Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to U.S. Navy Construction at Portsmouth Naval Shipyard, Kittery, Maine

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 217

[Docket No. 230321-0081]

RIN 0648-BL78

Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to U.S. Navy Construction at Portsmouth Naval Shipyard, Kittery, Maine

AGENCY:

National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.

ACTION:

Final rule; notification of issuance of Letter of Authorization.

SUMMARY:

NMFS, upon request from the U.S. Navy (Navy), hereby issues regulations to govern the unintentional taking of marine mammals incidental to construction at the Portsmouth Naval Shipyard in Kittery, Maine, over the course of 5 years (2023-2028). These regulations, which allow for the issuance of a Letter of Authorization (LOA) for the incidental take of marine mammals during the described activities and specified timeframes, prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on marine mammal species or stocks and their habitat, as well as requirements pertaining to the monitoring and reporting of such taking.

DATES:

Effective from April 1, 2023, through March 31, 2028.

ADDRESSES:

A copy of the Navy's application and any supporting documents, as well as a list of the references cited in this document, may be obtained online at:

https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-navy-construction-portsmouth-naval-shipyard-kittery-maine-0.

In case of problems accessing these documents, please call the contact listed below.

FOR FURTHER INFORMATION CONTACT:

Reny Tyson Moore, Office of Protected Resources, NMFS,

ITP.tyson.moore@noaa.gov,

(301) 427-8401.

SUPPLEMENTARY INFORMATION:

Purpose and Need for Regulatory Action

We received an application from the Navy requesting 5-year regulations and authorization to take multiple species of marine mammals. This rule establishes a framework under the authority of the MMPA (16 U.S.C. 1361

et seq.

) to allow for the authorization of take by Level A and Level B harassment of marine mammals incidental to the Navy's construction activities related to the multifunctional expansion and modification of Dry Dock 1 at the Portsmouth Naval Shipyard in Kittery, Maine. Please see the Background section below for definitions of harassment.

Legal Authority for the Action

Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1371(a)(5)(A)) directs the Secretary of Commerce 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 for up to 5 years if, after notice and public comment, the agency makes certain findings and issues regulations that set forth permissible methods of taking pursuant to that activity and other means of effecting the “least practicable adverse impact” on the affected species or stocks and their habitat (see the discussion below in the Mitigation section), as well as monitoring and reporting requirements. Section 101(a)(5)(A) of the MMPA and the implementing regulations at 50 CFR part 216, subpart I provide the legal basis for issuing this rule containing 5 year regulations, and for any subsequent Letters of Authorization (LOAs). As directed by this legal authority, this rule contains mitigation, monitoring, and reporting requirements.

Summary of Major Provisions Within the Regulations

Following is a summary of the major provisions of this rule regarding the Navy's construction activities. These measures include:

• Required monitoring of the in-water construction areas to detect the presence of marine mammals before beginning in-water construction activities;

• Shutdown of in-water construction activities under certain circumstances to avoid injury of marine mammals;

• Soft start for impact pile driving to allow marine mammals the opportunity to leave the area prior to beginning impact pile driving at full power; and

• Implementation of a bubble curtain during rock hammering and down-the-hole (DTH) cluster drilling to reduce underwater noise impacts.

Background

The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361

et seq.

) 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 proposed or, if the taking is limited to harassment, a notice of a proposed incidental take authorization is provided to the public for review.

Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) 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 the species or stocks for taking for certain subsistence uses (referred to in shorthand as “mitigation”); and requirements pertaining to the mitigation, monitoring and reporting of the takings are set forth. The definitions of all applicable MMPA statutory terms cited above are included in the relevant sections below.

Summary of Request

On May 9, 2022, NMFS received a request from the Navy for authorization to take marine mammals incidental to construction activities related to the multifunctional expansion and modification of Dry Dock 1 at Portsmouth Naval Shipyard in Kittery, Maine. We provided comments on the application, and the Navy submitted revised versions and responses to our comments on July 5, 2022, August 15, 2022, August 19, 2022, and August 25, 2022, with the latter version deemed adequate and complete. On September 1, 2022, we published a notice of receipt of the Navy's application in the

Federal Register

(87 FR 53731), requesting comments and information related to the request. During the 30-day comment period, we received two supportive letters from private citizens.

On October 19 and 25, 2022, NMFS was notified by the Navy of project modifications and shifting Fleet submarine schedules that required the resequencing of certain activities associated with the construction at Dry Dock 1 in order to accommodate the modifications and meet the new vessel docking demands. On October 31, 2022, the Navy submitted an addendum to its

application describing these changes. We published a notice of the proposed rulemaking in the

Federal Register

on January 18, 2023 (88 FR 3146) incorporating these changes and requested comments and information from the public. Please see Comments and Responses below. The regulations are valid for 5 years, from April 1, 2023 through March 31, 2028, and authorize the Navy to take five species of marine mammals by Level A and Level B harassment incidental to construction activities related to the multifunctional expansion and modification of Dry Dock 1 at the Portsmouth Naval Shipyard in Kittery, Maine. Neither the Navy nor NMFS expect serious injury or mortality to result from this activity.

NMFS previously issued five IHAs to the Navy for waterfront improvement work at the Portsmouth Naval Shipyard: in 2016 (81 FR 85525, November 28, 2016), 2018 (83 FR 3318, January 24, 2018), 2019 (84 FR 24476, May 28, 2019), a renewal of the 2019 IHA (86 FR 14598, March 17, 2021), and in 2022 (87 FR 19886, April 6, 2022). The most recent IHA (87 FR 19886) provided authorization to take marine mammals during the first year of the construction project described in this final rule. As required, the applicant provided monitoring reports (available at:

https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities

) which confirm that the applicant has implemented the required mitigation and monitoring, and which also shows that no impacts of a scale or nature not previously analyzed or authorized have occurred as a result of the activities conducted.

Description of the Specified Activity

Overview

Multifunctional Expansion of Dry Dock 1 (P-381) is one of three projects that support the overall expansion and modification of Dry Dock 1, located in the western extent of the Portsmouth Naval Shipyard. The two additional projects, construction of a super flood basin (P-310) and extension of portal crane rail and utilities (P-1074), are currently under construction. In-water work associated with these projects was completed under the aforementioned separate IHAs issued by NMFS. The projects have been phased to support Navy mission schedules. P-381 will be constructed within the same footprint of the super flood basin over an approximate 7-year period, during which 5 years of in-water work will occur. An IHA was issued by NMFS for the first year of P-381 construction activities between April 1, 2022 and March 31, 2023 (87 FR 19866, April 6, 2022). This request is associated with the remaining 4 years of P-381 in-water construction activities planned to occur from April 1, 2023 through March 31, 2028, as well as for additional in-water construction activities associated with the removal of emergency repair components of the super flood basin that will occur during the period of effectiveness for the regulations. Although the in-water construction described in this rule is anticipated to be completed by December 2026, unanticipated schedule delays could result in the Navy conducting construction activity over the full 5 years.

The purpose of the Navy's project (P-381) is to modify the super flood basin to create two additional dry docking positions (Dry Dock 1 North and Dry Dock 1 West) in front of the existing Dry Dock 1 East. The Navy's specified activity also includes emergency repairs of the P-310 super flood basin. Construction activities will include the excavation and/or installation of 1,118 holes, 198 shafts, and 580 sheet piles via impact and vibratory pile driving, hydraulic rock hammering, rotary drilling, and mono and cluster DTH. The construction activities are expected to require approximately 2,498 days if the activities are considered independently over the 5-year period. However, the actual construction duration is expected to be within 4 years as many of the construction activities will occur concurrently.

Dates and Duration

The in-water construction activities associated with this rule are anticipated to begin in April 2023 and proceed to December 2026 (4 years); however, the incidental take authorization is valid for 5 years in the event of unexpected scheduled delays. In-water construction activities will occur consecutively over a 4-year period. The Navy plans to conduct all in-water work activities with expected potential for incidental harassment of marine mammals during daylight hours.

Table 1 provides the estimated schedule and production rates for P-381 construction activities. Many of the activities included in Table 1 will span across multiple construction years and/or will occur concurrently. Because of mission requirements and operational schedules at the dry docking positions and berths, this schedule is subject to change. In-water construction activities for P-381 will occur consecutively over a 4-year period. Note, for the purposes of this analysis, the construction years are identified as years 2 through 5; Year 1 of the Navy's construction activities is currently ongoing in association with a previously issued IHA (87 FR 19886, April 6, 2022). Vibratory pile driving and extraction is assumed to occur for 141 days. Impact pile driving will occur for 34 days. DTH excavation (mono-hammer and cluster drill) will occur for 1,446 days. Rotary drilling will occur for 238 days (assuming that casings and sockets for cluster drills will be set, excavated, and removed in a single day). Rock hammering will occur for 277 days. Note that pile driving days are not necessarily consecutive, and certain activities may occur at the same time, decreasing the total number of actual in-water construction days. The contractor could be working in more than one area of the berths at a time.

Table 1—In-Water Construction Activities

Activity ID

Activity

Total amount and

estimated dates

(construction years *)

Activity component

Method

Daily production

rate

Total

production

days

A1

1

Center Wall—Install Foundation Support Piles

Drill 18 shafts Apr 23

3

to Aug 23 (2)

Install 102-inch diameter outer casing

Rotary drill

1 shaft/day 1 hour/day

4

18

A2

1

Pre-drill 102-inch diameter socket

Rotary drill

1 shaft/day 9 hours/day

4

18

A3

1

Remove 102-inch outer casing

Rotary drill

1 casing/day 15 minutes/casing

4

18

A4

1

Drill 78-inch diameter shaft

Cluster drill DTH

6.5 days/shaft 10 hours/day

4

117

R

1

Dry Dock 1 North Entrance—Install Temporary Cofferdam

Install 48 sheet piles Apr 23

3

to May 23 (2)

28-inch wide Z-shaped sheets

Impact with initial vibratory set

8 sheets/day 5 minutes and 300 blows/pile

4

6

1

Berth 11—Remove Shutter Panels

Remove 112 panels Apr 23

3

to May 23 (2)

Concrete shutter panels

Hydraulic rock hammering

5 hours/day

4

56

2

Berth 1—Remove Sheet Piles

Remove 168 sheet piles Apr 23

3

to Jun 24 (2, 3)

25-inch-wide Z-shaped

Vibratory extraction

4 piles/day

4

42

3

Berth 1—Remove Granite Block Quay Wall

2,800 cubic yards (cy) Apr 23

3

to Jun 24 (2, 3)

Removal of granite blocks

Hydraulic rock hammering

2.5 hours/day

4

47

4

Berth 1—Top of Wall Removal for Waler Installation

320 linear feet (lf) Apr 23

3

to Jun 24 (2, 3)

Mechanical concrete removal

Hydraulic rock hammering

10 hours/day

4

74

5

Berth 1—Install southeast corner Support of Excavation (SOE)

Install 28 sheet piles Apr 23 to Jul 23 (2)

28-inch-wide Z-shaped

Impact with initial vibratory set

4 piles/day 5 minutes/pile and 300 blows/pile

4

8

6

Berth 11—Mechanical Rock Removal at Basin Floor

700 cy Apr 23

3

to Aug 23 (2)

Excavate Bedrock

Hydraulic rock hammering

12 hours/day

3

4

60

7

Berth 11 Face—Mechanical Rock Removal at Basin Floor

Drill 924 relief holes Apr 23

3

to Aug 23 (2)

4-6 inch diameter holes

DTH mono-hammer

27 holes/day 22 min/hole

4

35

8

Install Temporary Cofferdam Extension

Install 14 sheet piles Apr 23 to Jun 23 (2)

28-inch-wide Z-shaped

Impact with initial vibratory set

4 piles/day 5 minutes/pile and 300 blows/pile

4

9a

Gantry Crane Support Piles at Berth 1 West

Drill 16 shafts Apr 23 to Aug 23 (2)

Set 102-inch diameter casing

Rotary drill

1 shaft/day 1 hours/day

16

9b

Pre-drill 102-inch rock socket

Rotary drill

1 shaft/day 9 hours/day

16

9c

Remove 102-inch casing

Rotary drill

1 casing/day 15 minutes/casing

16

9d

72-inch diameter shafts

Cluster drill DTH

5 days/shaft 10 hours/day

80

10

2

Berth 1—Mechanical Rock Removal at Basin Floor

300 cy Apr 23

3

to Sep 23 (2)

Excavate Bedrock

Hydraulic rock hammering

13 cy/day 12 hours/day

5

25

11

Dry Dock 1 North Entrance—Drill Tremie Tie Downs

Drill 50 rock anchors Apr 23

3

to Oct 23 (2)

9-inch diameter holes

DTH mono-hammer

2 holes/day 5 hours/hole

4

25

12

Center Wall—Install Tie-In to Existing West Closure Wall

Install 15 sheet piles Apr 23 to Dec 23 (2)

28-inch wide Z-shaped

Impact with initial vibratory set

4 piles/day 5 minutes/pile and 300 blows/pile

4

13a

Dry Dock 1 North—Temporary Work Trestle Piles

Drill 20 shafts May 23 to Nov 24 (2, 3)

Set 102-inch diameter casing

Rotary drill

1 shaft/day 1 hours/day

20

13b

Pre-drill 102-inch rock socket

Rotary drill

1 shaft/day 9 hours/day

20

13c

Remove 102-inch casing

Rotary drill

1 casing/day 15 minutes/casing

20

13d

84-inch diameter shafts

Cluster drill DTH

3.5 days/shaft 10 hours/day

70

14

Dry Dock 1 North—Remove Temporary Work Trestle Piles

Remove 20 piles May 23 to Nov 24 (2, 3)

84-inch diameter drill piles

Rotary drill

1 day/pile 15 minutes/pile

20

15a

Dry Dock 1 North—Install Leveling Piles (Diving Board Shafts)

Drill 18 shafts May 23 to Nov 24 (2, 3)

Set 84-inch casing

Rotary drill

1 shaft/day 1 hours/day

18

15b

Pre-drill 84-inch rock socket

Rotary drill

1 shaft/day 9 hours/day

18

15c

Remove 84-inch casing

Rotary drill

1 casing/day 15 minutes/casing

18

15d

78-inch diameter shaft

Cluster drill DTH

7.5 days/shaft 10 hours/day

135

16a

Wall Support Shafts for Dry Dock 1 North (Berth 11 Face and Head Wall)

Drill 20 shafts Jun 23 to Nov 24 (2, 3)

Set 102-inch diameter casing

Rotary drill

1 shaft/day 1 hours/day

20

16b

Pre-drill 102-inch rock socket

Rotary drill

1 shaft/day 9 hours/day

20

16c

Remove 102-inch casing

Rotary drill

1 casing/day 15 minutes/casing

20

16d

Drill 78-inch diameter shaft

Cluster drill DTH

7.5 days/shaft 10 hours/day

150

17a

Foundation (Floor) Shafts for Dry Dock 1 North (Foundation Support Piles)

Drill 23 shafts Jun 23 to Nov 24 (Const. years 2, 3)

Set 126-inch diameter Casing

Rotary drill

1 shaft/day 1 hours/day

23

17b

Pre-drill 126-inch rock socket

Rotary drill

1 shaft/day 9 hours/day

23

17c

Remove 126-inch casing

Rotary drill

1 casing/day 60 minutes/casing

23

17d

Drill 108-inch diameter shafts

Cluster drill DTH

8.5 days/shaft 10 hours/day

196

18

Berth 11 End Wall—Remove Temporary Guide Wall

Remove 60 sheet piles Jul 23 to Aug 23 (2, 3)

28-inch wide Z-shaped

Vibratory extraction

8 piles/day 5 minutes/pile

5

10

19

Remove Berth 1 southeast corner SOE

Remove 28 sheet piles Jul 23 to Sep 23 (2)

28-inch-wide Z-shaped

Vibratory extraction

8 piles/day 5 minutes/pile

4

5

20

2

Removal of Berth 1 Emergency Repair Sheet Piles

Remove 108 sheet piles Apr 23

3

to Jul 23 (2)

28-inch-wide Z-shaped

Vibratory extraction

6 piles/day 5 minutes/pile

18

21

2

Removal of Berth 1 Emergency Repair Tremie Concrete

500 cy Apr 23

3

to Aug 23 (2)

Mechanical concrete removal

Hydraulic rock hammering

4 hours/day

15

22

Center Wall Foundation—Drill in Monolith Tie Downs

Install 72 rock anchors Aug 23 to May 24 (2, 3)

9-inch diameter holes

DTH mono-hammer

2 holes/day 5 hours/hole

36

23

Center Wall—Remove Tie-In to Existing West Closure Wall (Dry Dock 1 North)

4

Remove 16 sheet piles

6

Aug 23 to Aug 24 (2, 3)

28-inch-wide Z-shaped

Vibratory extraction

8 piles/day 5 minutes/pile

5

3

24

Center Wall East—Sheet Pile Tie-In to Existing Wall

Install 23 sheet piles Aug 23 to Oct 24 (2, 3)

28-inch wide Z-shaped

Impact with initial vibratory set

2 piles/day 5 minutes/pile and 300 blows/pile

12

25

Remove Tie-In to West Closure Wall (Dry Dock 1 West)

