underwater explosives to or near the mine or using remotely operated vehicles to destroy the mine. Towed influence mine sweep systems mimic a particular ship's magnetic and acoustic signature, which would trigger a real mine, causing it to explode. Testing and development of mine warfare systems is conducted to improve acoustic, optical, and magnetic detectors intended to hunt, locate, and record the positions of mines for avoidance or subsequent neutralization. Mine warfare testing and development falls into two primary categories: Mine detection and classification, and mine countermeasure and neutralization testing. Mine detection and classification testing involves the use of air, surface, and subsurface vessels; it uses sonar, including towed and side-scan sonar, and unmanned vehicles to locate and identify objects underwater. Mine detection and classification systems are sometimes used in conjunction with a mine neutralization system. Mine countermeasure and neutralization testing includes the use of air, surface, and subsurface units and uses tracking devices, countermeasure and neutralization systems, and general purpose bombs to evaluate the effectiveness of neutralizing mine threats. Most neutralization tests use mine shapes, or non-explosive practice mines, to accomplish the requirements of the activity. For example, during a mine neutralization test, a previously located mine is destroyed or rendered nonfunctional using a helicopter or manned/unmanned surface vehicle-based system that may involve the deployment of a towed neutralization system. A small percentage of mine warfare activities require the use of high-explosives to evaluate and confirm the ability of the system or the crews conducting the training to neutralize a high-explosive mine under operational conditions. The majority of mine warfare systems are deployed by ships, helicopters, and unmanned vehicles. Tests may also be conducted in support of scientific research to support these new technologies. Surface Warfare The mission of surface warfare is to obtain control of sea space from which naval forces may operate, which entails offensive action against surface targets while also defending against aggressive actions by enemy forces. In the conduct of surface warfare, aircraft use guns, air-launched cruise missiles, or other precision-guided munitions; ships employ naval guns and surface-to-surface missiles; and submarines attack surface ships using torpedoes or submarine-launched, anti-ship cruise missiles. Surface warfare training includes surface-to-surface gunnery and missile exercises, air-to-surface gunnery and missile exercises, submarine missile or torpedo launch events, and other munitions against surface targets. Testing of weapons used in surface warfare is conducted to develop new technologies and to assess weapon performance and operability with new systems and platforms, such as unmanned systems. Tests include various air-to-surface guns and missiles, surface-to-surface guns and missiles, and bombing tests. Testing events may be integrated into training activities to test aircraft or aircraft systems in the delivery of munitions on a surface target. In most cases the tested systems are used in the same manner in which they are used for training activities. Other Activities The Navy conducts other training and testing activities in the Study Area that fall outside of the primary mission areas, but support overall readiness. Surface ship crews conduct Maritime Security Operations events, including maritime security escorts for Navy vessels such as Fleet Ballistic Missile Submarines; Visit, Board, Search, and Seizure; Maritime Interdiction Operations; Force Protection; Anti-Piracy Operations, Acoustic Component Testing, Cold Water Support, and Hydrodynamic and Maneuverability testing. Anti-terrorism/Force-protection training will occur as small boat attacks against moored ships at one of the Navy's piers inside Puget Sound. Pierside and at-sea maintenance of ship and submarine sonar is required for systems upkeep and systems evaluation. Description of Stressors The Navy uses a variety of sensors, platforms, weapons, and other devices, including ones used to ensure the safety of Sailors, to meet its mission. Training and testing with these systems may introduce acoustic (sound) energy or shock waves from explosives into the environment. The proposed training and testing activities were evaluated to identify specific components that could act as stressors by having direct or indirect impacts on the environment. This analysis included identification of the spatial variation of the identified stressors. The following subsections describe the acoustic and explosive stressors for marine mammals and their habitat (including prey species) within the NWTT Study Area. Each description contains a list of activities that may generate the stressor. Stressor/resource interactions that were determined to have de minimis or no impacts ( e.g., vessel noise, aircraft noise, weapons noise, and explosions in air) were not carried forward for analysis in the Navy's rulemaking/LOA application. No Major Training Exercises (MTEs) or Sinking Exercise (SINKEX) events are proposed in the NWTT Study Area. NMFS reviewed the Navy's analysis and conclusions on de minimis sources and finds them complete and supportable. Acoustic Stressors Acoustic stressors include acoustic signals emitted into the water for a specific purpose, such as sonar, other transducers (devices that convert energy from one form to another—in this case, into sound waves), incidental sources of broadband sound produced as a byproduct of vessel movement, aircraft transits, and use of weapons or other deployed objects. Explosives also produce broadband sound but are characterized separately from other acoustic sources due to their unique hazardous characteristics. Characteristics of each of these sound sources are described in the following sections. In order to better organize and facilitate the analysis of approximately 300 sources of underwater sound used in training and testing activities by the Navy, including sonar and other transducers and explosives, a series of source classifications, or source bins, were developed. The source classification bins do not include the broadband noise produced incidental to vessel and aircraft transits and weapons firing. Noise produced from vessel, aircraft, and weapons firing activities are not carried forward because those activities were found to have de minimis or no impacts, as stated above. The use of source classification bins provides the following benefits: • Provides the ability for new sensors or munitions to be covered under existing authorizations, as long as those sources fall within the parameters of a “bin;” • Improves efficiency of source utilization data collection and reporting requirements anticipated under the MMPA authorizations; • Ensures a precautionary approach to all impact estimates, as all sources within a given class are modeled as the most impactful source (highest source level, longest duty cycle, or largest net explosive weight) within that bin; • Allows analyses to be conducted in a more efficient manner, without any compromise of analytical results; and • Provides a framework to support the reallocation of source usage (hours/explosives) between different source bins, as long as the total numbers of takes remain within the overall analyzed and authorized limits. This flexibility is required to support evolving Navy training and testing requirements, which are linked to real world events. Sonar and Other Transducers Active sonar and other transducers emit non-impulsive sound waves into the water to detect objects, navigate safely, and communicate. Passive sonars differ from active sound sources in that they do not emit acoustic signals; rather, they only receive acoustic information about the environment, or listen. In this proposed rule, the terms sonar and other transducers will be used to indicate active sound sources unless otherwise specified. The Navy employs a variety of sonars and other transducers to obtain and transmit information about the undersea environment. Some examples are mid-frequency hull-mounted sonars used to find and track enemy submarines; high-frequency small object detection sonars used to detect mines; high-frequency underwater modems used to transfer data over short ranges; and extremely high-frequency (greater than 200 kilohertz (kHz)) doppler sonars used for navigation, like those used on commercial and private vessels. The characteristics of these sonars and other transducers, such as source level, beam width, directivity, and frequency, depend on the purpose of the source. Higher frequencies can carry more information or provide more information about objects off which they reflect, but attenuate more rapidly. Lower frequencies attenuate less rapidly, so they may detect objects over a longer distance, but with less detail. Propagation of sound produced underwater is highly dependent on environmental characteristics such as bathymetry, bottom type, water depth, temperature, and salinity. The sound received at a particular location will be different than near the source due to the interaction of many factors, including propagation loss; how the sound is reflected, refracted, or scattered; the potential for reverberation; and interference due to multi-path propagation. In addition, absorption greatly affects the distance over which higher-frequency sounds propagate. The effects of these factors are explained in Appendix D ( Acoustic and Explosive Concepts ) of the 2019 NWTT DSEIS/OEIS. Because of the complexity of analyzing sound propagation in the ocean environment, the Navy relies on acoustic models in its environmental analyses that consider sound source characteristics and varying ocean conditions across the Study Area. The sound sources and platforms typically used in naval activities analyzed in the Navy's rulemaking/LOA application are described in Appendix A ( Navy Activities Descriptions ) of the 2019 NWTT DSEIS/OEIS. Sonars and other transducers used to obtain and transmit information underwater during Navy training and testing activities generally fall into several categories of use described below. Anti-Submarine Warfare Sonar used during anti-submarine warfare training and testing would impart the greatest amount of acoustic energy of any category of sonar and other transducers analyzed in this proposed rule. Types of sonars used to detect potential enemy vessels include hull-mounted, towed, line array, sonobuoy, helicopter dipping, and torpedo sonars. In addition, acoustic targets and decoys (countermeasures) may be deployed to emulate the sound signatures of vessels or repeat received signals. Most anti-submarine warfare sonars are mid-frequency (1-10 kHz) because mid-frequency sound balances sufficient resolution to identify targets with distance over which threats can be identified. However, some sources may use higher or lower frequencies. Duty cycles can vary widely, from rarely used to continuously active. Anti-submarine warfare sonars can be wide-ranging in a search mode or highly directional in a track mode. Most anti-submarine warfare activities involving submarines or submarine targets would occur in waters greater than 600 feet (ft) deep due to safety concerns about running aground at shallower depths. Sonars used for anti-submarine warfare activities would typically be used beyond 12 nmi from shore. Exceptions include use of dipping sonar by helicopters, pierside testing and maintenance of systems while in port, and system checks while transiting to or from port. Mine Warfare, Small Object Detection, and Imaging Sonars used to locate mines and other small objects, as well as those used in imaging ( e.g., for hull inspections or imaging of the seafloor), are typically high frequency or very high frequency. Higher frequencies allow for greater resolution and, due to their