Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Testing and Training Operations in the Eglin Gulf Test and Training Range

Federal RegisterFeb 7, 2023

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

[Docket No. 230127-0029]

RIN 0648-BL77

Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Testing and Training Operations in the Eglin Gulf Test and Training Range

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. Department of the Air Force (USAF) to take marine mammals incidental to testing and training military operations proposed to be conducted in the Eglin Gulf Test and Training Range (EGTTR) from 2023 to 2030 in the Gulf of Mexico. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue regulations and subsequent Letter of Authorization (LOA) to the USAF 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 LOA. Agency responses to public comments will be summarized in the notice of the final decision in the final rule. The USAF'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 March 9, 2023.

ADDRESSES:

Submit all electronic public comments via the Federal e-Rulemaking Portal. Go to

https://www.regulations.gov

and enter NOAA-NMFS-2021-0064 in the Search box. Click on the “Comment” icon, complete the required fields, and enter or attach your comments.

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 USAF's application and other supporting documents and documents cited herein may be obtained online at:

https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-air-force-eglin-gulf-testing-and-training.

In case of problems accessing these documents, please use the contact listed here (see

FOR FURTHER INFORMATION CONTACT

FOR FURTHER INFORMATION CONTACT:

Robert Pauline, 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 USAF's training and testing activities (which qualify as military readiness activities) from air-to-surface operations that involve firing live or inert munitions, including missiles, bombs, and gun ammunition, from aircraft at various types of targets on the water surface. Live munitions used in the EGTTR are set to detonate either in the air a few feet above the water, instantaneously upon contact with the water or target, or approximately 5 to 10 feet (ft) (1.5 to 3 meters (m)) below the water surface. There would also be training exercises for Navy divers that require the placement of small explosive charges by hand to disable live mines.

Eglin Air Force Base (AFB) would conduct operations in the existing Live Impact Area (LIA). In addition, the USAF is also proposing to create and use a new, separate LIA within the EGTTR that would be used for live missions in addition to the existing LIA. Referred to as the East LIA, it is located approximately 40 nautical miles (nmi)/(74 kilometers (km)) southeast of the existing LIA. (See Figure 1).

NMFS received an application from the USAF requesting 7-year regulations and an authorization to incidentally take individuals of multiple species of marine mammals (“USAF's rulemaking/LOA application” or “USAF's application”). Take is anticipated to occur by Level A and Level B harassment incidental to the USAF's training and testing activities, with no serious injury or mortality expected or proposed for authorization.

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, a notice of a proposed authorization is provided to the public for review and the opportunity to 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”). NMFS also must prescribe the 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 7 years. Prior to this amendment, all incidental take rules under section 101(a)(5)(A) were limited to 5 years.

National Environmental Policy Act

To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321

et seq.

) and NOAA Administrative Order (NAO) 216-6A, NMFS must evaluate our USAF's proposed activities and alternatives with respect to potential impacts on the human environment. Accordingly, NMFS plans to adopt the Eglin Gulf Test and Training Range Environmental Assessment (2022 REA) (USAF 2022), provided our independent evaluation of the document finds that it includes adequate information analyzing the effects on the human environment of issuing regulations and LOAs under the MMPA. NMFS is a cooperating agency on the 2022 REA and has worked with the USAF developing the document. The draft 2022 REA was made available for public comment on December 13, 2022 through January 28, 2023. We will review all comments submitted in response to the request for comments on the 2022 REA and in response to the request for comments on this proposed rule prior to concluding our NEPA process or making a final decision on this proposed rule for the issuance of regulations under the MMPA and any subsequent issuance of a Letter of Authorization (LOA) to the USAF to incidentally take marine mammals during the specified activities.

Summary of Request

On January 18, 2022, NMFS received an application from the USAF for authorization to take marine mammals by Level A and Level B harassment incidental to training and testing activities (categorized as military readiness activities) in the EGTTR for a period of 7 years. On June 17, 2022 NMFS received an adequate and complete application for missions that would include air-to-surface operations that involve firing live or inert munitions, including missiles, bombs, and gun ammunition from aircraft at targets on the water surface. The types of targets used vary by mission and primarily include stationary, remotely controlled, and towed boats, inflatable targets, and marker flares. Live munitions used in the EGTTR are set to detonate either in the air a few feet above the water surface (airburst detonation), instantaneously upon contact with the water or target (surface detonation), or approximately 5 to 10 feet (1.5 to 3 m) below the water surface (subsurface detonation). On July 17, 2022, we published a notice of receipt (NOR) of application in the

Federal Register

(87 FR 42711), requesting comments and information related to the USAF's request. The public comment period was open for 30 days. We reviewed and considered all comments and information received on the NOR in development of this proposed rule.

On February 8, 2018, NMFS promulgated a rulemaking and issued an LOA for takes of marine mammals incidental to Eglin AFB's training and testing operations in the EGTTR (83 FR 5545). Current EGTTR operations are authorized under the 2018 EGTTR LOA which will expire on February 12, 2023. Under this proposed rulemaking action, the EGTTR would continue to be used during the next mission period based on the maritime training and testing requirements of the various military units that use the EGTTR. The next mission period would span 7 years, from 2023 to 2030. Most operations during this period would be a continuation of the same operations conducted by the same military units during the previous mission period. There would, however, be an increase in the annual quantities of all general categories of munitions (bombs, missiles, and gun ammunition) under the USAF's proposed activities, except for live gun ammunition, which is proposed to be used less over the next mission period. The highest net explosive weight (NEW) of the munitions under the USAF's proposed activities would be 945 pounds (lb) (430 kilograms (kg), which was also the highest NEW for the previous mission period. Live missions proposed for the 2023-2030 period would be conducted in the existing Live Impact Area (LIA) within the EGTTR. Certain missions may also be conducted in the proposed East LIA, which would be a new, separate area within the EGTTR where live munitions would be used. The USAF's rulemaking/LOA application reflects the most up-to-date compilation of training and testing activities deemed necessary to accomplish military readiness requirements. EGTTR training and testing operations are critical for achieving military readiness and the overall goals of the National Defense Strategy. The regulations proposed in this action, if issued, would be effective for seven years, beginning from the date of issuance.

Description of the Proposed Activity

The USAF requests authorization to take marine mammals incidental to conducting training and testing activities. The USAF has determined that acoustic and explosives stressors are most likely to result in impacts on marine mammals that could qualify as take under the MMPA, and NMFS concurs with this determination. Eglin AFB proposes to conduct military aircraft missions within the EGTTR that involve the employment of multiple types of live (explosive) and inert (non-explosive) munitions (

i.e.,

missiles, bombs, and gun ammunition) against various surface targets. Munitions may be delivered by multiple types of aircraft including, but not limited to, fighter jets, bombers, and gunships.

Detailed descriptions of these activities are described in the Eglin Gulf Test and Training Range (EGTTR) Range Environmental Assessment (REA) (USAF 2022), currently under preparation as well as the USAF's rulemaking/LOA application. (

https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-air-force-eglin-gulf-testing-and-training

). A summary of the proposed activities and are presented below.

Dates and Duration

The specified activities would occur at any time during the 7-year period of validity of the regulations. The proposed amount of training and testing activities are described in the Detailed Description of the Specified Activities section.

Geographical Region

The Eglin Military Complex encompasses approximately 724 square miles (1,825 km

of land in the Florida Panhandle and consists of the Eglin Reservation in Santa Rosa, Okaloosa, and Walton Counties, and property on Santa Rosa Island and Cape San Blas. The EGTTR is the airspace controlled by Eglin AFB over the Gulf of Mexico, beginning 3 nautical miles (nmi) (5.56

km) from shore, and the underlying Gulf of Mexico waters. The EGTTR extends southward and westward off the coast of Florida and encompasses approximately 102,000 nmi (349,850 km

). It is subdivided into blocks of airspace that consist of Warning Areas W-155, W-151, W-470, W-168, and W-174 and Eglin Water Test Areas 1 through 6 (Figure 1). Most of the blocks are further subdivided into smaller airspace units for scheduling purposes (for example, W-151A, B, C, and D). Although Eglin AFB may use any portion of the EGTTR, the majority of training and testing operations proposed for the 2023-2030 mission period would occur in Warning Area W-151. The nearshore boundary of W-151 parallels much of the coastline of the Florida Panhandle and extends horizontally from 3 nmi (5.56 km) offshore to approximately 85 to 100 nmi (158 to185 km) to offshore, depending on the specific portion of its outer boundary. W-151 encompasses approximately 10,247 nmi

(35146 km

) and includes water depths that range from approximately 5 to 720 m. The existing LIA, which is the portion of the EGTTR where the use of live munitions is currently authorized, lies mostly within W-151. The existing LIA encompasses approximately 940 nmi

(3,224 km

and includes water depths that range from approximately 30 to 145 m (Figure 2). This is where live munitions within the EGTTR are currently used in the existing LOA (83 FR 5545; February 8, 2018) and where the Gulf Range Armament Test Vessel (GRATV) is anchored. The GRATV remains anchored at a specific location during a given mission; however, it is mobile and relocated within the LIA based on mission needs.

The USAF's proposed activities provide for the creation of a new, separate area within the EGTTR that would be used for live missions in addition to the existing LIA. This area, herein referred to as the East LIA, would be located approximately 40 NM offshore of Eglin AFB property on Cape San Blas. Cape San Blas is located on St. Joseph Peninsula in Gulf County, Florida, approximately 90 mi (144 km) southeast of the Eglin Reservation. Eglin AFB facilities on Cape San Blas remotely support EGTTR operations via radar tracking, telemetry, and other functions. The proposed East LIA would be circular-shaped and have a radius of approximately 10 nmi (18.5 km) and a total area of approximately 314 NM

. Water depths range from approximately 35 to 95 m. The general location of the proposed East LIA is shown in Figure 2. Establishment of the East LIA would allow Eglin AFB to maximize the flight range for large-footprint weapons and minimize the distance, time, and cost of deploying support vessels and targets. Based on these factors, the East LIA would allow testing of weapon systems and flight profiles that cannot be conducted within the constraints of the existing LIA.

BILLING CODE 3510-22-P

EP07FE23.046

EP07FE23.047

BILLING CODE 3510-22-C

Detailed Description of the Specified Activities

This section provides descriptions of each military user group's proposed EGTTR operations, as well as information regarding munitions proposed to be used during the operations. This information includes munition type, category, net explosive weight (NEW), detonation scenario, and annual quantity proposed to be expended in the EGTTR. NEW applies only to live munitions and is the total mass of the explosive substances in a given munition, without packaging, casings, bullets, or other non-explosive components of the munition. Note that for some munitions the warhead is removed and replaced with a telemetry package that tracks the munition's path and/or Flight Termination System (FTS) that ends the flight of the munition in a controlled manner. These munitions have been categorized as live munitions with NEWs that range from 0.30 to 0.70

lb (0.13 to 0.31 kg) While certain munitions with only FTS may be considered inert due to negligible NEW, those contained here are considered to be live with small amounts of NEW. The detonation scenario applies only to live munitions which are set to detonate in one of three ways: (1) in the air a few feet above the water surface, referred to as airburst or height of burst (HOB); (2) instantaneously upon contact with the water or target on the water surface; or (3) after a slight delay, up to 10 milliseconds, after impact, which would correspond to a subsurface detonation at a water depth of approximately 5 to 10 ft (1.5 to 3 m). Estimated take is only modeled for scenarios (2) and (3). The proposed annual expenditures of munitions are the quantities determined necessary to meet the mission requirements of the user groups.

Live missions proposed for the 2023-2030 period would be conducted in the existing LIA and potentially in the proposed East LIA, depending on the mission type and objectives. Live missions that involve only airburst or aerial target detonations would continue to be conducted in or outside the LIA in any portion of the EGTTR; such detonations have no appreciable effect on marine mammals because there is negligible transmission of pressure or acoustic energy across the air-water interface. Use of inert munitions and live air-to-surface gunnery operations would also continue to occur in or outside the LIA, subject to proposed mitigation and monitoring measures.

Eglin AFB proposes the following actions in the EGTTR which would be conducted in the existing LIA and potentially in the proposed East LIA, depending on the mission type and objectives:

(1) 53rd Weapons Evaluation Group missions that involve air-to-ground Weapons System Evaluation Program (WSEP) known as Combat Hammer which tests various types of munitions against small target boats and air-to-air missile testing known as Combat Archer;

(2) Continuation of the Air Force Special Operations Command (AFSOC) training missions in the EGTTR primarily involving air-to-surface gunnery, bomb, and missile exercises including AC-130 gunnery training, CV-22 training, and bomb and missile training;

(3) 96th Operations Group missions including AC-130 gunnery testing against floating marker targets on the water surface, MQ-9 air-to-surface testing, and 780th Test Squadron Precision Strike Weapons testing including air-launched cruise missile tests, air-to-air missile tests, Longbow and Joint Air-to-Ground Missile (JAGM) testing; Spike Non-Line-of-Sight (NLOS) air-to-surface missile testing, Patriot missile testing, Hypersonic Weapon Testing, sink at-sea live-fire training exercises (SINKEX), and testing using live and inert munitions against targets on the water surface; and

(4) Naval School Explosive Ordnance Disposal (NAVSCOLEOD) training missions that involve students diving and placing small explosive charges adjacent to inert mines.

53rd Weapons Evaluation Group

The 53rd Weapons Evaluation Group (53 WEG) conducts the USAF's air-to-ground Weapons System Evaluation Program (WSEP). The Combat Hammer program involves testing various types of live and inert munitions against small target boats. This testing is conducted to develop tactics, techniques, and procedures (TTP) to be used by USAF aircraft to counter small, maneuvering, hostile vessels. Combat Hammer missions proposed in the EGTTR for the 2023-2030 period would involve the use of several types of aircraft, including F-15, F-16, F-18, F-22, F-35, and A-10 fighter aircraft, AC-130 gunships, B-1, B-2, and B-52 bomber aircraft, and MQ-1 and MQ-9 drone aircraft. USAF, Air National Guard, and U.S. Navy units would support these missions. Live munitions would be deployed against static (anchored), remotely controlled, and towed targets. Static and remotely controlled targets would consist of stripped boat hulls with simulated systems and, in some cases, heat sources. Various types of live and inert munitions are used during Combat Hammer missions in the EGTTR, including missiles, bombs, and gun ammunition. Table 1 presents information on the munitions proposed for Combat Hammer missions in the EGTTR during the 2023-2030 period.