Remove 15 sheet pile Dec 23 to Dec 24 (2, 3)

28-inch wide Z-shaped

Vibratory extraction

8 piles/day 5 minutes/pile

5

3

26

Remove Center Wall East—Sheet Pile Tie-In to Existing Wall (Dry Dock 1 West)

Remove 23 sheet piles Dec 23 to Dec 24 (2, 3)

28-inch wide Z-shaped

Vibratory extraction

8 piles/day 5 minutes/pile

5

12

27

Dry Dock 1 North Entrance—Remove Temporary Cofferdam

Remove 96 sheet piles Jan 24 to Sep 24 (Const. years 2, 3)

28-inch wide Z-shaped

Vibratory extraction

8 piles/day 5 minutes/pile

12

28

Remove Temporary Cofferdam Extension

Remove 14 sheet piles Jan 24 to Sep 24 (2, 3)

28-inch wide Z-shaped

Vibratory extraction

8 piles/day 5 minutes/pile

2

29a

Dry Dock 1 West—Install Temporary Work Trestle Piles

Drill 20 shafts Apr 24 to Feb 26 (3, 4)

Set 102-inch diameter casing

Rotary drill

1 shaft/day 1 hours/day

20

29b

Pre-drill 102-inch rock socket

Rotary drill

1 shaft/day 9 hours/day

20

29c

Remove 102-inch casing

Rotary drill

1 casing/day 15 minutes/casing

20

29d

84-inch diameter shafts

Cluster drill DTH

3.5 days/shaft 10 hours/day

70

30

Dry Dock 1 West—Remove Temporary Work Trestle Piles

Remove 20 piles Apr 24 to Feb 26 (3, 4)

84-inch diameter piles

Rotary drill

1 day/pile 15 minutes/pile

20

31a

Wall Support Shafts for Dry Dock 1 West (Berth 1 Face)

Drill 22 shafts Jun 24 to Feb 26 (3, 4)

Set 102-inch diameter casing

Rotary drill

1 shaft/day 1 hours/day

22

31b

Pre-drill 102-inch rock socket

Rotary drill

1 shaft/day 9 hours/day

22

31c

Remove 102-inch casing

Rotary drill

1 casing/day 15 minutes/casing

22

31d

78-inch diameter shaft

Cluster drill DTH

7.5 days/shaft 10 hours/day

165

32a

Foundation (Floor) Shafts for Dry Dock 1 West (Foundation Support Piles)

Drill 23 shafts Jun 24 to Feb 26 (3, 4)

Set 126-inch casing

Rotary drill

1 shaft/day 1 hours/day

23

32b

Pre-drill 126-inch rock socket

Rotary drill

1 shaft/day 9 hours/day

23

32c

Remove 126-inch casing

Rotary drill

1 casing/day 15 minutes/casing

23

32d

Drill 108-inch diameter shaft

Cluster drill DTH

8.5 days/shaft 10 hours/day

196

33a

Dry Dock 1 West—Install Leveling Piles (Diving Board Shafts)

Drill 18 shafts Jun 24 to Feb 26 (3, 4)

Set 84-inch casing

Rotary Drill

1 shaft/day 1 hours/day

18

33b

Pre-drill 84-inch rock socket

Rotary drill

1 shaft/day 9 hours/day

18

33c

Remove 84-inch casing

Rotary drill

1 casing/day 15 minutes/casing

18

33d

Drill 78-inch diameter shaft

Cluster drill DTH

7.5 days/shaft 10 hours/day

135

34

Dry Dock 1 North—Tie Downs

Install 36 rock anchors Jul 24 to Jul 25 (3, 4)

9-inch diameter holes

DTH mono-hammer

2 holes/day 5 hours/hole

18

35

Dry Dock 1 West—Install Tie Downs

Install 36 rock anchors Dec 25 to Dec 26 (4, 5)

9-inch diameter hole

DTH mono-hammer

2 holes/day 5 hours/hole

18

Total excavated holes/drilled shafts/sheet piles

1,118/198/580

2,498

*

Note:

for the purposes of this analysis, the construction years are identified as years 2 through 5; potential marine mammal takes incidental to Year 1 of the Navy's construction activities were authorized under a previously issued IHA (87 FR 19886, April 6, 2022).

1

These activities were not included in the original application made available for public review during the Notice of Receipt comment period (NOR; 87 FR 53731), but have been added due to changes needed in the construction schedule.

2

These activities were included in the original application, but the amount of activity has been modified due to changes needed in the construction schedule.

3

These activities began in construction year 1.

4

These activities began in year 1. Only the number of production days occurring in construction years 2 through 6 are presented.

5

Additional production days are included to account for equipment repositioning.

6

Sheet piles were installed in construction year 1.

Specific Geographic Region

The shipyard is located in the Piscataqua River in Kittery, Maine. The Piscataqua River originates at the boundary of Dover, New Hampshire, and Eliot, Maine (Figure 1). The river flows in a southeasterly direction for 2,093 meters (m) (13 miles (mi)) before entering Portsmouth Harbor and emptying into the Atlantic Ocean. The lower Piscataqua River is part of the Great Bay Estuary system and varies in width and depth. Many large and small islands break up the straight-line flow of the river as it continues toward the Atlantic Ocean. Seavey Island, the location of the specified activities, is located in the lower Piscataqua River approximately 500 m, 1,640 feet (ft) from its southwest bank, 200 m (656 ft) from its north bank, and approximately 4 kilometers (km) (2.5 mi) from the mouth of the river.

Water depths in the project area range from 6.4 m (21 ft) to 11.9 m (39 ft) at Berths 11, 12, and 13. Water depths in the lower Piscataqua River near the project area range from 4.6 m (15 ft) in the shallowest areas to 21 m (69 ft) in the deepest areas. The river is approximately 914 m (3,300 ft) wide near the project area, measured from the Kittery shoreline north of Wattlebury Island to the Portsmouth shoreline west of Peirce Island. The furthest direct line of sight from the project area is 1,287 m (0.8 mi) to the southeast and 418 m (0.26 mi) to the northwest.

The nearshore environment of the Shipyard is characterized by a mix of hard bottom, gravel, soft sediments, rock outcrops, and rocky shoreline associated with fast tidal currents near the installation. The nearshore areas surrounding Seavey Island are predominately hard bottom (65 percent of benthic habitat) and gravel (26 percent) habitat, with only 9 percent soft bottom sediments within the surveyed area around Seavey Island (Tetra Tech, 2016). Much of the shoreline in the project area is composed of hard shores (rocky intertidal). In general, rocky intertidal areas consist of bedrock that alternates between marine and terrestrial habitats, depending on the tide. Rocky intertidal areas consist of “bedrock, stones, or boulders that singly or in combination cover 75 percent or more of an area that is covered less than 30 percent by vegetation” (Federal Geographic Data Committee, 2013).

The lower Piscataqua River is home to Portsmouth Harbor and is used by commercial, recreational, and military vessels. Between 150 and 250 commercial shipping vessels transit the lower Piscataqua River each year (Magnusson

et al.,

2012). Commercial fishing vessels are also very common in the river year-round, as are recreational vessels, which are more common in the warmer summer months. The shipyard is a dynamic industrial facility situated on an island with a narrow separation of waterways between the installation and the communities of Kittery and Portsmouth (Figure 2). The predominant noise sources from Shipyard industrial operations consist of dry dock cranes; passing vessels; and industrial equipment (

e.g.,

forklifts, loaders, rigs, vacuums, fans, dust collectors, blower belts, heating, air conditioning, and ventilation (HVAC) units, water pumps, and exhaust tubes and lids). Other components such as construction, vessel ground support equipment for maintenance purposes, vessel traffic across the Piscataqua River, and vehicle traffic on the shipyard's bridges and on local roads in Kittery and Portsmouth produce noise, but such noise generally represents a transitory contribution to the average noise level environment (Blue Ridge Research and Consulting (BRRC), 2015; ESS Group, 2015). Ambient sound levels recorded at the shipyard are considered typical of a large outdoor industrial facility and vary widely in space and time (ESS Group, 2015).

BILLING CODE 3510-22-P

ER31MR23.000

ER31MR23.001

BILLING CODE 3510-22-C

Detailed Description of the Specified Activity

The Navy's P-381 project will modify the super flood basin to create two additional dry docking positions (Dry Dock 1 North and Dry Dock 1 West) in front of the existing Dry Dock 1 East. The super flood basin provides the starting point for the P-381 work. Several steps are required to convert the super flood basin to a dry dock with two positions fully capable of supporting the maintenance of submarines while maintaining access to the existing interior dry dock (Dry Dock 1 East). The dry dock positions (including the center wall) will be constructed using large precast segments (referred to as monoliths) that require both sidewall and base support. The monoliths will be manufactured offsite and transported to the construction site. Segments will be floated and/or lifted into place to create the center wall, followed by Dry Dock 1 North, and finally Dry Dock 1 West. Once the monoliths are set and grouted in place, the respective dry docks can be dewatered allowing the remaining interior construction to be performed in dry conditions.

P-381 years 2 through 5 (

i.e.,

the time period of the Navy's specified activity for this rule) construction activities will complete bedrock removal and the preparation of the walls and floors of the super flood basin to support the placement of the monoliths and the construction of the two dry dock positions. Most of the in-water construction will occur behind the existing super flood basin walls that will act as a barrier to sound and will contain underwater noise to within a small portion of the Piscataqua River. However, the west closure wall will be removed in order to install the Dry Dock 1 North entrance structure and caisson. In addition, the caissons may not always be in place throughout in-water construction. As such, the analyses presented herein conservatively assume the west closure wall, as well as the future caissons, will not be present throughout in-water construction activities.

The Navy's request also considers emergency repairs of the P-310 super flood basin. During P-310 super flood testing in January 2022, excessive exfiltration (

i.e.,

transport of material outside of the basin) was observed along Berths 1 and 2 and between the west closure wall and super flood basin entrance structure. Emergency structural repairs were required to reduce excessive transport of material through the berths and west closure wall/entrance structure and prevent further damage. As a result, 216 28-inch Z-shaped sheet piles were installed along the Berth 1 face. After installation, these sheet piles were cut off approximately 3 m (10 ft) above the mudline and concrete was tremie placed behind them to plug any gaps in the existing structure that contributed to the exfiltration. The removal of these 216 Berth 1 emergency repair piles and excess tremie concrete (approximately 382 cubic meters, 500 cubic yards (cy)) will be completed during this LOA period and are accounted for in the Navy's request. Similarly, 10 28-inch wide, Z-shaped sheet piles were installed between the super flood basin entrance structure and the west closure wall, cut off approximately 3 m (10 ft) above the mudline, and had concrete tremie placed behind them. These 10 sheet piles will be removed during the P-381 year 1 IHA period (covered under the IHA issued by NMFS for the first year of P-381 construction activities; 87 FR 19866, April 6, 2022).

Several additional preparatory activities (

e.g.,

torch cutting, dredging,

etc.

) will not create noise expected to result in harassment of marine mammals. Noise created during dredging of sediment and demolition debris (

e.g.,

bedrock, granite blocks, concrete) is unlikely to exceed that generated by other normal shipyard activities and is not expected to result in incidental take of marine mammals. Activities such as grouting (

i.e.,

pouring of concrete) and torch cutting are not noisy by design and will not result in incidental take of marine mammals. These activities are not addressed in the analyses of noise producing actions in the Navy's request, and are not considered by NMFS in our analysis, but are included in the work descriptions to clarify the construction progression.

P-381 In-Water Construction Activities

The work remaining for P-381 can be generally grouped into five categories for ease of explanation: temporary structures, mechanical bedrock removal, continued demolition of super flood basin wall components, center wall tie-downs, and dry dock foundation and gantry crane support. Each category involves one or more activities expected to generate noise that could result in injury or harassment of marine mammals. Some of these activities are a continuation of work started in year 1, which were covered under a separate IHA issued by NMFS on April 6, 2022 (87 FR 19886).

Temporary Structures

—Several temporary structures will be installed and removed to facilitate the construction of the dry docks. The conversion of the existing west closure wall to the Dry Dock 1 North entrance requires reinforcement of the section of the west closure wall that will become the new dry dock entrance. The existing west closure wall structure will be surrounded by a temporary cofferdam. The cofferdam will be constructed with 48 28-inch wide, Z-shaped sheet piles. The sheet piles will be installed using an initial vibratory set followed by driving with impact hammers to refusal.

The temporary guide wall along the Berth 11 end wall installed during year 1 (60 28-inch wide, Z-shaped sheet piles) will be removed with a vibratory hammer. An extension to the temporary cofferdam around the Dry Dock 1 entrance structure installed during P-381 year 1 will also be constructed. The extension will consist of 14 28-inch wide, Z-shaped sheet piles. The extension and the cofferdam (96 28-inch wide, Z-shaped sheet piles) will be removed in 2024 using a vibratory hammer.

A temporary work trestle will be constructed to support the excavation of large shafts within the individual dry docking positions. The trestle will be installed in Dry Dock 1 North first and then relocated to Dry Dock 1 West. The trestle system will be supported by 4 84-inch steel pipe piles and will be relocated five times within each dry dock. As a result, the piles will be installed and removed 20 times in Dry Dock 1 North and 20 times in Dry Dock 1 West. The piles will be installed with a cluster drill consisting of multiple DTH hammers and removed with a rotary drill. Before the cluster drill will be deployed, a 102-inch casing will be set into bedrock and a 5-ft (1.5-m) deep rock socket will be excavated with a rotary drill (see Figure 1-4 in the Navy's application). The socket will be filled with concrete and a second, 84-inch casing will be installed inside the larger casing and set in the concrete. No drilling will be required to install the second casing. The outer casing will then be removed with a rotary drill. The 84-inch diameter cluster drill will operate independently inside the second casing to excavate the shaft. Once the shaft is drilled the inner casing will be removed by torch cutting.

A temporary tie-in consisting of 15 28-inch wide, Z-shaped sheet piles will be installed between the center wall foundation and the west closure wall at Dry Dock 1 West. Twenty-three 28-inch wide, Z-shaped sheet piles will also be installed on the easterly end of Dry Dock 1 West to provide a similar temporary tie-in to the center wall foundation near the entrance to Dry

Dock 1 East. The sheet piles will be installed using an initial vibratory set followed by driving with impact hammers. These tie-ins will be removed using a vibratory hammer along with the Dry Dock 1 North tie-in to the west closure wall (16 28-inch wide, Z-shaped sheet piles) that was installed under the P-381 year 1 IHA (87 FR 19886).

To support excavation activities along Berth 1, 28 28-inch wide, Z-shaped sheet piles will be installed at the southeast corner of the berth using a combination of vibratory and impact hammers. These piles will be removed using a vibratory hammer.

Mechanical Bedrock Removal

—Mechanical removal of bedrock will be completed by the end of 2023 using various methods appropriate for the removal location and as needed to avoid damage to adjacent structures. Bedrock removal will occur along the Berth 11 face and abutment and along Berth 1.

Bedrock will be removed by breaking it up with a hydraulic hammer (

i.e.,

hoe ram or breaker). To protect adjacent structures during mechanical bedrock removal, 924 4-6-inch diameter relief holes will be drilled using a DTH mono-hammer. A total of approximately 918 cubic meters (1,200 cy) of bedrock are anticipated to be removed.

Demolition of Super Flood Basin Wall Components

—Demolition of existing wall components will include the removal of shutter panels, granite quay walls, sheet piles, and concrete making up the super flood basin. Demolition of existing wall structures will be conducted using a rock hammer. Specifically, the remaining sections of the existing concrete shutter panels making up the face of Berth 11 (112 panels), portions of the granite block quay wall (2,141 cm, 2,800 cy) at Berth 1, and the remaining existing sheet pile wall at Berth 1 (168 25-inch wide, Z-shaped sheet piles) will be removed.

The installation of a structural support waler (steel beam) at Berth 1 will also be completed. To complete the installation of the waler, about 98 m (320 linear ft) of concrete wall will be demolished using a hydraulic rock hammer.

Center Wall Tie-downs

—Additional work in the center wall area will involve the installation of support tie downs for future tremie concrete work. The tie downs require the placement of a total of 194 rock anchors requiring 9-inch diameter holes. The rock anchors will be installed using a DTH mono-hammer.

Dry Dock and Gantry Crane Support

—The location of the future center wall requires reinforcement to allow placement of the large pre-cast monolith structures forming the separation between the two new dry docking positions. Specifically, the floor of the existing basin must be able to provide an adequate foundation for the pre-cast monoliths that will make up the dry dock interiors and center wall. The basin floor will be reinforced by excavating 18 78-inch diameter shafts throughout the footprint of the center wall that will be filled with concrete to create the structural support piles for the center wall. The shafts will be excavated using a cluster drill consisting of multiple DTH mono-hammers. Before the cluster drill is deployed, a 102-inch diameter casing will be set into bedrock and a 1.5 m (5 ft) deep rock socket will be excavated using a 102-inch diameter rotary drill (see Figure 1-4 of the Navy's application). The rock socket will be filled with concrete and a second, 78-inch diameter casing will be installed inside the 102-inch casing and set in the concrete. No drilling is required to install the second casing. The 102-inch diameter outer casing will then be removed with a rotary drill.