greater attenuation, are most effective over shorter distances. Mine detection sonar can be deployed (towed or vessel hull-mounted) at variable depths on moving platforms (ships, helicopters, or unmanned vehicles) to sweep a suspected mined area. Hull-mounted anti-submarine sonars can also be used in an object detection mode known as “Kingfisher” mode. Sonars used for imaging are usually used in close proximity to the area of interest, such as pointing downward near the seafloor. Mine detection sonar use would be concentrated in areas where practice mines are deployed, typically in water depths less than 200 ft, and at temporary minefields close to strategic ports and harbors, or at targets of opportunity such as navigation buoys. Kingfisher mode on vessels is most likely to be used when transiting to and from port. Sound sources used for imaging could be used throughout the NWTT Study Area. Navigation and Safety Similar to commercial and private vessels, Navy vessels employ navigational acoustic devices, including speed logs, Doppler sonars for ship positioning, and fathometers. These may be in use at any time for safe vessel operation. These sources are typically highly directional to obtain specific navigational data. Communication Sound sources used to transmit data (such as underwater modems), provide location (pingers), or send a single brief release signal to bottom-mounted devices (acoustic release) may be used throughout the NWTT Study Area. These sources typically have low duty cycles and are usually only used when it is desirable to send a detectable acoustic message. Classification of Sonar and Other Transducers Sonars and other transducers are grouped into classes that share an attribute, such as frequency range or purpose. As detailed below, classes are further sorted by bins based on the frequency or bandwidth; source level; and, when warranted, the application in which the source would be used. Unless stated otherwise, a reference distance of 1 meter (m) is used for sonar and other transducers. • Frequency of the non-impulsive acoustic source: ○ Low-frequency sources operate below 1 kHz; ○ Mid-frequency sources operate at and above 1 kHz, up to and including 10 kHz; ○ High-frequency sources operate above 10 kHz, up to and including 100 kHz; and ○ Very-high-frequency sources operate above 100 kHz but below 200 kHz. • Sound pressure level: ○ Greater than 160 decibels (dB) referenced to 1 micropascal (re: 1 μPa), but less than 180 dB re: 1 μPa; ○ Equal to 180 dB re: 1 μPa and up to 200 dB re: 1 μPa; and ○ Greater than 200 dB re: 1 μPa. • Application in which the source would be used: ○ Sources with similar functions that have similar characteristics, such as pulse length (duration of each pulse), beam pattern, and duty cycle. The bins used for classifying active sonars and transducers that are quantitatively analyzed in the Study Area are shown in Table 1. While general parameters or source characteristics are shown in the table, actual source parameters are classified. Table 1—Sonar and Other Transducers Quantitatively Analyzed in the NWTT Study Area Source class category Bin Description Low-Frequency (LF): Sources that produce signals less than 1 kHz LF4 LF5 LF sources equal to 180 dB and up to 200 dB. LF sources less than 180 dB. Mid-Frequency (MF): Tactical and non-tactical sources that produce signals between 1 and 10 kHz MF1 MF1K Hull-mounted surface ship sonars ( e.g., AN/SQS-53C and AN/SQS-60). Kingfisher mode associated with MF1 sonars. MF2 Hull-mounted surface ship sonars ( e.g., AN/SQS-56). MF3 Hull-mounted submarine sonars ( e.g., AN/BQQ-10). MF4 Helicopter-deployed dipping sonars ( e.g., AN/AQS-22). MF5 Active acoustic sonobuoys ( e.g., DICASS). MF6 Underwater sound signal devices ( e.g., MK 84 SUS). MF9 Sources (equal to 180 dB and up to 200 dB) not otherwise binned. MF10 Active sources (greater than 160 dB, but less than 180 dB) not otherwise binned. MF11 Hull-mounted surface ship sonars with an active duty cycle greater than 80%. MF12 Towed array surface ship sonars with an active duty cycle greater than 80%. High-Frequency (HF): Tactical and non-tactical sources that produce signals between 10 and 100 kHz HF1 HF3 Hull-mounted submarine sonars ( e.g., AN/BQQ-10). Other hull-mounted submarine sonars (classified). HF4 Mine detection, classification, and neutralization sonar ( e.g., AN/SQS-20). HF5 Active sources (greater than 200 dB) not otherwise binned. HF6 Sources (equal to 180 dB and up to 200 dB) not otherwise binned. HF8 Hull-mounted surface ship sonars ( e.g., AN/SQS-61). HF9 Weapon-emulating sonar source. Very High-Frequency (VHF): Tactical and non-tactical sources that produce signals greater than 100 kHz but less than 200 kHz VHF1 VHF2 Active sources greater than 200 dB. Active sources with a source level less than 200 dB. Anti-Submarine Warfare (ASW): Tactical sources ( e.g., active sonobuoys and acoustic countermeasures systems) used during ASW training and testing activities ASW1 ASW2 ASW3 MF systems operating above 200 dB. MF Multistatic Active Coherent sonobuoy ( e.g., AN/SSQ-125). MF towed active acoustic countermeasure systems ( e.g., AN/SLQ-25). ASW4 MF expendable active acoustic device countermeasures ( e.g., MK 3). ASW5 1 MF sonobuoys with high duty cycles. Torpedoes (TORP): Active acoustic signals produced by torpedoes TORP1 TORP2 Lightweight torpedo ( e.g., MK 46, MK 54, or Anti-Torpedo Torpedo). Heavyweight torpedo ( e.g., MK 48). TORP3 Heavyweight torpedo ( e.g., MK 48). Looking Sonar (FLS): Forward or upward looking object avoidance sonars used for ship navigation and safety FLS2 HF sources with short pulse lengths, narrow beam widths, and focused beam patterns. Acoustic Modems (M): Sources used to transmit data M3 MF acoustic modems (greater than 190 dB). Synthetic Aperture Sonars (SAS): Sonars used to form high-resolution images of the seafloor SAS2 HF SAS systems. Broadband Sound Sources (BB): Sonar systems with large frequency spectra, used for various purposes BB1 BB2 MF to HF mine countermeasure sonar. HF to VHF mine countermeasure sonar. 1 Formerly ASW2 in the 2015-2020 (Phase II) rulemaking. Explosive Stressors The near-instantaneous rise from ambient to an extremely high peak pressure is what makes an explosive shock wave potentially damaging. Farther from an explosive, the peak pressures decay and the explosive waves propagate as an impulsive, broadband sound. Several parameters influence the effect of an explosive: The weight of the explosive in the warhead, the type of explosive material, the boundaries and characteristics of the propagation medium, and the detonation depth in water. The net explosive weight, which is the explosive power of a charge expressed as the equivalent weight of trinitrotoluene (TNT), accounts for the first two parameters. The effects of these factors are explained in Appendix D ( Acoustic and Explosive Concepts ) of the 2019 NWTT DSEIS/OEIS. The activities analyzed in the Navy's rulemaking/LOA application that use explosives are described in Appendix A ( Navy Activities Descriptions ) of the 2019 NWTT DSEIS/OEIS. Explanations of the terminology and metrics used when describing explosives are provided in Appendix D ( Acoustic and Explosive Concepts ) of the 2019 NWTT DSEIS/OEIS. Explosives in Water Explosive detonations during training and testing activities are associated with high-explosive munitions, including, but not limited to, bombs, missiles, naval gun shells, torpedoes, mines, demolition charges, and explosive sonobuoys. Explosive detonations during training and testing involving the use of high-explosive munitions, including bombs, missiles, and naval gun shells, could occur in the air or near the water's surface. Explosive detonations associated with torpedoes and explosive sonobuoys would occur in the water column; mines and demolition charges could be detonated in the water column or on the ocean bottom. Detonations would typically occur in waters greater than 200 ft in depth, and greater than 50 nmi from shore, with the exception of mine countermeasure and neutralization testing proposed in the Offshore Area, and existing mine warfare areas in Inland Waters ( i.e., Crescent Harbor and Hood Canal Explosive Ordnance Disposal Training Ranges). Mine countermeasure and neutralization testing is a new proposed testing activity that would occur closer to shore than other in-water explosive activities analyzed in the 2015 NWTT Final EIS/OEIS for the Offshore Area of the NWTT Study Area. This activity would occur in waters 3 nmi or greater from shore in the Quinault Range Site (outside the Olympic Coast National Marine Sanctuary), or 12 nmi or greater from shore elsewhere in the Offshore Area. Two of the three events would involve the use of explosives, and would typically occur in water depths shallower than 1,000 ft. The two multi-day events (1-10 days per event) would include up to 36 E4 explosives (>2.5-5 lb net explosive weight) and 5 E7 explosives (>20-60 lb net explosive weight). In order to better organize and facilitate the analysis of explosives used by the Navy during training and testing that could detonate in water or at the water surface, explosive classification bins were developed. The use of explosive classification bins provides the same benefits discussed above and as described for acoustic source classification bins in Section 1.4.1 (Acoustic Stressors) of the Navy's rulemaking/LOA application. Explosives detonated in water are binned by net explosive weight. The bins of explosives that are proposed for use in the Study Area are shown in Table 2 below. Table 2—Explosive Sources Quantitatively Analyzed That Could Be Used Underwater or at the Water Surface in the Study Area Bin Net explosive weight (lb) Example explosive source Modeled detonation depths (ft) E1 0.1-0.25 Medium-caliber projectiles 0.3, 60. E2 >0.25-0.5 Medium-caliber projectiles 0.3. E3 >0.5-2.5 Explosive Ordnance Disposal Mine Neutralization 33, 60. E4 >2.5-5 Mine Countermeasure and Neutralization 197, 262, 295, 394. E5 >5-10 Large-caliber projectile 0.3. E7 >20-60 Mine Countermeasure and Neutralization 33, 98, 230, 295. E8 >60-100 Lightweight torpedo 150. E10 >250-500 1,000 lb bomb 0.3. E11 >500-650 Heavyweight torpedo 300, 656. Notes: Net Explosive Weight refers to the equivalent amount of TNT, the actual weight of a munition may be larger due to other components; in = inch(es), lb = pound(s), ft = feet. Propagation of explosive pressure waves in water is highly dependent on environmental characteristics such as bathymetry, bottom type, water depth, temperature, and salinity, which affect how the pressure waves are reflected, refracted, or scattered; the potential for reverberation; and interference due to multi-path propagation. In addition, absorption greatly affects the distance over which higher-frequency components of explosive broadband noise can propagate. Appendix D ( Acoustic and Explosive Concepts ) of the 2019 NWTT DSEIS/OEIS explains the characteristics of explosive detonations and how the above factors affect the propagation of explosive energy in the water. Because of the complexity of analyzing sound propagation in the ocean environment, the Navy relies on acoustic models in its environmental analyses that consider sound source characteristics and varying ocean conditions across the Study Area. Explosive Fragments Marine mammals could be exposed to fragments from underwater explosions associated with the specified activities. When explosive ordnance (e.g., bomb or missile) detonates, fragments of the weapon are thrown at high-velocity from the detonation point, which can injure or kill marine mammals if they are struck. These fragments may be of variable size and are ejected at supersonic speed from the detonation. The casing fragments will be ejected at velocities much greater than debris from any target due to the proximity of the casing to the explosive material. Risk of fragment injury reduces exponentially with distance