Table 1—Proposed Munitions for WSEP Combat Hammer Missions in the EGTTR

Type

Category

Net explosive weight (lb)/(kg)

Destination scenario

Annual quantity

Live Munitions:

AGR-20

Rocket

9.1 (4.1)

Surface

AGM-158D JASSM XR

Missile

240.26 (108.9)

Surface

AGM-158B JASSM ER

Missile

240.26 (108.9)

Surface

AGM-158A JASSM

Missile

240.26 (108.9)

Surface

AGM-65D

Missile

150 (68)

Surface

AGM-65G2

Missile

145 (65.7)

Surface

AGM-65H2

Missile

150 (68)

Surface

AGM-65K2

Missile

145 (65.7)

Surface

AGM-65L

Missile

150 (68)

Surface

AGM-114 N-6D with TM

Missile

29.1 (13.2)

Surface

AGM-114 N-4D with TM

Missile

29.94 (13.6)

Surface

AGM-114 R2 with TM (R10)

Missile

27.41 (12.4)

Surface

AGM-114 R-9E with TM (R11)

Missile

27.38 (12.4)

Surface

AGM-114Q with TM

Missile

20.16 (9.1)

Surface

CBU-105D

Bomb

108.6 (49.5)

HOB

GBU-53/B (GTV)

Bomb

0.34(0.1)

HOB/Surface

GBU-39 SDB (GTV)

Bomb

0.39(0.1)

Surface

AGM-88C w/FTS

Missile

0.70 (0.31)

Surface

AGM-88B w/FTS

Missile

0.70 (0.31)

Surface

AGM-88F w/FTS

Missile

0.70(0.31)

Surface

AGM-88G w/FTS

Missile

0.70(0.31)

Surface

AGM-179 JAGM

Missile

27.47(12.5)

Surface

GBU-69

Bomb

6.88 (3.1)

Surface

GBU-70

Bomb

6.88 (3.1)

Surface

AGM-176

Missile

8.14 (3.7)

Surface

GBU-54 KMU-572C/B

Bomb

193 (87.5)

Surface

GBU-54 KMU-572B/B

Bomb

193

Surface

PGU-43 (105 mm)

Gun Ammunition

4.7

Surface

100

Inert Munitions:

ADM-160B MALD

Missile

N/A

ADM-160C MALD-J

Missile

N/A

ADM-160C-1 MALD-J

Missile

N/A

ADM-160D MALD-J

Missile

N/A

GBU-10

Bomb

N/A

GBU-12

Bomb

N/A

GBU-49

Bomb

N/A

GBU-24/B (84)

Bomb

N/A

GBU-24A/B (109)

Bomb

N/A

GBU-31B(v)1

Bomb

N/A

GBU-31C(v)1

Bomb

N/A

GBU-31B(v)3

Bomb

N/A

GBU-31C(v)3

Bomb

N/A

GBU-32C

Bomb

N/A

GBU-38B

Bomb

N/A

GBU-38C w/BDU-50 (No TM)

Bomb

N/A

GBU-38C

Bomb

N/A

GBU-54 KMU-572C/B

Bomb

N/A

GBU-54 KMU-572B/B

Bomb

N/A

GBU-69

Bomb

N/A

BDU-56A/B

Bomb

N/A

PGU-27 (20 mm)

Gun Ammunition

0.09 (0.04)

N/A

16,000

PGU-15 (30 mm)

Gun Ammunition

N/A

16,000

PGU-25 (25 mm)

Gun Ammunition

N/A

16,000

ALE-50

Decoy System

N/A

Warhead replaced by FTS/TM. Identified NEW is for the FTS.

ADM = American Decoy Missile; AGM = Air-to-Ground Missile; ALE = Ammunition Loading Equipment; BDU = Bomb Dummy Unit; CBU = Cluster Bomb Unit; EGTTR = Eglin Gulf Test and Training Range; ER = Extended Range; FTS = Flight Termination System; GBU = Guided Bomb Unit; GTV = Guided Test Vehicle; HOB = height of burst; JAGM = Joint Air-to-Ground Missile; JASSM = Joint Air-to-Surface Standoff Missile; lb = pound(s); MALD = Miniature Air-Launched Decoy; mm = millimeter(s); N/A = not applicable; PGU = Projectile Gun Unit; SDB = Small-Diameter Bomb, TM = telemetry; WSEP = Weapons System Evaluation Program.

The Combat Archer program involves live air-to-air missile testing in the EGTTR. Combat Archer missions also include firing inert gun ammunition and releasing flares and chaff from aircraft. Air-to-air missile testing during these missions specifically involves firing live AIM-9 Sidewinder and AIM-120 Advanced Medium-Range Air-to-Air Missiles (AMRAAMs) at BOM-167 Subscale Aerial Targets and QF-16 Full-Scale Aerial Targets to evaluate the effectiveness of missile delivery techniques. Combat Archer missions involve the use of several types of fighter aircraft, including the F-15, F-16, F-18, F-22, F-35, and A-10. Table 2 presents information on the munitions proposed to be used during Combat Archer missions in the EGTTR.

Table 2—Proposed Munitions for Combat Archer Missions in the EGTTR

Type

Category

Net explosive weight

(lb)/(kg)

Detonation scenario

Annual quantity

Live Munitions:

AIM-120D

Missile

113.05 (51.3)

HOB

AIM-120C7

Missile

113.05 (51.3)

HOB

AIM-120C5/6

Missile

113.05 (51.3)

HOB

AIM-120C3

Missile

102.65 (46.5)

HOB

AIM-120C3

Missile

117.94 (63.5)

HOB/Surface

AIM-120B

Missile

102.65 (46.5)

HOB

AIM-9X Blk I

Missile

60.25 (27.3)

HOB

AIM-9X Blk I

Missile

67.9 (30.8)

HOB/Surface

AIM-9X Blk II

Missile

60.25 (27.3)

HOB

AIM-9M-9

Missile

60.55 (27.3)

HOB

Inert Munitions:

AIM-260A JATM

Missile

N/A

PGU-27 (20 mm)

Gun Ammunition

N/A

80,000

PGU-23 (25 mm)

Gun Ammunition

N/A

6,000

MJU-7A/B Flare

Flare

N/A

1,800

R-188 Chaff

Chaff

N/A

6,000

R-196 (T-1) Chaff

Chaff

N/A

1,500

AIM = Air Intercept Missile; EGTTR = Eglin Gulf Test and Training Range; HOB = height of burst; JATM = Joint Advanced Tactical Missile; lb = pound(s); MJU = Mobile Jettison Unit; mm = millimeter(s); N/A = not applicable; PGU = Projectile Gun Unit; WSEP = Weapons System Evaluation Program.

Air Force Special Operations Command Training

The Air Force Special Operations Command (AFSOC) proposes to continue conducting training missions during the 2023-2030 period. These missions primarily involve air-to-surface gunnery, bomb, and missile exercises. Gunnery training in the EGTTR involves firing live rounds from AC-130 gunships at targets on the water surface. Gun ammunition used for this training primarily includes 30-millimeter (mm) High Explosive (HE) and 105 mm HE rounds. A standard 105 mm HE round has a NEW of 4.7 lb. The Training Round (TR) variant of the 105 mm HE round, which has a NEW of 0.35 lb, is used by AFSOC for nighttime missions. This TR was developed to have less explosive material to minimize potential impacts to protected marine species, which could not be adequately surveyed at night by earlier aircraft instrumentation. Since the development of the 105 mm HE TR, AC-130s have been equipped with low-light electro-optical and infrared sensor systems that provide excellent night vision. Targets used for AC-130 gunnery training include Mark (Mk)-25 marine markers and inflatable targets. During each gunnery training mission, gun firing can last up to 90 minutes but typically lasts approximately 30 minutes. Live firing is continuous, with pauses usually lasting well under 1 minute and rarely up to 5 minutes. Table 3 presents information on the rounds proposed for AC-130 gunnery training by AFSOC.

Table 3—Proposed Rounds for AC-130 Gunnery Training in the EGTTR

Type

Net explosive weight

(lb)/(kg)

Detonation scenario

Number of missions

Rounds per mission

Annual

quantity

Daytime Missions:

105 mm HE (FU)

4.7 (2.1)

Surface

750

30 mm HE

0.1 (0.04)

500

12,500

Nighttime Missions:

105 mm HE (TR)

0.35 (0.2

Surface

1,350

30 mm HE

0.1 (0.04)

500

22,500

Total

37,100

EGTTR = Eglin Gulf Test and Training Range; FU = Full Up; HE = High Explosive; mm = millimeter(s); lb = pound(s); TR = Training Round.

The 8th Special Operations Squadron (8 SOS) under AFSOC conducts training in the EGTTR using the tiltrotor CV-22 Osprey. This training involves firing .50 caliber rounds from CV-22s at floating marker targets on the water surface. The .50 caliber rounds do not contain explosive material and, therefore, do not detonate. Flight procedures for CV-22 training are similar to those described for AC-130 gunnery training, except that CV-22 aircraft typically operate at much lower altitudes (100 to 1,000 feet (30.48 to 304.8 m) (AGL) than AC-130 gunships (6,000 to 20,000 feet (1,828 to6,96 m) AGL). Like AC-130 gunships, CV-22s are equipped with highly sophisticated electro-optical and infrared sensor systems that allow advanced detection capability during day and night. Table 4 presents information on the rounds proposed for CV-22 training missions.

Table 4—Proposed Rounds for CV-22 Training in the EGTTR

Type

Net explosive weight

(lb)

Detonation scenario

Number of missions

Rounds per mission

Annual

quantity

Daytime Missions:

.50 Caliber

N/A

Surface

600

15,000

Nighttime Missions:

.50 Caliber

N/A

Surface

600

15,000

Total

30,000

In addition to AC-130 gunnery and CV-22 training, AFSOC also conducts other air-to-surface training in the EGTTR using various types of bombs and missiles as shown in Table 5. This training is conducted primarily to develop TTPs and train strike aircraft to counter small moving boats. Munitions used for this training primarily include live AGM-176 Griffin missiles, live AGM-114 Hellfire missiles, and various types of live and inert bombs. These

munitions are launched from various types of aircraft against small target boats, and they either detonate on impact with the target or at a programmed HOB.

Table 5—Proposed Munitions for AFSOC Bomb and Missile Training in the EGTTR

Type

Category

Net explosive weight

(lb)(kg)

Detonation scenario

Annual quantity

Live Munitions:

AGM-176 Griffin

Missile

4.58 (2.1)

HOB

100

AGM-114R9E/R2 Hellfire

Missile

20.0 (9.07)

HOB

2.75-inch Rocket (including APKWS)

Rocket

2.3 (1.0)

Surface

400

GBU-12

Bomb

198.0 (89.8)/298.0 (135.1)

Surface

Mk-81 (GP 250 lb)

Bomb

151.0 (98.4)

Surface

GBU-39 (SDB I)

Bomb

37.0 (16.7)

HOB

GBU-69

Bomb

36.0 (16.3)

HOB

Inert Munitions:

.50 caliber

Gun Ammunition

N/A

30,000

GBU-12

Bomb

N/A

MkK-81 (GP 250 lb)

Bomb

N/A

BDU-50

Bomb

N/A

BDU-33

Bomb

N/A

AFSOC = Air Force Special Operations Command; AGM = Air-to-Ground Missile; APKWS = Advanced Precision Kill Weapon System; BDU = Bomb Dummy Unit; EGTTR = Eglin Gulf Test and Training Range; GBU = Guided Bomb Unit; GP = General Purpose; HOB = height of burst; lb = pound(s); Mk = Mark; N/A = not applicable; SDB = Small-Diameter Bomb.

96th Operations Group

Three units under the 96th Operations Group (96 OG) propose to conduct missions in the EGTTR during the 2023-2030 period: the 417th Flight Test Squadron (417 FLTS), the 96th Operational Support Squadron (96 OSS), and the 780th Test Squadron (780 TS).

The 417 FLTS proposes to continue conducting AC-130 testing in the EGTTR to evaluate the capabilities of the Precision Strike Package (PSP), Stand Off Precision Guided Munitions (SOPGM), and other systems on AC-13O aircraft. AC-130 gunnery testing is generally similar to activities previously described for AFSOC AC-130 gunnery training.

Table 6 presents information on the munitions proposed for AC-130 testing in the EGTTR during the 2023-2030 mission period.

Table 6—Proposed Rounds for AC-130 Gunnery Testing in the EGTTR

Type

Category

Net explosive weight

(lb)/(kg)

Detonation scenario

Annual quantity

Live Munitions:

AGM-176 Griffin

Missile

4.58 (2.1)

Surface

AGM-114 Hellfire

Missile

20.0 (9.1)

Surface

GBU-39 (SDB I)

Bomb

37.0 (16.8)

Surface

GBU-39 (LSDB)

Bomb

37.0 (16.8)

Surface

105 mm HE (FU)

Gun Ammunition

4.7 (2.1)

Surface

105 mm HE (TR)

Gun Ammunition

0.35 (0.2)

Surface

30 mm HE

Gun Ammunition

0.1 (0.1)

Surface

AGM = Air-to-Ground Missile; EGTTR = Eglin Gulf Test and Training Range; FU = Full Up; GBU = Guided Bomb Unit; HE = High Explosive; lb = pound(s); mm = millimeter(s); LSDB = Laser Small-Diameter Bomb; SDB = Small-Diameter Bomb; TR = Training Round.

The 96 OSS proposes to conduct air-to-surface testing in the EGTTR using assorted live missiles and live and inert precision-guided bombs to support testing requirements of the MQ-9 Reaper unmanned aerial vehicle (UAV) program. The proposed munitions would be tested for MQ-9 integration and would include captive carry and munitions employment tests. During munition employment tests, the proposed munitions would be launched from MQ-9 aircraft at various types of static and moving targets on the water surface. Table 7 presents information on the munitions proposed by the 96 OSS for MQ-9 testing in the EGTTR.

Table 7—Proposed Munitions for MQ-9 Testing in the EGTTR

Type

Category

Net explosive weight

(lb)/(kg)

Detonation scenario

Annual quantity

Live Munitions:

AGM-114R Hellfire

Missile

20.0 (9.1)

Surface

AIM-9X

Missile

7.9 (3.6)

HOB

GBU-39B/B LSDB

Bomb

37.0 (16.8)

Surface

Inert Munitions:

GBU-39B/B LSDB

Bomb

N/A

GBU-49

Bomb

N/A

GBU-48

Bomb

N/A

AGM = Air-to-Ground Missile; AIM = Air Intercept Missile; EGTTR = Eglin Gulf Test and Training Range; GBU = Guided Bomb Unit; lb = pound(s); LSDB = Laser Small-Diameter Bomb.

The 780 TS, the Air Force Life Cycle Management Center, and the U.S. Navy jointly conduct Precision Strike Weapons (PSW) test missions in the EGTTR. These missions use the AGM-158 JASSM and GBU-39 SDB precision-guided bomb. The JASSM is an air-launched cruise missile with a range of more than 200 nmi (370 km). During test missions, the JASSM would be launched from aircraft more than 200 nmi (370 km) from the target location at altitudes greater than 25,000 ft (7,620 m) km above ground level (AGL). The JASSM would cruise at altitudes greater than 12,000 ft (3,657 m) AGL for most of the flight profile until its terminal descent toward the target. The GBU-39 SDB is a precision-guided glide bomb with a range of more than 50 nmi (92.6 km). This bomb would be launched from aircraft more than 50 nmi (92.6 km) from the target location at altitudes greater than 5,000 ft (1,524 m) AGL. The bomb would travel via a non-powered glide to the intended target. Instrumentation in the bomb self-controls the bomb's flight path. Live JASSMs would detonate at a HOB of approximately 5 ft (0.30 m); however, these detonations are assumed to occur at the surface for the impact analysis. The SDBs would detonate either at a HOB of approximately 7 to 14 ft (2.1 to 4.2 m) or upon impact with the target (surface). For simultaneous SDB launches, two SDBs would be launched from the same aircraft at approximately the same time to strike the same target. The SDBs would strike the target within approximately 5 seconds or less of each other. Such detonations would be considered a single event, with the associated NEW being doubled for a conservative impact analysis.

Two types of targets are typically used for PSW tests: Container Express (CONEX) targets and hopper barge targets. CONEX targets typically consist of up to five CONEX containers strapped, braced, and welded together to form a single structure. A hopper barge is a common type of barge that cannot move itself; a typical hopper barge measures approximately 30 ft (9.1 m) by 12 ft (3.6 m) by 125 ft (38.1 m).

Other SDB tests in the EGTTR during the 2023-2030 mission period may include operational testing of the GBU-53 (SDB II). These tests may involve live and inert testing of the munition against target boats.

Table 8 presents information on the munitions proposed for PSW missions in the EGTTR during the 2023-2030 period.

Table 8—Proposed Munitions for Precision Strike Weapon Missions

Type

Category

Net explosive weight

(lb)/(kg)

Detonation scenario

Annual quantity

Live Munitions:

AGM-158 (JASSM)

Missile

240.26 (108.9)

Surface

GBU-39 (SDB I)

Bomb

37.0 (16.8)

HOB/Surface

GBU-39 (SDB I) Simultaneous Launch

Bomb

74.0 (33.35)

HOB/Surface

GBU-53 (SDB II)

Bomb

22.84 (10.4)

HOB/Surface

Inert Munitions:

AGM-158 (JASSM)

Missile

N/A

GBU-39 (SDB I)

Bomb

N/A

GBU-39 (SDB I) Simultaneous Launch

Bomb

N/A

GBU-53 (SDB II)

Bomb

N/A

NEW is doubled for simultaneous launch.