The future Dry Dock 1 North and Dry Dock 1 West require significant structural reinforcement to provide an adequate foundation for the installation of the large pre-cast monolith structures forming the dry dock interior. Reinforcement of the individual dry dock foundations and walls will begin first at Dry Dock 1 North and, once completed, continue at Dry Dock 1 West. Twenty 78-inch diameter shafts will be excavated along the Berth 11 face and head wall to support the walls of Dry Dock 1 North. Along the floor of Dry Dock 1 North, 23 108-inch diameter shafts will be excavated for the installation of the foundation support piles and 18 78-inch diameter shafts will be excavated for the installation of leveling piles (

i.e.,

diving board shafts).

The dry dock foundation and wall support pile and leveling pile shafts will be filled with concrete to create the support piles for the dry dock walls and floors. The shafts will be excavated using a cluster drill consisting of multiple DTH hammers in the same manner as previously described for the temporary work trestle piles. Once the wall and foundation support piles and leveling piles for Dry Dock 1 North have been installed, foundation and wall support piles and leveling piles will be installed for Dry Dock 1 West. Twenty-two 78-inch diameter shafts will be excavated along the Berth 1 face to support the walls of Dry Dock 1 West. Twenty-three 108-inch diameter shafts will be excavated along the floor of Dry Dock 1 West for the installation of foundation support piles and 18 78-inch shafts will be excavated for the installation of leveling piles (

i.e.,

diving board shafts). The casing sizes and rotary drill sizes for each shaft are specified in Table 1.

The large concrete monolithic sections used to create the dry docks and the center wall separation will be placed using a gantry crane. The gantry crane system will be structurally supported by the installation of 16 72-inch diameter shafts installed along the western extent of the Berth 1 face. The shafts will be installed using a DTH cluster drill as described for the temporary work trestle piles. The casing sizes and rotary drill sizes for the gantry crane support shafts are specified in Table 1.

P-310 Emergency Repairs

Testing of the super flood basin on January 5, 2022 resulted in excess exfiltration through Berths 1 and 2, prompting the need for emergency repairs along Berth 1 as well as between the super flood basin entrance structure and the west closure wall. Emergency repairs consisted of the installation of sheet piles and the tremie pouring of concrete to fill in gaps along the structure walls and floor. Installation of emergency repairs at Berth 1 and the installation and removal of emergency repairs at the west closure wall and entrance structure occurred before the period described in the Navy's LOA application. Only the removal of Berth 1 emergency repair components will occur during the requested LOA period.

The removal of the 216 28-inch wide, Z-shaped sheet piles along the Berth 1 face will be completed through direct pulling via barge-mounted crane or by vibratory hammer. Specific methods will be determined by the contractor based on resistance to extraction from the seabed. Direct pulling via crane is not anticipated to generate harmful levels of underwater sound. If required, the use of the vibratory hammer to extract the installed sheet piles will be limited to an initial effort to break the sheets loose, allowing them to be directly pulled out. As a conservative measure, vibratory extraction of these sheet piles is assumed for all analyses.

The removal of 765 cubic meters (1,000 cy) of tremie concrete is anticipated to require use of a hydraulic rock hammer to break up material into smaller pieces. Smaller pieces will then be retrieved via excavator bucket for offsite disposal. The Navy estimates daily active use of the rock hammer for the removal of concrete from emergency repairs to be 4 hours per day.

Means and Methods for Noise Producing Activities

Only 28-inch wide, Z-shaped sheet piles will be installed or removed with pile-driving equipment during P-381 construction. The installation of 28-inch wide, Z-shaped steel sheet piles will be installed initially using vibratory means and then finished with impact hammers, if necessary. Impact hammers will also be used to push obstructions out of the way and where sediment conditions do not permit the efficient use of vibratory hammers. Pile removal activities will use cranes and vibratory hammers exclusively.

The removal of bedrock and concrete and the demolition of concrete shutter panels at Berth 11 and granite blocks and sheet piles at Berth 1 during P-381 construction will be by mechanical means. These features will be demolished using a hydraulic rock hammer (

i.e.,

hoe ram). The type/size of rock hammers used will be determined by the contractor selected to perform the work.

Two methods of rock excavation will be used during P-381 construction; DTH excavation and rotary drilling. During P-381 construction, rotary drilling will be used to set the casings and pre-drill rock sockets for DTH cluster drills. DTH excavation using mono-hammers will be used to create shafts for rock anchors and tie downs and for the excavation of relief holes during mechanical bedrock removal. For the largest shafts (greater than 42-inches in diameter), DTH excavation will use a cluster drill. A cluster drill uses multiple mono-hammers within a single bit to efficiently break up bedrock and create large diameter holes (see Figure 1-5 in the Navy's application).

Concurrent Activities

In order to maintain project schedules, it is likely that multiple pieces of equipment will operate at the same time within the basin. No ancillary activities are anticipated during the construction period that will require unimpeded access to the super flood basin. Therefore, it is anticipated that there will be space available within the project area for additional construction equipment. A maximum of 13 pieces of equipment could potentially operate in the project area at a single time. While this is an unlikely scenario, it could occur for a very brief period. Construction equipment will be staged along the perimeter of the super flood basin (Berth 11, Berth 1 and head wall) as well on multiple barges within the super flood basin. Table 2 provides a summary of possible equipment combinations that could be used simultaneously over the course of the construction period.

Table 2—Summary of Multiple Equipment Scenarios

Year

Quantity

Equipment

2023

5

Rock Hammer (2), Vibratory Hammer (2), Impact Hammer (1).

5

Rock Hammer (2), Vibratory Hammer (1), Impact Hammer (1), DTH Mono-hammer (1).

5

Rock Hammer (1), Vibratory Hammer (1), Impact Hammer (1), DTH Mono-hammer (1), Rotary Drill (1).

5

Rock Hammer (1), Vibratory Hammer (1), DTH Mono-hammer (1), Cluster Drill (2).

5

Cluster Drill (2), Vibratory Hammer (1), Mono-hammer DTH (1), Rotary Drill (1).

5

Rock Hammer (1), Impact Hammer (1), DTH Mono-hammer (1), Cluster Drill (2).

6

Rock Hammer (2), DTH Mono-hammer (2), Cluster Drill (1), Rotary Drill (1).

6

Rock Hammer (2), Vibratory Hammer (1), DTH Mono-hammer (1), Rotary Drill (2).

8

Rock Hammer (2), Vibratory Hammer (2), DTH Mono-hammer (2), Cluster Drill (2).

10

Rock Hammer (3), Vibratory Hammer (2), Impact hammer (1), DTH Mono-hammer (2), Cluster Drill (2).

13

Rock Hammer (5), Cluster Drill (2), Vibratory Hammer (2), Impact Hammer (1), Mono-hammer DTH (3).

2024

8

Rock Hammer (2), Vibratory Hammer (2), DTH Mono-hammer (2), Cluster Drill (2).

5

Cluster Drill (2), DTH mono-hammer (1), Vibratory hammer (1), Impact Hammer (1).

3

Cluster Drill (2), DTH mono-hammer (1).

3

Cluster Drill (1), Rotary Drill (1), DTH mono-hammer (1).

3

Rotary Drill (2), DTH mono-hammer (1).

2025

3

Cluster Drill (2), DTH mono-hammer (1).

3

Cluster Drill (1), Rotary Drill (1), DTH mono-hammer (1).

3

Rotary Drill (2), DTH mono-hammer (1).

2

Rotary Drill (2).

2

Cluster Drill (2).

Source: 381 Constructors, 2022.

Mitigation, monitoring, and reporting measures are described in detail later in this document (please see Mitigation and Monitoring and Reporting).

Comments and Responses

A notice of NMFS' proposed rulemaking to the Navy was published in the

Federal Register

on January 18, 2023 (88 FR 3146). That proposed rule described, in detail, the Navy's activities, the marine mammal species that may be affected by the activities, and the anticipated effects on marine mammals. In that proposed rule, we requested public input on the request for authorization described therein, our analyses, the proposed authorization, and any other aspect of the notice of proposed rulemaking, and requested that interested persons submit relevant information, suggestions, and comments. This proposed rule was available for a 30-day public comment period.

During the 30-day public comment period, NMFS received no comments.

Changes From the Proposed IHA to Final IHA

No public comments were received during the comment period; however, NMFS made a few minor clarifications and corrections in this final rule. In the sections of the documents that refer to the use of a bubble curtain, it was established that the bubble curtain will be used in cases where the Level A harassment zone extends to the full region of influence (ROI). To clarify this further, NMFS adds that this refers to all rock hammering and DTH cluster drilling. In addition, for bubble curtains, NMFS clarified that the air flow to the bubblers will be balanced across the entrance openings to the super flood basin, rather than the piles. Finally, NMFS removed the mitigation condition requiring that protected species observers (PSOs) work in shifts lasting no longer than 4 hours (hrs) with at least

a 1-hr break between shifts and limiting PSO duties to no more than 12 hrs in a 24-hr period. This is not a required condition for the Navy for these construction activities, rather it is related to other activity types, such as offshore seismic surveys, but was accidentally included. That said, NMFS communicated to the Navy that observers should be given adequate breaks and work in shifts to reduce observer fatigue to ensure their ability to best monitor for marine mammals.

Description of Marine Mammals in the Area of Specified Activities

Sections 3 and 4 of the application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species. NMFS fully considered all of this information, and we refer the reader to these descriptions, referenced here, instead of reprinting the information. Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs;

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

) and more general information about these species (

e.g.,

physical and behavioral descriptions) may be found on NMFS' website (

https://www.fisheries.noaa.gov/find-species

).

Table 3 lists all species or stocks for which take is expected and 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' U.S. Atlantic and Gulf of Mexico SARs. All values presented in Table 3 are the most recent available at the time of publication (including from the 2022 draft SARs) and are available online at:

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

).

Table 3—Species Likely Impacted by the Specified Activities

Common name

Scientific name

MMPA stock

ESA/MMPA status; strategic

(Y/N)

1

Stock abundance Nbest,

(CV, N

min

, most recent abundance survey)

2

PBR

Annual M/SI

3

Order Cetartiodactyla—Superfamily Odontoceti (toothed whales, dolphins, and porpoises)

Family Phocoenidae (porpoises):

Harbor Porpoise

Phocoena

Gulf of Maine/Bay of Fundy

-; N

95,543 (0.31; 74,034; 2016)

851

164

Order Carnivora—Superfamily Pinnipedia

Family Phocidae (earless seals):

Harbor seal

Phoca vitulina

Western North Atlantic

-; N

61,336 (0.08, 57,637; 2018)

1,729

339

Gray seal

Halichoerus grypus

Western North Atlantic

-; N

27,300

4

(0.22; 22,785; 2016)

1,389

4,453

Harp seal

Pagophilus groenlandicus

Western North Atlantic

-; N

7,600,000 (unk,7,100.000, 2019)

426,000

178,573

Hooded seal

Cystophora cristata

Western North Atlantic

-; N

593,500

Unknown

1,680

1

Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.

2

NMFS marine mammal stock assessment reports online at:

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

CV is coefficient of variation; N

min

is the minimum estimate of stock abundance. In some cases, CV is not applicable (N.A.).

3

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

e.g.,

commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial fisheries is presented in some cases.

4

This abundance value and the associated PBR value reflect the US population only. Estimated abundance for the entire Western North Atlantic stock, including animals in Canada, is 451,600. The annual M/SI estimate is for the entire stock.

As indicated above, all five species (with five managed stocks) in Table 3 temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur.

A detailed description of the species likely to be affected by the Navy's construction activities, including brief introductions to the species and relevant stocks as well as available information regarding population trends and threats, and information regarding local occurrence, were provided in the

Federal Register

notice for the proposed rule (88 FR 3146, January 18, 2023). Since that time, we are not aware of any changes in the status of these species and stocks; therefore, detailed descriptions are not provided here. Please refer to that

Federal Register

notice for these descriptions. Please also refer to the NMFS website (

https://www.fisheries.noaa.gov/find-species

) for generalized species accounts.

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 (2018a) 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 4.

Table 4—Marine Mammal Hearing Groups

[NMFS, 2018a]

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 (2018a) for a review of available information.

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

The effects of underwater noise from the Navy's construction activities have the potential to result in behavioral harassment of marine mammals in the vicinity of the project area. The notice of the proposed rulemaking (88 FR 3146, January 18, 2023) included a discussion of the effects of anthropogenic noise on marine mammals and the potential effects of underwater noise from the Navy's construction activities on marine mammals and their habitat. That information and analysis is referenced in this final rule and is not repeated here; please refer to the notice of the proposed rulemaking (88 FR 3146, January 18, 2023).

Estimated Take

This section provides an estimate of the number of incidental takes authorized under the rule, which will inform both NMFS' consideration of “small numbers” and NMFS' negligible impact determinations.

As described previously, no serious injury or mortality is anticipated or authorized for this activity. Harassment is the only type of take expected to result from these activities. Except with respect to certain activities not pertinent here, section 3(18) of the MMPA defines “harassment” as any act of pursuit, torment, or annoyance, which (i) has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment).

Authorized takes will primarily be by Level B harassment, as use of the acoustic sources (

i.e.,

impact and vibratory pile installation and removal, rotary drilling, DTH, and rock hammering) has the potential to result in disruption of behavioral patterns for individual marine mammals. There is also some potential for auditory injury (Level A harassment) to result, primarily for high frequency species and/or phocids because predicted auditory injury zones are larger than for mid-frequency species and/or otariids. The requirements pertaining to mitigation and monitoring are expected to minimize the severity of the taking to the extent practicable. Below we describe how the authorized take numbers are estimated.

For acoustic impacts, generally speaking, we estimate take by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals will be behaviorally harassed or incur some degree of permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day; (3) the density or occurrence of marine mammals within these ensonified areas; and, (4) the number of days of activities. We note that while these factors can contribute to a basic calculation to provide an initial prediction of potential takes, additional information that can qualitatively inform take estimates is also sometimes available (

e.g.,

previous monitoring results or average group size). Below, we describe the factors considered here in more detail and present the estimated take numbers.

Acoustic Thresholds

NMFS recommends the use of acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur PTS of some degree (equated to Level A harassment).

Level B Harassment

—Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source or exposure context (

e.g.,

frequency, predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the source), the environment (

e.g.,

bathymetry, other noises in the area, predators in the area), and the receiving animals (hearing, motivation, experience, demography, life stage, depth) and can be difficult to predict

(

e.g.,

Southall

et al.,

2007, 2021; Ellison

et al.,

2012). Based on what the available science indicates and the practical need to use a threshold based on a metric that is both predictable and measurable for most activities, NMFS typically uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS generally predicts that marine mammals are likely to be behaviorally harassed in a manner considered to be Level B harassment when exposed to underwater anthropogenic noise above root-mean-squared pressure received levels (RMS SPL) of 120 dB (referenced to 1 micropascal (re 1 μPa)) for continuous (

e.g.,

vibratory pile-driving, drilling) and above RMS SPL 160 dB re 1 μPa for non-explosive impulsive (

e.g.,

seismic airguns) or intermittent (

e.g.,

scientific sonar) sources. Generally speaking, Level B harassment take estimates based on these behavioral harassment thresholds are expected to include any likely takes by TTS as, in most cases, the likelihood of TTS occurs at distances from the source less than those at which behavioral harassment is likely. TTS of a sufficient degree can manifest as behavioral harassment, as reduced hearing sensitivity and the potential reduced opportunities to detect important signals (conspecific communication, predators, prey) may result in changes in behavior patterns that would not otherwise occur.

The Navy's activities include the use of continuous (vibratory pile driving/removal, rotary drilling) and intermittent (impact pile driving, rock hammering) sources, and therefore the RMS SPL thresholds of 120 and 160 dB re 1 μPa, respectively, are applicable. DTH systems have both continuous and intermittent components as discussed in the

Description of Sound Sources

section in the proposed rule (88 FR 3146, January 18, 2023). When evaluating Level B harassment, NMFS recommends treating DTH as a continuous source and applying the RMS SPL thresholds of 120 dB re 1 μPa (see NMFS recommended guidance on DTH systems at

https://media.fisheries.noaa.gov/2022-11/PUBLIC%20DTH%20Basic%20Guidance_November%202022.pdf;

NMFS, 2022).

Level A harassment

—NMFS' Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0) (NMFS, 2018a) 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 Navy's activities include the use of impulsive (impact pile driving, rock hammering, DTH) and non-impulsive (vibratory pile driving/removal, rotary drilling, DTH) sources.

These thresholds are provided in the table below. The references, analysis, and methodology used in the development of the thresholds are described in NMFS' 2018 Technical Guidance, which may be accessed at:

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

Table 5—Thresholds Identifying the Onset of Permanent Threshold Shift

Hearing group

PTS onset acoustic thresholds *

(received level)

Impulsive

Non-impulsive

Low-Frequency (LF) Cetaceans

Cell 1: L

pk,flat

:

219 dB;

L

E,LF,24h

:

183 dB

Cell 2: L

E,LF,24h

:

199 dB.

Mid-Frequency (MF) Cetaceans

Cell 3: L

pk,flat

:

230 dB;

L

E,MF,24h

:

185 dB

Cell 4: L

E,MF,24h

:

198 dB.