as the fragment density is reduced. Fragments underwater tend to be larger than fragments produced by in-air explosions (Swisdak and Montaro, 1992). Underwater, the friction of the water would quickly slow these fragments to a point where they no longer pose a threat. Opposingly, the blast wave from an explosive detonation moves efficiently through the seawater. Because the ranges to mortality and injury due to exposure to the blast wave are likely to far exceed the zone where fragments could injure or kill an animal, the ranges for assessing the likelihood of mortality and injury from a blast, which are also used to inform mitigation zones, are assumed to encompass risk due to fragmentation. Other Stressor—Vessel Strike NMFS also considered the chance that a vessel utilized in training or testing activities could strike a marine mammal. Vessel strikes have the potential to result in incidental take from serious injury and/or mortality. Vessel strikes are not specific to any particular training or testing activity, but rather are a limited, sporadic, and incidental result of Navy vessel movement during training and testing activities within a Study Area. Vessel strikes from commercial, recreational, and military vessels are known to seriously injure and occasionally kill cetaceans (Abramson et al., 2011; Berman-Kowalewski et al., 2010; Calambokidis, 2012; Douglas et al., 2008; Laggner, 2009; Lammers et al., 2003; Van der Hoop et al., 2012; Van der Hoop et al., 2013), although reviews of the literature on ship strikes mainly involve collisions between commercial vessels and whales (Jensen and Silber, 2003; Laist et al., 2001). Vessel speed, size, and mass are all important factors in determining both the potential likelihood and impacts of a vessel strike to marine mammals (Conn and Silber, 2013; Gende et al., 2011; Silber et al., 2010; Vanderlaan and Taggart, 2007; Wiley et al., 2016). For large vessels, speed and angle of approach can influence the severity of a strike. Navy vessels transit at speeds that are optimal for fuel conservation and to meet training and testing requirements. Vessels used as part of the proposed Specified Activities include ships, submarines, unmanned vessels, and boats ranging in size from small, 22 ft (7 m) rigid hull inflatable boats to aircraft carriers with lengths up to 1,092 ft (333 m). The average speed of large Navy ships ranges between 10 and 15 knots (kn) and submarines generally operate at speeds in the range of 8 to 13 kn, while a few specialized vessels can travel at faster speeds. Small craft (for purposes of this analysis, less than 60 ft (18 m) in length) have much more variable speeds (0 to 50+ kn, dependent on the activity), but generally range from 10 to 14 kn. From unpublished Navy data, average median speed for large Navy ships in the other Navy ranges from 2011-2015 varied from 5 to 10 kn with variations by ship class and location ( i.e., slower speeds close to the coast). Similar patterns would occur in the NWTT Study Area. A full description of Navy vessels that are used during training and testing activities can be found in Chapter 2 ( Description of Proposed Action and Alternatives ) of the 2019 NWTT DSEIS/OEIS. While these speeds are representative of most events, some vessels need to temporarily operate outside of these parameters for certain times or during certain activities. For example, to produce the required relative wind speed over the flight deck, an aircraft carrier engaged in flight operations must adjust its speed through the water accordingly. Conversely, there are other instances, such as launch and recovery of a small rigid hull inflatable boat; vessel boarding, search, and seizure training events; or retrieval of a target when vessels will be dead in the water or moving slowly ahead to maintain steerage. Large Navy vessels (greater than 60 ft (18 m) in length) within the offshore areas of range complexes and testing ranges operate differently from commercial vessels in ways that may reduce potential whale collisions. Surface ships operated by or for the Navy have multiple personnel assigned to stand watch at all times, when a ship or surfaced submarine is moving through the water (underway). A primary duty of personnel standing watch on surface ships is to detect and report all objects and disturbances sighted in the water that may indicate a threat to the vessel and its crew, such as debris, a periscope, surfaced submarine, or surface disturbance. Per vessel safety requirements, personnel standing watch also report any marine mammals sighted in the path of the vessel as a standard collision avoidance procedure. All vessels proceed at a safe speed so they can take proper and effective action to avoid a collision with any sighted object or disturbance, and can be stopped within a distance appropriate to the prevailing circumstances and conditions. Detailed Description of Proposed Activities Proposed Training and Testing Activities The training and testing activities that the Navy proposes to conduct in the NWTT Study Area are summarized in Table 3 (training) and Table 4 (testing). The tables are organized according to primary mission areas and include the activity name, associated stressor(s) of Navy's activities, description and duration of the activity, sound source bin, the areas where the activities are conducted in the NWTT Study Area, and the number of activities. Under the “Annual # of Events” column, events show either a single number or a range of numbers to indicate the maximum number of times that activity could occur during any single year. The “7-Year # of Events” is the maximum number of times an activity would occur over the 7-year period of proposed regulations. For further information regarding the primary platform used ( e.g., ship or aircraft type) see Appendix A ( Training and Testing Activities Descriptions ) of the 2019 NWTT DSEIS/OEIS. The Navy's proposed activities reflect a representative year of training and testing to account for the natural fluctuation of training and testing cycles and deployment schedules that generally prevents the maximum level of activities from occurring year after year in any 7-year period. As shown in the tables of activities, the number of some activities may vary from year to year, and the level of variability can differ by activity. Still, the annual analysis assumes a “maximum” year. For the purposes of this request, the Navy assumes that some unit-level training would be conducted using synthetic means ( e.g., simulators). Additionally, the request assumes that some unit-level active sonar training and some testing will be completed during other scheduled activities. Table 3—Proposed Training Activities Analyzed for the Seven-Year Period in the NWTT Study Area Stressor category Activity Description Typical duration Source bin Location Annual # of events 7-Year # of events Anti-Submarine Warfare Acoustic; Explosive Torpedo Exercise—Submarine (TORPEX—Sub) Submarine crews search for, track, and detect submarines. Event would include one MK-48 torpedo used during this event. 8 hours TORP2 Offshore Area >12 nmi from land 0-2 5 Acoustic Tracking Exercise—Helicopter (TRACKEX—Helo) Helicopter crews search for, track, and detect submarines. 2-4 hours MF4, MF5 Offshore Area >12 nmi from land 0-2 5 Acoustic Tracking Exercise—Maritime Patrol Aircraft (TRACKEX—MPA) Maritime patrol aircraft crews search for, track, and detect submarines. 2-8 hours ASW2, ASW5, MF5, TORP1 Offshore Area >12 nmi from land 373 2,611 Acoustic Tracking Exercise—Ship (TRACKEX—Ship) Surface ship crews search for, track, and detect submarines. 2-4 hours ASW3, MF1, MF11 Offshore Area 62 434 Acoustic Tracking Exercise—Submarine (TRACKEX—Sub) Submarine crews search for, track, and detect submarines. 8 hours HF1, MF3 Offshore Area 75-100 595 Mine Warfare Acoustic Civilian Port Defense—Homeland Security Anti-Terrorism/Force Protection Exercises Maritime security personnel train to protect civilian ports and harbors against enemy efforts to interfere with access to those ports. Multiple days HF4, SAS2 Inland Waters 0-1 5 Explosive Mine Neutralization—Explosive Ordnance Disposal (EOD) Personnel disable threat mines using explosive charges. Up to 4 hours E3 Crescent Harbor EOD Training Range, Hood Canal EOD Training Range 12 84 Surface Warfare Explosive Bombing Exercise (Air-to-Surface) (BOMBEX [A-S]) Fixed-wing aircrews deliver bombs against surface targets. 1 hour E10 Offshore Area (W-237) >50 nmi from land * 0-2 5 Explosive Gunnery Exercise (Surface-to-Surface)—Ship (GUNEX [S-S]—Ship) Surface ship crews fire large- and medium-caliber guns at surface targets. Up to 3 hours E1, E2, E5 Offshore Area >50 nmi from land * 90 504 Explosive Missile Exercise (Air-to-Surface) (MISSILEX [A-S]) Fixed-wing aircrews simulate firing precision-guided missiles, using captive air training missiles (CATMs) against surface targets. Some activities include firing a missile with a high-explosive (HE) warhead. 2 hours E10 Offshore Area (W-237) >50 nmi from land 0-2 5 Other Training Acoustic Submarine Sonar Maintenance Maintenance of submarine sonar and other system checks are conducted pierside or at sea. Up to 1 hour LF5, MF3 NBK Bangor, NBK Bremerton, and Offshore Area >12 nmi from land 26 182 Acoustic Surface Ship Sonar Maintenance Maintenance of surface ship sonar and other system checks are conducted pierside or at sea. Up to 4 hours MF1 NBK Bremerton, NS Everett, and Offshore Area >12 nmi from land 25 175 Acoustic Unmanned Underwater Vehicle Training Unmanned underwater vehicle certification involves training with unmanned platforms to ensure submarine crew proficiency. Tactical development involves training with various payloads for multiple purposes to ensure that the systems can be employed effectively in an operational environment. Up to 24 hours FLS2, M3 Inland Waters, Offshore Area 60 420 * (Counts only the explosive events). Table 4—Proposed Testing Activities Analyzed for the Seven-Year Period in the NWTT Study Area Stressor category Activity Description Typical duration Source bin Location Annual # of events 7-Year # of events Naval Sea Systems Command Testing Activities Anti-Submarine Warfare: Acoustic Anti-Submarine Warfare Testing Ships and their supporting platforms (rotary-wing aircraft and unmanned aerial systems) detect, localize, and prosecute submarines. 4-8 hours of active sonar use ASW1, ASW2, ASW3, ASW5, MF1K, MF4, MF5, MF10, MF11, MF12, TORP1 Offshore Area 44 308 Acoustic At-Sea Sonar Testing At-sea testing to ensure systems are fully functional in an open ocean environment. From 4 hours to 11 days ASW3, HF1, HF5, M3, MF3 ASW3, HF5, TORP1 Offshore Area Inland Waters (DBRC) 4 4-6 28 34 Acoustic Countermeasure Testing Countermeasure testing involves the testing of systems that will detect, localize, and track incoming weapons, including marine vessel targets. Countermeasures may be systems to obscure the vessel's location or systems to rapidly detect, track, and counter incoming threats. Testing includes surface ship torpedo defense systems and marine vessel stopping payloads. From 4 hours to 6 days ASW3, ASW4, HF8, MF1, TORP2 ASW3, ASW4 ASW4 Offshore Area (QRS) Inland Waters (DBRC, Keyport Range Site) Western Behm Canal, AK 14 29 1 98 203 5 Acoustic Pierside-Sonar Testing Pierside testing to ensure systems are fully functional in a controlled pierside environment prior to at-sea test activities. Up to 3 weeks ASW3, HF3, MF1, MF2, MF3, MF9, MF10, MF12 Inland Waters (NS Everett, NBK Bangor, NBK Bremerton) 88-99 635 Acoustic Submarine Sonar Testing/Maintenance Pierside, moored, and underway testing of submarine systems occurs periodically following major maintenance periods and for routine maintenance. Up to 3 weeks HF6, MF9 Western Behm Canal, AK 1-2 10 Acoustic; Explosive Torpedo (Explosive) Testing Air, surface, or submarine crews employ explosive and non-explosive torpedoes against artificial targets. 