AGM = Air-to-Ground Missile; EGTTR = Eglin Gulf Test and Training Range; GBU = Guided Bomb Unit; HOB = height of burst; JASSM = Joint Air-to-Surface Standoff Missile; lb = pound(s); N/A = not applicable; SDB = Small-Diameter Bomb.

The 780 TS, along with the Air Force Life Cycle Management Center and U.S. Navy, propose to jointly conduct air-to-air missile testing in the EGTTR. These missions would involve the use of the AIM-260A Joint Advanced Tactical Missile (JATM), AIM-9X Sidewinder, and AIM-120 AMRAAM missiles; all missiles used in these tests would be inert. Table 9 presents information on the munitions proposed for air-to-air missile testing missions in the EGTTR during the 2023-2030 mission period.

Table 9—Proposed Munitions for Air-to-Air Missile Testing in the EGTTR

Type

Category

Net explosive weight

(lb)

Detonation

scenario

Annual quantity

AIM-260 JATM—Inert

Missile

N/A

AIM-9X—Inert

Missile

N/A

AIM-120 AMRAAM—Inert

Missile

N/A

AIM = Air Intercept Missile; AMRAAM = Advanced Medium-Range Air-to-Air Missile; EGTTR = Eglin Gulf Test and Training Range; lb = pound(s); JATM = Joint Advanced Tactical Missile; N/A = not applicable.

The 780 TS proposes to test the ability of the AGM-114L Longbow missile and AGM-179A Joint Air-to-Ground Missile (JAGM) missile to track and impact moving target boats in the EGTTR as shown in Table 10. These missiles are typically launched from an AH-64D Apache helicopter. The test targets would be remotely controlled boats, including the 25-foot High-Speed Maneuverable Surface Target (HSMST) (foam filled) and 41-foot (12.5 m) Coast Guard Utility Boat (metal hull). The missiles would be launched approximately 0.9 to 4.3 nmi (1.7 to 7.9 km) from the targets.

Table 10—Proposed Munitions for Longbow and JAGM Missile Testing in the EGTTR

Type

Category

Net explosive weight

(lb)/(kg)

Detonation

scenario

Annual quantity

AGM-114L Longbow

Missile

35.95 (16.3)

HOB

AGM-179A JAGM

Missile

27.47 (11.1)

HOB

AGM = Air-to-Ground Missile; EGTTR = Eglin Gulf Test and Training Range; HOB = height of burst; JAGM = Joint Air-to-Ground Missile; lb = pound(s).

The 780 TS proposes to test the Spike Non-Line-of-Sight (NLOS) air-to-surface tactical missile system against static and moving target boats in the EGTTR in support of the U.S. Army's initiative to incorporate the Spike NLOS missile system onto the AH-64E Apache helicopter. These missiles shown in Table 11 would be launched from an AH-64D Apache helicopter and the test targets would include foam-filled fiberglass boats approximately 25 ft (7.62 m) in length that are either anchored or towed by a remotely controlled (HSMST).

Table 11—Proposed Munitions for NLOS Spike Missile Testing in the EGTTR

Type

Category

Net explosive weight

(lb)/(kg)

Detonation

scenario

Annual quantity

Spike NLOS

Missile

34.08 (14.5)

Surface

The 780 TS proposes to conduct surface-to-air testing of Patriot Advanced Capability (PAC)-2 and PAC-3 missiles in the EGTTR. These missiles are expected to be fired from the A-15 launch site on Santa Rosa Island at drones in the EGTTR. Detailed operational data for this testing are not yet available. Standard inventory missiles would be used and up to eight PAC-2 tests and two PAC-3 tests per year are proposed as shown in Table 12.

Table 12—Proposed Munitions for Patriot Missile Testing in the EGTTR

Type

Category

Net explosive weight

(lb)/(kg)

Detonation

scenario

Annual quantity

PAC-2

Missile

145.0 (65.7)

N/A (drone target)

PAC-3

Missile

145.0 (65.7)

N/A (drone target)

Assumed for impact analysis.

Hypersonic weapons are capable of traveling at least five times the speed of sound, referred to as Mach 5. While conventional weapons typically rely on explosive warheads to inflict damage on a target, hypersonic weapons typically rely on kinetic energy from high-velocity impact to inflict damage on targets. For the purpose of assessing impacts, the kinetic energy of a hypersonic weapon may be correlated to energy release in units of feet-lb or trinitrotoluene (TNT) equivalency.

The 780 TS supports several hypersonic weapon programs, including the Hypersonic Attack Cruise Missile (HACM) and Precision Strike Missile (PrSM) programs, which are presented in Table 13.

HACM is a developmental air-breathing hypersonic cruise missile that uses scramjet technology for propulsion. This weapon would air-launched. The 780 TS proposes to conduct HACM

testing, which would involve air launches through a north-south corridor within the EGTTR to a target location on the water surface. The dimensions and orientation of the test flight corridor within the EGTTR for HACM tests are to be determined; the flight corridor is preliminarily expected to be 300 to 400 nmi (555 to 740 km) in total length. Live HACMs would be fired from the southern portion of the EGTTR into either the existing LIA or proposed East LIA. Up to two live HACMs per year are proposed to be tested in the EGTTR during the 2023-2030 mission period.

The PrSM is being developed by the U.S. Army as a surface-to-surface, long-range, precision-strike guided missile to be fired from the M270A1 Multiple Launch Rocket System and the M142 High Mobility Artillery Rocket System. The 780 TS in coordination with the U.S. Army proposes to conduct PrSM testing in the EGTTR. Some PrSM testing is expected to involve surface launches of the PrSM from the A-15 launch site on Santa Rosa Island. The dimensions and orientation of the test flight corridor within the EGTTR for PrSM tests are to be determined; the flight corridor is preliminarily expected to be 162 to 270 nmi (300 to 500 km) in total length. For tests that involve a live warhead on the PrSM, the PrSM would be preset to detonate at a specific height above the water surface (HOB/airburst) and could occur in any portion of the EGTTR. Any surface strikes proposed with live PrSMs would be required to be in the existing LIA or proposed East LIA. Like inert HACM tests, inert PrSM tests could occur in any portion of the EGTTR, except between the 100-m and 400-m isobaths to prevent impacts to the Rice's whale.

Table 13—Proposed Munitions for Hypersonic Weapon Testing in the EGTTR

Type

Category

Net explosive weight

(lb)/(kg)

Detonation

scenario

Annual quantity

Live Munitions:

HACM

Hypersonic Weapon

350 (158.7)

Surface

PrSM

Hypersonic Weapon

46 (158.7)

HOB

Inert Munitions:

PrSM—Inert

Hypersonic Weapon

N/A

Net explosive weight at impact/detonation.

The 780 TS, in coordination with the Air Force Research Laboratory, proposes to conduct SINKEX testing in the EGTTR. SINKEX exercises would involve the sinking of vessels, typically 200-400 ft (61 -122 m) in length, in the existing LIA. The types of munitions that would be used for SINKEX testing is controlled information and, therefore, not identified (Table 14).

Table 14—Proposed SINKEX Exercises in the EGTTR

Type

Category

Net explosive weight

(lb)

Detonation

scenario

Annual quantity

SINKEX

Vessel Sinking Exercise

Not Available

The 780 TS plans to lead or support other types of testing in the EGTTR as shown in Table 15. These missions would primarily include testing live and inert munitions against targets on the water surface, such as boats and barges. Some of the tests would involve munitions with NEWs of up to 945 lb, which is the highest NEW associated with the munitions analyzed in this LOA application.

Table 15—Proposed Munitions for Other 780 Test Squadron Testing in the EGTTR

Type

Category

Net explosive weight

(lb)/(kg)

Detonation

scenario

Target type

Annual quantity

Live Munitions:

GBU-10, 24, or 31 (QUICKSINK)

Bomb

945 (428.5)

Subsurface

TBD

4 to 8

2,000 lb bomb with JDAM kit

Bomb

945 (428.5) or less

HOB

TBD

Inert GBU-39 (LSDB)

with live fuze

Bomb

0.4 (0.2)

HOB/Surface

Small Boat

Inert GBU-53 (SDB II)

with live fuze

Bomb

0.4 (0.2)

HOB/Surface

Small Boat

Inert Munitions:

SiAW AARGM-ER

Missile

N/A

TBD

Multipurpose Booster

Booster

N/A

TBD

JDAM ER

Bomb

N/A

Water Surface and Barge

Navy HAAWC

Torpedo

N/A

Water Surface

AARGM-ER = Advanced Anti-Radiation Guided Missile—Extended Range; EGTTR = Eglin Gulf Test and Training Range; Guided Bomb Unit; HOB = height of burst; HAAWC = High Altitude Anti-Submarine Warfare Weapon Capability; JDAM = Joint Direct Attack Munition; lb = pound(s); LSDB = Laser Small-Diameter Bomb; N/A = not applicable; SDB = Small-Diameter Bomb; SiAW = Stand-in Attack Weapon; TBD = to be determined.

The 96 OG proposes to continue expending approximately nine inert bombs a year in the EGTTR for testing purposes. The bombs are expected to be up to 2,000 lb (907 kg) in total weight. For the impact analysis, the bombs to be used by the 96 OG in the EGTTR during the 2023-2030 mission period are assumed to be Mk-84 2,000 lb (907 kg) General Purpose (GP) inert bombs (Table 16).

Table 16—Proposed Munitions for Inert Bomb Testing in the EGTTR

Type

Category

Net explosive weight

(lb)

Detonation

scenario

Annual quantity

Mk-84 (GP 2,000 lb)

Bomb

N/A

Assumed for impact analysis.

EGTTR = Eglin Gulf Test and Training Range; GP = General Purpose; lb = pound(s); Mk = Mark; N/A = not applicable.

Naval School Explosive Ordnance Disposal (NAVSCOLEOD)

NAVSCOLEOD proposes to conduct training missions in the EGTTR which would include Countermeasures (MCM) exercises to teach NAVSCOLEOD students techniques for neutralizing mines underwater (Table 17). Underwater MCM training exercises are conducted in nearshore waters and primarily involve diving and placing small explosive charges adjacent to inert mines by hand; the detonation of such charges disables live mines. NAVSCOLEOD training is conducted offshore of Santa Rosa Island and in other locations and has not yet extended into the EGTTR. NAVSCOLEOD training proposed for the 2023-2030 mission period would extend approximately 5 nmi (9.26 km) offshore of Santa Rosa Island, in the EGTTR. Up to 8 MCM training missions would be conducted annually in the EGTTR during the 2023-2030 period. Each mission would involve 4 underwater detonations of charges hand placed adjacent to inert mines, for a total of 32 annual detonations. The MCM neutralization charges consist of C-4 explosives, detonation cord, non-electric blasting caps, time fuzes, and fuze igniters; each charge has a NEW of approximately 20 lb. (9.07 kg). During each mission, with a maximum of 4 charges, would detonate with a delay no greater than 20 minutes between shots. After the final detonation, or a delay greater than 20 minutes, a 30-minute environmental observation would be conducted. Additionally, NAVSCOLEOD proposes to conduct up to 80 floating mine training missions, which would involve detonations of charges on the water surface; these charges would have a NEW of approximately 5 lb (2.3 kg). All NAVSCOLEOD missions would occur only during daylight hours.

Table 17—Proposed Munitions for NAVSCOLEOD Training in the EGTTR

Type

Category

Net Explosive weight

(lb)/(kg)

Detonation scenario

Annual quantity

Underwater Mine Charge

Charge

20 (9.1)

Subsurface

Floating Mine Charge

Charge

5 (2.3)

Surface

Estimated

Description of Stressors

The USAF uses the EGTTR for training purposes and for testing of a variety of weapon systems described in this proposed rule. All of the weapons systems considered likely to cause the take of marine mammals involve explosive detonations. Training and testing with these systems may introduce acoustic (sound) energy or shock waves from explosives into the environment. The following section describes explosives detonated at or just below the surface of the water within the EGTTR. Because of the complexity of analyzing sound propagation in the ocean environment, the USAF relied on acoustic models in its environmental analyses and rulemaking/LOA application that considered sound source characteristics and conditions across the EGTTR.

Explosive detonations at the water surface send a shock wave and sound energy through the water and can release gaseous by-products, create an oscillating bubble, or cause a plume of water to shoot up from the water surface. When an air-to-surface munition impacts the water, some of the kinetic energy displaces water in the formation of an impact “crater” in the water, some of the kinetic energy is transmitted from the impact point as underwater acoustic energy in a pressure impulse, and the remaining kinetic energy is retained by the munition continuing to move through the water. Following impact, the warhead of a live munition detonates at or slightly below the water surface. The warhead detonation converts explosive

material into gas, further displacing water through the rapid creation of a gas bubble in the water, and creates a much larger pressure wave than the pressure wave created by the impact. These impulse pressure waves radiate from the impact point at the speed of sound in water, roughly 1,500 m per second. If the detonation is sufficiently deep, the gas bubble goes through a series of expansions and contractions, with each cycle being of successively lower energy. When detonations occur below but near the water surface, the initial gas bubble reaches the surface and causes venting, which also dissipates energy through the ejection of water and release of detonation gases into the atmosphere. When a detonation occurs below the water surface after the impact crater has fully or partially closed, water can be violently ejected upward by the pressure impulse and through venting of the gas bubble formed by the detonation.

With radii of up to 15 m, the gas bubbles that would be generated by EGTTR munition detonations would be larger than the depth of detonation but much smaller than the water depth, so all munitions analyzed are considered to fully vent to the surface without forming underwater bubble expansion and contraction cycles. When detonations occur at the water surface, a large portion of the energy and gases that would otherwise form a detonation bubble are reflected upward from the water. Likewise, when a shallow detonation occurs below the water surface but prior to the impact crater closing, considerable energy is reflected upward from the water. As a conservative assumption, no energy losses from surface effects are included in the acoustic model.

The impulsive pressure waves generated by munition impact and warhead detonation radiate spherically and are reflected between the water surface and the sea bottom. There is generally some attenuation of the pressure waves by the sea bottom but relatively little attenuation of the pressure waves by the water surface. As a conservative assumption, the water surface is assumed to be flat (no waves) to allow for maximum reflectivity. Additionally, is it assumed that all detonations occur in the water and none of the detonations occur above the water surface when a munition impacts a target. This conservative assumption implies that all munition energy is imparted to the water rather than the intended targets. The potential impacts of exposure to explosive detonations are discussed in detail in the Potential Effects of Specified Activities on Marine Mammals and their Habitat section.

Description of Marine Mammals in the Area of the Specified Activities

Table 18 lists all species or stocks for which take is expected and proposed to be authorized for this activity, and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. PBR is defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population (as described in NMFS' SARs). While no serious injury or mortality is expected to occur, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species or stocks and other threats.

Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock or the total number estimated within a particular study or survey area. NMFS' stock abundance estimates for most species represent the total estimate of individuals within the geographic area, if known, that comprises that stock. For some species, this geographic area may extend beyond U.S. waters. All stocks managed under the MMPA in this region are assessed in NMFS' 2021 U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessment (Hayes

et al.

2022;

https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports

). All values presented in Table 18 are the most recent available at the time of publication and are available online at:

www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments

Table 18—Marine Mammals Potentially Present in the Specified Geographical Region

Common name

Scientific name

Stock

ESA/MMPA status; strategic (Y/N)

NMFS stock abundance (CV, N

min

, most recent abundance survey)

PBR

Annual M/SI

Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)

Family Balaenopteridae (rorquals):

Rice's whale

Balaenoptera ricei

Gulf of Mexico

E/D; Y

51 (0.50; 34; 2017-18)

0.1

0.5

Superfamily Odontoceti (toothed whales, dolphins, and porpoises)

Family Delphinidae:

Common bottlenose dolphin

Tursiops 939runcates truncatus

Northern GOM Continental Shelf

-; N

63,280 (0.11; 57,917; 2018)

556

Atlantic spotted dolphin

Stenella frontalis

GOM

-; N

21,506 (0.26; 17,339; 2017-18)

166

ESA status: Endangered/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 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.