High-Frequency (HF) Cetaceans

Cell 5: L

pk,flat

:

202 dB;

L

E,HF,24h

:

155 dB

Cell 6: L

E,HF,24h

:

173 dB.

Phocid Pinnipeds (PW) (Underwater)

Cell 7: L

pk,flat

:

218 dB;

L

E,PW,24h

:

185 dB

Cell 8: L

E,PW,24h

:

201 dB.

Otariid Pinnipeds (OW) (Underwater)

Cell 9: L

pk,flat

:

232 dB;

L

E,OW,24h

:

203 dB

Cell 10: L

E,OW,24h

:

219 dB.

* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should also be considered.

Note:

Peak sound pressure (

L

pk

) has a reference value of 1 μPa, and cumulative sound exposure level (

L

E

) has a reference value of 1μPa

2

s. In this Table, thresholds are abbreviated to reflect American National Standards Institute standards (ANSI, 2013). However, peak sound pressure is defined by ANSI as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript “flat” is being included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could be exceeded in a multitude of ways (

i.e.,

varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be exceeded.

Ensonified Area

Here, we describe operational and environmental parameters of the activity that are used in estimating the area ensonified above the acoustic thresholds, including source levels and transmission loss coefficient.

The sound field in the project area is the existing background noise plus additional construction noise from the project. Marine mammals are expected to be affected via sound generated by the primary components of the project (

i.e.,

impact pile driving, vibratory pile driving, vibratory pile removal, rotary drilling, rock hammering, and DTH).

Sound Source Levels

—The intensity of pile driving sounds is greatly influenced by factors such as the type of piles, hammers, and the physical environment (

e.g.,

sediment type) in which the activity takes place. The Navy evaluated sound source level (SL) measurements available for certain pile types and sizes from similar environments from other Navy pile driving projects, including from past projects conducted at the Shipyard, and used them as proxy SLs to determine reasonable SLs likely to result from the pile driving and drilling activities in their application. Projects reviewed were those most similar to the specified activity in terms of drilling and rock hammering activities, type and size of piles installed, method of pile installation, and substrate conditions. Some of the proxy source levels used are expected to be more conservative as compared to what may be realized by the actual pile driving to take place, as the values are from larger pile sizes. In some instances, for reasons described below, NMFS relied on alternative proxy SLs in our evaluation of the impacts of the Navy's activities on marine mammals (Table 6). Note that the source levels in Table 6 represent the SPL referenced at a distance of 10 m from the source.

Table 6—Summary of Unattenuated In-Water Pile Driving Source Levels

Pile type

Installation method

Pile diameter

Peak SPL

(dB re 1 μPa)

RMS SPL

(dB re 1 μPa)

SEL

ss

(dB re 1 μPa

2

sec)

Casing/Socket

Rotary Drill

126-inch

NA

154 (169 at 1 m)

NA

102-inch

NA

154 (169 at 1 m)

NA

84-inch

NA

154 (169 at 1 m)

NA

Shaft

DTH Cluster Drill

108-inch

NA

201.6

5

(Level A)

174

6

(Level B)

NA

84-inch

NA

196.7

5

(Level A)

174

6

(Level B)

NA

78-inch

NA

195.2

5

(Level A)

174

6

(Level B)

181

72-inch

NA

193.7

5

(Level A)

174

6

(Level B)

NA

Rock anchor

DTH mono-hammer

9-inch

172

167

146

Relief hole

DTH mono-hammer

4 to 6-inch

170

6

156

144

Z-shaped Sheet

Impact

1

28-inch

211

196

181

Vibratory

28-inch

2

NA

167

167

Vibratory

25-inch

3

NA

167

167

Bedrock and concrete demolition

Rock Hammer

4

NA

197

186

4

4

171

1

An appropriate proxy value for impact driving 28-inch wide, Z-shaped sheet piles is not available, so a value for 30-inch steel pipe piles was used as a proxy value (NAVFAC SW, 2020 [p. A-4]).

2

An appropriate proxy value for vibratory pile driving 28-inch wide, Z-shaped sheet piles is not available, so a value for 30-inch steel pipe piles was used as a proxy value (Navy, 2015 [p. 14]).

3

An appropriate proxy value for vibratory pile driving 25-inch sheet piles is not available, so the value for 28-inch wide, Z-shaped sheet piles was used as a proxy.

4

Escude, 2012.

5

RMS SPL values were derived from regression and extrapolation calculations of existing data by NMFS.

6

SPLs vary from those proposed in the Navy's application as the NMFS DTH recommended guidance updated the source level proxy it recommends for some DTH systems after the Navy's application was deemed adequate and complete (NMFS, 2022).

Notes:

All SPLs are unattenuated and represent the SPL referenced at a distance of 10 m from the source; NA = Not applicable; single strike SEL are the proxy source levels for impact pile driving used to calculate distances to PTS; dB re 1 μPa = decibels (dB) referenced to a pressure of 1 microPascal, measures underwater SPL.; dB re 1 μPa

2

-sec = dB referenced to a pressure of 1 microPascal squared per second, measures underwater SEL.

With regards to the proxy values summarized in Table 6, very little information is available regarding source levels for in-water rotary drilling activities. As a conservative measure and to be consistent with previously issued IHAs for similar projects in the region, a proxy of 154 dB RMS is used for all rotary drilling activities (Dazey, 2012).

NMFS recommends treating DTH systems as both impulsive and continuous, non-impulsive sound source types simultaneously. Thus, impulsive thresholds are used to evaluate Level A harassment, and the continuous threshold is used to evaluate Level B harassment. The Navy consulted with NMFS to obtain the appropriate proxy values for DTH mono- and cluster-hammers. With regards to DTH mono-hammers, NMFS recommended proxy levels for Level A harassment based on available data regarding DTH systems of similar sized piles and holes (Table 6) (Denes

et al.,

2019; Guan and Miner, 2020; Reyff and Heyvaert, 2019; Reyff, 2020; Heyvaert and Reyff, 2021). No hydroacoustic data exist for cluster DTH systems; therefore, NMFS recommends proxy values based off of regression and extrapolation calculations of existing data for mono-hammers until hydroacoustic data on DTH cluster drills be obtained (NMFS, 2022). Because of the high number of hammers and strikes for this system, DTH cluster drills are treated as a continuous sound source for the time component of Level A harassment (

i.e.,

for the entire duration DTH cluster drills are operational, they are considered to be producing strikes, rather than indicating the number of strikes per second, which is unknown), but still used the impulsive thresholds.

At the time of the Navy's application submission, NMFS recommended that the RMS SPL at 10 m should be 167 dB when evaluating Level B harassment (Heyvaert and Reyff, 2021 as cited in NMFS, 2021b) for all DTH pile/hole sizes. However, since that time, NMFS has received additional clarifying information regarding DTH data presented in Reyff and Heyvaert (2019) and Reyff (2020) that allows for different RMS SPL at 10 m to be recommended for piles/holes of varying diameters (NMFS, 2022). Therefore, the following proxy RMS SPLs at 10 m are used to evaluate Level B harassment from this sound source in this analysis (Table 6): 156 dB RMS for the 4 to 6 inch mono hammers (Reyff and Heyvaert, 2019; Reyff, 2020), 167 dB RMS for the 9 inch mono-hammers (Heyvaert and Reyff, 2021), and 174 dB RMS for all DTH cluster drills greater or equal to 74 inches (Reyff and Heyvaert, 2019; Reyff, 2020). See Footnote 6 in Table 6.

Rock hammering is analyzed as an impulsive noise source. For purposes of this analysis, it is assumed that the hammer will have a maximum strike rate of 460 strikes per minute and will operate for a maximum duration of 15 minutes before needing to reposition or stop to check progress. Therefore, noise impacts for rock hammering activities are assessed using the number of blows per 15-minute interval (6,900 blows) and the number of 15-minute intervals anticipated over the course of the day based on the durations provided in Tables 1, 7, and 8. As with rotary drilling, very little information is available regarding source levels associated with nearshore rock hammering. In previous IHAs related to the Shipyard, NMFS relied on preliminary measurements from the Tappan Zee Bridge replacement project (Reyff, 2018a, 2018b) as well as data from a WSDOT concrete pier demolition project (Escude, 2012) to inform proxy SLs for rock hammering. However, a few discrepancies in the preliminary data of the Tappan Zee Bridge reports have been identified resulting from NMFS' further inspection into the report's data. Therefore, the SLs reported only from the Escude (2012) concrete pier demolition project are used as proxy values for rock hammering activities associated with P-381 (Table 6).

Level B Harassment Zones

—Transmission loss (TL) is the decrease in acoustic intensity as an acoustic pressure wave propagates out from a source. TL parameters vary with frequency, temperature, sea conditions, current, source and receiver depth, water depth, water chemistry, and

bottom composition and topography. The general formula for underwater TL is:

TL = B * log10 (R1/R2),

Where:

B = transmission loss coefficient (assumed to be 15)

R1 = the distance of the modeled SPL from the driven pile, and

R2 = the distance from the driven pile of the initial measurement.

This formula neglects loss due to scattering and absorption, which is assumed to be zero here. The degree to which underwater sound propagates away from a sound source is dependent on a variety of factors, most notably the water bathymetry and presence or absence of reflective or absorptive conditions including in-water structures and sediments. The recommended TL coefficient for most nearshore environments is the practical spreading value of 15. This value results in an expected propagation environment that would lie between spherical and cylindrical spreading loss conditions, which is the most appropriate assumption for the Navy's activities in the absence of specific modelling. All Level B harassment isopleths are reported in Tables 7 and 8 considering RMS SLs.

Level A Harassment Zones

—The ensonified area associated with Level A harassment is more technically challenging to predict due to the need to account for a duration component. Therefore, NMFS developed an optional User Spreadsheet tool to accompany the Technical Guidance (NMFS, 2018a) that can be used to relatively simply predict an isopleth distance for use in conjunction with marine mammal density or occurrence to help predict potential takes. We note that because of some of the assumptions included in the methods underlying this optional tool, we anticipate that the resulting isopleth estimates are typically going to be overestimates of some degree, which may result in an overestimate of potential take by Level A harassment. However, this optional tool offers the best way to estimate isopleth distances when more sophisticated modeling methods are not available or practical. For stationary sources (such as from impact and vibratory pile driving, drilling, DTH, and rock hammering), the optional User Spreadsheet tool predicts the distance at which, if a marine mammal remained at that distance for the duration of the activity, it would be expected to incur PTS. Inputs used in the User Spreadsheet can be found in Appendix A of the Navy's application, Appendix A of the Navy's addendum, and the resulting isopleths are reported in Tables 7 and 8.

Table 7—Calculated Distance and Areas of Level A and Level B Harassment for Impulsive Noise

[DTH, impact pile driving, hydraulic rock hammering]

Activity

ID

Year

1

/activity

Purpose

Duration, count, size, and or rate

Total

production

days

Level A harassment

2

High frequency cetaceans

(harbor porpoise)

Phocid pinnipeds

Level B harassment

All species

1

2 Hydraulic Rock Hammer

Shutter Panel Demolition (112 panels)

5 hours/day (20 intervals/day at 15 each)

56

5,034.5 m/0.417417 km

2

2,261.9 m/0.417417 km

2

541.17 m/0.277858 km

2

.

3

2-3 Hydraulic Rock Hammer

Removal of Granite Quay Wall (2,800 cy)

2.5 hours/day (10 intervals/day at 15 min each)

47

3,171.6 m/0.417417 km

2

1,424.9 m/0.417417 km

2

541.17 m/0.277858 km

2

.

4

2-3 Hydraulic Rock Hammer

Berth 1 Top of Wall Demolition for Waler Install (320 lf)

10 hours/day (40 intervals/day at 15 min each)

74

7,991.8 m/0.417417 km

2

3,590.5 m/0.417417 km

2

541.17 m/0.277858 km

2

.

6

2 Hydraulic Rock Hammer

Mechanical Rock Removal (700 cy) at Berth 11 Basin Floor

12 hours/day (48 intervals/day at 15 min each)

60

9,024.7 m/0.417417 km

2

4,054.5 m/0.417417 km

2

541.17 m/0.277858 km

2

.

10

2 Hydraulic Rock Hammer

Mechanical Rock Removal (300 cy) at Berth 1 Basin Floor

12 hours/day (48 intervals/day at 15 min each)

25

9,024.7 m/0.417417 km

2

4,054.5 m/0.417417 km

2

541.17 m/0.277858 km

2

.

21

2 Hydraulic Rock Hammer

Removal of Emergency Repair Concrete (500 cy) at Berth 1

4 hours/day (16 intervals/day at 15 min each)

15

4,388.6 m/0.417417 km

2

1,949.2 m/0.417417 km

2

541.17 m/0.277858 km

2

.

7

2 DTH Mono-hammer

Relief Holes at Berth 11 Basin Floor

924 4-6 inch holes 27 holes/day

35

178.9 m/0.047675 km

2

80.4 m/0.014413 km

2

2,512 m/0. 417417 km

2

.

11

2 DTH Mono-hammer

Dry Dock 1 North entrance Rock Anchors

50 9-inch holes 2 holes/day

25

244.8 m/0.073751 km

2

110 m/0.022912 km

2

13,594 m/0.417417 km

2

.

22

2-3 DTH Mono-hammer

Center Wall Foundation Rock Anchors

72 9-inch holes 2 holes/day

36

244.8 m/0.073751 km

2

110 m/0.022912 km

2

13,594 m/0.417417 km

2

.

34

3-4 DTH Mono-hammer

Dry Dock 1 North Rock Anchors

36 9-inch holes 2 holes/day

18

244.8 m/0.073751 km

2

110 m/0.022912 km

2

13,594 m/0.417417 km

2

.

35

4-5 DTH Mono-hammer

Dry Dock 1 West Rock Anchors

36 9-inch holes 2 holes/day

18

244.8 m/0.073751 km

2

110 m/0.022912 km

2

13,594 m/0. 417417 km

2

.

R

2 Impact Pile Driving

Dry Dock 1 North Entrance Temporary Cofferdam

48 28-inch Z-shaped sheets 8 sheets/day

6

1,568.6 m/0.417417 km

2

704.7 m/0.364953 km

2

2,512 m/0.417417 km

2

.

5

2 Impact Pile Driving

Berth 1 Support of Excavation

28 28-inch Z-shaped sheets 4 piles/day

8

988.2 m/0.403411 km

2

444.0 m/0.201158 km

2

2,512 m/0.417417 km

2

.

8

2 Impact Pile Driving

Temporary Cofferdam Extension

14 28-inch Z-shaped sheets 4 piles/day

4

988.2 m/0.403411 km

2

444.0 m/0.201158 km

2

2,512 m/0.417417 km

2

.

12

2 Impact Pile Driving

Center Wall Tie-in to West Closure Wall

15 28-inch Z-shaped sheets 4 piles/day

4

988.2 m/0.403411 km

2

444.0 m/0.201158 km

2

2,512 m/0.417417 km

2

.

24

2-3 Impact Pile Driving

Center Wall East Tie-in to Existing Wall

23 28-inch Z-shaped sheets 2 piles/day

12

622.5 m/0.334747 km

2

279.7 m/0.090757 km

2

2,512 m/0.417417 km

2

.

A4

2 DTH Cluster Drill

Dry Dock 1 North Entrance Foundation Support Piles

18 78-inch shafts 10 hours/day 6.5 days/shaft

117

84,380.4 m/0.417417 km

2

37,909.7 m/0.417417 km

2

39,811 m/0.417417 km

2

.

9d

2 DTH Cluster Drill

Gantry Crane Support Piles

16 72-inch shafts 10 hours/day 5 days/shaft

80

67,025.7 m/0.417417 km

2

30,112.8 m/0.417417 km

2

39,811 m/0.417417 km

2

.

13d

2-3 DTH Cluster Drill

Dry Dock 1 North Temporary Work Trestle

20 84-inch shafts 10 hours/day 3.5 days/shaft

70

106,228.6 m/0.417417 km

2

47,725.5 m/0.417417 km

2

39,811 m/0.417417 km

2

.

15d

2-3 DTH Cluster Drill

Dry Dock 1 North Leveling Piles (Diving Board Shafts)

18 78-inch shafts 10 hours/day 7.5 days/shaft

135

84,380.4 m/0.417417 km

2

37,909.7 m/0.417417 km

2

39,811 m/0.417417 km

2

.

16d

2-3 DTH Cluster Drill

Wall Shafts for Dry Dock 1 North

20 78-inch shafts 10 hours/day 7.5 days/shaft

150

84,380.4 m/0.417417 km

2

37,909.7 m/0.417417 km

2

39,811 m/0.417417 km

2

.

17d

2-3 DTH Cluster Drill

Foundation Shafts for Dry Dock 1 North

23 108-inch shafts 10 hours/day 8.5 days/shaft

196

225,376.2 m/0.417417 km

2

101,255.2 m/0.417417 km

2

39,811 m/0.417417 km

2

.

29d

3-4 DTH Cluster Drill

Dry Dock 1 West Temporary Work Trestle

20 84-inch shafts 10 hours/day 3.5 days/shaft

70

106,228.6 m/0.417417 km

2

47,725.5 m/0.417417 km

2

39,811 m/0.417417 km

2

.