1-2 hours during daylight only E8, E11, ASW3, HF1, HF6, MF1, MF3, MF4, MF5, MF6, TORP1, TORP2 Offshore Area >50 nmi from land 4 28 Acoustic Torpedo (Non-explosive) Testing Air, surface, or submarine crews employ non-explosive torpedoes against targets, submarines, or surface vessels. Up to 2 weeks ASW3, ASW4, HF1, HF5, HF6, MF1, MF3, MF4, MF5, MF6, MF9, MF10, TORP1, TORP2 Offshore Area 22 154 HF6, LF4, TORP1, TORP2, TORP3 Inland Waters (DBRC) 61 427 Mine Warfare: Acoustic; Explosive Mine Countermeasure and Neutralization Testing Air, surface, and subsurface vessels neutralize threat mines and mine-like objects. 1-10 days E4, E7, HF4 HF4 Offshore Area Inland Waters 3 3 15 13 Acoustic Mine Detection and Classification Testing Air, surface, and subsurface vessels and systems detect and classify mines and mine-like objects. Vessels also assess their potential susceptibility to mines and mine-like objects. Up to 24 days BB1, BB2, LF4 BB1, BB2, HF4, LF4 Offshore Area (QRS) Inland Waters (DBRC, Keyport Range Site) 1 42 7 294 Unmanned Systems: Acoustic Unmanned Underwater Vehicle Testing Testing involves the production or upgrade of unmanned underwater vehicles. This may include testing of mission capabilities ( e.g., mine detection), evaluating the basic functions of individual platforms, or conducting complex events with multiple vehicles. Typically 1-2 days, up to multiple months FLS2, HF5, TORP1, VHF1 DS3, FLS2, HF5, HF9, M3, SAS2, VHF1, TORP1 Offshore Area (QRS) Inland Waters (DBRC, Keyport Range Site, Carr Inlet) 38-39 371-379 269 2,615 Vessel Evaluation: Acoustic Undersea Warfare Testing Ships demonstrate capability of countermeasure systems and underwater surveillance, weapons engagement, and communications systems. This tests ships' ability to detect, track, and engage undersea targets. Up to 10 days ASW3, ASW4, HF4, MF1, MF4, MF5, MF6, MF9, TORP1, TORP2 Offshore Area 1-12 27 Other Testing: Acoustic Acoustic and Oceanographic Research Research using active transmissions from sources deployed from ships, aircraft, and unmanned underwater vehicles. Research sources can be used as proxies for current and future Navy systems. Up to 14 days LF4, MF9 Offshore Area (QRS) Inland Waters (DBRC, Keyport Range Site) 1 3 7 21 Acoustic Acoustic Component Testing Various surface vessels, moored equipment, and materials are tested to evaluate performance in the marine environment. 1 day to multiple months HF3, HF6, LF5, MF9 Western Behm Canal, AK 13-18 99 Acoustic Cold Water Support Fleet training for divers in a cold water environment, and other diver training related to Navy divers supporting range/test site operations and maintenance. 8 hours HF6 Inland Waters (Keyport Range Site, DBRC, Carr Inlet) Western Behm Canal, AK 4 1 28 7 Acoustic Post-Refit Sea Trial Following periodic maintenance periods or repairs, sea trials are conducted to evaluate submarine propulsion, sonar systems, and other mechanical tests. 8 hours HF9, M3, MF10 Inland Waters (DBRC) 30 210 Acoustic Semi-Stationary Equipment Testing Semi-stationary equipment ( e.g., hydrophones) is deployed to determine functionality. From 10 minutes to multiple days HF6, HF9, LF4, MF9, VHF2 HF6, HF9 Inland Waters (DBRC, Keyport Range Site) Western Behm Canal, AK 120 2-3 840 12 Naval Air Systems Command Testing Activities Anti-Submarine Warfare: Acoustic; Explosive Tracking Test—Maritime Patrol Aircraft The test evaluates the sensors and systems used by maritime patrol aircraft to detect and track submarines and to ensure that aircraft systems used to deploy the tracking systems perform to specifications and meet operational requirements. 4-8 flight hours E1, E3, ASW2, ASW5, MF5, MF6 Offshore Area 8 56 Summary of Acoustic and Explosive Sources Analyzed for Training and Testing Tables 5 through 8 show the acoustic and explosive source classes, bins, and quantity used in either hours or counts associated with the Navy's proposed training and testing activities over a seven-year period in the NWTT Study Area that were analyzed in the Navy's rulemaking/LOA application. Table 5 describes the acoustic source classes ( i.e., low-frequency (LF), mid-frequency (MF), and high-frequency (HF)) and numbers that could occur over seven years under the proposed training activities. Acoustic source bin use in the proposed activities would vary annually. The seven-year totals for the proposed training activities take into account that annual variability. Table 5—Acoustic Source Class Bins Analyzed and Numbers Used for Seven-Year Period for Training Activities in the NWTT Study Area Source class category Bin Description Unit Annual 7-Year total Low-Frequency (LF): Sources that produce signals less than 1 kHz LF5 LF sources less than 180 dB H 1 5 Mid-Frequency (MF): Tactical and non-tactical sources that produce signals between 1 and 10 kHz MF1 Hull-mounted surface ship sonars ( e.g., AN/SQS-53C and AN/SQS-61) H 164 1,148 MF3 Hull-mounted submarine sonars ( e.g., AN/BQQ-10) H 70 490 MF4 Helicopter-deployed dipping sonars ( e.g., AN/AQS-22 and AN/AQS-13) H 0-1 1 MF5 Active acoustic sonobuoys ( e.g., DICASS) C 918-926 6,443 MF11 Hull-mounted surface ship sonars with an active duty cycle greater than 80% H 16 112 High-Frequency (HF): Tactical and non-tactical sources that produce signals between 10 and 100 kHz HF1 Hull-mounted submarine sonars ( e.g., AN/BQQ-10) H 48 336 HF4 Mine detection, classification, and neutralization sonar ( e.g., AN/SQS-20) H 0-65 269 Anti-Submarine Warfare (ASW): Tactical sources ( e.g., active sonobuoys and acoustic countermeasures systems) used during ASW training and testing activities ASW2 MF Multistatic Active Coherent sonobuoy ( e.g., AN/SSQ-125) C 350 2,450 ASW3 MF towed active acoustic countermeasure systems ( e.g., AN/SLQ-25) H 86 602 ASW5 MF sonobuoys with high duty cycles H 50 350 Torpedoes (TORP): Source classes associated with the active acoustic signals produced by torpedoes TORP1 Lightweight torpedo ( e.g., MK 46, MK 54, or Anti-Torpedo Torpedo) C 16 112 TORP2 Heavyweight torpedo ( e.g., MK 48) C 0-2 5 Forward Looking Sonar (FLS): Forward or upward looking object avoidance sonars used for ship navigation and safety FLS2 HF sources with short pulse lengths, narrow beam widths, and focused beam patterns H 240 1,680 Acoustic Modems (M): Systems used to transmit data through the water M3 MF acoustic modems (greater than 190 dB) H 30 210 Synthetic Aperture Sonars (SAS): Sonars in which active acoustic signals are post-processed to form high-resolution images of the seafloor SAS2 HF SAS systems H 0-561 2,353 Notes: H = hours; C = count. Table 6 describes the acoustic source classes and numbers that could occur over seven years under the proposed testing activities. Acoustic source bin use in the proposed activities would vary annually. The seven-year totals for the proposed testing activities take into account that annual variability. Table 6—Acoustic Source Class Bins Analyzed and Numbers Used for Seven-Year Period for Testing Activities in the NWTT Study Area Source class category Bin Description Unit Annual 7-Year total Low-Frequency (LF): Sources that produce signals less than 1 kHz LF4 LF sources equal to 180 dB and up to 200 dB H 177 1,239 LF5 LF sources less than 180 dB H 0-18 23 Mid-Frequency (MF): Tactical and non-tactical sources that produce signals between 1 and 10 kHz MF1 Hull-mounted surface ship sonars ( e.g., AN/SQS-53C and AN/SQS-61) H 20-169 398 MF1K Kingfisher mode associated with MF1 sonars H 48 336 MF2 Hull-mounted surface ship sonars ( e.g., AN/SQS-56) H 32 224 MF3 Hull-mounted submarine sonars ( e.g., AN/BQQ-10) H 34-36 239 MF4 Helicopter-deployed dipping sonars ( e.g., AN/AQS-22 and AN/AQS-13) H 41-50 298 MF5 Active acoustic sonobuoys ( e.g., DICASS) C 300-673 2,782 MF6 Active underwater sound signal devices ( e.g., MK 84 SUS) C 60-232 744 MF9 Active sources (equal to 180 dB and up to 200 dB) not otherwise binned H 644-959 5,086 MF10 Active sources (greater than 160 dB, but less than 180 dB) not otherwise binned H 886 6,197 MF11 Hull-mounted surface ship sonars with an active duty cycle greater than 80 percent H 48 336 MF12 Towed array surface ship sonars with an active duty cycle greater than 80 percent H 100 700 High-Frequency (HF): Tactical and non-tactical sources that produce signals between 10 and 100 kHz HF1 Hull-mounted submarine sonars ( e.g., AN/BQQ-10) H 10 68 HF3 Other hull-mounted submarine sonars (classified) H 1-19 30 HF4 Mine detection, classification, and neutralization sonar ( e.g., AN/SQS-20) H 1,860-1,868 11,235 HF5 Active sources (greater than 200 dB) not otherwise binned H 352-400 2,608 HF6 Active sources (equal to 180 dB and up to 200 dB) not otherwise binned H 1,705-1,865 12,377 HF8 Hull-mounted surface ship sonars ( e.g., AN/SQS-61) H 24 168 HF9 Weapon emulating sonar source H 257 1,772 Very High-Frequency (VHF): Tactical and non-tactical sources that produce signals greater than 100 kHz but less than 200 kHz VHF1 Very high frequency sources greater than 200 dB H 320 2,240 VHF2 Active sources with a frequency greater than 100 kHz, up to 200 kHz with a source level less than 200 dB H 135 945 Anti-Submarine Warfare (ASW): Tactical sources ( e.g., active sonobuoys and acoustic countermeasures systems) used during ASW training and testing activities ASW1 MF systems operating above 200 dB H 80 560 ASW2 MF systems operating above 200 dB C 240 1,680 ASW3 MF towed active acoustic countermeasure systems ( e.g., AN/SLQ-25) H 487-1,015 4,091 ASW4 MF expendable active acoustic device countermeasures ( e.g., MK 3) C 1,349-1,389 9,442 ASW5 MF sonobuoys with high duty cycles H 80 560 Torpedoes (TORP): Source classes associated with the active acoustic signals produced by torpedoes TORP1 Lightweight torpedo ( e.g., MK 46, MK 54, or Anti-Torpedo Torpedo) C 298-360 2,258 TORP2 Heavyweight torpedo ( e.g., MK 48) C 332-372 2,324 TORP3 Heavyweight torpedo test ( e.g., MK 48) C 6 42 Forward Looking Sonar (FLS): Forward or upward looking object avoidance sonars used for ship navigation and safety FLS2 HF sources with short pulse lengths, narrow beam widths, and focused beam patterns H 24 168 Acoustic Modems (M): Systems used to transmit data through the water M3 MF acoustic modems (greater than 190 dB) H 1,088 7,616 Synthetic Aperture Sonars (SAS): Sonars in which active acoustic signals are post-processed to form high-resolution images of the seafloor SAS2 HF SAS systems H 1,312 9,184 Broadband Sound Sources (BB): Sonar systems with large frequency spectra, used for various purposes BB1 MF to HF mine countermeasure sonar H 48 336 BB2 HF to VHF mine countermeasure sonar H 48 336 Notes: H = hours; C = count. Table 7 describes the explosive source classes and numbers that could occur over seven years under the proposed training activities. Under the proposed activities bin use would vary annually, and the seven-year totals for the proposed training activities take into account that annual variability. Table 7—Explosive Source Class Bins Analyzed and Numbers Used for Seven-Year Period for Training Activities in the NWTT Study Area Bin Net explosive weight (lb) Example explosive source Annual 7-Year total E1 0.1-0.25 Medium-caliber projectiles 60-120 672 E2 >0.25-0.5 Medium-caliber projectiles 65-130 728 E3 >0.5-2.5 Explosive Ordnance Disposal Mine Neutralization 6 42 E5 >5-10 Large-caliber projectile 56-112 628 E10 >250-500 1,000 lb bomb 0-4 9 Notes: (1) Net explosive weight refers to the equivalent amount of TNT. The actual weight of a munition may be larger due to other components. lb = pound(s), ft = feet. Table 8 describes the explosive source classes and numbers that could occur over seven years under the proposed testing activities. Under the proposed activities bin use would vary annually, and the seven-year totals for the proposed testing activities take into account that annual variability. Table 8—Explosive Source Class Bins Analyzed and Numbers Used for Seven-Year Period for Testing Activities in the NWTT Study Area Bin Net explosive weight (lb) Example explosive