NMFS marine mammal stock assessment reports online at:

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.

These values, found in NMFS' SARs, represent annual levels of human-caused mortality (M) plus serious injury (SI) from all sources combined (

e.g.,

commercial fisheries, ship strike). These values are generally considered minimums because, among other reasons, not all fisheries that could interact with a particular stock are observed and/or observer coverage is very low, and, for some stocks (such as the Atlantic spotted dolphin and continental shelf stock of bottlenose dolphin), no estimate for injury due to the

Deepwater Horizon

oil spill has been included. See SARs for further discussion.

The 2021 final rule refers to the Gulf of Mexico (GOM) Bryde's whale (

Balaenoptera edeni

). These whales were subsequently described as a new species, Rice's whale (

Balaenoptera ricei

) (Rosel

et al.,

2021).

As indicated above, all three species (with three managed stocks) in Table 18 temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur. These species are generally categorized into those species that occur over the continental shelf, which is typically considered to extend from shore to the 200-m (656-ft) isobath, and those species that occur beyond the continental shelf break in waters deeper than 200 m. Since water depths range from approximately 30 to 145 m in the existing LIA and from approximately 35 to 95 m in the proposed new East LIA, most of EGTTR activities would occur in waters over the continental shelf. Any live munitions would be set to detonate above the water surface if used outside the LIA beyond the 200-m isobath. Airburst detonations are not considered to affect marine mammals because there is little transmission of pressure or sound energy across the air-water interface. For these reasons, only cetacean species that predominantly occur landward of the 200-m isobath are carried forward in the analysis. These species include common bottlenose dolphin, Atlantic spotted dolphin, and Rice's whale.

Common Bottlenose Dolphin

The common bottlenose dolphin is abundant in the northeastern Gulf from inshore to upper continental slope waters less than 1,000 m deep (Mullin and Fulling 2004). It is the most common cetacean species found in the coastal waters of the Gulf of Mexico. Genetically distinct coastal and offshore ecotypes of the bottlenose dolphin occur in the Gulf of Mexico and in other locations (Hoelzel

et al.

1998). A total of 36 common bottlenose dolphin stocks have been identified in the northern Gulf of Mexico including coastal, continental shelf, and oceanic stocks, as well as 31 bay, sound, and estuarine stocks (Waring

et al.

2016). Stocks that may be found near or within the EGTTR include the Gulf of Mexico Northern Coastal, Northern Gulf of Mexico Continental Shelf, and Northern Gulf of Mexico Oceanic stocks, in addition to three inshore stocks, which include the Choctawhatchee Bay, Pensacola/East Bay, and St. Andrew Bay stocks. However, the designated inshore stock areas are landward of the EGTTR boundary; therefore, individuals from these stocks are not anticipated to be exposed to or affected by EGTTR operations. The Gulf of Mexico Northern Coastal Stock inhabits waters from shore to the 20-m (65-ft) isobath and, therefore, has potential to occur within the EGTTR, which starts at 3 nmi (5.5 km) offshore, where water depths can be 20 m or slightly less. However, given that most EGTTR operations would occur in either the existing LIA, where water depths range from approximately 30 to 145 m, or in the proposed East LIA, where water depths range from approximately 35 to 85 m, EGTTR operations are expected to have no appreciable effect on this stock. The Northern Gulf of Mexico Continental Shelf Stock inhabits waters that are 20 to 200 m deep and, therefore, is expected to be the primary bottlenose dolphin stock that occurs in the existing LIA. The Northern Gulf of Mexico Oceanic Stock inhabits waters deeper than 200 m and, therefore, is not expected to be exposed to or affected by EGGTR operations in either LIA.

The bottlenose dolphin reaches a length ranging from about 6 to 13 ft (1.8 to 3.9 m) and a weight ranging from about 300 to 1,400 lb (136 to 635 kg). The diet of bottlenose dolphins consists primarily of fish, squid, and crustaceans. They hunt for prey using a variety of techniques individually and cooperatively. For example, they may work as a group to herd and trap fish as well as use high-frequency echolocation, to catch prey.

Atlantic Spotted Dolphin

The Atlantic spotted dolphin occurs throughout the Atlantic Ocean and the Gulf of Mexico. There is a single stock of the Atlantic spotted dolphin in U.S. Gulf waters, which is the Northern Gulf of Mexico Stock. Animals occur primarily from continental shelf waters of 10-200 m deep to slope waters <500 m deep and were spotted in all seasons during aerial and vessel surveys of the northern Gulf of Mexico (

i.e.,

U.S. Gulf of Mexico; Hansen

et al.

1996; Mullin and Hoggard 2000; Fulling

et al.

2003; Mullin and Fulling 2004; Maze-Foley and Mullin 2006). Atlantic spotted dolphins are about 5 to 7.5 ft (1.5 to 2.3 m) long and weigh about 220 to 315 lb (99.8 to 142.8 kg). Their diet consists primarily of small fish, invertebrates, and cephalopods, which they catch using a variety of techniques including echolocation. Atlantic spotted dolphins are social animals and form groups of up to 200 individuals. Most groups consist of fewer than 50 individuals, and in coastal waters groups typically consist of 5 to 15 individuals (NMFS 2021b).

Rice's Whale

The Gulf of Mexico Bryde's whale was listed as endangered throughout its entire range on April 15, 2019, under the Endangered Species Act (ESA). Based on genetic analyses and new morphological information NOAA Fisheries recently revised the common and scientific names to recognize this new species (

Balaenoptera ricei

) as being separate from other Bryde's whale populations (86 FR 47022; August 21, 2021). Rosel and Wilcox (2014) first identified a new, evolutionarily distinct lineage of whale in the Gulf of Mexico. Genetic analysis of whales sampled in the northeastern Gulf of Mexico revealed that this population is evolutionarily distinct from all other whales within the Bryde's whale complex and all other known balaenopterid species (Rosel and Wilcox 2014).

The Rice's whale is the only year-round resident baleen whale species in the Gulf of Mexico. Rosel

et.al.

(2021) reported that based on a compilation of sighting and stranding data from 1992 to 2019, the primary habitat of the Rice's whale is the northeastern Gulf of Mexico, particularly the De Soto Canyon area, at water depths of 150 to 410 m.

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. In 2015, a year round small and resident population BIA for Bryde's whales (later designated as Rice's whales) was identified from the De Soto Canyon along the shelf break to the southeast (LaBrecque

et al.

2015). The 23,559 km

BIA covers waters between 100 and 300 m deep from approximately south of Pensacola to approximately west of Fort Myers, FL (LaBrecque

et al.

2015). The deepest location where a Rice's whale has been sighted is 408 m (Rosel

et al.

2021). Habitat for the Rice's whale is currently considered by NMFS to be primarily within the depth range of 100 to 400 m in this part of the Gulf of Mexico (NMFS 2016, 2020a), and in 2019 NMFS delineated a Core Distribution Area (

https://www.fisheries.noaa.gov/resource/map/rices-whale-core-distribution-area-map-gis-data

) based on visual and tag data available through 2019. No critical habitat has yet been designated for the species, and no recovery plan has yet been developed.

The Rice's whale is a medium-sized baleen whale. To date, the largest verified Rice's whale to strand was a lactating female about 12.65 m long; the largest male was 11.26 m (Rosel

et al.

2021). Little is known about their

foraging ecology and diet. However, data from two Rice's whales suggest they may mostly forage at or near the seafloor.

Unusual Mortality Events (UMEs)

An UME is defined under Section 410(6) of the MMPA as a stranding that is unexpected; it involves a significant die-off of any marine mammal population and demands immediate response. There are currently no UMEs with ongoing investigations in the EGTTR. There was a UME for bottlenose dolphins that was active beginning in February 2019 and closing in November of the same year that included the northern Gulf of Mexico. Dolphins developed lesions that were thought to be caused by exposure to low salinity water stemming from extreme freshwater discharge. This UME is closed.

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. 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, 2019) recommended that marine mammals be divided into hearing groups based on directly measured (behavioral or auditory evoked potential techniques) or estimated hearing ranges (behavioral response data, anatomical modeling, etc.). 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 decibel (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. Marine mammal hearing groups and their associated hearing ranges are provided in Table 19.

Table 19—Marine Mammal Hearing Groups

[NMFS, 2018]

Hearing group

Generalized hearing range *

Low-frequency (LF) cetaceans

(baleen whales)

7 Hz to 35 kHz.

Mid-frequency (MF) cetaceans

(dolphins, toothed whales, beaked whales, bottlenose whales)

150 Hz to 160 kHz.

High-frequency (HF) cetaceans

(true porpoises,

Kogia,

river dolphins, Cephalorhynchid,

Lagenorhynchus cruciger

L. australis

)

275 Hz to 160 kHz.

Phocid pinnipeds (PW) (underwater)

(true seals)

50 Hz to 86 kHz.

Otariid pinnipeds (OW) (underwater)

(sea lions and fur seals)

60 Hz to 39 kHz.

* Represents the generalized hearing range for the entire group as a composite (

i.e.,

all species within the group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen based on ~65 dB threshold from normalized composite audiogram, with the exception for lower limits for LF cetaceans (Southall

et al.

2007) and PW pinniped (approximation).

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 detail concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of available information.

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

This section includes a summary 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 USAF has requested authorization for the take of marine mammals that may occur incidental to training and testing activities in the EGTTR. The USAF analyzed potential impacts to marine mammals from air-to-surface operations that involve firing live or inert munitions, including missiles, bombs, and gun ammunition, from aircraft at targets on the water surface in the LOA application as well as the 2022 REA, for which NMFS served as a cooperating agency. The proposed training and testing exercises have the potential to cause take of marine mammals by exposing them to impulsive noise and pressure waves generated by explosive detonation at or near the surface of the water. Exposure to noise or pressure resulting from these detonations could result in non-lethal injury (Level A harassment) or disturbance (Level B harassment). As explained in the Estimated Take of Marine Mammals section, neither mortality nor non-auditory injury are anticipated or authorized.

A summary of the potential impacts of the pressure waves generated by explosive detonations is included below. Following, a brief technical background is provided here on sound, on the characteristics of certain sound types, and on metrics used in this proposal. Last, a brief overview of the potential effects (

e.g.,

tolerance, masking, hearing threshold shift, behavioral disturbance, and stress responses) to marine mammals associated with the USAF's proposed activities is included.

Impacts from Pressure Waves Caused by Explosive Detonations

Exposure to the pressure waves generated by explosive detonations has the potential to cause injury, serious injury, or mortality, although those impacts are not anticipated here. (This conclusion is based on the size, type, depth, and duration of the explosives in combination with the density of marine mammals, which together predict a low probability of exposures, as well as the required mitigation measures, as described in detail the Estimated Take of Marine Mammals section.) The potential acoustic impacts of explosive detonations

(e.g.,

permanent threshold shift (PTS), temporary threshold shift (TTS), and behavioral disturbance) are described in subsequent sections.

Generally speaking, the pressure from munition detonations have the potential to cause mortality, injury, hearing impairment, or behavioral disturbances in marine mammals, depending on the explosive energy released by the munition and the distance of the animal from the detonation. The impulsive noise from these detonations may also cause hearing impairment or behavioral disturbances. The most potentially severe effects would occur close to the detonation point, including tissue damage, barotrauma, or even death. Serious injury or mortality to marine mammals from explosive detonations, if they occurred, which is not expected here, would consist of primary blast injury, which refers to those injuries that result from the compression of a body exposed to a blast wave and which is usually observed as barotrauma of gas-containing structures (

e.g.,

lung and gut) and structural damage to the auditory system (Richmond

et al.

1973). The near instantaneous high magnitude pressure change near an explosion can injure an animal where tissue material properties significantly differ from the surrounding environment, such as around air-filled cavities in the lungs or gastrointestinal (GI) tract. The gas-containing organs (lungs and GI tract) are most vulnerable to primary blast injury. Severe injuries to these organs are presumed to result in mortality (

e.g.,

severe lung damage may introduce air into the cardiopulmonary vascular system, resulting in lethal air emboli). Large pressure changes at tissue-air interfaces in the lungs and GI tract may cause tissue rupture, resulting in a range of injuries depending on degree of exposure. Recoverable injuries would include slight lung injury, such as capillary interstitial bleeding, and contusions to the GI tract. More severe injuries, such as tissue lacerations, major hemorrhage, organ rupture, or air in the chest cavity (pneumothorax), would significantly reduce fitness and likely cause death in the wild. Rupture of the lung may also introduce air into the vascular system, producing air emboli that can cause a stroke or heart attack and restrict oxygen delivery to critical organs. Susceptibility would increase with depth, until normal lung collapse (due to increasing hydrostatic pressure) and increasing ambient pressures again reduce susceptibility.

Exposures to higher levels of impulse and pressure levels would generally result in greater impacts to an individual animal. However, the effects of noise on marine mammals are highly variable, often depending on species and contextual factors (Richardson

et al.

1995). As described in the Estimated Take of Marine Mammals section, the more serious impacts (

i.e.,

mortality, serious injury, and non-auditory injury) are not anticipated to result from this action.

The USAF performed a quantitative analysis to estimate the probability that marine mammals could be exposed to the sound and energy from explosions during USAF activities and the effects of those exposures (Appendix A in LOA Application). The effects of underwater explosions on marine mammals depend on a variety of factors including animal size and depth; charge size and depth; depth of the water column; and distance between the animal and the charge. In general, an animal would be less susceptible to injury near the water surface because the pressure wave reflected from the water surface would interfere with the direct path pressure wave, reducing positive pressure exposure. There are a limited number of explosives that would detonate just below the water surface as outlined previously in the section, Description of Stressors. Most explosives would detonate at or near the surface of the water and are unlikely to transfer energy underwater sufficient to result in non-auditory injury (GI injury or lung injury) or mortality. For reasons described in the Estimated Take of Marine Mammals section, NMFS agrees with USAF's analysis that no mortality or serious injury from tissue damage in the form of GI injury or lung injury is anticipated to result from the proposed activities. The USAF did not request, and NMFS does not propose, mortality or serious injury for authorization, and therefore this proposed rule will not discuss it further. For additional details on the criteria for estimating non-auditory physiological impacts on marine mammals due to naval underwater explosions, we refer the reader to the report, Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III) (U.S. Department of the Navy, 2017e).

Sections 6, 7, and 9 of the USAF's application include summaries of the ways that components of the specified activity may impact marine mammals and their habitat, including specific discussion of potential effects to marine mammals from noise and pressure waves produced through the use explosives detonating at or near the surface. We have reviewed the USAF's discussion of potential effects for accuracy and completeness in its application and refer to that information rather than repeating it in full here. Below we include a summary of the potential effects to marine mammals.

Description of Sound Sources

This section contains a brief technical background on sound, on the characteristics of certain sound types, and on metrics used in this proposal inasmuch as the information is relevant to the specified activity and to a discussion of the potential effects of the specified activity on marine mammals found later in this document. For general information on sound and its interaction with the marine environment, please see Au and Hastings (2008); Richardson

et al.

(1995); and Urick (1983).

Sound travels in waves, the basic components of which are frequency, wavelength, velocity, and amplitude. Frequency is the number of pressure waves that pass by a reference point per unit of time and is measured in hertz or cycles per second. Wavelength is the distance between two peaks or corresponding points of a sound wave (length of one cycle). Higher frequency sounds have shorter wavelengths than lower frequency sounds, and typically attenuate (decrease) more rapidly, except in certain cases in shallower water. Amplitude is the height of the sound pressure wave or the “loudness” of a sound and is typically described using the relative unit of the decibel (dB). A sound pressure level (SPL) in dB is described as the ratio between a measured pressure and a reference pressure (for underwater sound, this is 1 microPascal (μPa)), and is a logarithmic unit that accounts for large variations in amplitude. Therefore, a relatively small change in dB corresponds to large changes in sound pressure. The source level (SL) represents the SPL referenced at a distance of 1 m from the source (referenced to 1 μPa), while the received level is the SPL at the listener's position (referenced to 1 μPa).