31d

3-4 DTH Cluster Drill

Wall Shafts for Dry Dock 1 West

22 78-inch shafts 10 hours/day 7.5 days/shaft

165

84,380.4 m/0.417417 km

2

37,909.7 m/0.417417 km

2

39,811 m/0.417417 km

2

.

32d

3-4 DTH Cluster Drill

Foundation Shafts for Dry Dock 1 West

23 108-inch shafts 10 hours/day 8.5 days/pile

196

225,376.2 m/0.417417 km

2

101,255.2 m/0.417417 km

2

39,811 m/0.417417 km

2

.

33d

3-4 DTH Cluster Drill

Dry Dock 1 West Leveling Piles (Diving Board Shafts)

18 78-inch shafts 10 hours/day 7.5 days/pile

135

84,380.4 m/0.417417 km

2

37,909.7 m/0.417417 km

2

39,811 m/0.417417 km

2

.

1

Note, for the purposes of this analysis, the construction years are identified as years 2 through 5; takes for marine mammals during Year 1 of the Navy's construction activities were authorized in a previously issued IHA (87 FR 19886, April 6, 2022).

2

To determine underwater harassment zone size, ensonified areas from the source were clipped along the shoreline using Geographical Information Systems (GIS).

Table 8—Calculated Distance and Areas of Level A and Level B Harassment for Non-Impulsive Noise

[Rotary drilling and vibratory pile driving/extracting]

Activity

ID

Year

1

/

activity

Purpose

Duration, count, size, and or rate

Total

production

days

Level A harassment

2

High frequency cetaceans

(harbor porpoise)

Phocid pinnipeds

Level B harassment

All species

R

2 Vibratory Pile Driving

Dry Dock 1 North Entrance Temporary Cofferdam

48 28-inch Z-shaped sheets 8 sheets/day

6

19.4 m/0.001041 km

2

8.0 m/0.0002 km

2

13,594 m/0.417417 km

2

.

2

2-3 Vibratory Extraction

Remove Berth 1 Sheet Piles

168 25-inch Z-shaped sheets 4 piles/day

42

12.2 m/0.000454 km

2

5.0 m/0.000078 km

2

13,594 m/0.417417 km

2

.

5

2 Vibratory Pile Driving

Install Berth 1 Support of Excavation

28 28-inch Z-shaped sheets 4 piles/day

8

12.2 m/0.000454 km

2

5.0 m/0.000078 km

2

13,594 m/0.417417 km

2

.

8

2 Vibratory Pile Driving

Install Temporary Cofferdam Extension

14 28-inch Z-shaped sheets 4 piles/day

4

12.2 m/0.000454 km

2

5.0 m/0.000078 km

2

13,594 m/0.417417 km

2

.

12

2 Vibratory Pile Driving

Center Wall Tie-In to Existing West Closure Wall

15 28-inch Z-shaped sheets 4 piles/day

4

12.2 m/0.000454 km

2

5.0 m/0.000078 km

2

13,594 m/0.417417 km

2

.

18

2 Vibratory Extraction

Berth 11 End Wall Temporary Guide Wall

60 28-inch Z-shaped sheets 8 piles/day

10

19.4 m/0.001041 km

2

8.0 m/0.0002 km

2

13,594 m/0.417417 km

2

.

19

2 Vibratory Extraction

Remove Berth 1 Support of Excavation

28 28-inch Z-shaped sheets 8 piles/day

5

19.4 m/0.001041 km

2

8.0 m/0.0002 km

2

13,594 m/0.417417 km

2

.

20

2 Vibratory Extraction

Remove Berth 1 Emergency Repairs

108 28-inch Z-shaped sheets 6 piles/day

18

16.0 m/0.000733 km

2

6.6 m/0.000136 km

2

13,594 m/0.417417 km

2

.

23

2-3 Vibratory Extraction

Dry Dock 1 North-Remove Center Wall Tie-in to West Closure Wall

16 28-inch Z-shaped sheets 8 piles/day

3

19.4 m/0.001041 km

2

8.0 m/0.0002 km

2

13,594 m/0.417417 km

2

.

24

2-3 Vibratory Pile Driving

Center Wall East Tie-in to Existing Wall

23 28-inch Z-shaped sheets 2 piles/day

12

7.7 m/0.000185 km

2

3.2 m/0.000032 km

2

13,594 m/0.417417 km

2

.

25

2-3 Vibratory Extraction

Dry Dock 1 West Remove Center Wall Tie-in to West Closure Wall

15 28-inch Z-shaped sheets 8 piles/day

3

19.4 m/0.001041 km

2

8.0 m/0.0002 km

2

13,594 m/0.417417 km

2

.

26

2-3 Vibratory Extraction

Remove Center Wall Tie-in to Existing Wall

23 28-inch Z-shaped sheets 8 piles/day

12

19.4 m/0.001041 km

2

8.0 m/0.0002 km

2

13,594 m/0.417417 km

2

.

27

2-3 Vibratory Extraction

Remove Temporary Cofferdam

96 28-inch Z-shaped sheets 8 piles/day

12

19.4 m/0.001041 km

2

8.0 m/0.0002 km

2

13,594 m/0.417417 km

2

.

28

2-3 Vibratory Extraction

Remove Temporary Cofferdam Extension

14 28-inch Z-shaped sheets 8 piles/day

2

19.4 m/0.001041 km

2

8.0 m/0.0002 km

2

13,594 m/0.417417 km

2

.

A1

2 Rotary Drill

Dry Dock 1 North Entrance Foundation Support Piles—Install Outer Casing

18 102-inch borings 1 hour/day 1 casing/day

18

2.1 m/0.000014 km

2

1.3 m/0.000005 km

2

1,848 m/0.417417 km

2

.

A2

2 Rotary Drill

Dry Dock 1 North Entrance Foundation Support Piles—Pre-Drill Socket

18 102-inch borings 9 hours/day 1 socket/day

18

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.41747 km

2

.

A3

2 Rotary Drill

Dry Dock 1 North Entrance Foundation Support Piles—Remove Outer Casing

18 102-inch borings 15 minutes/casing 1 casing/day

18

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

9a

2 Rotary Drill

Gantry Crane Support—Install Outer Casing

16 102-inch borings 1 hour/day 1 casing/day

16

2.1 m/0.000014 km

2

1.3 m/0.000005 km

2

1,848 m/0.417417 km

2

.

9b

2 Rotary Drill

Gantry Crane Support—Pre-Drill Socket

16 102-inch borings 9 hours/day 1 socket/day

16

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.417417 km

2

.

9c

2 Rotary Drill

Gantry Crane Support—Remove Outer Casing

16 102-inch borings 15 minutes/casing 1 casing/day

16

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

13a

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Install Outer Casing

20 102-inch borings 1 hour/day 1 casing/day

20

2.1 m/0.000014 km

2

1.3 m/0.000005 km

2

1,848 m/0.417417 km

2

.

13b

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Pre-Drill Socket

20 102-inch borings 9 hours/day 1 socket/day

20

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.417417 km

2

.

13c

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Remove Outer Casing

20 102-inch borings 15 minutes/casing 1 casing//day

20

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

14

2-3 Rotary Drill

Remove Dry Dock 1 North Temporary Work Trestle Piles

20 84-inch borings 15 minutes/casing 1 casing/day

20

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

15a

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Install Outer Casing

18 84-inch borings 1 hour/day 1 casing/day

18

2.1 m/0.000014 km

2

1.3 m/0.000005km

2

1,848 m/0.417417 km

2

.

15b

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Pre-Drill Socket

18 84-inch borings 9 hours/day 1 socket/day

18

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.417417 km

2

.

15c

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Remove Outer Casing

18 84-inch borings 15 minutes/casing 1 casing/day

18

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

16a

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Install Outer Casing

20 102-inch borings 1 hour/day 1 casing/day

20

2.1 m/0.000014 km

2

1.3 m/0.000005 km

2

1,848 m/0.417417 km

2

.

16b

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Pre-Drill Socket

20 102-inch borings 9 hours/day 1 socket/day

20

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.417417 km

2

.

16c

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Remove Outer Casing

20 102-inch borings 15 minutes/casing 1 casing/day

20

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

17a

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts—Install Outer Casing

23 126-inch borings 1 hour/day 1 casing/day

23

2.1 m/0.000014 km

2

1.3 m/0.000005 km

2

1,848 m/0.417417 km

2

.

17b

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts Pre-Drill Sockets

23 126-inch borings 9 hours/day 1 socket/day

23

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.417417 km

2

.

17c

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts—Remove Outer Casing

23 126-inch borings 15 minutes/casing 1 casing/day

23

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

29a

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Install Outer Casing

20 102-inch borings 1 hour/day 1 casing/day

20

2.1 m/0.000014 km

2

1.3 m/0.000005 km

2

1,848 m/0.417417 km

2

.

29b

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Pre-Drill Socket

20 102-inch borings 9 hours/day 1 socket/day

20

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.417417 km

2

.

29c

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Remove Outer Casing

20 102-inch borings 15 minutes/casing 1 casing/day

20

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

30

3-4 Rotary Drill

Dry Dock 1 West Remove Temporary Work Trestle Piles

20 84-inch borings 15 minutes/pile 1 pile/day

20

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

31a

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Install Outer Casing

22 102-inch borings 1 hour/day 1 casing/day

22

2.1 m/0.000014 km

2

1.3 m/0.000005km

2

1,848 m/0.417417 km

2

.

31b

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Pre-Drill Socket

22 102-inch borings 9 hours/day 1 socket/day

22

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.417417 km

2

.

31c

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Remove Outer Casing

22 102-inch borings 15 minutes/casing 1 casing/day

22

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

32a

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts—Install Outer Casing

23 126-inch borings 1 hour/day 1 casing/day

23

2.1 m/0.000014 km

2

1.3 m/0.000005 km

2

1,848 m/0.417417 km

2

.

32b

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts Pre-Drill Sockets

23 126-inch borings 9 hours/day 1 socket/day

23

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.417417 km

2

.

32c

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts—Remove Outer Casing

23 126-inch borings 15 minutes/casing 1 casing/day

23

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

33a

3-4 Rotary Drill

Dry Dock 1 North Leveling Piles—Install Outer Casing

18 84-inch borings 1 hour/day 1 casing/day

18

2.1 m/0.000014 km

2

1.3 m/0.000005 km

2

1,848 m/0.417417 km

2

.

33b

3-4 Rotary Drill

Dry Dock 1 West Leveling Piles—Pre-Drill Socket

18 84-inch borings 9 hours/day 1 socket/day

18

8.9 m/0.000248 km

2

5.4 m/0.000091 km

2

1,848 m/0.417417 km

2

.

33c

3-4 Rotary Drill

Dry Dock 1 North Leveling Piles—Remove Outer Casing

18 84-inch borings 15 minutes/casing 1 casing/day

18

0.8 m/0.000002 km

2

0.5 m/0.000001 km

2

1,848 m/0.417417 km

2

.

1

Note, for the purposes of this analysis, the construction years are identified as years 2 through 5; takes for marine mammals during Year 1 of the Navy's construction activities were authorized in a previously issued IHA (87 FR 19886, April 6, 2022).

2

To determine underwater harassment zone size, ensonified areas from the source were clipped along the shoreline using Geographical Information Systems (GIS).

The calculated maximum distances corresponding to the underwater marine mammal harassment zones from impulsive (impact pile driving, rock hammering, DTH) and non-impulsive (vibratory pile driving, rotary drilling) noise and the area of the harassment zone within the ROI are summarized in Tables 7 and 8, respectively. Sound source locations were chosen to model the greatest possible affected areas; typically, these locations will be at the riverward end of the super flood basin. The calculated distances do not take the land masses into consideration, but the ensonified areas do. Neither consider the reduction that will be achieved by the required use of a bubble curtain and therefore all take estimates are considered conservative. Refer to Figures 6-1 through 6-20 of the Navy's application for visual representations of the calculated maximum distances corresponding to the underwater marine mammal harassment zones from impulsive (impact pile driving, rock hammering, DTH) and non-impulsive (vibratory pile driving, rotary drilling) noise and the corresponding area of the harassment zone within the ROI.

Calculated distances to Level A harassment and Level B harassment thresholds are large, especially for DTH and rock hammering activities. However, in most cases the full distance of sound propagation will not be reached due to the presence of land masses and anthropogenic structures that will prevent the noise from reaching nearly the full extent of the harassment isopleths. Refer to Figure 1-3 in the Navy's application for the ROI, which illustrates that the land masses preclude the sound from traveling more than approximately 870 m (3,000 ft) from the source, at most. Areas encompassed within the threshold (harassment zones) were calculated by using a Geographical Information System (GIS) to clip the maximum calculated distances to the extent of the ROI (see Figure 2).

Concurrent Activities

—Simultaneous use of pile drivers, hammers, and drills could result in increased SPLs and harassment zone sizes given the proximity of the component sites and the rules of decibel addition (see Table 9 below). Due to the relatively small size of the ROI, the use of a single DTH cluster drill or rock hammer will ensonify the entire ROI to the Level A (PTS Onset) harassment thresholds (refer to Table 7). Therefore, when this equipment is operated in conjunction with other noise-generating equipment, there will be no change in the size of the harassment zone. The entire ROI will remain ensonified to the Level A harassment thresholds for the duration of the activity and there will be no Level B harassment zone. However, when DTH cluster drills or rock hammers are not in use, increased SPLs and harassment zone sizes within the ROI could result. Due to the substantial amount of rock hammering and DTH excavation required for the construction of the multifunctional expansion of Dry Dock 1, the only scenarios identified in which cluster drills and/or rock hammers will not be in operation will be at the end of the project (construction years 3 and 4) when two rotary drills or two rotary drills and a DTH mono-hammer (9-inch) could be used simultaneously (refer to Table 2).

When two noise sources have overlapping sound fields, there is potential for higher sound levels than for non-overlapping sources because the isopleth of one sound source encompasses the sound source of another isopleth. In such instances, the sources are considered additive and combined using the rules of decibel addition, presented in Table 9 below (NMFS, 2021d; WSDOT, 2020).

Table 9—Adjustments for Sound Exposure Level Criterion

Source types

Difference in sound level

(at specified

meters)

Adjustments to specifications for Level A harassment RMS/SEL

ss

* calculations

Non-impulsive, continuous/Non-impulsive, continuous, OR

0 or 1 dB

Add 3 dB to the highest sound level (at specified meters) AND adjust number of piles per day to account for overlap (space and time).

2 or 3 dB

Add 2 dB to the highest sound level (at specified meters) AND adjust number of piles per day to account for overlap (space and time).

Impulsive source (multiple strikes per second)/Impulsive source (multiple strikes per second

4 to 9 dB

Add 1 dB to the highest sound level (at specified meters) AND adjust number of piles per day to account for overlap (space and time).

10 dB or more

Add 0 dB to the highest sound level (at specified meters) AND adjust number of piles per day to account for overlap (space and time).

* RMS level for vibratory pile driving/rotary hammer and single strike SEL (SEL

ss

) level for DTH/rock hammer.

For simultaneous usage of three or more continuous sound sources, the three overlapping sources with the highest SLs are identified. Of the three highest SLs, the lower two are combined using the above rules, then the combination of the lower two is combined with the highest of the three. For example, with overlapping isopleths from 24-, 36-, and 42-inch diameter steel pipe piles with sound source levels of 161, 167, and 168 dB RMS respectively, the 24- and 36-inch would be added together; given that 167-161 = 6 dB, then 1 dB is added to the highest of the two sound source levels (167 dB), for a combined noise level of 168 dB. Next, the newly calculated 168 dB is added to the 42-inch steel pile with sound source levels of 168 dB. Since 168−168 = 0 dB, 3 dB is added to the highest value, or 171 dB in total for the combination of 24-, 36-, and 42-inch steel pipe piles (NMFS, 2021d). By using this method, revised proxy SPLs were determined for the use of two 102-inch diameter rotary drills and the use of two 108-inch rotary drills and one 9-inch DTH mono-hammer. The revised proxy values are presented in Table 10 and the resulting harassment zones are summarized in Table 11 (visually depicted in Figures 6-21 and 6-22 in the Navy's application).

Table 10—Revised Proxy Values for Simultaneous Use of Non-Impulsive Sources

Source A

Equipment

RMS SPL

(dB re 1 µPa)

Source B

Equipment

RMS SPL

(dB re 1 µPa)

Revised proxy RMS SPL

(dB re 1 µPa)

Rotary Drill

154

Rotary Drill

154

157

Two Rotary Drills

157

DTH Mono-Hammer

167

167

Table 11—Level A and Level B Harassment Zones Resulting From Concurrent Activities

Multiple source scenario

Level A harassment

High frequency cetaceans

(harbor porpoise)

Phocid pinnipeds

Level B harassment

All species

2 Rotary Drills (9 hrs)

23.6 m/0.001514 km

2

9.7 m/0.000294 km

2

2,929 m/0.417417 km

2

.

2 Rotary Drills (9 hrs) and 1 DTH Mono-Hammer (5 hrs)

74.2 m/0.012773 km

2

30.5 m/0.002489 km

2

13,594 m/0.417417 km

2

.