source Annual 7-Year total E1 0.1-0.25 SUS buoy 8 56 E3 >0.5-2.5 Explosive sonobuoy 72 504 E4 >2.5-5 Mine Countermeasure and Neutralization 36 180 E7 >20-60 Mine Countermeasure and Neutralization 5 25 E8 >60-100 Lightweight torpedo 4 28 E11 >500-650 Heavyweight torpedo 4 28 Notes: (1) Net explosive weight refers to the equivalent amount of TNT. The actual weight of a munition may be larger due to other components. lb = pound(s), ft = feet. Vessel Movement Vessels used as part of the proposed activities include ships, submarines, unmanned vessels, and boats ranging in size from small, 22 ft rigid hull inflatable boats to aircraft carriers with lengths up to 1,092 ft. Large ships greater than 60 ft generally operate at speeds in the range of 10-15 kn for fuel conservation. Submarines generally operate at speeds in the range of 8-13 kn in transits and less than those speeds for certain tactical maneuvers. Small craft (for purposes of this discussion—less than 60 ft in length) have much more variable speeds (dependent on the mission). While these speeds are representative of most events, some vessels need to temporarily operate outside of these parameters. For example, to produce the required relative wind speed over the flight deck, an aircraft carrier engaged in flight operations must adjust its speed through the water accordingly. Conversely, there are other instances, such as launch and recovery of a small rigid hull inflatable boat; vessel boarding, search, and seizure training events; or retrieval of a target when vessels will be dead in the water or moving slowly ahead to maintain steerage. The number of military vessels used in the NWTT Study Area varies based on military training and testing requirements, deployment schedules, annual budgets, and other unpredictable factors. Many training and testing activities involve the use of vessels. These activities could be widely dispersed throughout the NWTT Study Area, but would be typically conducted near naval ports, piers, and range areas. Training and testing activities involving vessel movements occur intermittently and are variable in duration, ranging from a few hours to up to two weeks. There is no seasonal differentiation in military vessel use. Large vessel movement primarily occurs with the majority of the traffic flowing between the installations and the Operating Areas (OPAREAS). Smaller support craft would be more concentrated in the coastal waters in the areas of naval installations, ports, and ranges. The number of activities that include the use of vessels for training events is lower (approximately 10 percent) than the number for testing activities. Testing can occur jointly with a training event, in which case that testing activity could be conducted from a training vessel. Additionally, a variety of smaller craft will be operated within the NWTT Study Area. Small craft types, sizes, and speeds vary. During training and testing, speeds generally range from 10-14 kn; however, vessels can and will, on occasion, operate within the entire spectrum of their specific operational capabilities. In all cases, the vessels/craft will be operated in a safe manner consistent with the local conditions. Standard Operating Procedures For training and testing to be effective, personnel must be able to safely use their sensors and weapon systems as they are intended to be used in military missions and combat operations and to their optimum capabilities. While standard operating procedures are designed for the safety of personnel and equipment and to ensure the success of training and testing activities, their implementation often yields benefits to environmental, socioeconomic, public health and safety, and cultural resources. Navy standard operating procedures have been developed and refined over years of experience and are broadcast via numerous naval instructions and manuals, including, but not limited to the following materials: • Ship, submarine, and aircraft safety manuals; • Ship, submarine, and aircraft standard operating manuals; • Fleet Area Control and Surveillance Facility range operating instructions; • Fleet exercise publications and instructions; • Naval Sea Systems Command test range safety and standard operating instructions; • Navy-instrumented range operating procedures; • Naval shipyard sea trial agendas; • Research, development, test, and evaluation plans; • Naval gunfire safety instructions; • Navy planned maintenance system instructions and requirements; • Federal Aviation Administration regulations; and • International Regulations for Preventing Collisions at Sea. Because standard operating procedures are essential to safety and mission success, the Navy considers them to be part of the proposed Specified Activities, and has included them in the environmental analysis. Standard operating procedures that are recognized as having a potential benefit to marine mammals during training and testing activities are noted below and discussed in more detail within the 2019 NWTT DSEIS/OEIS. • Vessel Safety; • Weapons Firing Procedures; • Target Deployment Safety; and • Towed In-Water Device Safety. Standard operating procedures (which are implemented regardless of their secondary benefits) are different from mitigation measures (which are designed entirely for the purpose of avoiding or reducing environmental impacts). Information on mitigation measures is provided in the Proposed Mitigation section below. Additional information on standard operating procedures is presented in Section 2.3.3 (Standard Operating Procedures) in the 2019 NWTT DSEIS/OEIS. Description of Marine Mammals and Their Habitat in the Area of the Specified Activities Marine mammal species and their associated stocks that have the potential to occur in the NWTT Study Area are presented in Table 9 along with an abundance estimate, an associated coefficient of variation value, and best and minimum abundance estimates. The Navy requests authorization to take individuals of 29 marine mammal species by Level A harassment and Level B harassment incidental to training and testing activities from the use of sonar and other transducers and in-water detonations. In addition, the Navy requests authorization for three takes of large whales by serious injury or mortality from vessel strikes over the seven-year period. Currently, the Southern Resident killer whale has critical habitat designated under the Endangered Species Act (ESA) in the NWTT Study Area (described below). However, NMFS has recently published two proposed rules, proposing new or revised ESA-designated critical habitat for humpback whales (84 FR 54354; October 9, 2019) and Southern Resident killer whales (84 FR 49214; September 19, 2019). Information on the status, distribution, abundance, population trends, habitat, and ecology of marine mammals in the NWTT Study Area may be found in Chapter 4 of the Navy's rulemaking/LOA application. NMFS has reviewed this information and found it to be accurate and complete. Additional information on the general biology and ecology of marine mammals is included in the 2019 NWTT DSEIS/OEIS. Table 9 incorporates data from the U.S. Pacific and the Alaska Marine Mammal Stock Assessment Reports (SARs; Carretta et al., 2019; Muto et al., 2019) and the most recent revised data in the draft SARs (see https://www.fisheries.noaa .gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports ); as well as incorporates the best available science, including monitoring data from the Navy's marine mammal research efforts. Species Not Included in the Analysis The species carried forward for analysis (and described in Table 9 below) are those likely to be found in the NWTT Study Area based on the most recent data available, and do not include species that may have once inhabited or transited the area but have not been sighted in recent years ( e.g., species which were extirpated from factors such as 19th and 20th century commercial exploitation). Several species that may be present in the northwest Pacific Ocean have an extremely low probability of presence in the NWTT Study Area. These species are considered extralimital (not anticipated to occur in the Study Area) or rare (occur in the Study Area sporadically, but sightings are rare). These species/stocks include the Eastern North Pacific stock of Bryde's whale ( Balaenoptera edeni ), Eastern North Pacific stock of North Pacific right whale ( Eubalaena japonica ), false killer whale ( Pseudorca crassidens ), long-beaked common dolphin ( Delphinus capensis ), Western U.S. stock of Steller sea lion ( Eumetopias jubatus ), and Alaska stock of Cuvier's beaked whale ( Ziphius cavirostris ). Despite rare stranding or sighting reports, the Study Area is outside the normal range of the Eastern North Pacific stock of Bryde's whale and the California stock of the long-beaked common dolphin. The Study Area is also outside the normal range of the false killer whale's distribution in the Pacific Ocean. The Eastern North Pacific stock of North Pacific right whale is estimated to have an abundance of 31 individuals (Muto et al., 2020) and is anticipated to be extremely rare in the Study Area. The Western U.S. stock of Steller sea lions is considered rare in the Offshore Area of the Study Area, and is not expected to occur in the Inland Waters portion of the Study Area. In Western Behm Canal, there is a low probability of juvenile male Steller sea lion occurrence from the Western U.S. stock, however these individuals are anticipated to be very rare. Finally, the Alaska stock of Cuvier's beaked whales is not expected to occur in either the Offshore Area or Inland Waters of the NWTT Study Area, and are considered extralimital in Western Behm Canal as this area does not overlap with their range of distribution. NMFS agrees with the Navy's assessment that these species are unlikely to occur in the NWTT Study Area and they are not discussed further. Table 9—Marine Mammal Occurrence Within the NWTT Study Area Common name Scientific name Stock ESA/MMPA status; strategic (Y/N) 1 Stock abundance (CV, N min , most recent abundance survey) 2 PBR Annual M/SI 3 Occurrence Offshore area Inland waters Western Behm Canal Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales) Family Eschrichtiidae: Gray whale Eschrichtius robustus Eastern North Pacific -, -, N 26.960 (0.05, 25,849, 2016) 801 139 Seasonal Seasonal Family Balaenopteridae (rorquals): Blue whale Balaenoptera musculus Eastern North Pacific E, D, S 1,496 (0.44, 1,050, 2014) 1.2 ≥19.4 Seasonal Fin whale Balaenoptera physalus Northeast Pacific E, D, S 3,168 (0.26, 2,554, 2013) 4 5.1 0.4 Rare. CA/OR/WA E, D, S 9,029 (0.12, 8,127, 2014) 81 ≥43.5 Seasonal Rare Humpback whale Megaptera novaeangliae Central North Pacific T/E, 5 D, S 10,103 (0.3, 7,891, 2006) 83 25 Regular Regular Regular. CA/OR/WA T/E, 5 D, S 2,900 (0.05, 2,784, 2014) 16.7 ≥42.1 Regular Regular Regular. Minke whale Balaenoptera acutorostrata Alaska -, -, N UNK UND 0 Rare. CA/OR/WA -, -, N 636 (0.72, 369, 2014) 3.5 ≥1.3 Regular Seasonal Sei whale Balaenoptera borealis Eastern North Pacific E, D, S 519 (0.4, 374, 2014) 0.75 ≥0.2 Regular Superfamily Odontoceti (toothed whales, dolphins, and porpoises) Family Physeteridae: Sperm whale Physeter macrocephalus CA/OR/WA E, D, S 1.997 (0.57, 1,270, 2014) 2.5 0.4 Rare Family Kogiidae: Dwarf sperm whale Kogia sima CA/OR/WA -, -, N UNK UND 0 Rare Pygmy sperm whale Kogia breviceps CA/OR/WA -, -, N 4,111 (1.12, 1,924, 2014) 19.2 0 Regular Family Ziphiidae (beaked whales): Baird's beaked whale Berardius bairdii CA/OR/WA -, -, N 2,697 (0.6, 1,633, 2014) 16 0 Regular Cuvier's beaked whale Ziphius cavirostris CA/OR/WA -, -, N 3,274 (0.67, 2,059, 2014) 21 < 0.1 Regular Mesoplodont beaked whales Mesoplodon species CA/OR/WA -, -, N 3,044 (0.54, 1,967, 2014) 20 0.1 Regular Family Delphinidae: Common bottlenose dolphin Tursiops truncatus CA/OR/WA Offshore -, -, N 1,924 (0.54, 1,255, 2014) 11 ≥1.6 Regular Killer whale Orcinus orca Eastern