Root mean square (rms) is the quadratic mean sound pressure over the duration of an impulse. Root mean square is calculated by squaring all of the sound amplitudes, averaging the squares, and then taking the square root of the average (Urick 1983). Root mean square accounts for both positive and negative values; squaring the pressures makes all values positive so that they may be accounted for in the summation of pressure levels (Hastings and Popper 2005). This measurement is often used in the context of discussing behavioral effects, in part because behavioral effects, which often result from auditory cues, may be better expressed through averaged units than by peak pressures.

Sound exposure level (SEL; represented as dB re 1 μPa

-s) represents the total energy in a stated frequency band over a stated time interval or event and considers both intensity and duration of exposure. The per-pulse SEL is calculated over the time window containing the entire pulse (

i.e.,

100 percent of the acoustic energy). SEL is a cumulative metric; it can be accumulated over a single pulse, or calculated over periods containing multiple pulses. Cumulative SEL represents the total energy accumulated by a receiver over a defined time window or during an event. Peak sound pressure (also referred to as zero-to-peak sound pressure or 0-pk) is the maximum instantaneous sound pressure measurable in the water at a specified distance from the source and is represented in the same units as the rms sound pressure.

When underwater objects vibrate or activity occurs, sound-pressure waves are created. These waves alternately compress and decompress the water as the sound wave travels. Underwater sound waves radiate in a manner similar to ripples on the surface of a pond and may be either directed in a beam or beams or may radiate in all directions (omnidirectional sources). The compressions and decompressions associated with sound waves are detected as changes in pressure by aquatic life and man-made sound receptors such as hydrophones.

Even in the absence of sound from the specified activity, the underwater environment is typically loud due to ambient sound, which is defined as environmental background sound levels lacking a single source or point (Richardson

et al.

1995). The sound level of a region is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical (

e.g.,

wind and waves, earthquakes, ice, atmospheric sound), biological (

e.g.,

sounds produced by marine mammals, fish, and invertebrates), and anthropogenic (

e.g.,

vessels, dredging, construction) sound. A number of sources contribute to ambient sound, including wind and waves, which are a main source of naturally occurring ambient sound for frequencies between 200 Hz and 50 kHz (Mitson 1995). In general, ambient sound levels tend to increase with increasing wind speed and wave height. Precipitation can become an important component of total sound at frequencies above 500 Hz, and possibly down to 100 Hz during quiet times. Marine mammals can contribute significantly to ambient sound levels, as can some fish and snapping shrimp. The frequency band for biological contributions is from approximately 12 Hz to over 100 kHz. Sources of ambient sound related to human activity include transportation (surface vessels), dredging and construction, oil and gas drilling and production, geophysical surveys, sonar, and explosions. Vessel noise typically dominates the total ambient sound for frequencies between 20 and 300 Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz and, if higher frequency sound levels are created, they attenuate rapidly.

The sum of the various natural and anthropogenic sound sources that comprise ambient sound at any given location and time depends not only on the source levels (as determined by current weather conditions and levels of biological and human activity) but also on the ability of sound to propagate through the environment. In turn, sound propagation is dependent on the spatially and temporally varying properties of the water column and sea floor, and is frequency-dependent. As a result of the dependence on a large number of varying factors, ambient sound levels can be expected to vary widely over both coarse and fine spatial and temporal scales. Sound levels at a given frequency and location can vary by 10-20 decibels (dB) from day to day (Richardson

et al.

1995). The result is that, depending on the source type and its intensity, sound from the specified activity may be a negligible addition to the local environment or could form a distinctive signal that may affect marine mammals. Details of source types are described in the following text.

Sounds are often considered to fall into one of two general types: Pulsed and non-pulsed (defined in the following). The distinction between these two sound types is important because they have differing potential to cause physical effects, particularly with regard to hearing (

e.g.,

Ward 1997 in Southall

et al.

2007). Please see Southall

et al.

(2007) and NMFS' Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0) Underwater Thresholds for Onset of Permanent and Temporary Threshold Shift (Acoustic Technical Guidance) (NMFS 2018) for an in-depth discussion of these concepts. The distinction between these two sound types is not always obvious, as certain signals share properties of both pulsed and non-pulsed sounds. A signal near a source could be categorized as a pulse, but due to propagation effects as it moves farther from the source, the signal duration becomes longer (

e.g.,

Greene and Richardson 1988).

Pulsed sound sources (

e.g.,

airguns, explosions, gunshots, sonic booms, impact pile driving) produce signals that are brief (typically considered to be less than one second), broadband, atonal transients (ANSI 1986, 2005; Harris 1998; NIOSH 1998; ISO 2003) and occur either as isolated events or repeated in some succession. Pulsed sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a rapid decay period that may include a period of diminishing, oscillating maximal and minimal pressures, and generally have an increased capacity to induce physical injury as compared with sounds that lack these features.

Non-pulsed sounds can be tonal, narrowband or broadband, brief or prolonged, and may be either continuous or intermittent (ANSI, 1995; NIOSH, 1998). Some of these non-pulsed sounds can be transient signals of short duration but without the essential properties of pulses (

e.g.,

rapid rise time). Examples of non-pulsed sounds include those produced by vessels, aircraft, machinery operations such as drilling or dredging, vibratory pile driving, and active sonar systems. The duration of such sounds, as received at a distance, can be greatly extended in a highly reverberant environment.

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).

Irreparable damage to the inner or outer cochlear hair cells may cause PTS; however, other mechanisms are also involved, such as exceeding the elastic limits of certain tissues and membranes in the middle and inner ears and resultant changes in the chemical composition of the inner ear fluids (Southall

et al.

2007). PTS is considered an injury and Level A harassment while TTS is considered to be Level B harassment and not considered an injury.

Hearing loss, or threshold shift (TS), is typically quantified in terms of the amount (in decibels) that hearing thresholds at one or more specified frequencies are elevated, compared to their pre-exposure values, at some specific time after the noise exposure. The amount of TS measured usually decreases with increasing recovery time—the amount of time that has elapsed since a noise exposure. If the TS eventually returns to zero (

i.e.,

the hearing threshold returns to the pre-exposure value), the threshold shift is called a TTS. If the TS does not completely recover (the threshold remains elevated compared to the pre-exposure value), the remaining TS is a PTS.

Hearing loss has only been studied in a few species of marine mammals, although hearing studies with terrestrial mammals are also informative. There are no direct measurements of hearing loss in marine mammals due to exposure to explosive sources. The sound resulting from an explosive detonation is considered an impulsive sound and shares important qualities (

i.e.,

short duration and fast rise time) with other impulsive sounds such as those produced by air guns. General research findings regarding TTS and PTS in marine mammals, as well as findings specific to exposure to other impulsive sound sources, are discussed below.

Many studies have examined noise-induced hearing loss in marine mammals (see Finneran (2015) and Southall

et al.

(2019) for summaries), however for cetaceans, published data on the onset of TTS are limited to the captive bottlenose dolphin, beluga, harbor porpoise, and Yangtze finless porpoise, and, for pinnipeds in water, measurements of TTS are limited to harbor seals, elephant seals, and California sea lions. These studies examine hearing thresholds measured in marine mammals before and after exposure to intense sounds. The difference between the pre-exposure and post-exposure thresholds can then be used to determine the amount of threshold shift at various post-exposure times. NMFS has reviewed the available studies, which are summarized below:

• The method used to test hearing may affect the resulting amount of measured TTS, with neurophysiological measures producing larger amounts of TTS compared to psychophysical measures (Finneran

et al.

2007; Finneran 2015).

• The amount of TTS varies with the hearing test frequency. As the exposure SPL increases, the frequency at which the maximum TTS occurs also increases (Kastelein

et al.

2014). For high-level exposures, the maximum TTS typically occurs one-half to one octave above the exposure frequency (Finneran

et al.

2007; Mooney

et al.

2009a; Nachtigall

et al.

2004; Popov

et al.

2011; Popov

et al.

2013; Schlundt

et al.

2000; Kastelein

et al.

2021b; Kastelein

et al.

2022). The overall spread of TTS from tonal exposures can therefore extend over a large frequency range (

i.e.,

narrowband exposures can produce broadband (greater than one octave) TTS).

• The amount of TTS increases with exposure SPL and duration and is correlated with SEL, especially if the range of exposure durations is relatively small (Kastak

et al.

2007; Kastelein

et al.

2014b; Popov

et al.

2014). As the exposure duration increases, however, the relationship between TTS and SEL begins to break down. Specifically, duration has a more significant effect on TTS than would be predicted on the basis of SEL alone (Finneran

et al.

2010a; Kastak

et al.

2005; Mooney

et al.

2009a). This means if two exposures have the same SEL but different durations, the exposure with the longer duration (thus lower SPL) will tend to produce more TTS than the exposure with the higher SPL and shorter duration. In most acoustic impact assessments, the scenarios of interest involve shorter duration exposures than the marine mammal experimental data from which impact thresholds are derived; therefore, use of SEL tends to over-estimate the amount of TTS. Despite this, SEL continues to be used in many situations because it is relatively simple, more accurate than SPL alone, and lends itself easily to scenarios involving multiple exposures with different SPL.

• Gradual increases of TTS may not be directly observable with increasing exposure levels before the onset of PTS (Reichmuth

et al.

2019). Similarly, PTS can occur without measurable behavioral modifications (Reichmuth

et al.

2019).

• The amount of TTS depends on the exposure frequency. Sounds at low frequencies, well below the region of best sensitivity, are less hazardous than those at higher frequencies, near the region of best sensitivity (Finneran and Schlundt, 2013). The onset of TTS—defined as the exposure level necessary to produce 6 dB of TTS (

i.e.,

clearly above the typical variation in threshold measurements)—also varies with exposure frequency. At low frequencies, onset-TTS exposure levels are higher compared to those in the region of best sensitivity. For example, for harbor porpoises exposed to one-sixth octave noise bands at 16 kHz (Kastelein

et al.

2019a), 32 kHz (Kastelein

et al.

2019b), 63 kHz (Kastelein

et al.

2020a), and 88.4 kHz (Kastelein

et al.

2020b), less susceptibility to TTS was found as frequency increased, whereas exposure frequencies below ~6.5 kHz showed an increase in TTS susceptibility as frequency increased and approached the region of best sensitivity. Kastelein

et al.

(2020b) showed a much higher onset of TTS for a 88.5 kHz exposure as compared to lower exposure frequencies (

i.e.,

16 kHz (Kastelein

et al.,

2019) 1.5 kHz and 6.5 kHz (Kastelein

et al.

2020a)). For the 88.4 kHz test frequency, a 185 dB re 1 micropascal squared per second (µPa

-s) exposure resulted in 3.6 dB of TTS, and a 191 dB re 1 µPa

-s exposure produced 5.2 dB of TTS at 100 kHz and 5.4 dB of TTS at 125 kHz. Together, these new studies demonstrate that the criteria for high-frequency (HF) cetacean auditory impacts is likely to be conservative.

• TTS can accumulate across multiple exposures, but the resulting TTS will be less than the TTS from a single, continuous exposure with the same SEL (Finneran

et al.

2010a; Kastelein

et al.

2014b; Kastelein

et al.

2015b; Mooney

et al.

2009b). This means that TTS predictions based on the total, cumulative SEL will overestimate the amount of TTS from intermittent exposures such as sonars and impulsive sources. The importance of duty cycle in predicting the likelihood of TTS is demonstrated further in Kastelein

et al.

(2021b). The authors found that reducing the duty cycle of a sound generally reduced the potential for TTS in California sea lions, and that, further, California sea lions are more susceptible to TTS than previously believed at the 2 and 4 kHz frequencies tested.

• The amount of observed TTS tends to decrease with increasing time following the exposure; however, the relationship is not monotonic (

i.e.,

increasing exposure does not always increase TTS). The time required for complete recovery of hearing depends on the magnitude of the initial shift; for relatively small shifts recovery may be complete in a few minutes, while large

shifts (

e.g.,

approximately 40 dB) may require several days for recovery. Recovery times are consistent for similar-magnitude TTS, regardless of the type of fatiguing sound exposure (impulsive, continuous noise band, or sinusoidal wave; (Kastelein

et al.

2019c)). Under many circumstances TTS recovers linearly with the logarithm of time (Finneran

et al.,

2010a, 2010b; Finneran and Schlundt 2013; Kastelein

et al.

2012a; Kastelein

et al.

2012b; Kastelein

et al.

2014b; Kastelein

et al.

2014c; Popov

et al.

2011; Popov

et al.

2013; Popov

et al.

2014). This means that for each doubling of recovery time, the amount of TTS will decrease by the same amount (e.g

6 dB recovery per doubling of time).

Nachtigall

et al.

(2018) and Finneran (2018) describe the measurements of hearing sensitivity of multiple odontocete species (bottlenose dolphin, harbor porpoise, beluga, and false killer whale) when a relatively loud sound was preceded by a warning sound. These captive animals were shown to reduce hearing sensitivity when warned of an impending intense sound. Based on these experimental observations of captive animals, the authors suggest that wild animals may dampen their hearing during prolonged exposures or if conditioned to anticipate intense sounds. Another study showed that echolocating animals (including odontocetes) might have anatomical specializations that might allow for conditioned hearing reduction and filtering of low-frequency ambient noise, including increased stiffness and control of middle ear structures and placement of inner ear structures (Ketten

et al.

2021). Finneran recommends further investigation of the mechanisms of hearing sensitivity reduction in order to understand the implications for interpretation of existing TTS data obtained from captive animals, notably for considering TTS due to short duration, unpredictable exposures.

Marine mammal TTS data from impulsive sources are limited. Two studies with measured TTS of 6 dB or more, with Finneran

et al.

(2002) reporting behaviorally measured TTSs of 6 and 7 dB in a beluga exposed to single impulses from a seismic water gun, and with Lucke

et al.

(2009) reporting Audio-evoked Potential measured TTS of 7-20 dB in a harbor porpoise exposed to single impulses from a seismic air gun. Kastelein

et al.

(2017) quantified TTS caused by exposure to 10-20 consecutive shots from 2 airguns simultaneously in harbor porpoises. Statistically significant initial TTS (1-4 min after sound exposure stopped) of ~4.4 dB occurred. However, recovery occurred within 12 min post-exposure.

Several impulsive noise exposure studies have also been conducted without behaviorally measurable TTS. Specifically, Finneran

et al.

(2000) exposed dolphins and belugas to single impulses from an explosion simulator, and Finneran

et al.

(2015) exposed three dolphins to sequences of 10 impulses from a seismic air gun (maximum cumulative SEL = 193-195 dB re 1 μPa

s, peak SPL =196-210 dB re 1 μPa) without measurable TTS. The proposed activities include both TTS and a limited amount of PTS in some marine mammals.

Behavioral Disturbance

Behavioral responses to sound are highly variable and context-specific. Many different variables can influence an animal's perception of and response to an acoustic event. An animal's prior experience with a sound or sound source affects whether it is less likely (habituation) or more likely (sensitization) to respond to certain sounds in the future (animals can also be innately predisposed to respond to certain sounds in certain ways) (Southall

et al.

2007). Related to the sound itself, the perceived nearness of the sound, bearing of the sound (approaching vs. retreating), the similarity of a sound to biologically relevant sounds in the animal's environment (

i.e.,

calls of predators, prey, or conspecifics), and familiarity of the sound may affect the way an animal responds to the sound (Southall

et al.

2007, DeRuiter

et al.

2013). Individuals (of different age, gender, reproductive status,

etc.

) among most populations will have variable hearing capabilities, and differing behavioral sensitivities to sounds that will be affected by prior conditioning, experience, and current activities of those individuals. Often, specific acoustic features of the sound and contextual variables (

i.e.,

proximity, duration, or recurrence of the sound or the current behavior that the marine mammal is engaged in or its prior experience), as well as entirely separate factors such as the physical presence of a nearby vessel, may be more relevant to the animal's response than the received level alone.