Marine Mammal Occurrence and Take Estimation

In this section we provide information about the occurrence of marine mammals, including density or other relevant information, that inform the take calculations. We also describe how the information provided above is synthesized to produce a quantitative estimate of the take that is reasonably likely to occur.

Potential exposures to impact and vibratory pile driving, rotary drilling, DTH, and rock hammering noise for each acoustic threshold were estimated using marine mammal density estimates (N) from the Navy Marine Species Density Database (NMSDD; Navy, 2017) or from monitoring reports from the Berth 11 Waterfront Improvements and P-310 construction projects. Specifically, where monitoring data specific to the project area were available, they were used, and the NMSDD data were used when there were no monitoring data available. The take estimate was determined using the following equation: take estimate = N * days of activity * area of harassment. A 10 m shutdown zone designed to prevent animal interactions with equipment was subtracted from the Level A harassment zone, and the area of the Level A harassment zone was subtracted from the Level B harassment zone to avoid double counting of takes during these take calculations. Days of construction were conservatively based on relatively slow daily production rates. The pile type, size, and installation method that produce the largest zone of influence were used to estimate exposure of marine mammals to noise impacts. In instances where an activity will ensonify the entire ROI to the Level A harassment threshold, all potential takes are assumed to be by Level A harassment.

Because some construction activities will occur over more than 1 construction year, the number of takes per year were determined by the percent duration of each construction activity occurring each year (calculated by months). For example, if an activity were to occur for 6 months, with 3 months occurring in year 2 and 3 months occurring in year 3, then 50 percent of the takes were assigned to year 2 and 50 percent to year 3. In instances where only one take was calculated but activities spanned more than 1 construction year, one take was authorized for each construction year. Table 12 summarizes the calculated duration percentages for each activity that were used to divide take numbers by year.

Table 12—Division of Takes by Construction Year

Activity ID

Total amount and estimated dates

Activity component

Year 2

1

% takes

Year 3

1

% takes

Year 4

1

% takes

Year 5

1

% takes

(A1,2,3,4) Center Wall—Install Foundation Support Piles

Drill 18 shafts

Apr 23 to Aug 23

Install 102-inch diameter outer casing

100

0

0

0

Pre-drill 102-inch outer casing

100

0

0

0

Remove 102-inch outer casing

100

0

0

0

Drill 79-inch diameter shaft

100

0

0

0

(R) Dry Dock 1 North Entrance—Install Temporary Cofferdam

Install 48 sheet piles

Apr 23 to May 23

28-inch wide Z-shaped sheets

100

0

0

0

(1) Berth 11—Remove Shutter Panels

Remove 112 panels

Apr 23 to Apr 23

Concrete shutter panels

100

0

0

0

(2) Berth 1—Remove Sheet Piles

Remove 168 sheet piles

Apr 23 to Jun 24

25-inch-wide Z-shaped

80

20

0

0

(3) Berth 1—Remove Granite Block Quay Wall

2,800 cy

Apr 23 to Jun 24

Removal of granite blocks

80

20

0

0

(4) Berth 1—Top of Wall Removal for Waler Installation

320 lf

Apr 23 to Jun 24

Mechanical concrete removal

80

20

0

0

(5) Berth 1—Install southeast corner SOE

Install 28 sheet piles Apr 23 to Jul 23

28-inch-wide Z-shaped

100

0

0

0

(6) Berth 11—Mechanical Rock Removal at Basin Floor

700 cy

Apr 23 to Aug 23

Excavate Bedrock

100

0

0

0

(7) Berth 11 Face—Mechanical Rock Removal at Basin Floor

Drill 924 relief holes

Apr 23 to Aug 23

4-6 inch diameter holes

100

0

0

0

(8) Temporary Cofferdam Extension

Install 14 sheet piles

Apr 23 to Jun 23

28-inch-wide Z-shaped

100

0

0

0

(9a, b, c, d) Gantry crane Support Piles at Berth 1 West

Drill 16 shafts

Apr 23 to Aug 23

Set 102-inch diameter casing

Pre-drill 102-inch rock socket

100

100

0

0

0

0

0

0

Remove 102-inch casing

100

0

0

0

72-inch diameter shafts

100

0

0

0

(10) Berth 1—Mechanical Rock Removal at Basin Floor

500 cy

Apr 23 to Sep 23

Excavate Bedrock

100

0

0

0

(11) Dry Dock 1 North Entrance—Drill Tremie Tie Downs

Drill 50 rock anchors

Apr 23 to Oct 23

9-inch diameter holes

100

0

0

0

(12) Center Wall—Install Tie-In to Existing West Closure Wall

Install 15 sheet piles

Apr 23 to Dec 23

28-inch wide Z-shaped

100

0

0

0

(13a, b, c, d) Dry Dock 1 North—Temporary Piles

Drill 20 shafts

May 23 to Nov 24

Set 102-inch diameter casing

60

40

0

0

Pre-drill 102-inch rock socket

60

40

0

0

Remove 102-inch casing

60

40

0

0

84-inch diameter shafts

60

40

0

0

(14) Dry Dock 1 North—Remove Temporary Work Trestle Piles

Remove 20 piles

May 23 to Nov 24

84-inch diameter drill piles

60

40

0

0

(15a, b, c, d) Dry Dock 1 North—Install Leveling Piles (Diving Board Shafts)

Drill 18 shafts

May 23—Nov 24

Set 84-inch casing

Pre-drill 84-inch rock socket

Remove 84-inch casing

60

60

60

40

40

40

0

0

0

0

0

0

78-inch diameter shaft

60

40

0

0

(16a, b, c, d) Wall Shafts for Dry Dock 1 North

Drill 20 shafts

Jun 23 to Nov 24

Set 102-inch diameter casing

Pre-drill 102-inch rock socket

60

60

40

40

0

0

0

0

Remove 102-inch casing

60

40

0

0

Drill 78-inch diameter shaft

60

40

0

0

(17a, b, c, d) Foundation Shafts for Dry Dock 1 North

Drill 23 shafts

Jun 23 to Nov 24

Set 126-inch diameter Casing

Pre-drill 126-inch rock socket

60

60

40

40

0

0

0

0

Remove 126-inch casing

60

40

0

0

Drill 108-inch diameter shafts

60

40

0

0

(18) Berth 11 End Wall—Remove Temporary Guide Wall

Remove 60 sheet piles

Jul 23 to Aug 23

28-inch wide Z-shaped

100

0

0

0

(19) Remove Berth 1 southeast corner SOE

Remove 28 sheet piles

Jul 23 to Sep 23

28-inch-wide Z-shaped

100

0

0

0

(20) Removal of Berth 1 Emergency Repair Sheet Piles

Remove 216 sheet piles

Aug 23 to Mar 24

28-inch-wide Z-shaped

100

0

0

0

(21) Removal of Berth 1 Emergency Repair Tremie Concrete

765 cubic meters (1,000 cy)

Aug 23 to Mar 24

Mechanical concrete removal

100

0

0

0

(22) Center wall foundation—Drill in monolith Tie Downs

Install 72 rock anchors

Aug 23 to May 24

9-inch diameter holes

80

20

0

0

(23) Center Wall—Remove tie-in to existing west closure wall (Dry Dock 1 North)

Remove 16 sheet piles

Aug 23 to Aug 24

28-inch-wide Z-shaped

60

40

0

0

(24) Center wall East—sheet pile tie-in to Existing Wall

Install 23 sheet piles

Aug 23 to Oct 24

28-inch wide Z-shaped

50

50

0

0

(25) Remove tie-in to West Closure Wall (Dry Dock 1 West)

Remove 15 sheet pile

Dec 23 to Dec 24

28-inch wide Z-shaped

30

70

0

0

(26) Remove Center wall East—sheet pile tie-in to Existing Wall (Dry Dock 1 West)

Remove 23 sheet piles

Dec 23 to Dec 24

28-inch wide Z-shaped

30

70

0

0

(27) Dry Dock 1 north entrance—Remove Temporary Cofferdam

Remove 96 sheet piles

Jan 24 to Sep 24

28-inch wide Z-shaped

33

66

0

0

(28) Remove Temporary Cofferdam Extension

Remove 14 sheet piles

Jan 24 to Sep 24

28-inch wide Z-shaped

33

66

0

0

(29a, b, c, d) Dry Dock 1 West—Install Temporary Piles

Drill 20 shafts

Apr 24 to Feb 26

Set 102-inch diameter casing

Pre-drill 102-inch rock socket

0

0

50

50

50

50

0

0

Remove 102-inch casing

0

50

50

0

84-inch diameter shafts

0

50

50

0

(30) Dry Dock 1 West—Remove Temporary Work Trestle Piles

Remove 20 piles

Apr 24 to Feb 26

84-inch diameter piles

0

50

50

0

(31a, b, c, d) Wall Shafts for Dry Dock 1 West

Drill 22 shafts

Jun 24 to Feb 26

Set 102-inch diameter casing

Pre-drill 102-inch rock socket

0

0

50

50

50

50

0

0

Remove 102-inch casing

0

50

50

0

78-inch diameter shaft

0

50

50

0

(32a, b, c, d) Foundation Shafts for Dry Dock 1 West

Drill 23 shafts

Jun 24 to Feb 26

Set 126-inch casing

Pre-drill 126-inch rock socket

0

0

50

50

50

50

0

0

Remove 126-inch casing

0

50

50

0

Drill 108-inch diameter shaft

0

50

50

0

(33a, b, c, d) Dry Dock 1 West—Install Leveling Piles (Diving Board Shafts)

Drill 18 shafts

Jun 24 to Feb 26

Set 84-inch casing

Pre-drill 84-inch rock socket

Remove 84-inch casing

0

0

0

50

50

50

50

50

50

0

0

0

Drill 78-inch diameter shaft

0

50

50

0

(34) Dry Dock 1 North—Tie Downs

Install 36 rock anchors

Jul 24 to Jul 25

9-inch diameter holes

0

70

30

0

(35) Dry Dock 1 West—Install Tie Downs

Install 36 rock anchors

Dec 25 to Dec 26

9-inch diameter hole

0

0

30

70

* Note, for the purposes of this analysis, the construction years are identified as years 2 through 5; takes for marine mammals during Year 1 of the Navy's construction activities were authorized in a previously issued IHA (87 FR 19886, April 6, 2022).

We describe how the information provided above is brought together to produce a quantitative take estimate in the species sections below. A summary of authorized take is available in Table 16.

Harbor Porpoise

Harbor porpoises are expected to be present in the project area from April to December. Based on density data from the NMSDD, their presence is highest in spring, decreases in summer, and slightly increases in fall. During construction monitoring in the project area, there were three harbor porpoise observations between April and December of 2017; two harbor porpoise observations in early August of 2018; and one harbor porpoise observation in 2020 (Cianbro, 2018; Navy, 2019; NAVFAC, 2021). There were no harbor porpoise observations in the project area in 2021 (NAVFAC, 2022). Given that monitoring data specific to the project area are available, the more general NMSDD data were not used to determine species density in the project area. Instead, the Navy used observation data from the 2017 and 2018 construction monitoring for the Berth 11 Waterfront Improvements Project and determined that the density of harbor porpoise for the largest harassment zone was equal to 0.04/km

2

. Estimated take was calculated with this density estimate multiplied by the harassment zone multiplied by the days for each activity (see Table 13).

Table 13—Estimated Take of Harbor Porpoise by Project Activity

Activity ID

Year/activity

Purpose

Density

Total

production

days

Level A

harassment

zone

(km

2

)

Take by Level A harassment

Total

Year 2

Year 3

Year 4

Year 5

Level B

harassment

zone

(km

2

)

Take by Level B harassment

Total

Year 2

Year 3

Year 4

Year 5

A

2 Rotary Drill

Center Wall—Install Foundation Support Piles

0.04

18

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

2 Rotary Drill

Center Wall—Install Foundation Support Piles

0.04

18

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

2 Rotary Drill

Center Wall—Install Foundation Support Piles

0.04

18

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

2 DTH Cluster Drill

Center Wall—Install Foundation Support Piles

0.04

117

0.417417

2

2

0

0

0

0.417417

0

0

0

0

0

R

2 Vibratory Pile Driving

Dry Dock 1 North Entrance—Install Temporary Cofferdam

0.04

6

0.0014041

0

0

0

0

0

0.417417

0

0

0

0

0

2 Impact Pile Driving

Dry Dock 1 North Entrance—Install Temporary Cofferdam

0.04

6

0.417417

0

0

0

0

0

0.417417

0

0

0

0

0

1

2 Hydraulic Rock Hammer

Shutter Panel Demolition (112 panels)

0.04

56

0.417417

1

1

0

0

0

0.277858

0

0

0

0

0

2

2-3 Vibratory Extraction

Remove Berth 1 Sheet Piles

0.04

42

0.000454

0

0

0

0

0

0.417417

1

2

1

1

0

0

3

2-3 Hydraulic Rock Hammer

Removal of Granite Quay Wall (2,800 cy)

0.04

47

0.417417

1

2

1

1

0

0

0.277858

0

0

0

0

0

4

2-3 Hydraulic Rock Hammer

Berth 1 Top of Wall Demolition for Waler Install (320 lf)

0.04

74

0.417417

1

2

1

1

0

0

0.277858

0

0

0

0

0

5

2 Vibratory Pile Driving

Install Berth 1 Support of Excavation

0.04

8

0.000454

0

0

0

0

0

0.417417

0

0

0

0

0

2 Impact Pile Driving

Berth 1 Support of Excavation

0.04

8

0.403411

0

0

0

0

0

0.417417

0

0

0

0

0

6

2 Hydraulic Rock Hammer

Mechanical Rock Removal (700 cy) at Berth 11 Basin Floor

0.04

60

0.417417

1

1

0

0

0

0.277858

0

0

0

0

0

7

2 DTH Mono-hammer

Relief Holes at Berth 11 Basin Floor

0.04

35

0.047675

0

0

0

0

0

0.417417

1

1

0

0

0

8

2 Vibratory Pile Driving

Install Temporary Cofferdam Extension

0.04

4

0.000454

0

0

0

0

0

0.417417

0

0

0

0

0

2 Impact Pile Driving

Temporary Cofferdam Extension

0.04

4

0.403411

0

0

0

0

0

0.417417

0

0

0

0

0

9

2 Rotary Drill

Gantry Crane Support—Install Outer Casing

0.04

16

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

2 Rotary Drill

Gantry Crane Support—Pre-Drill Socket

0.04

16

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

2 Rotary Drill

Gantry Crane Support—Remove Outer Casing

0.04

16

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

2 DTH Cluster Drill

Gantry Crane Support Piles

0.04

80

0.417417

1

1

0

0

0

0.417417

0

0

0

0

0

10

2 Hydraulic Rock Hammer

Mechanical Rock Removal (300 cy) at Berth 1 Basin Floor

0.04

25

0.417417

0

0

0

0

0

0.277858

0

0

0

0

0

11

2 DTH Mono-hammer

Dry Dock 1 North Entrance Rock Anchors

0.04

25

0.073751

0

0

0

0

0

0.417417

0

0

0

0

0

12

2 Vibratory Pile Driving

Center Wall Tie-In to Existing West Closure Wall

0.04

4

0.000454

0

0

0

0

0

0.417417

0

0

0

0

0

2 Impact Pile Driving

Center Wall Tie-in to West Closure Wall

0.04

4

0.403411

0

0

0

0

0

0.417417

0

0

0

0

0

13

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Install Outer Casing

0.04

20

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Pre-Drill Socket

0.04

20

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Remove Outer Casing

0.04

20

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 DTH Cluster Drill

Dry Dock 1 North Temporary Work Trestle

0.04

70

0.417417

1

2

1

1

0

0

0.417417

0

0

0

0

0

14

2-3 Rotary Drill

Remove Dry Dock 1 North Temporary Work Trestle Piles

0.04

20

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

15

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Install Outer Casing

0.04

18

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Pre-Drill Socket

0.04

18

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Remove Outer Casing

0.04

18

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 DTH Cluster Drill

Dry Dock 1 North Leveling Piles (Diving Board Shafts)