North Pacific Alaskan Resident -, -, N 2,347 (UNK, 2,347, 2012) 6 24 1 Regular. Eastern North Pacific Northern Resident -, -, N 302 (UNK, 302, 2018) 6 2.2 0.2 Seasonal Seasonal West Coast Transient -, -, N 243 (UNK, 243, 2009) 2.4 0 Regular Regular Regular. Eastern North Pacific Offshore -, -, N 300 (0.1, 276, 2012) 2.8 0 Regular Regular. Eastern North Pacific Southern Resident E, D, Y 75 (NA, 75, 2018) 0.13 0 Seasonal Regular Northern right whale dolphin Lissodelphus borealis CA/OR/WA -, -, N 26,556 (0.44, 18,608, 2014) 179 3.8 Regular Pacific white-sided dolphin Lagenorhynchus obliquidens North Pacific -, -, N 26,880 (UNK, NA, 1990) UND 0 Regular. CA/OR/WA -, -, N 26,814 (0.28, 21,195, 2014) 191 7.5 Regular Regular Risso's dolphin Grampus griseus CA/OR/WA -, -, N 6,336 (0.32, 4,817, 2014) 46 ≥3.7 Regular Rare Short-beaked common dolphin Delphinus delphis CA/OR/WA -, -, N 969,861 (0.17, 839,325, 2014) 8,393 ε40 Regular Rare Short-finned pilot whale Globicephala macrorhynchus CA/OR/WA -, -, N 836 (0.79, 466, 2014) 4.5 1.2 Regular Rare Striped dolphin Stenella coeruleoalba CA/OR/WA -, -, N 29,211 (0.2, 24,782, 2014) 238 ≥0.8 Regular Family Phocoenidae (porpoises): Dall's porpoise Phocoenoides dalli Alaska -, -, N 83,400 (0.097, NA, 1991) UND 38 Regular. CA/OR/WA -, -, N 25,750 (0.45, 17,954, 2014) 172 0.3 Regular Regular Harbor porpoise Phocoena phocoena Southeast Alaska -, -, Y 1,354 (0.12, 1,224, 2012) 12 34 Regular. Northern OR/WA Coast -, -, N 21,487 (0.44, 15, 123, 2011) 151 ≥3 Regular Northern CA/Southern OR -, -, N 35,769 (0.52, 23,749, 2011) 475 ≥0.6 Regular Washington Inland Waters -, -, N 11,233 (0.37, 8,308, 2015) 66 ≥7.2 Regular Order Carnivora—Superfamily Pinnipedia Family Otariidae (eared seals and sea lions): California sea lion Zalophus californianus U.S. -, -, N 257,606 (NA, 233,515, 2014) 14,011 ≥321 Seasonal Regular Guadalupe fur seal Arctocephalus townsendi Mexico to California T, D, Y 34,187 (NA, 31,109, 2013) 1,062 ≥3.8 Seasonal Northern fur seal Callorhinus ursinus Eastern Pacific -, D, Y 620,660 (0.2, 525,333, 2016) 11,295 399 Regular Seasonal. California -, -, N 14,050 (NA, 7,524, 2013) 451 1.8 Regular Steller sea lion Eumetopias jubatus Eastern U.S. -, -, N 43,201 (NA, 43,201, 2017) 7 2,592 113 Regular Seasonal Regular. Family Phocidae (earless seals): Harbor seal Phoca vitulina Southeast Alaska (Clarence Strait) -, -, N 27,659 (UNK, 24,854, 2015) 746 40 Regular. OR/WA Coast -, -, N UNK UND 10.6 Regular Seasonal California -, -, N 30,968 (0.157, 27,348, 2012) 1,641 43 Regular Washington Northern Inland Waters -, -, N UNK UND 9.8 Seasonal Regular Hood Canal -, -, N UNK UND 0.2 Seasonal Regular Southern Puget Sound -, -, N UNK UND 3.4 Seasonal Regular Northern Elephant seal Mirounga angustirostris California -, -, N 179,000 (NA, 81,368, 2010) 4,882 8.8 Regular Regular Seasonal. 1 Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds potential biological removal (PBR) or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock. 2 NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments. CV is coefficient of variation; N min is the minimum estimate of stock abundance. In some cases, CV is not applicable. For the Eastern North Pacific Southern Resident stock of killer whales Nbest/N min are based on a direct count of individually identifiable animals. The population size of the U.S. stock of California sea lion was estimated from a 1975-2014 time series of pup counts (Lowry et al. 2017), combined with mark-recapture estimates of survival rates (DeLong et al. 2017, Laake et al. 2018). The population size of the Mexico to California stock of Guadalupe fur seals was estimated from pup count data collected in 2013 and a range of correction factors applied to pup counts to account for uncounted age classes and pre-census pup mortality (García-Aguilar et al. 2018). The population size of the California stock of Northern fur seals was estimated from pup counts multiplied by an expansion factor (San Miguel Island) and maximum pup, juvenile, and adult counts (Farrallon Islands) at rookeries. The population size of the Eastern U.S. stock of Steller sea lions was estimated from pup counts and non-pup counts at rookeries in Southeast Alaska, British Columbia, Oregon, and California. The population size of the California stock of Northern Elephant seals was estimated from pup counts at rookeries multiplied by the inverse of the expected ratio of pups to total animals (McCann, 1985; Lowry et al., 2014). 3 These values, found in NMFS' SARs, represent annual levels of human-caused mortality and serious injury (M/SI) from all sources combined ( e.g., commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial fisheries is presented in some cases. 4 SAR reports this stock abundance assessment as provisional and notes that it is an underestimate for the entire stock because it is based on surveys which covered only a small portion of the stock's range. 5 Humpback whales in the Central North Pacific stock and the CA/OR/WA stock are from three Distinct Population Segments (DPSs) based on animals identified in breeding areas in Hawaii, Mexico, and Central America. Both stocks and all three DPSs co-occur in the NWTT Study Area. 6 Stock abundance estimate is based on counts of individual animals identified from photo-identification catalogues. Surveys for abundance estimates of these stocks are conducted infrequently. 7 Stock abundance estimate is the best estimate counts, which have not been corrected to account for animals at sea during abundance surveys. Note —Unknown (UNK); Undetermined (UND); Not Applicable (NA); California (CA); Oregon (OR); Washington (WA). Below, we include additional information about the marine mammals in the area of the Specified Activities that informs our analysis, such as identifying known areas of important habitat or behaviors, or where Unusual Mortality Events (UME) have been designated. Critical Habitat Currently, only the distinct population segment (DPS) of Southern Resident killer whale (SRKW) has ESA-designated critical habitat in the NWTT Study Area. NMFS has recently published two proposed rules, however, proposing new or revised ESA-designated critical habitat for SRKW (84 FR 49214; September 19, 2019) and humpback whales (84 FR 54354; October 9, 2019). NMFS designated critical habitat for the SRKW DPS on November 29, 2006 (71 FR 69054) in inland waters of Washington State. Based on the natural history of the SRKWs and their habitat needs, NMFS identified physical or biological features essential to the conservation of the SRKW DPS: (1) Water quality to support growth and development; (2) prey species of sufficient quantity, quality, and availability to support individual growth, reproduction and development, as well as overall population growth; and (3) passage conditions to allow for migration, resting, and foraging. ESA-designated critical habitat consists of three areas: (1) The Summer Core Area in Haro Strait and waters around the San Juan Islands; (2) Puget Sound; and (3) the Strait of Juan de Fuca, which comprise approximately 2,560 square miles (mi 2 ) (6,630 square kilometers (km 2 )) of marine habitat. In designating critical habitat, NMFS considered economic impacts and impacts to national security, and concluded the benefits of exclusion of 18 military sites, comprising approximately 112 mi 2 (291 km 2 ), outweighed the benefits of inclusion because of national security impacts. On January 21, 2014, NMFS received a petition requesting revisions to the SRKW critical habitat designation. The petition requested NMFS revise critical habitat to include “inhabited marine waters along the West Coast of the United States that constitute essential foraging and wintering areas,” specifically the region between Cape Flattery, Washington and Point Reyes, California extending from the coast to a distance of 47.2 mi (76 km) offshore. The petition also requested NMFS adopt a fourth essential habitat feature in both current and expanded critical habitat relating to in-water sound levels. On September 19, 2019 (84 FR 54354), NMFS published a proposed rule proposing to revise the critical habitat designation for the SRKW DPS by designating six new areas (using the same essential features determined in 2006) along the U.S. West Coast. Specific new areas proposed along the U.S. West Coast include 15,626.6 mi 2 (40,472.7 km 2 ) of marine waters between the 6.1 m (20 ft) depth contour and the 200 m (656.2 ft) depth contour from the U.S. international border with Canada south to Point Sur, California. On March 15, 2018, several non-governmental organizations filed a lawsuit seeking court-ordered deadlines for the issuance of proposed and final rules to designate ESA critical habitat for the Central American, Mexico, and Western North Pacific DPSs of humpback whales. In 2018, NMFS convened a critical habitat review team to assess and evaluate information in support of critical habitat designation for these DPSs. On October 9, 2019 (84 FR 54354), NMFS published a proposed rule proposing ESA-designated critical habitat areas located off the coasts of California, Oregon, Washington, and Alaska, including areas within the NWTT Study Area. Based on consideration of national security and economic impacts, NMFS also proposed to exclude multiple areas from the designation for each DPS. Biologically Important Areas Biologically Important Areas (BIAs) include areas of known importance for reproduction, feeding, or migration, or areas where small and resident populations are known to occur (Van Parijs, 2015). Unlike ESA critical habitat, these areas are not formally designated pursuant to any statute or law, but are a compilation of the best available science intended to inform impact and mitigation analyses. An interactive map of the BIAs may be found here: https://cetsound.noaa.gov/biologically-important-area-map. BIAs off the West Coast of the continental United States with the potential to overlap portions of the NWTT Study Area include the following feeding and migration areas: Northern Puget Sound Feeding Area for gray whales (March-May); Northwest Feeding Area for gray whales (May-November); Northbound Migration Phase A for gray whales (January-July); Northbound Migration Phase B for gray whales (March-July); Northern Washington Feeding Area for humpback whales (May-November); Stonewall and Heceta Bank Feeding Area for humpback whales (May-November); and Point St. George Feeding Area for humpback whales (July-November) (Calambokidis et al., 2015). When comparing the geographic area of the NWTT Study Area with the BIAs off the West Coast of the continental United States, there is no direct spatial overlap between the Study Area and four of the offshore gray whale feeding areas—Grays Harbor, WA; Depoe Bay, OR; Cape Blanco and Orford Reef, OR; and Pt. St. George, CA. The NWTT Study Area does overlap with the Northwest WA gray whale feeding area and the Northern Puget Sound gray whale feeding area. There is no overlap of the gray whale migration corridor BIAs and the NWTT Study Area, with the exception of a portion of the Northwest coast of Washington approximately from Pacific Beach and extending north to the Strait of Juan de Fuca. The offshore Northern WA humpback whale feeding area is located entirely within the NWTT Study Area boundaries. The humpback whale feeding area at Stonewall and Hecta Bank only partially overlaps with the Study Area, and the feeding area at Point St. George has extremely limited overlap with the Study Area. All proposed activities occurring in the Offshore Area of the Study Area could potentially occur in these BIAs, except activities limited to greater than 50 nmi from shore (as described in the Proposed Mitigation Measures section). To mitigate impacts to marine mammals in these BIAs, the Navy would implement several procedural mitigation measures and mitigation areas (described in the Proposed Mitigation Measures section). National Marine Sanctuaries Under Title III