Controlled experiments with captive marine mammals have shown pronounced behavioral reactions, including avoidance of loud underwater sound sources (Ridgway

et al.

1997; Finneran

et al.

2003). Observed responses of wild marine mammals to loud pulsed sound sources (typically seismic guns or acoustic harassment devices) have been varied but often consist of avoidance behavior or other behavioral changes suggesting discomfort (Morton and Symonds 2002; Thorson and Reyff 2006; see also Gordon

et al.,

2004; Nowacek

et al.

2007).

The onset of noise can result in temporary, short-term changes in an animal's typical behavior and/or avoidance of the affected area. These behavioral changes may include: reduced/increased vocal activities; changing/cessation of certain behavioral activities (such as socializing or feeding); visible startle response or aggressive behavior; avoidance of areas where sound sources are located; and/or flight responses (Richardson

et al.

1995).

The biological significance of many of these behavioral disturbances is difficult to predict, especially if the detected disturbances appear minor. However, the consequences of behavioral modification could potentially be biologically significant if the change affects growth, survival, or reproduction. The onset of behavioral disturbance from anthropogenic sound depends on both external factors (characteristics of sound sources and their paths) and the specific characteristics of the receiving animals (hearing, motivation, experience, demography) and is difficult to predict (Southall

et al.

2007).

Ellison

et al.

(2011) outlined an approach to assessing the effects of sound on marine mammals that incorporates contextual-based factors. The authors recommend considering not just the received level of sound, but also the activity the animal is engaged in at the time the sound is received, the nature and novelty of the sound (

i.e.,

is this a new sound from the animal's perspective), and the distance between the sound source and the animal. They submit that this “exposure context,” as described, greatly influences the type of behavioral response exhibited by the animal. Forney

et al.

(2017) also point out that an apparent lack of response (

e.g.,

no displacement or avoidance of a sound source) may not necessarily mean there is no cost to the individual or population, as some resources or habitats may be of such high value that animals may choose to stay, even when experiencing stress or hearing loss. Forney

et al.

(2017) recommend considering both the costs of remaining in an area of noise exposure such as TTS, PTS, or masking, which could lead to an increased risk of predation or other threats or a decreased capability to forage, and the costs of displacement,

including potential increased risk of vessel strike, increased risks of predation or competition for resources, or decreased habitat suitable for foraging, resting, or socializing. This sort of contextual information is challenging to predict with accuracy for ongoing activities that occur over large spatial and temporal expanses. However, distance is one contextual factor for which data exist to quantitatively inform a take estimate, and the method for predicting Level B harassment in this proposed rule does consider distance to the source. Other factors are often considered qualitatively in the analysis of the likely consequences of sound exposure, where supporting information is available.

Exposure of marine mammals to sound sources can result in, but is not limited to, no response or any of the following observable responses: increased alertness; orientation or attraction to a sound source; vocal modifications; cessation of feeding; cessation of social interaction; alteration of movement or diving behavior; habitat abandonment (temporary or permanent); and, in severe cases, panic, flight, stampede, or stranding, potentially resulting in death (Southall

et al.

2007). A review of marine mammal responses to anthropogenic sound was first conducted by Richardson (1995). More recent reviews (Nowacek

et al.

2007; DeRuiter

et al.

2012 and 2013; Ellison

et al.

2012; Gomez

et al.

2016) address studies conducted since 1995 and focused on observations where the received sound level of the exposed marine mammal(s) was known or could be estimated. Gomez

et al.

(2016) conducted a review of the literature considering the contextual information of exposure in addition to received level and found that higher received levels were not always associated with more severe behavioral responses and vice versa. Southall

et al.

(2016) states that results demonstrate that some individuals of different species display clear yet varied responses, some of which have negative implications, while others appear to tolerate high levels, and that responses may not be fully predictable with simple acoustic exposure metrics (

e.g.,

received sound level). Rather, the authors state that differences among species and individuals along with contextual aspects of exposure (

e.g.,

behavioral state) appear to affect response probability.

During an activity with a series of explosions (not concurrent multiple explosions shown in a burst), an animal is expected to exhibit a startle reaction to the sound of the first detonation followed by another behavioral response after multiple detonations. At close ranges and high sound levels, avoidance of the area around the explosions is the assumed behavioral response in most cases. In certain circumstances, exposure to loud sounds can interrupt feeding behaviors and potentially decrease foraging success, interfere with communication or migration, or disrupt important reproductive or young-rearing behaviors, among other effects.

Many animals perform vital functions, such as feeding, resting, traveling, and socializing, on a diel cycle (24-hour cycle). Behavioral reactions to noise exposure (such as disruption of critical life functions, displacement, or avoidance of important habitat) are more likely to be significant for fitness if they last more than one diel cycle or recur on subsequent days (Southall

et al.

2007). Consequently, a behavioral response lasting less than one day and not recurring on subsequent days is not considered particularly severe unless it could directly affect reproduction or survival (Southall

et al.

2007). It is important to note the difference between behavioral reactions lasting or recurring over multiple days and anthropogenic activities lasting or recurring over multiple days. For example, just because a given anthropogenic activity lasts for multiple days (

e.g.,

a training event) does not necessarily mean that individual animals will be either exposed to those activity-related stressors (

i.e.,

explosions) for multiple days or further exposed at a level would result in sustained multi-day substantive behavioral responses.

Auditory Masking

Sound can disrupt behavior through masking, or interfering with, an animal's ability to detect, recognize, or discriminate between acoustic signals of interest (

e.g.,

those used for intraspecific communication and social interactions, prey detection, predator avoidance, or navigation) (Richardson

et al.

1995; Erbe and Farmer 2000; Tyack 2000; Erbe

et al.

2016). Masking occurs when the receipt of a sound is interfered with by another coincident sound at similar frequencies and at similar or higher intensity, and may occur whether the sound is natural (

e.g.,

snapping shrimp, wind, waves, precipitation) or anthropogenic (

e.g.,

shipping, sonar, seismic exploration) in origin. The ability of a noise source to mask biologically important sounds depends on the characteristics of both the noise source and the signal of interest (

e.g.,

signal-to-noise ratio, temporal variability, direction), in relation to each other and to an animal's hearing abilities (

e.g.,

sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age, or TTS hearing loss), and existing ambient noise and propagation conditions. Masking these acoustic signals can disturb the behavior of individual animals, groups of animals, or entire populations. Masking can lead to behavioral changes including vocal changes (

e.g.,

Lombard effect, increasing amplitude, or changing frequency), cessation of foraging, and leaving an area, to both signalers and receivers, in an attempt to compensate for noise levels (Erbe

et al.

2016). Masking only occurs in the presence of the masking noise and does not persist after the cessation of the noise. Masking may lead to a change in vocalizations or a change in behavior (

e.g.,

cessation of foraging, leaving an area). Masking by explosive detonation sounds would not be expected, given the short duration, and there are no direct observations of masking in marine mammals due to exposure to sound from explosive detonations.

Physiological Stress

There is growing interest in monitoring and assessing the impacts of stress responses to sound in marine animals. Classic stress responses begin when an animal's central nervous system perceives a potential threat to its homeostasis. That perception triggers stress responses regardless of whether a stimulus actually threatens the animal; the mere perception of a threat is sufficient to trigger a stress response (Moberg 2000; Sapolsky

et al.

2005; Seyle 1950). Once an animal's central nervous system perceives a threat, it mounts a biological response or defense that consists of a combination of the four general biological defense responses: behavioral responses, autonomic nervous system responses, neuroendocrine responses, or immune responses.

According to Moberg (2000), in the case of many stressors, an animal's first and sometimes most economical (in terms of biotic costs) response is behavioral avoidance of the potential stressor or avoidance of continued exposure to a stressor. An animal's second line of defense to stressors involves the sympathetic part of the autonomic nervous system and the classical “fight or flight” response which includes the cardiovascular system, the gastrointestinal system, the exocrine glands, and the adrenal medulla to produce changes in heart rate, blood pressure, and gastrointestinal activity that humans commonly

associate with “stress.” These responses have a relatively short duration and may or may not have a significant long-term effect on an animal's welfare.

An animal's third line of defense to stressors involves its neuroendocrine systems or sympathetic nervous systems; the system that has received the most study has been the hypothalamus-pituitary-adrenal system (also known as the HPA axis in mammals or the hypothalamus-pituitary-interrenal axis in fish and some reptiles). Unlike stress responses associated with the autonomic nervous system, virtually all neuro-endocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction (Moberg, 1987; Rivier and Rivest 1991), altered metabolism (Elasser

et al.

2000), reduced immune competence (Blecha 2000), and behavioral disturbance (Moberg 1987; Blecha 2000). Increases in the circulation of glucocorticosteroids (cortisol, corticosterone, and aldosterone in marine mammals; see Romano

et al.

2004) have been equated with stress for many years.

Because there are many unknowns regarding the occurrence of acoustically induced stress responses in marine mammals, it is assumed that any physiological response (

e.g.,

hearing loss or injury) or significant behavioral response is also associated with a stress response.

Munition Strike

Another potential risk to marine mammals is direct strike by ordnance, in which the ordnance physically hits an animal. Based on the dispersed distribution of marine mammals in the open ocean, the relatively short amount of time they spend at the water surface compared with the time they spend underwater, and the annual quantities of munitions proposed to be expended, it is highly improbable that a marine mammal would be directly struck by a munition during EGTTR operations. This conclusion, which NMFS concurs with, was reached in the previous 2015 REA (USAF 2015). The Air Force did not request take of marine mammals by direct munition strikes, as it is not anticipated, and it is not analyzed further.

Marine Mammal Habitat

Impacts on marine mammal habitat are part of the consideration in making a finding of negligible impact on the species and stocks of marine mammals. Habitat includes, but is not necessarily limited to, rookeries, mating grounds, feeding areas, and areas of similar significance. We have preliminarily determined USAF's proposed activities would not result in permanent effects on the habitats used by the marine mammals in the EGTTR, including the availability of prey (

i.e.

fish and invertebrates). While it is anticipated that the proposed activity may result in marine mammals avoiding certain areas due to temporary ensonification, any impact to habitat is temporary and reversible and was considered in further detail earlier in this document, as behavioral modification. The main impact associated with the proposed activity will be temporarily elevated noise levels and the associated direct effects on marine mammals, previously discussed in this proposed rule.

Sound may affect marine mammals through impacts on the abundance, behavior, or distribution of prey species (

e.g.,

crustaceans, cephalopods, fish, zooplankton). Marine mammal prey varies by species, season, and location and, for some species, is not well documented. Here, we describe studies regarding the effects of noise on known marine mammal prey.

Effects on Fish

—Fish utilize the soundscape and components of sound in their environment to perform important functions such as foraging, predator avoidance, mating, and spawning (

e.g.,

Zelick

et al.

1999; Fay 2009). The most likely effects on fishes exposed to loud, intermittent, low-frequency sounds are behavioral responses (

i.e.,

flight or avoidance). Short duration, sharp sounds (such as pile driving or air guns) can cause overt or subtle changes in fish behavior and local distribution. The reaction of fish to acoustic sources depends on the physiological state of the fish, past exposures, motivation (

e.g.,

feeding, spawning, migration), and other environmental factors. Key impacts to fishes may include behavioral responses, hearing damage, barotrauma (pressure-related injuries), and mortality.

Fishes, like other vertebrates, have a variety of different sensory systems to glean information from ocean around them (Astrup and Mohl 1993; Astrup 1999; Braun and Grande 2008; Carroll

et al.

2017; Hawkins and Johnstone 1978; Ladich and Popper 2004; Ladich and Schulz-Mirbach 2016; Nedwell

et al.

2004; Popper

et al.

2003; Popper

et al.

2005). Depending on their hearing anatomy and peripheral sensory structures, which vary among species, fishes hear sounds using pressure and particle motion sensitivity capabilities and detect the motion of surrounding water (Fay

et al.

2008) (terrestrial vertebrates generally only detect pressure). Most marine fishes primarily detect particle motion using the inner ear and lateral line system, while some fishes possess additional morphological adaptations or specializations that can enhance their sensitivity to sound pressure, such as a gas-filled swim bladder (Braun and Grande 2008; Popper and Fay 2011).

Hearing capabilities vary considerably between different fish species with data only available for just over 100 species out of the 34,000 marine and freshwater fish species (Eschmeyer and Fong 2016). In order to better understand acoustic impacts on fishes, fish hearing groups are defined by species that possess a similar continuum of anatomical features which result in varying degrees of hearing sensitivity (Popper and Hastings 2009a). There are four hearing groups defined for all fish species (modified from Popper

et al.

2014) within this analysis and they include: fishes without a swim bladder (

e.g.,

flatfish, sharks, rays,

etc.

); fishes with a swim bladder not involved in hearing (

e.g.,

salmon, cod, pollock,

etc.

); fishes with a swim bladder involved in hearing (

e.g.,

sardines, anchovy, herring,

etc.

); and fishes with a swim bladder involved in hearing and high-frequency hearing (

e.g.,

shad and menhaden). Currently, less data are available to estimate the range of best sensitivity for fishes without a swim bladder.

In terms of behavioral responses of fish, Juanes

et al.

(2017) discuss the potential for negative impacts from anthropogenic soundscapes on fish, but the authors' focus was on broader based sounds, such as ship and boat noise sources. Occasional behavioral reactions to intermittent explosions occurring at or near the surface are unlikely to cause long-term consequences for individual fish or populations; there are no detonations of explosives occurring underwater from the proposed activities. Fish that experience hearing loss as a result of exposure to explosions may have a reduced ability to detect relevant sounds, such as predators, prey, or social vocalizations. However, PTS has not been known to occur in fishes and any hearing loss in fish may be as temporary as the timeframe required to repair or replace the sensory cells that were damaged or destroyed (Popper

et al.

2005; Popper

et al.

2014; Smith

et al.

2006). It is not known if damage to auditory nerve fibers could occur, and if so, whether fibers would recover during this process. It is also possible for fish to be injured or killed by an explosion in the immediate

vicinity of the surface from dropped or fired ordnance. Physical effects from pressure waves generated by detonations at or near the surface could potentially affect fish within proximity of training or testing activities. The shock wave from an explosion occurring at or near the surface may be lethal to fish at close range, causing massive organ and tissue damage and internal bleeding (Keevin and Hempen, 1997). At greater distance from the detonation point, the extent of mortality or injury depends on a number of factors including fish size, body shape, orientation, and species (Keevin and Hempen, 1997; Wright, 1982). At the same distance from the source, larger fish are generally less susceptible to death or injury, elongated forms that are round in cross-section are less at risk than deep-bodied forms, and fish oriented sideways to the blast suffer the greatest impact (Edds-Walton and Finneran 2006; Wiley

et al.

1981; Yelverton

et al.

1975). Species with gas-filled organs are more susceptible to injury and mortality than those without them (Gaspin, 1975; Gaspin

et al.

1976; Goertner

et al.

1994).

Training and testing exercises involving explosions at or near the surface are dispersed in space and time; therefore, repeated exposure of individual fishes are unlikely. Mortality and injury effects to fishes from explosives would be localized around the area of a given explosion at or above the water surface, but only if individual fish and the explosive at the surface were co-located at the same time. Fishes deeper in the water column or on the bottom would not be affected by surface explosions. Most acoustic effects, if any, are expected to be short term and localized. Long-term consequences for fish populations, including key prey species within the EGTTR Area, would not be expected.

Effects on Invertebrates

—In addition to fish, prey sources such as marine invertebrates could potentially be impacted by sound stressors as a result of the proposed activities. However, most marine invertebrates' ability to sense sounds is very limited. In most cases, marine invertebrates would not respond to impulsive sounds. Data on response of invertebrates such as squid, another marine mammal prey species, to anthropogenic sound has been documented (de Soto 2016; Sole

et al.