0.04

135

0.417417

2

1

1

0

0

0.417417

0

0

0

0

0

16

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Install Outer Casing

0.04

20

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Pre-Drill Socket

0.04

20

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Remove Outer Casing

0.04

20

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 DTH Cluster Drill

Wall Shafts for Dry Dock 1 North

0.04

150

0.417417

3

2

1

0

0

0.417417

0

0

0

0

0

17

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts—Install Outer Casing

0.04

23

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts Pre-Drill Sockets

0.04

23

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts—Remove Outer Casing

0.04

23

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 DTH Cluster Drill

Foundation Shafts for Dry Dock 1 North

0.04

196

0.417417

3

2

1

0

0

0.417417

0

0

0

0

0

18

2 Vibratory Extraction

Berth 11 End Wall Temporary Guide Wall

0.04

10

0.001041

0

0

0

0

0

0.417417

0

0

0

0

0

19

2 Vibratory Extraction

Remove Berth 1 Support of Excavation

0.04

5

0.001041

0

0

0

0

0

0.417417

0

0

0

0

0

20

2 Vibratory Extraction

Remove Berth 1 Emergency Repairs

0.04

18

0.000733

0

0

0

0

0

0.417417

1

1

0

0

0

21

2 Hydraulic Rock Hammer

Removal of Emergency Repair Concrete (500 cy) at Berth 1

0.04

15

0.417417

0

0

0

0

0

0.277858

0

0

0

0

0

22

2-3 DTH Mono-hammer

Center Wall Foundation Rock Anchors

0.04

36

0.073751

0

0

0

0

0

0.417417

0

0

0

0

0

23

2-3 Vibratory Extraction

Dry Dock 1 North-Remove Center Wall Tie-in to West Closure Wall

0.04

3

0.001041

0

0

0

0

0

0.417417

0

0

0

0

0

24

2-3 Vibratory Pile Driving

Center Wall East Tie-in to Existing Wall

0.04

12

0.000185

0

0

0

0

0

0.417417

0

0

0

0

0

2-3 Impact Pile Driving

Center Wall East Tie-in to Existing Wall

0.04

12

0.334747

0

0

0

0

0

0.417417

0

0

0

0

0

25

2-3 Vibratory Extraction

Dry Dock 1 West Remove Center Wall Tie-in to West Closure Wall

0.04

3

0.001041

0

0

0

0

0

0.417417

0

0

0

0

0

26

2-3 Vibratory Extraction

Remove Center Wall Tie-in to Existing Wall

0.04

12

0.001041

0

0

0

0

0

0.417417

0

0

0

0

0

27

2-3 Vibratory Extraction

Remove Temporary Cofferdam

0.04

12

0.001041

0

0

0

0

0

0.417417

0

0

0

0

0

28

2-3 Vibratory Extraction

Remove Temporary Cofferdam Extension

0.04

2

0.001041

0

0

0

0

0

0.417417

0

0

0

0

0

29

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Install Outer Casing

0.04

20

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Pre-Drill Socket

0.04

20

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Remove Outer Casing

0.04

20

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 DTH Cluster Drill

Dry Dock 1 West Temporary Work Trestle

0.04

70

0.417417

1

2

0

1

1

0

0.417417

0

0

0

0

0

30

3-4 Rotary Drill

Dry Dock 1 West Remove Temporary Work Trestle Piles

0.04

20

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

31

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Install Outer Casing

0.04

22

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Pre-Drill Socket

0.04

22

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Remove Outer Casing

0.04

22

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 DTH Cluster Drill

Wall Shafts for Dry Dock 1 West

0.04

165

0.417417

3

0

1

2

0

0.417417

0

0

0

0

0

32

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts—Install Outer Casing

0.04

23

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts Pre-Drill Sockets

0.04

23

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts—Remove Outer Casing

0.04

23

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 DTH Cluster Drill

Foundation Shafts for Dry Dock 1 West

0.04

196

0.417417

3

0

1

2

0

0.417417

0

0

0

0

0

33

3-4 Rotary Drill

Dry Dock 1 North Leveling Piles—Install Outer Casing

0.04

18

0.000014

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Leveling Piles—Pre-Drill Socket

0.04

18

0.000248

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 North Leveling Piles—Remove Outer Casing

0.04

18

0.000002

0

0

0

0

0

0.417417

0

0

0

0

0

3-4 DTH Cluster Drill

Dry Dock 1 West Leveling Piles (Diving Board Shafts)

0.04

135

0.417417

2

0

1

1

0

0.417417

0

0

0

0

0

34

3-4 DTH Mono-hammer

Dry Dock 1 North Rock Anchors

0.04

18

0.073751

0

0

0

0

0

0.417417

0

0

0

0

0

35

4-5 DTH Mono-hammer

Dry Dock 1 West Rock Anchors

0.04

18

0.073751

0

0

0

0

0

0.417417

0

0

0

0

0

Total

29

13

10

6

0

4

3

2

2

0

0

*

Note:

for the purposes of this analysis, the construction years are identified as years 2 through 5; takes for marine mammals during Year 1 of the Navy's construction activities were authorized in a previously issued IHA (87 FR 19886, April 6, 2022).

1

In instances where only 1 take was calculated but activities spanned more than 1 construction year, 1 take was requested by the Navy for each construction year.

2

1 take by Level B harassment was added to construction year 3 to account for average group size of harbor porpoises (see

https://www.fisheries.noaa.gov/species/harbor-porpoise#:~:text=The%20harbor%20porpoise%20is%20a,estuaries%2C%20harbors%2C%20and%20fjords

).

** No additional takes are expected to result from the simultaneous use of 2 rotary drills and a DTH mono-hammer in construction years 3 and 4 and the simultaneous use of 2 rotary drills in construction year 4.

Although no construction activity is currently planned for the final year of the LOA period (construction year 6), potential schedule slips may occur as a result of equipment failure, inclement weather, or other unforeseen events. However, potential takes that could occur during year 6 as a result of delays to activities scheduled for years 2-5 are accounted for through the analyses for those years, and no additional take is authorized.

Harbor Seal

Harbor seals may be present year-round in the project vicinity, with consistent densities throughout the year. Harbor seals are the most common pinniped in the Piscataqua River near the Shipyard. Sightings of this species were recorded during monthly surveys conducted in 2017 and 2018 (NAVFAC Mid-Atlantic, 2018, 2019b) as well as during Berth 11 and P-310 construction monitoring in 2017, 2018, 2020 and 2021 (Cianbro, 2018; Navy, 2019; NAVFAC, 2021, 2022), and therefore density estimates from these efforts were considered in the analysis. Based on observations recorded during the Berth 11 Waterfront Improvements (199 observations of harbor seals during year 1 and 249 observations of harbor seals during year 2 [448 total] over 322 days) and P-310 project construction monitoring (721 observations of harbor seals during year 1 and 451 observations of harbor seals during year 2 [1,172 total] over 349 days), harbor seal density was estimated to be 3.0/km

2

in the project area (Cianbro, 2018; Navy, 2019; NAVFAC, 2021, 2022).

Takes by Level A harassment were calculated for harbor seals where the density of animals (3 harbor seals/km

2

) was multiplied by the harassment zone and the number of days per construction activity. This method was deemed to be inappropriate by the Navy for calculating takes by Level B harassment for harbor seals as it produced take numbers that were lower than the number of harbor seals that has been previously observed in the Navy's monitoring reports. Therefore, the Navy proposed (and NMFS concurred) to increase the estimated take by Level B harassment to more accurately reflect harbor seal observations in the monitoring reports, by using the value of three harbor seals observed a day multiplied by the total number of construction days (

i.e.,

349 days), resulting in 1,047 takes per year by Level B harassment. This method is consistent with the methodology used to estimate takes by Level B harassment in IHA issued by NMFS for the first year of P-381 construction activities (87 FR 19866, April 6, 2022).

Additional takes by Level B harassment may occur during the simultaneous use of two rotary drills and a DTH mono-hammer in construction years 3 and 4 and the simultaneous use of two rotary drills in construction year 4. The simultaneous use of 2 rotary drills will result in 28 additional takes by Level B harassment of harbor seals. The simultaneous use of 2 rotary drills and a DTH mono-hammer will result in 22 additional takes by Level B harassment of harbor seals. Note, the use of cluster drills and rock hammers in construction years 2 and 3 result in the entire ROI being ensonified to Level A harassment thresholds; therefore, there will be no change to the size of the harassment zones from concurrent construction activities during these years and thus no need to authorize additional takes. To account for concurrent activities in construction years 3 and 4, the Navy requested to add additional takes by Level B harassment to the estimated take numbers (22 harbor seal in construction year 3 and 50 harbor seal in construction year 4). Therefore the Navy requests and NMFS authorizes 1,047 takes by Level B harassment for harbor seals in construction year 2, 1,069 takes by Level B harassment for harbor seals in construction year 3, 1,097 takes by Level B harassment for harbor seals in construction year 4, and 1,047 takes by Level B takes for harbor seals in construction year 5 (note the division of takes over the construction years is summarized in Table 12).

Take by Level A harassment of harbor seals is shown in Table 14 below. Note that where the Level A harassment zone is as large as the Level B harassment zone and fills the entire potentially ensonified area, the enumerated takes in the Level A harassment column may be in the form of Level A harassment and/or Level B harassment, but are authorized as takes by Level A harassment. The authorized takes by Level B harassment are not included in Table 14 as they were calculated by a different method (

i.e.,

by using the value of three harbor seals observed per day multiplied by the total number of construction days;

i.e.,

349 days).

Table 14—Estimated Take by Level A Harassment of Harbor Seal by Project Activity

Activity

ID

Year/

activity

Purpose

Density

Total

production

days

Level A

harassment

zone

(km

2

)

Take by Level A harassment

Total

Year

2

Year

3

Year

4

Year

5

A

2 Rotary Drill

Center Wall—Install Foundation Support Piles

3

18

0.000005

0

0

0

0

0

2 Rotary Drill

Center Wall—Install Foundation Support Piles

3

18

0.000091

0

0

0

0

0

2 Rotary Drill

Center Wall—Install Foundation Support Piles

3

18

0.000001

0

0

0

0

0

2 DTH Cluster Drill

Center Wall—Install Foundation Support Piles

3

117

0.417417

147

147

0

0

0

R

2 Vibratory Pile Driving

Dry Dock 1 North Entrance—Install Temporary Cofferdam

3

6

0.0002

0

0

0

0

0

2 Impact Pile Driving

Dry Dock 1 North Entrance—Install Temporary Cofferdam

3

6

0.364953

7

7

0

0

0

1

2 Hydraulic Rock Hammer

Shutter Panel Demolition (112 panels)

3

56

0.417417

70

70

0

0

0

2

2-3 Vibratory Extraction

Remove Berth 1 Sheet Piles

3

42

0.000078

0

0

0

0

0

3

2-3 Hydraulic Rock Hammer

Removal of Granite Quay Wall (2,800 cy)

3

47

0.417417

59

47

12

0

0

4

2-3 Hydraulic Rock Hammer

Berth 1 Top of Wall Demolition for Waler Install (320 lf)

3

74

0.417417

93

74

19

0

0

5

2 Vibratory Pile Driving

Install Berth 1 Support of Excavation

3

8

0.000078

0

0

0

0

0

2 Impact Pile Driving

Berth 1 Support of Excavation

3

8

0..201158

5

5

0

0

0

6

2 Hydraulic Rock Hammer

Mechanical Rock Removal (700 cy) at Berth 11 Basin Floor

3

60

0.417417

75

75

0

0

0

7

2 DTH Mono-hammer

Relief Holes at Berth 11 Basin Floor

3

35

0.014413

1

1

0

0

0

8

2 Vibratory Pile Driving

Install Temporary Cofferdam Extension

3

4

0.000078

0

0

0

0

0

2 Impact Pile Driving

Temporary Cofferdam Extension

3

4

0.201158

2

2

0

0

0

9

2 Rotary Drill

Gantry Crane Support—Install Outer Casing

3

16

0.000005

0

0

0

0

0

2 Rotary Drill

Gantry Crane Support—Pre-Drill Socket

3

16

0.000091

0

0

0

0

0

2 Rotary Drill

Gantry Crane Support—Remove Outer Casing

3

16

0.000091

0

0

0

0

0

2 DTH Cluster Drill

Gantry Crane Support Piles

3

80

0.417417

100

100

0

0

0

10

2 Hydraulic Rock Hammer

Mechanical Rock Removal (300 cy) at Berth 1 Basin Floor

3

25

0.417417

31

31

0

0

0

11

2 DTH Mono-hammer

Dry Dock 1 North Entrance Rock Anchors

3

25

0.022912

2

2

0

0

0

12

2 Vibratory Pile Driving

Center Wall Tie-In to Existing West Closure Wall

3

4

0.000078

0

0

0

0

0

2 Impact Pile Driving

Center Wall Tie-in to West Closure Wall

3

4

0.201158

2

2

0

0

0

13

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Install Outer Casing

3

20

0.000005

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Pre-Drill Socket

3

20

0.000091

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Remove Outer Casing

3

20

0.000001

0

0

0

0

0

2-3 DTH Cluster Drill

Dry Dock 1 North TemporaryWork Trestle

3

70

0.417417

88

53

35

0

0

14

2-3 Rotary Drill

Remove Dry Dock 1 North Temporary Work Trestle Piles

3

20

0.000002

0

0

0

0

0

15

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Install Outer Casing

3

18

0.000005

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Pre-Drill Socket

3

18

0.000091

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Remove Outer Casing

3

18

0.000001

0

0

0

0

0

2-3 DTH Cluster Drill

Dry Dock 1 North Leveling Piles (Diving Board Shafts)

3

135

0.417417

169

101

68

0

0

16

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Install Outer Casing

3

20

0.000005

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Pre-Drill Socket

3

20

0.000091

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Remove Outer Casing

3

20

0.000001

0

0

0

0

0

2-3 DTH Cluster Drill

Wall Shafts for Dry Dock 1 North

3

150

0.417417

188

113

75

0

0

17

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts—Install Outer Casing

3

23

0.000005

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts Pre-Drill Sockets

3

23

0.000091

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts—Remove Outer Casing

3

23

0.000001

0

0

0

0

0

2-3 DTH Cluster Drill

Foundation Shafts for Dry Dock 1 North

3

196

0.417417

245

147

98

0

0

18

2 Vibratory Extraction

Berth 11 End Wall Temporary Guide Wall

3

10

0.0002

0

0

0

0

0

19

2 Vibratory Extraction

Remove Berth 1 Support of Excavation

3

5

0.0002

0

0

0

0

0

20

2 Vibratory Extraction

Remove Berth 1 Emergency Repairs

3

18

0.000136

0

0

0

0

0

21

2 Hydraulic Rock Hammer

Removal of Emergency Repair Concrete (500 cy) at Berth 1

3

15

0.417417

19

19

0

0

0

22

2-3 DTH Mono-hammer

Center Wall Foundation Rock Anchors

3

36

0.022912

2

1

1

0

0

23

2-3 Vibratory Extraction

Dry Dock 1 North—Remove Center Wall Tie-in to West Closure Wall

3

3

0.0002

0

0

0

0

0

24

2-3 Vibratory Pile Driving

Center Wall East Tie-in to Existing Wall

3

12

0.000032

0

0

0

0

0

2-3 Impact Pile Driving

Center Wall East Tie-in to Existing Wall

3

12

0.090757

3

2

1

0

0

25

2-3 Vibratory Extraction

Dry Dock 1 West Remove Center Wall Tie-in to West Closure Wall

3

3

0.0002

0

0

0

0

0

26

2-3 Vibratory Extraction

Remove Center Wall Tie-in to Existing Wall

3

12

0.0002

0

0

0

0

0

27

2-3 Vibratory Extraction

Remove Temporary Cofferdam

3

12

0.0002

0

0

0

0

0

28

2-3 Vibratory Extraction

Remove Temporary Cofferdam Extension

3

2

0.0002

0

0

0

0

0

29

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Install Outer Casing

3

20

0.000005

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Pre-Drill Socket

3

20

0.000091

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Remove Outer Casing

3

20

0.000001

0

0

0

0

0

3-4 DTH Cluster Drill

Dry Dock 1 West Temporary Work Trestle

3

70

0.417417

88

0

44

44

0

30

3-4 Rotary Drill

Dry Dock 1 West Remove Temporary Work Trestle Piles

3

20

0.000002

0

0

0

0

0

31

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Install Outer Casing

3

22

0.000005

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Pre-Drill Socket

3

22

0.000091

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Remove Outer Casing

3

22

0.000001

0

0

0

0

0

3-4 DTH Cluster Drill

Wall Shafts for Dry Dock 1 West

3

165

0.417417

206

0

103

103

0

32

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts—Install Outer Casing

3

23

0.000005

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts Pre-Drill Sockets

3

23

0.000091

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts—Remove Outer Casing

3

23

0.000001

0

0

0

0

0

3-4 DTH Cluster Drill

Foundation Shafts for Dry Dock 1 West

3

196

0.417417

245

0

122

123

0

33

3-4 Rotary Drill

Dry Dock 1 North Leveling Piles—Install Outer Casing

3

18

0.000005

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Leveling Piles—Pre-Drill Socket

3

18

0.000091

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 North Leveling Piles—Remove Outer Casing

3

18

0.000001

0

0

0

0

0

3-4 DTH Cluster Drill

Dry Dock 1 West Leveling Piles (Diving Board Shafts)

3

135

0.417417

169

0

84

85

0

34

3-4 DTH Mono-hammer

Dry Dock 1North Rock Anchors

3

18

0.022912

1

0

1

0

0

35

4-5 DTH Mono-hammer

Dry Dock 1 West Rock Anchors

3

18

0.022912

1

0

0

0

1

Total

2,018

999

663

355

1

*

Note:

for the purposes of this analysis, the construction years are identified as years 2 through 5; takes for marine mammals during Year 1 of the Navy's construction activities were authorized in a previously issued IHA (87 FR 19886, April 6, 2022).

Although no construction activity is currently planned for the final year of the LOA period (construction year 6), potential schedule slips may occur as a result of equipment failure, inclement weather, or other unforeseen events. However, potential takes that could occur during year 6 as a result of delays to activities scheduled for years 2-5 are accounted for through the analyses for those years, and no additional take is authorized.