of the Marine Protection, Research, and Sanctuaries Act of 1972 (also known as the National Marine Sanctuaries Act (NMSA)), NOAA can establish as national marine sanctuaries (NMS), areas of the marine environment with special conservation, recreational, ecological, historical, cultural, archaeological, scientific, educational, or aesthetic qualities. Sanctuary regulations prohibit or regulate activities that could destroy, cause the loss of, or injure sanctuary resources pursuant to the regulations for that sanctuary and other applicable law (15 CFR part 922). NMSs are managed on a site-specific basis, and each sanctuary has site-specific regulations. Most, but not all, sanctuaries have site-specific regulatory exemptions from the prohibitions for certain military activities. Separately, section 304(d) of the NMSA requires Federal agencies to consult with the Office of National Marine Sanctuaries whenever their activities are likely to destroy, cause the loss of, or injure a sanctuary resource. One NMS, the Olympic Coast NMS managed by the Office of National Marine Sanctuaries, is located within the offshore portion of the NWTT Study Area (for a map of the location of this NMS see Chapter 6 of the 2019 NWTT DSEIS/OEIS and Figure 6-1). The Olympic Coast NMS includes 3,188 mi 2 of marine waters and submerged lands off the Olympic Peninsula coastline. The sanctuary extends 25-50 mi. (40.2-80.5 km) seaward, covering much of the continental shelf and portions of three major submarine canyons. The boundaries of the sanctuary as defined in the Olympic Coast NMS regulations (15 CFR part 922, subpart O) extend from Koitlah Point, due north to the United States/Canada international boundary, and seaward to the 100-fathom isobath (approximately 180 m in depth). The seaward boundary of the sanctuary follows the 100-fathom isobath south to a point due west of Copalis River, and cuts across the tops of Nitinat, Juan de Fuca, and the Quinault Canyons. The shoreward boundary of the sanctuary is at the mean lower low-water line when adjacent to American Indian lands and state lands, and includes the intertidal areas to the mean higher high-water line when adjacent to federally managed lands. When adjacent to rivers and streams, the sanctuary boundary cuts across the mouths but does not extend up river or up stream. The Olympic Coast NMS includes many types of productive marine habitats including kelp forests, subtidal reefs, rocky and sand intertidal zones, submarine canyons, rocky deep-sea habitat, and plankton-rich upwelling zones. These habitats support the Sanctuary's rich biodiversity which includes 29 species of marine mammals that reside in or migrate through the Sanctuary (Office of National Marine Sanctuaries 2008). Additional information on the Olympic Coast NMS can be found at https://olympiccoast.noaa.gov. Unusual Mortality Events (UMEs) An UME is defined under Section 410(6) of the MMPA as a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response. Three UMEs with ongoing investigations in the NWTT Study Area that inform our analysis are discussed below. The California sea lion UME in California is still open, but will be closed soon. The Guadalupe fur seal UME in California and the gray whale UME along the west coast of North America are active and involve ongoing investigations. California Sea Lion UME From January 2013 through September 2016, a greater than expected number of young malnourished California sea lions ( Zalophus californianus ) stranded along the coast of California. Sea lions stranding from an early age (6-8 months old) through two years of age (hereafter referred to as juveniles) were consistently underweight without other disease processes detected. Of the 8,122 stranded juveniles attributed to the UME, 93 percent stranded alive (n = 7,587, with 3,418 of these released after rehabilitation) and 7 percent (n = 531) stranded dead. Several factors are hypothesized to have impacted the ability of nursing females and young sea lions to acquire adequate nutrition for successful pup rearing and juvenile growth. In late 2012, decreased anchovy and sardine recruitment (CalCOFI data, July 2013) may have led to nutritionally stressed adult females. Biotoxins were present at various times throughout the UME, and while they were not detected in the stranded juvenile sea lions (whose stomachs were empty at the time of stranding), biotoxins may have impacted the adult females' ability to support their dependent pups by affecting their cognitive function ( e.g., navigation, behavior towards their offspring). Therefore, the role of biotoxins in this UME, via its possible impact on adult females' ability to support their pups, is unclear. The proposed primary cause of the UME was malnutrition of sea lion pups and yearlings due to ecological factors. These factors included shifts in distribution, abundance and/or quality of sea lion prey items around the Channel Island rookeries during critical sea lion life history events (nursing by adult females, and transitioning from milk to prey by young sea lions). These prey shifts were most likely driven by unusual oceanographic conditions at the time due to the “Warm Water Blob” and El Niño. This investigation will soon be closed. Please refer to: https://www.fisheries.noaa.gov/national/marine-life-distress/2013-2017-california-sea-lion-unusual-mortality-event-california for more information on this UME. Guadalupe Fur Seal UME Increased strandings of Guadalupe fur seals began along the entire coast of California in January 2015 and were eight times higher than the historical average (approximately 10 seals/yr). Strandings have continued since 2015 and remained well above average through 2019. Numbers by year are as follows: 2015 (98), 2016 (76), 2017 (62), 2018 (45), 2019 (116), 2020 (3 as of March 6, 2020). The total number of Guadalupe fur seals stranding in California from January 1, 2015, through March 6, 2020, in the UME is 400. Additionally, strandings of Guadalupe fur seals became elevated in the spring of 2019 in Washington and Oregon; subsequently, strandings for seals in these two states have been added to the UME starting from January 1, 2019. The current total number of strandings in Washington and Oregon is 94 seals, including 91 in 2019 and 3 in 2020 of 3/6/2020. Strandings are seasonal and generally peak in April through June of each year. The Guadalupe fur seal strandings have been mostly weaned pups and juveniles (1-2 years old) with both live and dead strandings occurring. Current findings from the majority of stranded animals include primary malnutrition with secondary bacterial and parasitic infections. The California portion of this UME was occurring in the same area as the 2013-2016 California sea lion UME. This investigation is ongoing. Please refer to: https://www.fisheries.noaa.gov/national/marine-life-distress/2015-2019-guadalupe-fur-seal-unusual-mortality-event-california for more information on this UME. Gray Whale UME Since January 1, 2019, elevated gray whale strandings have occurred along the west coast of North America, from Mexico to Canada. As of March 13, 2020, there have been a total of 264 strandings along the coasts of the United States, Canada, and Mexico, with 129 of those strandings occurring along the U.S. coast. Of the strandings on the U.S. coast, 48 have occurred in Alaska, 35 in Washington, 6 in Oregon, and 40 in California. Partial necropsy examinations conducted on a subset of stranded whales have shown evidence of poor to thin body condition. As part of the UME investigation process, NOAA is assembling an independent team of scientists to coordinate with the Working Group on Marine Mammal Unusual Mortality Events to review the data collected, sample stranded whales, and determine the next steps for the investigation. Please refer to: https://www.fisheries.noaa.gov/national/marine-life-distress/2019-gray-whale-unusual-mortality-event-along-west-coast for more information on this UME. Marine Mammal Hearing Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Current data indicate that not all marine mammal species have equal hearing capabilities ( e.g., Richardson et al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al. (2007) recommended that marine mammals be divided into functional hearing groups based on directly measured or estimated hearing ranges on the basis of available behavioral response data, audiograms derived using auditory evoked potential techniques, anatomical modeling, and other data. Note that no direct measurements of hearing ability have been successfully completed for mysticetes ( i.e., low-frequency cetaceans). Subsequently, NMFS (2018) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65 dB threshold from the normalized composite audiograms, with the exception for lower limits for low-frequency cetaceans where the lower bound was deemed to be biologically implausible and the lower bound from Southall et al. (2007) retained. The functional groups and the associated frequencies are indicated below (note that these frequency ranges correspond to the range for the composite group, with the entire range not necessarily reflecting the capabilities of every species within that group): • Low-frequency cetaceans (mysticetes): Generalized hearing is estimated to occur between approximately 7 Hz and 35 kHz; • Mid-frequency cetaceans (larger toothed whales, beaked whales, and most delphinids): Generalized hearing is estimated to occur between approximately 150 Hz and 160 kHz; • High-frequency cetaceans (porpoises, river dolphins, and members of the genera Kogia and Cephalorhynchus; including two members of the genus Lagenorhynchus, on the basis of recent echolocation data and genetic data): Generalized hearing is estimated to occur between approximately 275 Hz and 160 kHz; • Pinnipeds in water; Phocidae (true seals): Generalized hearing is estimated to occur between approximately 50 Hz to 86 kHz; and • Pinnipeds in water; Otariidae (eared seals): Generalized hearing is estimated to occur between 60 Hz and 39 kHz. The pinniped functional hearing group was modified from Southall et al. (2007) on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range (Hemilä et al., 2006; Kastelein et al., 2009; Reichmuth and Holt, 2013). For more details concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of the available information. Potential Effects of Specified Activities on Marine Mammals and Their Habitat This section includes a discussion of the ways that components of the specified activity may impact marine mammals and their habitat. The Estimated Take of Marine Mammals section later in this rule includes a quantitative analysis of the number of instances of take that could occur from these activities. The Preliminary Analysis and Negligible Impact Determination section considers the content of this section, the Estimated Take of Marine Mammals section, and the Proposed Mitigation Measures section to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and whether those impacts on individuals are likely to adversely affect the species through effects on annual rates of recruitment or survival. The Navy has requested authorization for the take of marine mammals that may occur incidental to training and testing activities in the NWTT Study Area. The Navy analyzed potential impacts to marine mammals from acoustic and explosive sources and from vessel use in its rulemaking/LOA application. NMFS carefully reviewed the information provided by the Navy along with independently reviewing applicable scientific research and literature and other information to evaluate the potential effects of the Navy's activities on marine mammals, which are presented in this section. Other potential impacts to marine mammals from training and testing activities in the NWTT Study Area were analyzed in the 2019 NWTT DSEIS/OEIS, in consultation with NMFS as a cooperating agency, and determined to be unlikely to result in marine mammal