2017). Explosions could kill or injure nearby marine invertebrates. Vessels also have the potential to impact marine invertebrates by disturbing the water column or sediments, or directly striking organisms (Bishop 2008). The propeller wash (water displaced by propellers used for propulsion) from vessel movement and water displaced from vessel hulls can potentially disturb marine invertebrates in the water column and are a likely cause of zooplankton mortality (Bickel

et al.

2011). The localized and short-term exposure to explosions or vessels at or near the surface could displace, injure, or kill zooplankton, invertebrate eggs or larvae, and macro-invertebrates. However, mortality or long-term consequences for a few animals is unlikely to have measurable effects on overall populations. As with fish, cumulatively individual and population-level impacts from exposure to explosives at or above the water surface are not anticipated, and impacts would be short term and localized, and would likely be inconsequential to invertebrate populations, and to the marine mammals that use them as prey.

Expended Materials

—Military expended materials resulting from training and testing activities could potentially result in minor long-term changes to benthic habitat, however the impacts of small amounts of expended materials are unlikely to have measurable effects on overall populations. Military expended materials may be colonized over time by benthic organisms that prefer hard substrate and would provide structure that could attract some species of fish or invertebrates.

Overall, the combined impacts of explosions and military expended materials resulting from the proposed activities would not be expected to have measurable effects on populations of marine mammal prey species. Prey species exposed to sound might move away from the sound source or show no obvious direct effects at all, but a rapid return to normal recruitment, distribution, and behavior is anticipated. Long-term consequences to fish or marine invertebrate populations would not be expected as a result of exposure to sounds or vessels in the EGTTR.

Acoustic Habitat

—Acoustic habitat is the soundscape which encompasses all of the sound present in a particular location and time, as a whole, when considered from the perspective of the animals experiencing it. Animals produce sound for, or listen for sounds produced by, conspecifics (communication during feeding, mating, and other social activities), other animals (finding prey or avoiding predators), and the physical environment (finding suitable habitats, navigating). Together, sounds made by animals and the geophysical environment (

e.g.,

produced by earthquakes, lightning, wind, rain, waves) make up the natural contributions to the total acoustics of a place. These acoustic conditions, termed acoustic habitat, are one attribute of an animal's total habitat.

Soundscapes are also defined by, and acoustic habitat influenced by, the total contribution of anthropogenic sound. This may include incidental emissions from sources, such as vessel traffic or may be intentionally introduced to the marine environment for data acquisition purposes (

e.g.,

as in the use of air gun arrays) or USAF training and testing purposes (as in the use of explosives). Anthropogenic noise varies widely in its frequency, content, duration, and loudness, and these characteristics greatly influence the potential habitat-mediated effects to marine mammals, which may range from local effects for brief periods of time to chronic effects over large areas and for long durations. Depending on the extent of effects to habitat, animals may alter their communications signals (thereby potentially expending additional energy) or miss acoustic cues (either conspecific or adventitious). Problems arising from a failure to detect cues are more likely to occur when noise stimuli are chronic and overlap with biologically relevant cues used for communication, orientation, and predator/prey detection (Francis and Barber, 2013). For more detail on these concepts see Pijanowski

et al.

2011; Francis and Barber 2013; Lillis

et al.

2014. We do not anticipate these problems arising from at or near surface explosions during training and testing activities as they would be either widely dispersed or concentrated in small areas for shorter periods of time. Sound produced from training and testing activities in the EGTTR would be temporary and transitory; the affected area would be expected to immediately return to the original state when these activities cease.

Marine Water Quality

—Training and testing activities may introduce water quality constituents into the water column. Metals are the dominant constituent by weight of bombs, missiles, gun ammunition, and other munitions, including inert munitions, used during EGTTR training and testing operations. Some targets used during EGTTR missions also contain metals, including CONEX and hopper barge targets used for PSW tests and certain components of remotely controlled target boats. Metals contained in casing fragments of detonated munitions, intact inert munitions, unexploded ordnance, and other mission-related debris will corrode from exposure to seawater. The

rate of corrosion depends on the metal type and the extent to which the item is directly exposed to seawater, which can be influenced by existing corrosion on the item, and how much the item may be encrusted by marine organisms and/or buried in sediments. Aluminum and steel, which is composed mostly of iron, comprise the bulk of the metal that enters the marine environment from EGTTR operations. Iron and aluminum are relatively benign metals in terms of toxicity. Chromium, lead, and copper, which make up a relatively small percentage of the overall metal input into the marine environment from EGTTR operations, have higher toxicity effects. Through its lifetime in the marine environment, a portion of the overall metal content would dissolve, depending on the solubility of the material. Dissolved metals would readily undergo mixing and dilution and would have no appreciable effect on water quality or marine life within the water column. Metals in particulate form would be released into sediments through the corrosion process. Elevated levels of undissolved metals in sediments would be restricted to a relatively small area around the metal-containing item and any associated impacts to water quality would be negligible.

Munitions used for EGTTR training and testing operations contain a wide variety of explosives, including TNT, RDX, HMX, Composition B, Tritonal, AFX-757, PBXN, and others. During live missions in the EGTTR, explosives can enter the marine environment via high-order detonations, which occur when the munition functions as intended and the vast majority of explosives are consumed; low-order detonations, which occur when the munition partially functions and only a portion of the explosives are consumed; and unexploded munitions, which fail to detonate with no explosives consumed. During high-order detonations, a residual amount of the explosive material, typically less than 1 percent, would be unconsumed and released into the environment (Walsh

et al.

2011). The majority of live munitions used during EGTTR operations are successfully detonated as intended. During low-order detonations, a residual amount of explosives associated with the detonation and the remaining unconsumed portion of the explosive fill would enter the marine environment. If the munition does not explode, it becomes unexploded ordnance (UXO). In this case, all the explosive material would remain within the munition casing and enter the marine environment with explosives potentially being released due to corrosion or rupture. Explosives and explosives by-products released into the marine environment can be removed via biodegradation, and expended or disposed military munitions on the seafloor do not result in excessive accumulation of explosives in sediments or significant degradation of sediment quality by explosives. Given that high-order detonations consume the vast majority of explosive material in the munition, successful detonations are considered a negligible source of explosives released into the marine environment.

Estimated Take of Marine Mammals

This section indicates the number of takes that NMFS is proposing to authorize, which is based on the maximum amount that is reasonably likely to occur, depending on the type of take and the methods used to estimate it, as described in detail below. NMFS preliminarily agrees that the methods the USAF has put forth described herein to estimate take (including the model, thresholds, and density estimates), and the resulting numbers estimated for authorization, are appropriate and based on the best available science.

All takes are by harassment. For a military readiness activity, the MMPA defines “harassment” as (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). No serious injury or mortality of marine mammals is expected to occur.

Proposed authorized takes would primarily be in the form of Level B harassment, as use of the explosive sources may result, either directly or as result of TTS, in the disruption of natural behavioral patterns to a point where they are abandoned or significantly altered (as defined specifically at the beginning of this section, but referred to generally as behavioral disruption). There is also the potential for Level A harassment, in the form of auditory injury to result from exposure to the sound sources utilized in training and testing activities. As described in this Estimated Take of Marine Mammals section, no non-auditory injury is anticipated or proposed for authorization, nor is any serious injury or mortality.

Generally speaking, for acoustic impacts NMFS estimates the amount and type of harassment by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals will be taken by Level B harassment or incur some degree of temporary or permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day or event; (3) the density or occurrence of marine mammals within these ensonified areas; and (4) the number of days of activities or events. This analysis of the potential impacts of the proposed activities on marine mammals was conducted by using the spatial density models developed by NOAA's Southeast Fisheries Science Center for the species in the Gulf of Mexico (NOAA 2022). The density model integrated visual observations from aerial and shipboard surveys conducted in the Gulf of Mexico from 2003 to 2019.

The munitions proposed to be used by each military unit were grouped into mission-day categories so the acoustic impact analysis could be based on the total number of detonations conducted during a given mission to account for the accumulated energy from multiple detonations over a 24-hour period. A total of 19 mission-day categories were developed for the munitions proposed to be used. Using the dBSea underwater acoustic model and associated analyses, the threshold distances associated with Level A harassment (PTS) and Level B (TTS and behavioral) harassment zones were estimated for each mission-day category for each marine mammal species. Takes were estimated based on the area of the harassment zones, predicted animal density, and annual number of events for each mission-day category. To assess the potential impacts of inert munitions on marine mammals, the proposed inert munitions were categorized into four classes based on their impact energies, and the threshold distances for each class were modeled and calculated as described for the mission-day categories.

Acoustic Thresholds

Using the best available science, NMFS has established acoustic thresholds that identify the most appropriate received level of underwater sound above which marine mammals exposed to these sound sources could be reasonably expected to directly experience a disruption in behavior patterns to a point where they are abandoned or significantly altered,

to incur TTS (equated to Level B harassment), or to incur PTS of some degree (equated to Level A harassment). Thresholds have also been developed to identify the pressure levels above which animals may incur non-auditory injury from exposure to pressure waves from explosive detonation. Refer to the Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III) report (U.S. Department of the Navy 2017c) for detailed information on how the criteria and thresholds were derived.

Hearing Impairment (TTS/PTS), Tissues Damage, and Mortality

NMFS' Acoustic Technical Guidance (NMFS 2018) identifies dual criteria to assess auditory injury (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). The Acoustic Technical Guidance also identifies criteria to predict TTS, which is not considered injury and falls into the Level B harassment category. The USAF's proposed activity only includes the use of impulsive (explosives) sources. These thresholds (Table 20) were developed by compiling and synthesizing the best available science and soliciting input multiple times from both the public and peer reviewers. The references, analysis, and methodology used in the development of the thresholds are described in Acoustic Technical Guidance, which may be accessed at:

https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.

Additionally, based on the best available science, NMFS uses the acoustic and pressure thresholds indicated in Table 20 to predict the onset of TTS, PTS, tissue damage, and mortality for explosives (impulsive) and other impulsive sound sources.

Table 20—Onset of TTS, PTS, Tissue Damage, and Mortality Thresholds for Marine Mammals for Explosives and Other Impulsive Sources

Functional hearing group

Species

Onset TTS

Onset PTS

Mean onset slight GI tract injury

Mean onset slight lung injury

Mean onset mortality

Low-frequency cetaceans

Rice's whale

168 dB SEL (weighted) or 213 dB Peak SPL

183 dB SEL (weighted) or 219 dB Peak SPL

237 dB Peak SPL

Equation 1

Equation 2

Mid-frequency cetaceans

Dolphins

170 dB SEL (weighted) or 224 dB Peak SPL

185 dB SEL (weighted) or 230 dB Peak SPL

237 dB Peak SPL.

Notes:

Equation 1: 47.5M

1/3

(1+[D

/10.1])

1/6

Pa-sec. Equation 2: 103M

1/3

(1+[D

/10.1])

1/6

Pa-sec. M = mass of the animals in kg; D

= depth of the receiver (animal) in meters; SPL = sound pressure level.

Refer to the Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III) report (U.S. Department of the Navy, 2017c) for detailed information on how the criteria and thresholds were derived. Non-auditory injury (

i.e.,

other than PTS) and mortality are so unlikely as to be discountable under normal conditions and are therefore not considered further in this analysis.

Behavioral Disturbance

Though significantly driven by received level, the onset of Level B harassment by direct behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source (

e.g.,

frequency, predictability, duty cycle, distance), the environment (

e.g.,

bathymetry), and the receiving animals (hearing, motivation, experience, demography, behavioral context) and can be difficult to predict (Ellison

et al.

2011; Southall

et al.

2007). Based on what the available science indicates and the practical need to use thresholds based on a factor or factors that are both predictable and measurable for most activities, NMFS uses generalized acoustic thresholds based primarily on received level (and distance in some cases) to estimate the onset of Level B harassment by behavioral disturbance.

Explosives

—Explosive thresholds for Level B harassment by behavioral disturbance for marine mammals are the hearing groups' TTS thresholds minus 5 dB (see Table 21 below for the TTS thresholds for explosives) for events that contain multiple impulses from explosives underwater. See the Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III) report (U.S. Department of the Navy 2017c) for detailed information on how the criteria and thresholds were derived. NMFS continues to concur that this approach represents the best available science for determining behavioral disturbance of marine mammals from multiple explosives. While marine mammals may also respond to single explosive detonations, these responses are expected to more typically be in the form of startle reaction, rather than a disruption in natural behavioral patterns to the point where they are abandoned or significantly altered. On the rare occasion that a single detonation might result in a more severe behavioral response that qualifies as Level B harassment, it would be expected to be in response to a comparatively higher received level. Accordingly, NMFS considers the potential for these responses to be quantitatively accounted for through the application of the TTS threshold, which, as noted above, is 5 dB higher than the behavioral harassment threshold for multiple explosives.

Table 21—Thresholds for Level B Harassment by Behavioral Disturbance for Explosives for Marine Mammals

Medium

Functional hearing group

SEL

(weighted)

Underwater

163

Underwater

165

Note:

Weighted SEL thresholds in dB re 1 μPa

s underwater. LF = low-frequency, MF = mid-frequency, HF = high-frequency.

USAF's Acoustic Effects Model

The USAF's Acoustic Effects Model calculates sound energy propagation from explosives during UASF activities in the EGTTR. The net explosive weight (NEW) of a munition at impact can be directly correlated with the energy in the impulsive pressure wave generated by the warhead detonation. The NEWs of munitions addressed as part of this proposed rule range from 0.1 lb (0.04 kg) for small projectiles to 945 lb (428.5kg) for the largest bombs. The explosive materials used in these munitions also vary considerably with different formulations used to produce different intended effects. The primary detonation metrics directly considered and used for modeling analysis are the peak impulse pressure and duration of the impulse. An integration of the

pressure of an impulse over the duration (time) of an impulse provides a measure of the energy in an impulse. Some of the NEWs of certain types of munitions, such as missiles, are associated with the propellant used for the flight of the munition. This propellant NEW is unrelated to the NEW of the warhead, which is the primary source of explosive energy in most munitions. The propellant of a missile fuels the flight phase and is mostly consumed prior to impact. Missile propellant typically has a lower flame speed than warhead explosives and is relatively insensitive to detonation from impacts but burns readily. A warhead detonation provides a high-pressure, high-velocity flame front that may cause burning propellant to detonate; therefore, this analysis assumes that the unconsumed residual propellant that remains at impact contributes to the detonation-induced pressure impulse in the water. The impact analysis assumes that 20 percent of the propellant remains unconsumed in missiles at impact; this assumption is based on input from user groups and is considered a reasonable estimate for the purpose of analysis. The NEW associated with this unconsumed propellant is added to the NEW of the warhead to derive the total energy released by the detonation. Absent a warhead detonation, it is assumed that continued burning or deflagration of unconsumed residual propellant does not contribute to the pressure impulse in the water; this applies to inert missiles that lack a warhead but contain propellant for flight.

In addition to the energy associated with the detonation, energy is also released by the physical impact of the munition with the water. This kinetic energy has been calculated and incorporated into the estimations of munitions energy for both live and inert munitions in this proposed rule. The kinetic energy of the munition at impact is calculated as one half of the munition mass times the square of the munition velocity. The initial impact event contributing to the pressure impulse in water is assumed to be 1 millisecond in duration. To calculate the velocity (and kinetic energy) immediately after impact, the deceleration contributing to the pressure impulse in the water is assumed for all munitions to be 1,500 g-forces, or 48,300 feet per square second over 1 millisecond. A substantial portion of the change in kinetic energy at impact is dissipated as a pressure impulse in the water, with the remainder being dissipated through structural deformation of the munition, heat, displacement of water, and other smaller energy categories. Even with 1,500 g-forces of deceleration, the change in velocity over this short time period is small and is proportional to the impact velocity and munition mass. The impact energy is the portion of the kinetic energy at impact that is transmitted as an underwater pressure impulse, expressed in units of trinitrotoluene-equivalent (TNTeq). The impact energies of the proposed live munitions were calculated and included in their total energy estimations. The impact energies of the inert munitions proposed to be used were also calculated. To assess the potential impacts of inert munitions on marine animals, the inert munitions were categorized based on their impact energies into the following four classes of 2 lb (0.9 kg), 1 lb (0.45 kg), 0.5 lb (0.22 kg), and 0.15 lb (0.07 kg) TNTeq; these values correspond closely to the actual or average impact energy values of the munitions and are rounded for the purpose of analysis. The 2 lb class represents the largest inert bomb, which includes the Mark (Mk)-84 General Purpose (GP), Guided Bomb Unit (GBU)-10, and GBU-31 bombs, whereas the 1 lb class represents the largest inert missile, which is the Air-to-Ground Missile (AGM)-158 Joint Air-to-Surface Standoff Missile (JASSM). The JASSM has greater mass but lower impact energy than the GBU-31; this is because of the JASSM's lower velocity at impact and associated change in velocity over the deceleration period, which contributes to the pressure impulse. The 0.5 lb and 0.15 lb impact energy classes each represent the approximate average impact energy of multiple munitions, with the 0.5 lb class representing munitions with mid-level energies, and the 0.15 lb class representing munitions with the lowest energies (Table 22).