Gray Seal

Gray seals may be present year-round in the project vicinity, with consistent densities throughout the year. Gray seals are less common in the Piscataqua River than the harbor seal. A total of nine sightings of gray seals were recorded during P-310 construction monitoring (NAVFAC, 2021, 2022). Density estimates of gray seals were based on the Berth 11 Waterfront Improvements (24 observations of gray seals during year 1 and 12 observations of gray seals during year 2 [36 total] over 322 days) and P-310 project construction monitoring (47 observations of gray seals during year 1 and 21 observations of gray seals during year 2 [68 total] over 349 days) and was estimated to be 0.2/km

2

(Cianbro, 2018; Navy, 2019; NAVFAC, 2021, 2022). These data were preferred in this analysis over the more general density data from the NMSDD.

Takes by Level A harassment were calculated for gray seals where the density of animals (0.2 gray seals/km

2

) was multiplied by the harassment zone and the number of days per construction activity. This method was deemed to be inappropriate by the Navy for calculating takes by Level B harassment for gray seals as it produced take that were fewer than the number of gray seals that has been previously observed in the Navy's monitoring reports. Therefore, the Navy proposed (and NMFS concurred), to increase the take by Level B harassment to more accurately reflect gray seal observations in the monitoring reports, by using the value of 0.2 gray seals a day multiplied by the total number of construction days (

i.e.,

349 days) resulting in 70 takes by Level B harassment authorized per year. This method is consistent with the methodology used to estimate takes by Level B harassment in IHA issued by NMFS for the first year of P-381 construction activities (87 FR 19866; April 6, 2022).

Additional takes by Level B harassment may occur during the simultaneous use of two rotary drills and a DTH mono-hammer in construction years 3 and 4 and the simultaneous use of two rotary drills in construction year 4. The simultaneous use of two rotary drills will result in two additional Level B takes of gray seals. The simultaneous use of two rotary drills and a DTH mono-hammer will result in one additional Level B take of

gray seals. Note, the use of cluster drills and rock hammers in construction years 2 and 3 result in the entire ROI being ensonified to Level A harassment thresholds; therefore, there will be no change to the size of the harassment zones from concurrent construction activities during these years and thus no need to request additional takes. To account for concurrent activities in construction years 3 and 4, the Navy requested additional takes by Level B harassment to the take numbers (one gray seal in construction year 3 and three gray seals in construction year 4). Therefore the Navy requests and NMFS authorizes 70 takes by Level B takes for gray seals in construction year 2, 71 takes by Level B harassment for gray seals in construction year 3, 73 takes by Level B harassment for gray seals in construction year 4, and 70 takes by Level B harassment for gray seals in construction year 5 (note the division of takes over the construction years is summarized in Table 12).

Take by Level A harassment of gray seals is shown in Table 15 below. Note that where the Level A harassment zone is as large as the Level B harassment zone and fills the entire potentially ensonified area, the enumerated takes in the Level A harassment column may be in the form of Level A harassment and/or Level B harassment, but will be authorized as takes by Level A harassment. The authorized takes by Level B harassment are not included in Table 15 as they were calculated by a different method (

i.e.,

by using the value of 0.2 gray seals observed a day multiplied by the total number of construction days;

i.e.,

349 days).

Table 15—Estimated Take by Level A Harassment of Gray Seal by Project Activity

Activity ID

Year/activity

Purpose

Density

Total

production

days

Level A

harassment zone

(km

2

)

Take by Level A harassment

Total

Year 2

Year 3

Year 4

Year 5

A

2 Rotary Drill

Center Wall—Install Foundation Support Piles

0.2

18

0.000005

0

0

0

0

0

2 Rotary Drill

Center Wall—Install Foundation Support Piles

0.2

18

0.000091

0

0

0

0

0

2 Rotary Drill

Center Wall—Install Foundation Support Piles

0.2

18

0.000001

0

0

0

0

0

2 DTH Cluster Drill

Center Wall—Install Foundation Support Piles

0.2

117

0.417417

10

10

0

0

0

R

2 Vibratory Pile Driving

Dry Dock 1 North Entrance—Install Temporary Cofferdam

0.2

6

0.0002

0

0

0

0

0

2 Impact Pile Driving

Dry Dock 1 North Entrance—Install Temporary Cofferdam

0.2

6

0.364953

0

0

0

0

0

1

2 Hydraulic Rock Hammer

Shutter Panel Demolition (112 panels)

0.2

56

0.417417

5

5

0

0

0

2

2-3 Vibratory Extraction

Remove Berth 1 Sheet Piles

0.2

42

0.000078

0

0

0

0

0

3

2-3 Hydraulic Rock Hammer

Removal of Granite Quay Wall (2,800 cy)

0.2

47

0.417417

4

3

1

0

0

4

2-3 Hydraulic Rock Hammer

Berth 1 Top of Wall Demolition for Waler Install (320 lf)

0.2

74

0.417417

6

5

1

0

0

5

2 Vibratory Pile Driving

Install Berth 1 Support of Excavation

0.2

8

0.000078

0

0

0

0

0

2 Impact Pile Driving

Berth 1 Support of Excavation

0.2

8

0.201158

0

0

0

0

0

6

2 Hydraulic Rock Hammer

Mechanical Rock Removal (700 cy) at Berth 11 Basin Floor

0.2

60

0.417417

5

5

0

0

0

7

2 DTH Mono-hammer

Relief Holes at Berth 11 Basin Floor

0.2

35

0.014413

0

0

0

0

0

8

2 Vibratory Pile Driving

Install Temporary Cofferdam Extension

0.2

4

0.000078

0

0

0

0

0

2 Impact Pile Driving

Temporary Cofferdam Extension

0.2

4

0.201158

0

0

0

0

0

9

2 Rotary Drill

Gantry Crane Support—Install Outer Casing

0.2

16

0.000005

0

0

0

0

0

2 Rotary Drill

Gantry Crane Support—Pre-Drill Socket

0.2

16

0.000091

0

0

0

0

0

2 Rotary Drill

Gantry Crane Support—Remove Outer Casing

0.2

16

0.000091

0

0

0

0

0

2 DTH Cluster Drill

Gantry Crane Support Piles

0.2

80

0.417417

7

7

0

0

0

10

2 Hydraulic Rock Hammer

Mechanical Rock Removal (300 cy) at Berth 1 Basin Floor

0.2

25

0.417417

2

2

0

0

0

11

2 DTH Mono-hammer

Dry Dock 1 North Entrance Rock Anchors

0.2

25

0.022912

0

0

0

0

0

12

2 Vibratory Pile Driving

Center Wall Tie- In to Existing West Closure Wall

0.2

4

0.000078

0

0

0

0

0

2 Impact Pile Driving

Center Wall Tie-in to West Closure Wall

0.2

4

0.201158

0

0

0

0

0

13

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Install Outer Casing

0.2

20

0.000005

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Pre-Drill Socket

0.2

20

0.000091

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Temporary Work Trestle—Remove Outer Casing

0.2

20

0.000001

0

0

0

0

0

2-3 DTH Cluster Drill

Dry Dock 1 North Temporary Work Trestle

0.2

70

0.417417

6

4

2

0

0

14

2-3 Rotary Drill

Remove Dry Dock 1 North Temporary Work Trestle Piles

0.2

20

0.000002

0

0

0

0

0

15

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Install Outer Casing

0.2

18

0.000005

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Pre-Drill Socket

0.2

18

0.000091

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Leveling Piles—Remove Outer Casing

0.2

18

0.000001

0

0

0

0

0

2-3 DTH Cluster Drill

Dry Dock 1 North Leveling Piles (Diving Board Shafts)

0.2

135

0.417417

11

7

4

0

0

16

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Install Outer Casing

0.2

20

0.000005

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Pre-Drill Socket

0.2

20

0.000091

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Wall Shafts—Remove Outer Casing

0.2

20

0.000001

0

0

0

0

0

2-3 DTH Cluster Drill

Wall Shafts for Dry Dock 1 North

0.2

150

0.417417

13

8

5

0

0

17

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts—Install Outer Casing

0.2

23

0.000005

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts Pre-Drill Sockets

0.2

23

0.000091

0

0

0

0

0

2-3 Rotary Drill

Dry Dock 1 North Foundation Shafts—Remove Outer Casing

0.2

23

0.000001

0

0

0

0

0

2-3 DTH Cluster Drill

Foundation Shafts for Dry Dock 1 North

0.2

196

0.417417

16

10

6

0

0

18

2 Vibratory Extraction

Berth 11 End Wall Temporary Guide Wall

0.2

10

0.0002

0

0

0

0

0

19

2 Vibratory Extraction

Remove Berth 1 Support of Excavation

0.2

5

0.0002

0

0

0

0

0

20

2 Vibratory Extraction

Remove Berth 1 Emergency Repairs

0.2

18

0.000136

0

0

0

0

0

21

2 Hydraulic Rock Hammer

Removal of Emergency Repair Concrete (500 cy) at Berth 1

0.2

15

0.417417

1

1

0

0

0

22

2-3 DTH Mono-hammer

Center Wall Foundation Rock Anchors

0.2

36

0.022912

0

0

0

0

0

23

2-3 Vibratory Extraction

Dry Dock North-Remove Center Wall Tie-in to West Closure Wall

0.2

3

0.0002

0

0

0

0

0

24

2-3 Vibratory Pile Driving

Center Wall East Tie-in to Existing Wall

0.2

12

0.000032

0

0

0

0

0

2-3 Impact Pile Driving

Center Wall East Tie-in to Existing Wall

0.2

12

0.090757

0

0

0

0

0

25

2-3 Vibratory Extraction

Dry Dock 1 West Remove Center Wall Tie-in to West Closure Wall

0.2

3

0.0002

0

0

0

0

0

26

2-3 Vibratory Extraction

Remove Center Wall Tie-in to Existing Wall

0.2

12

0.0002

0

0

0

0

0

27

2-3 Vibratory Extraction

Remove Temporary Cofferdam

0.2

12

0.0002

0

0

0

0

0

28

2-3 Vibratory Extraction

Remove Temporary Cofferdam Extension

0.2

2

0.0002

0

0

0

0

0

29

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Install Outer Casing

0.2

20

0.000005

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Pre-Drill Socket

0.2

20

0.000091

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Temporary Work Trestle—Remove Outer Casing

0.2

20

0.000001

0

0

0

0

0

3-4 DTH Cluster Drill

Dry Dock 1 West Temporary Work Trestle

0.2

70

0.417417

6

0

3

3

0

30

3-4 Rotary Drill

Dry Dock 1 West Remove Temporary Work Trestle Piles

0.2

20

0.000002

0

0

0

0

0

31

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Install Outer Casing

0.2

22

0.000005

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Pre-Drill Socket

0.2

22

0.000091

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Wall Shafts—Remove Outer Casing

0.2

22

0.000001

0

0

0

0

0

3-4 DTH Cluster Drill

Wall Shafts for Dry Dock 1 West

0.2

165

0.417417

14

0

7

7

0

32

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts—Install Outer Casing

0.2

23

0.000005

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts Pre-Drill Sockets

0.2

23

0.000091

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Foundation Shafts—Remove Outer Casing

0.2

23

0.000001

0

0

0

0

0

3-4 DTH Cluster Drill

Foundation Shafts for Dry Dock 1 West

0.2

196

0.417417

16

0

8

8

0

33

3-4 Rotary Drill

Dry Dock 1 North Leveling Piles—Install Outer Casing

0.2

18

0.000005

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 West Leveling Piles—Pre-Drill Socket

0.2

18

0.000091

0

0

0

0

0

3-4 Rotary Drill

Dry Dock 1 North Leveling Piles—Remove Outer Casing

0.2

18

0.000001

0

0

0

0

0

3-4 DTH Cluster Drill

Dry Dock 1 West Leveling Piles (Diving Board Shafts)

0.2

135

0.417417

11

0

6

5

0

34

3-4 DTH Mono-hammer

Dry Dock 1 North Rock Anchors

0.2

18

0.022912

0

0

0

0

0

35

4-5 DTH Mono-hammer

Dry Dock 1 West Rock Anchors

0.2

18

0.022912

0

0

0

0

0

Total

133

67

43

23

0

*

Note:

for the purposes of this analysis, the construction years are identified as years 2 through 5; takes for marine mammals during Year 1 of the Navy's construction activities were authorized in a previously issued IHA (87 FR 19886, April 6, 2022).

Although no construction activity is currently planned for the final year of the LOA period (construction year 6), potential schedule slips may occur as a result of equipment failure, inclement weather, or other unforeseen events. However, potential takes that could occur during year 6 as a result of delays to activities scheduled for years 2-5 are accounted for through the analyses for those years, and no additional take is authorized.

Hooded Seal

Hooded seals may be present in the project vicinity from January through May, though their exact seasonal densities are unknown. In general, hooded seals are much rarer than the harbor seal and gray seal in the Piscataqua River. NMFS authorized one take by Level B harassment per month from January to May of a hooded seal for the Berth 11 Waterfront Improvements Construction project (NMFS, 2018b) and for P-310 (Super Flood Basin) (NMFS, 2016; NMFS, 2019; NMFS, 2021c). To date, the monitoring for those projects and for the density surveys have not recorded a sighting of hooded seal in the project area (Cianbro, 2018; NAVFAC Mid-Atlantic, 2018, 2019b; Navy 2019; NAVFAC, 2021, 2022). In order to guard against the potential for unauthorized take, the Navy again requested one take by Level B harassment of hooded seal per month (between the months of January and May) for each construction year. Therefore NMFS authorizes five takes by Level B harassment per year. Given the size of the shutdown zones in relation to the Level A harassment isopleths (see the Mitigation section below), NMFS also authorizes five takes by Level A harassment per year to safeguard against unauthorized take of hooded seals that may occur unnoticed in the Level A harassment zone for sufficient duration to incur PTS.

Harp Seal

In general, harp seals are much rarer than the harbor seal and gray seal in the Piscataqua River. Harp seals were not observed during marine mammal monitoring or survey events that took place in 2017, 2018, or 2021 (Cianbro, 2018; NAVFAC Mid-Atlantic, 2018, 2019b; Navy, 2019; NAVFAC, 2021, 2022); however, two harp seals (n=2) were observed in the River in 2020 (Stantec, 2020), and another harp seal was observed in 2016 (NAVFAC Mid-Atlantic, 2016; NMFS, 2016). As above for hooded seals, NMFS is authorizing one take by Level B harassment of harp seal per month of construction (between the months of January and May) for each construction year as was authorized by NMFS for the Berth 11 Waterfront Improvements Project (NMFS, 2018b) and for P-310 (Super Flood Basin) construction activities (NMFS, 2019, 2021a). Harp seals may occur in the area from January through May. Anticipating one Level B harassment harp seal take per month for 5 months per year during in-water construction will guard against potential unauthorized take of this species. Given the size of the shutdown zones in relation to the Level A harassment isopleths (see the Mitigation section below), NMFS also authorizes five takes by Level A harassment per year to safeguard against unauthorized take of harp seals that may occur unnoticed in the Level A harassment zone for sufficient duration to incur PTS.

Table 16 below summarizes the authorized take for all the species described above as a percentage of stock abundance.

Table 16—Authorized Take as a Percentage of Stock Abundance

Construction year

Species

Stock (N

EST

)

Authorized

take by

Level A

harassment

Authorized

take by

Level B

harassment

Total

authorized

take

Percent

of stock

2—Apr 2023-Mar 2024

Harbor porpoise

Gulf of Maine/Bay of Fundy (95,543)

13

3

16

0.02

Harbor seal

Western North Atlantic (61,336)

999

1,047

2,046

3.33

Gray seal

Western North Atlantic (451,600)

67

70

137

0.03

Harp seal

Western North Atlantic (7.6 million)

5

5

10

<0.01

Hooded seal

Western North Atlantic (593,500)

5

5

10

<0.01

3—Apr 2024-Mar 2025

Harbor porpoise

Gulf of Maine/Bay of Fundy (95,543)

10

2

12

0.01

Harbor seal

Western North Atlantic (61,336)

663

1,069

1,732

2.82

Gray seal

Western North Atlantic (451,600)

43

71

114

0.03

Harp seal

Western North Atlantic (7.6 million)

5

5

10

<0.01

Hooded seal

Western North Atlantic (593,500)

5

5

10

<0.01

4—Apr 2025-Mar 2026

Harbor porpoise

Gulf of Maine/Bay of Fundy (95,543)

6

0

6

0.01

Harbor seal

Western North Atlantic (61,336)

355

1,097

1,452

2.37

Gray seal

Western North Atlantic (451,600)

23

73

96

0.02

Harp seal

Western North Atlantic (7.6 million)

5

5

10

<0.01

>Hooded seal

Western North Atlantic (593,500)

5

5

10

<0.01

5—Apr 2026-Mar 2027

Harbor porpoise

Gulf of Maine/Bay of Fundy (95,543)

0

0

0

0

Harbor seal

Western North Atlantic (61,336)

1

1,047

1,048

1.71

Gray seal

Western North Atlantic (451,600)

0

70

70

0.02

Harp seal

Western North Atlantic (7.6 million)

5

5

10

<0.01

Hooded seal

Western North Atlantic (593,500)

This text is long and has been trimmed here. Open the source document for the complete record.