take. This includes serious injury or mortality from explosives. Therefore, the Navy has not requested authorization for take of marine mammals incidental to other components of their proposed Specified Activities, and we agree that incidental take is unlikely to occur from those components. In this proposed rule, NMFS analyzes the potential effects on marine mammals from the activity components that may cause the take of marine mammals: Exposure to acoustic or explosive stressors including non-impulsive (sonar and other transducers) and impulsive (explosives) stressors and vessel movement. For the purpose of MMPA incidental take authorizations, NMFS' effects assessments serve four primary purposes: (1) To determine whether the specified activities would have a negligible impact on the affected species or stocks of marine mammals (based on whether it is likely that the activities would adversely affect the species or stocks through effects on annual rates of recruitment or survival); (2) to determine whether the specified activities would have an unmitigable adverse impact on the availability of the species or stocks for subsistence uses; (3) to prescribe the permissible methods of taking ( i.e., Level B harassment (behavioral harassment and temporary threshold shift (TTS)), Level A harassment (permanent threshold shift (PTS) and non-auditory injury), serious injury, or mortality), including identification of the number and types of take that could occur by harassment, serious injury, or mortality, and to prescribe other means of effecting the least practicable adverse impact on the species or stocks and their habitat ( i.e., mitigation measures); and (4) to prescribe requirements pertaining to monitoring and reporting. In this section, NMFS provides a description of the ways marine mammals may be generally affected by these activities in the form of mortality, physical trauma, sensory impairment (permanent and temporary threshold shifts and acoustic masking), physiological responses (particular stress responses), behavioral disturbance, or habitat effects. Explosives and vessel strikes, which have the potential to result in incidental take from serious injury and/or mortality, will be discussed in more detail in the Estimated Take of Marine Mammals section. The Estimated Take of Marine Mammals section also discusses how the potential effects on marine mammals from non-impulsive and impulsive sources relate to the MMPA definitions of Level A Harassment and Level B Harassment, and quantifies those effects that rise to the level of a take. The Preliminary Analysis and Negligible Impact Determination section assesses whether the proposed authorized take would have a negligible impact on the affected species and stocks. Potential Effects of Underwater Sound Anthropogenic sounds cover a broad range of frequencies and sound levels and can have a range of highly variable impacts on marine life, from none or minor to potentially severe responses, depending on received levels, duration of exposure, behavioral context, and various other factors. The potential effects of underwater sound from active acoustic sources can possibly result in one or more of the following: Temporary or permanent hearing impairment, non-auditory physical or physiological effects, behavioral disturbance, stress, and masking (Richardson et al., 1995; Gordon et al., 2004; Nowacek et al., 2007; Southall et al., 2007; Götz et al., 2009, Southall et al., 2019a). The degree of effect is intrinsically related to the signal characteristics, received level, distance from the source, and duration of the sound exposure. In general, sudden, high level sounds can cause hearing loss, as can longer exposures to lower level sounds. Temporary or permanent loss of hearing can occur after exposure to noise, and occurs almost exclusively for noise within an animal's hearing range. Note that in the following discussion, we refer in many cases to a review article concerning studies of noise-induced hearing loss conducted from 1996-2015 ( i.e., Finneran, 2015). For study-specific citations, please see that work. We first describe general manifestations of acoustic effects before providing discussion specific to the Navy's activities. Richardson et al. (1995) described zones of increasing intensity of effect that might be expected to occur, in relation to distance from a source and assuming that the signal is within an animal's hearing range. First is the area within which the acoustic signal would be audible (potentially perceived) to the animal, but not strong enough to elicit any overt behavioral or physiological response. The next zone corresponds with the area where the signal is audible to the animal and of sufficient intensity to elicit behavioral or physiological responsiveness. Third is a zone within which, for signals of high intensity, the received level is sufficient to potentially cause discomfort or tissue damage to auditory systems. Overlaying these zones to a certain extent is the area within which masking ( i.e., when a sound interferes with or masks the ability of an animal to detect a signal of interest that is above the absolute hearing threshold) may occur; the masking zone may be highly variable in size. We also describe more severe potential effects ( i.e., certain non-auditory physical or physiological effects). Potential effects from impulsive sound sources can range in severity from effects such as behavioral disturbance or tactile perception to physical discomfort, slight injury of the internal organs and the auditory system, or mortality (Yelverton et al., 1973). Non-auditory physiological effects or injuries that theoretically might occur in marine mammals exposed to high level underwater sound or as a secondary effect of extreme behavioral reactions ( e.g., change in dive profile as a result of an avoidance reaction) caused by exposure to sound include neurological effects, bubble formation, resonance effects, and other types of organ or tissue damage (Cox et al., 2006; Southall et al., 2007; Zimmer and Tyack, 2007; Tal et al., 2015). Acoustic Sources Direct Physiological Effects Non-impulsive sources of sound can cause direct physiological effects including noise-induced loss of hearing sensitivity (or “threshold shift”), nitrogen decompression, acoustically-induced bubble growth, and injury due to sound-induced acoustic resonance. Only noise-induced hearing loss is anticipated to occur due to the Navy's activities. Acoustically-induced (or mediated) bubble growth and other pressure-related physiological impacts are addressed briefly below, but are not expected to result from the Navy's activities. Separately, an animal's behavioral reaction to an acoustic exposure might lead to physiological effects that might ultimately lead to injury or death, which is discussed later in the Stranding subsection. Hearing Loss—Threshold Shift Marine mammals exposed to high-intensity sound, or to lower-intensity sound for prolonged periods, can experience hearing threshold shift, which is the loss of hearing sensitivity at certain frequency ranges after cessation of sound (Finneran, 2015). Threshold shift can be permanent (PTS), in which case the loss of hearing sensitivity is not fully recoverable, or temporary (TTS), in which case the animal's hearing threshold would recover over time (Southall et al., 2007). TTS can last from minutes or hours to days ( i.e., there is recovery back to baseline/pre-exposure levels), can occur within a specific frequency range ( i.e., an animal might only have a temporary loss of hearing sensitivity within a limited frequency band of its auditory range), and can be of varying amounts ( e.g., an animal's hearing sensitivity might be reduced by only 6 dB or reduced by 30 dB). While there is no simple functional relationship between TTS and PTS or other auditory injury ( e.g., neural degeneration), as TTS increases, the likelihood that additional exposure sound pressure level (SPL) or duration will result in PTS or other injury also increases (see also the 2019 NWTT DSEIS/OEIS for additional discussion). Exposure thresholds for the occurrence of PTS or other auditory injury can therefore be defined based on a specific amount of TTS; that is, although an exposure has been shown to produce only TTS, we assume that any additional exposure may result in some PTS or other injury. The specific upper limit of TTS is based on experimental data showing amounts of TTS that have not resulted in PTS or injury. In other words, we do not need to know the exact functional relationship between TTS and PTS or other injury, we only need to know the upper limit for TTS before some PTS or injury is possible. In severe cases of PTS, there can be total or partial deafness, while in most cases the animal has an impaired ability to hear sounds in specific frequency ranges (Kryter, 1985). When PTS occurs, there is physical damage to the sound receptors in the ear ( i.e., tissue damage), whereas TTS represents primarily tissue fatigue and is reversible (Southall et al., 2007). PTS is permanent ( i.e., there is incomplete recovery back to baseline/pre-exposure levels), but also can occur in a specific frequency range and amount as mentioned above for TTS. In addition, other investigators have suggested that TTS is within the normal bounds of physiological variability and tolerance and does not represent physical injury ( e.g., Ward, 1997). Therefore, NMFS does not consider TTS to constitute auditory injury. The following physiological mechanisms are thought to play a role in inducing auditory threshold shift: Effects to sensory hair cells in the inner ear that reduce their sensitivity; modification of the chemical environment within the sensory cells; residual muscular activity in the middle ear; displacement of certain inner ear membranes; increased blood flow; and post-stimulatory reduction in both efferent and sensory neural output (Southall et al., 2007). The amplitude, duration, frequency, temporal pattern, and energy distribution of sound exposure all can affect the amount of associated threshold shift and the frequency range in which it occurs. Generally, the amount of threshold shift, and the time needed to recover from the effect, increase as amplitude and duration of sound exposure increases. Human non-impulsive noise exposure guidelines are based on the assumption that exposures of equal energy (the same sound exposure level (SEL)) produce equal amounts of hearing impairment regardless of how the sound energy is distributed in time (NIOSH, 1998). Previous marine mammal TTS studies have also generally supported this equal energy relationship (Southall et al., 2007). However, some more recent studies concluded that for all noise exposure situations the equal energy relationship may not be the best indicator to predict TTS onset levels (Mooney et al., 2009a and 2009b; Kastak et al., 2007). These studies highlight the inherent complexity of predicting TTS onset in marine mammals, as well as the importance of considering exposure duration when assessing potential impacts. Generally, with sound exposures of equal energy, those that were quieter (lower SPL) with longer duration were found to induce TTS onset at lower levels than those of louder (higher SPL) and shorter duration. Less threshold shift will occur from intermittent sounds than from a continuous exposure with the same energy (some recovery can occur between intermittent exposures) (Kryter et al., 1966; Ward, 1997; Mooney et al., 2009a, 2009b; Finneran et al., 2010). For example, one short but loud (higher SPL) sound exposure may induce the same impairment as one longer but softer (lower SPL) sound, which in turn may cause more impairment than a series of several intermittent softer sounds with the same total energy (Ward, 1997). Additionally, though TTS is temporary, very prolonged or repeated expo [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2020-08533. Public record. Not legal advice.