Table 22—Impact Energy Classes for Proposed Inert Munitions

Impact energy class

(lb TNT

)/(kg)

Representative munitions

Approximate weight

(lb)/(kg)

Approximate velocity

(mach)

2 (0.9)

Mk-84, GBU-10, and GBU-31

2,000 (907)

1.1.

1 (0.45)

AGM-158 JASSM

2,250 (1020.3)

0.9.

0.5 (0.22)

GBU-54 and AIM-120

250 to 650 (113.4 to 294.8)

Variable.

0.15 (0.07)

AIM-9, GBU-39, and PGU-15

1 to 285 (0.5 to 129.2)

Variable.

The NEW associated with the physical impact of each munition and the unconsumed propellant in certain munitions is added to the NEW of the warhead to derive the NEW at impact (NEWi) for each live munition. The NEWi of each munition was then used to calculate the peak pressure and pressure decay for each munition. This results in a more accurate estimate of the actual energy released by each detonation. Extensive research since the 1940s has shown that each explosive formulation produces unique correlations to explosive performance metrics. The peak pressure and pressure decay constant depend on the NEW, explosive formulation, and distance from the detonation. The peak pressure and duration of the impulse for each munition can be calculated empirically using similitude equations, with constants used in these equations determined from experimental data (NSWC 2017). The explosive-specific similitude constants and munition-specific NEWi were used for calculating the peak pressure and pressure decay for each munition analyzed. It should be noted that this analysis assumes that all detonations occur in the water and none of the detonations occur above the water surface when a munition impacts a target. This exceptionally conservative assumption implies that all munition energy is imparted to the water rather than the intended targets. See Appendix A in the LOA application for detailed explanations of similitude equations.

The following standard metrics are used to assess underwater pressure and impulsive noise impacts on marine animals:

•

SPL:

The SPL for a given munition can be explicitly calculated at a radial distance using the similitude equations.

•

SEL:

A commercially available software package, dBSea (version 2.3), was used to calculate the SEL for each mission day.

•

Positive Impulse:

This is the time integral of the initial positive phase of

the pressure impulse. This metric provides a measure of energy in the form of time-integrated pressure. Units are typically pascal-seconds (Pa·s) or pounds per square inch (psi) per millisecond (msec) (psi·msec). The positive impulse for a given munition can be explicitly calculated at a given distance using the similitude equations and integrating the pressure over the initial positive phase of the pressure impulse.

The munition-specific peak pressure and pressure decay at various radii were used to determine the species-specific distance to effect threshold for mortality, non-auditory injury, peak pressure-induced permanent threshold shift (PTS) in hearing and peak pressure-induced temporary threshold shift (TTS) in hearing for each species. The munition-specific peak pressures and decays for all munitions in each mission-day category were used as a time-series input in the dBSea underwater acoustic model to determine the distance to effect for cumulative SEL-based (24-hour) PTS, TTS, and behavioral effects for each species for each mission day.

The dBSea model was conducted using a constant sound speed profile (SSP) of 1500 m/s to be both representative of local conditions and to prevent thermocline induced refractions from distorting the analysis results. Salinity was assumed to be 35 parts per thousand (ppt) and pH was 8. The water surface was treated as smooth (no waves) to conservatively eliminate diffraction induced attenuation of sound. Currents and tidal flow were treated as zero. Energy expended on the target and/or on ejecting water or transfer into air was ignored and all weapon energy was treated as going into underwater acoustic energy to be conservative. Finally, the bottom was treated as sand with a sound speed of 1650 m/s and an attenuation of 0.8 dB/wavelength.

The harassment zone is the area or volume of ocean in which marine animals could be exposed to various pressure and impulsive noise levels generated by a surface or subsurface detonation that would result in mortality; non-auditory injury and PTS (Level A harassment impacts); and TTS and behavioral impacts (Level B harassment impacts). The harassment zones for the proposed detonations were estimated using Version 2.3 of the dBSea model for cumulative SEL and using explicit similitude equations for SPL and positive impulse. The characteristics of the impulse noise at the source were calculated based on munition-specific data including munition mass at impact, munition velocity at impact, NEW of warheads, explosive-specific similitude data, and propellant data for missiles. Table 23 presents the source-level SPLs (at r = 1 meter) calculated for the proposed munitions.

Table 23—Calculated Source SPLs for Munitions

Type

Warhead NEW (lb)/(kg)

Modeled

explosive

Model NEWi

(lm)/(kg)

Peak pressure and decay values

Pmax @1 m (psi)

SPL @1 m dB re 1 mPa

msec

AGM-158 JASSM All Variants

240.26 (108.9)

Tritonal

241.36 (109.5)

45961.4858

290.0

0.320

GBU-54 KMU-572C/B, B/B

192 (87.1)

Tritonal

192.3 (87.2)

42101.8577

289.3

0.302

AGM-65 (all variants)

85 (38.5)

Comp B

98.3 (44.6)

37835.4932

288.3

0.200

AIM-120C3

15 (6.8)

PBXN-110

36.18 (13.4)

24704.864

284.6

0.167

AIM-9X Blk I

7.7 (3.5)

PBXN-110

20 (9.1)

19617.2833

282.6

0.143

AGM-114 (All ex R2 with TM(R10))

9 (4.1)

PBXN-110

13.08 (5.9)

16630.2435

281.2

0.128

AGM-179 JAGM

9 (4.1)

PBXN-110

13.08 (5.9)

16630.2435

281.2

0.128

AGM-114 R2 with TM (R10)

8 (3.6)

PBXN-9

13.08 (5.9)

17240.2131

281.5

0.124

AGR-20 (APKWS)

2.3 (1.0)

Comp B

3.8 (1.7)

10187.8419

276.9

0.090

PGU-43 (105 mm)

4.7 (2.1)

Comp B

4.72 (2.1)

11118.8384

277.7

0.095

GBU-69

36 (16.3)

Tritonal

36.1 (16.4)

22074.1015

283.7

0.198

GBU-70

36 (16.3)

Tritonal

36.1 (19.4)

22074.1015

283.7

0.198

GBU-39 SDB (GTV)

0.39 (0.2)

PBXN-9

0.49 (0.2)

4757.6146

270.3

0.054

GBU-53/B (GTV)

0.34 (0.2)

PBXN-9

0.44 (0.2)

4561.06062

270.0

0.053

GBU-12

192 (87.1)

Tritonal

192.3 (87.2)

42101.8577

289.3

0.302

Mk-81 (GP 250 lb)

100 (45.4)

H-6

100 (45.4)

38017.3815

288.4

0.237

θ = shock wave time constant; AGM = Air-to-Ground Missile; AIM = Air Intercept Missile; APKWS = Advanced Precision Kill Weapon System; dB re 1 µPa = decibel(s) referenced to 1 micropascal; FU = Full Up; GBU = Guided Bomb Unit; GP = General Purpose; GTV = Guided Test Vehicle; HACM = Hypersonic Attack Cruise Missile; HE = High Explosive; JASSM = Joint Air-to-Surface Standoff Missile; lb = pound(s); lbm = pound-mass; LSDB = Laser Small-Diameter Bomb; m = meter(s); Mk = Mark; mm = millimeter(s); msec = millisecond(s); NEW = net explosive weight; NEWi = net explosive weight at impact; NLOS = Non-Line-of-Sight; PGU = Projectile Gun Unit; Pmax = shock wave peak pressure; psi = pound(s) per square inch; SDB = Small-Diameter Bomb; SPL = sound pressure level; TM = telemetry.

For SEL analysis, the dBSea model was used with the ray-tracing option for calculating the underwater transmission of impulsive noise sources represented in a time series (1,000,000 samples per second) as calculated using similitude equations (r = 1 meter) for each munition for each mission day. All surface detonations are assumed to occur at a depth of 1 m, and all subsurface detonations, which would include the GBU-10, GBU-24, GBU-31, and subsurface mines, are assumed to occur at a depth of 3 m. The model used bathymetry for LIA with detonations occurring at the center of the LIA with a water depth of 70 m. The seafloor of the LIA is generally sandy, so sandy bottom characteristics for reflectivity and attenuation were used in the dBSea model, as previously described. The model was used to calculate impulsive acoustic noise transmission on one-third octaves from 31.5 hertz to 32 kilohertz. Maximum SELs from all depths projected to the surface were used for the analyses.

The cumulative SEL is based on multiple parameters including the acoustic characteristics of the detonation and sound propagation loss in the marine environment, which is influenced by a number of environmental factors including water depth and seafloor properties. Based on integration of these parameters, the dBSea model predicts the distances at which each marine animal species is estimated to experience SELs associated with the onset of PTS, TTS, and behavioral disturbance. As noted previously, thresholds for the onset of TTS and PTS used in the model and pressure calculations are based on those presented in Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III) (DoN 2017) for cetaceans with mid- to high-frequency hearing (dolphins) and low-frequency hearing (Rice's whale). Behavioral thresholds are set 5 dB

below the SEL-based TTS threshold. Table 24 shows calculated SPLs and SELs for the designated mission-day categories.

Table 24—Calculated Source SPLs and SELs for Mission-Day Categories

Mission day

Total warhead NEW, lbm

(kg)

Modeled NEWi, lbm/(kg)

Source

cumulative

SEL, dB

Source peak SPL, dB

2402.6 (108.6)

2413.6 (1094.6)

262.1

290

1961 (889.3)

2029.9 (920.6)

261.4

289.3

1145 (519.2)

1376.2 (624.1)

259.8

288.3

562 (254.8)

836.22 (379.2)

257.6

288.3

817.88 (370.9)

997.62 (452.0)

257.1

281.5

584 (264.8)

584.6 (265.1)

256.2

289.3

191(86.6)

191.6 (86.9)

250.4

277.7

60.5 (24.7)

61.1 (27.7)

245.2

268.8

18.4 (8.3)

30.4 (13.8)

242.5

276.9

945 (428.6)

946.8 (429.4)

258.1

294.6

Not available

350 (158.7)

253.4

291.5

624.52 (283.2)

627.12 (284.4)

256.2

290

324 (146.9)

324.9 (147.3)

253.2

283.6

219.92 (99.7)

238.08 (107.9)

252

285.3

72 (36.6)

104.64 (47.5)

248.3

281.2

90 (40.8)

130.8 (59.3)

249.3

281.2

94 (42.6)

94.4 (42.8)

247.5

277.7

35.12 (15.9)

35.82 (16.2)

241.7

270.3

130 (58.9)

249.4

283

lbm = pound-mass.

Mission-Day Categories

The munitions proposed to be used by each military unit were grouped into mission-day categories so the acoustic impact analysis could be based on the total number of detonations conducted during a given mission instead of each individual detonation. This analysis was done to account for the accumulated energy from multiple detonations over a 24-hour period.

The estimated number of mission days assigned to each category was based on historical numbers and projections provided by certain user groups. Although the mission-day categories may not represent the exact manner in which munitions would be used, they provide a conservative range of mission scenarios to account for accumulated energy from multiple detonations. It is important to note that only acoustic energy metrics (SEL) are affected by the accumulation of energy over a 24-hour period. Pressure metrics (

e.g.,

peak SPL and positive impulse) do not accumulate and are based on the highest impulse pressure value within the 24-hour period. Based on the categories developed, the total NEWi per mission day would range from 2,413.6 to 30.4 lb (1,094.6 to 13.8 kg). The highest detonation energy of any single munition used under the USAF's proposed activities would be 945 lb (428.5 kg) NEW, which was also the highest NEW for a single munition in the previous LOA Request. The munitions having this NEW include the GBU-10, GBU-24, and GBU-31.

Note that the types of munitions that would be used for SINKEX testing are controlled information and, therefore, not identified in this LOA Request. For the purpose of analysis, SINKEX exercises are assigned to mission-day category J, which represents a single subsurface detonation of 945 lb NEW. SINKEX exercises would not exceed this NEW. The 2 annual SINKEX exercises are added to the other 8 annual missions involving subsurface detonations of these bombs, resulting in 10 total annual missions under mission-day category J.

As indicated in Table 25, a total of 19 mission-day categories (A through S) were developed a part of this LOA application. The table also contains information on the number of munitions per day, number of mission days per year, annual quantity of munitions and the NEWi per mission day.

Table 25—Mission-Day Categories for Acoustic Impact Analysis

User group

Mission-day

Category

Warhead NEW (lb)/(kg)

NEWi (lb)/kg

Detonation scenario

Munitions per day

Mission days per year

Annual quantity

NEWi per mission day (lb)/(kg)

53 WEG

AGM-158D JASSM XR

Missile

240.26 (108.9)

241.36 (109.4)

Surface

2,413.6 (1,095.9)

AGM-158B JASSM ER

Missile

240.26 (108.9)

241.36 (109.4)

Surface

AGM-158A JASSM

Missile

240.26 (108.9)

241.36 (109.4)

Surface

GBU-54 KMU-572C/B

Bomb (Mk-82)

192 (87.1)

192.3 (87.2)

Surface

2,029.9 (920.5)

GBU-54 KMU-572B/B

Bomb (Mk-82)

192 (87.1)

192.3 (87.2)

Surface

AGM-65D

Missile

85 (38.5)

98.3 (44.6)

Surface

AGM-65H2

Missile

85 (37.5)

98.3 (44.6)

Surface

1,376.2 (624.1)

AGM-65G2

Missile

85 (38.5)

98.3 (44.6)

Surface

AGM-65K2

Missile

85 (38.5)

98.3 (44.6)

Surface

AGM-65L

Missile

85 (38.5)

98.3 (44.6)

Surface

836.22 (379.2)

AIM-120C3

Missile

15 (6.8)

36.18 (16.4)

Surface

AIM-9X Blk I

Missile

7.7 (4.5)

20 (9.1)

Surface

AGM-114 N-4D with TM

Missile

9 (4.1)

13.08 (5.9)

Surface

997.62 (452.4)

AGM-114 N-6D with TM

Missile

9 (4.1)

13.08 (5.9)

Surface

AGM-179 JAGM

Missile

9 (4.1)

13.08 (5.9)

Surface

AGM-114 R2 with TM (R10)

Missile

9 (4.1)

13.08 (5.9)

Surface

AGM-114 R-9E with TM (R11)

Missile

9 (4.1)

13.08 (5.9)

Surface

AGM-114Q with TM

Missile

9 (4.1)

13.08 (5.9)

Surface

AGR-20 (APKWS)

Rocket

2.3 (1.0)

3.8 (1.7)

Surface

AGM-176

Missile

9 (4.1)

13.08 (5.9)

Surface

PGU-43 (105 mm)

Gun Ammunition

4.7 (2.1)

4.72 (2.1)

Surface

100

GBU-69

Bomb

36 (16.3)

36.1 (13.3)

Surface

GBU-70

Bomb

36 (16.3)

36.1 (16.3)

Surface

AGM-88C w/FTS

Missile

0.70 (0.3)

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