Taking Marine Mammals Incidental to the Hampton Roads Bridge Tunnel Expansion Project in Norfolk, Virginia

Federal RegisterJan 8, 2021

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 217

[Docket No. 201228-0360]

RIN 0648-BK21

Taking Marine Mammals Incidental to the Hampton Roads Bridge Tunnel Expansion Project in Norfolk, Virginia

AGENCY:

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

ACTION:

Proposed rule; request for comments and information.

SUMMARY:

NMFS has received a request from the Hampton Roads Connector Partners (HRCP) for authorization to take small numbers of marine mammals incidental to pile driving and removal activities at the Hampton Roads Bridge Tunnel Expansion Project (HRBT) in Norfolk, Virginia over the course of five years (2021-2026). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is proposing regulations to govern that take, and requests comments on the proposed regulations. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorization, and agency responses will be summarized in the final notice of our decision.

DATES:

Comments and information must be received no later than February 8, 2021.

ADDRESSES:

You may submit comments, identified by NOAA-NMFS-2020-0164, by the following method:

•

Comment submissions:

Submit all public comments via the Federal eRulemaking Portal, Go to

www.regulations.gov/#!docketDetail;D=NOAA-NMFS-2020-0164,

click the “Comment Now!” icon, complete the required fields, and enter or attach your comments.

Instructions:

Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing on

www.regulations.gov

without change. All personal identifying information (

e.g.,

name, address), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible. NMFS will accept anonymous comments (enter “N/A” in the required fields if you wish to remain anonymous). Attachments to electronic comments will be accepted in Microsoft Word, Excel, or Adobe PDF file formats only.

FOR FURTHER INFORMATION CONTACT:

Robert Pauline, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Availability

A copy of HRCP'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-hampton-roads-bridge-tunnel-expansion-project-hampton-0.

In case of problems accessing these documents, please call the contact listed above (see

FOR FURTHER INFORMATION CONTACT

Purpose and Need for Regulatory Action

This proposed rule would establish a framework under the authority of the MMPA (16 U.S.C. 1361

et seq.

) to allow for the authorization of take of marine mammals incidental to construction activities including pile installation and pile replacement, as part of the (HRBT). The HRBT is a major road transport infrastructure project conducted by HRCP along the existing I-64 highway in Virginia, consisting of roadway improvements, trestle bridges, and bored tunnels crossing the James River between Norfolk and Hampton. The project will address severe traffic congestion at the existing HRBT crossing by increasing traffic capacity and upgrading lanes. We received an application from HRCP requesting five-year regulations and authorization to take multiple species of marine mammals. Take would occur by Level A and Level B harassment only incidental to impact pile driving, vibratory pile driving, vibratory pile removal, jetting, and down-the-hole (DTH) pile installation. Please see Background below for definitions of harassment.

Legal Authority for the Proposed 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 five 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 Proposed 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 proposed rule containing five-year regulations, and for any subsequent LOAs. As directed by this legal authority, this proposed rule contains mitigation, monitoring, and reporting requirements.

Summary of Major Provisions Within the Proposed Rule

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

• Shutdown of construction activities under certain circumstances to avoid injury of marine mammals.

• Required monitoring of the construction areas to detect the presence of marine mammals before beginning construction activities.

• Soft start for impact pile driving to allow marine mammals the opportunity to leave the area prior to initiating impact pile driving at full power.

• Use of bubble curtains during impact driving of steel piles except when water depth is less than 20 feet.

Background

Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1361

et seq.

) directs 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, regulations are issued, and notice is provided to the public.

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), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of the takings are set forth.

NMFS has defined “negligible impact” in 50 CFR 216.103 as an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.

Except with respect to certain activities not pertinent here, 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).

National Environmental Policy Act

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

et seq.

) and NOAA Administrative Order (NAO) 216-6A, NMFS must review the proposed action (

i.e.,

the promulgation of regulations and subsequent issuance of an incidental take authorization) with respect to potential impacts on the human environment.

This action is consistent with categories of activities identified in Categorical Exclusion B4 (Incidental harassment authorizations (IHAs) with no anticipated serious injury or mortality) of the Companion Manual for NOAA Administrative Order 216-6A, which do not individually or cumulatively have the potential for significant impacts on the quality of the human environment and for which we have not identified any extraordinary circumstances that would preclude this categorical exclusion. Accordingly, NMFS has preliminarily determined that the issuance of the proposed IHA qualifies to be categorically excluded from further NEPA review.

We will review all comments submitted in response to this notice prior to concluding our NEPA process or making a final decision on the incidental take authorization request.

Summary of Request

On November 19, 2019, NMFS received an application from HRCP requesting authorization for take of marine mammals incidental to construction activities related to a major road transport infrastructure project along the existing I-64 highway in Virginia, consisting of roadway improvements, trestle bridges, and bored tunnels crossing Hampton Roads between Norfolk and Hampton, Virginia. HRCP submitted a revised LOA application on June 27, 2020 which included changes to construction methods. We determined the application was adequate and complete on September 29, 2020. On October 7, 2020 (85 FR 63256), we published a notice of receipt (NOR) of HRCP's application in the

Federal Register

, requesting comments and information related to the request for thirty days. No comments were received on the NOR.

HRCP requests authorization to take a small number of five species of marine mammals by Level A and Level B harassment only. Neither HRCP nor NMFS expects serious injury or mortality to result from this activity. The proposed regulations would be valid for five years (2021-2026). Note that HRCP had previously applied for an IHA to cover initial in-water pile driving work. NMFS issued the IHA on July 10, 2020 (85 FR 48153; August 10, 2020).

Description of Proposed Activity

HRCP is proposing to conduct construction activities associated with the HRBT project. This is a major road transport infrastructure project along the existing I-64 highway in Virginia, consisting of roadway improvements, trestle bridges, and bored tunnels crossing Hampton Roads between Norfolk and Hampton. The Project will address severe traffic congestion at the existing HRBT crossing by increasing capacity. The Project will include widening I-64 to create an eight-lane facility with a consistent six-lanes between the I-64/I-664 and I-64/I-564 Interchange, which could expand to eight-lanes during peak travel periods with the use of drivable shoulder lanes within the Project limits. The Project will include the construction of two new two-lane tunnels, expansion of the existing portal islands, and full replacement of the existing North and South bridge-trestles.

The proposed HRBT project would include pile installation and pile removal. Pile installation methods will include impact and vibratory driving, jetting, and DTH pile installation. Pile removal techniques for temporary piles will include vibratory pile removal or cutting three feet below the mudline. Impact pile installation is projected to take place at 3 to 4 locations simultaneously and there is the potential for as many as 7 pile installation locations operating concurrently with different hammer types. Pile installation and removal can occur at variable rates, from a few minutes one day to several hours the next. HRCP anticipates that between 1 to 10 piles could be installed per day, depending on project scheduling.

The proposed action may incidentally expose marine mammals occurring in the vicinity to elevated levels of underwater sound, thereby resulting in incidental take, by Level A and Level B harassment.

Dates and Duration

The proposed regulations would be valid for a period of five years (2021-2026). The specified activities may occur at any time during the five-year period of validity of the proposed regulations. HRCP expects pile driving and removal to occur six days per week. The overall number of anticipated days of pile installation and removal is 312 each year for years 1-4 and 181 days for year 5, based on a 6-day work week. Over five years this would result in an estimated total of 1,429 days of in-water construction work, which may last from a few minutes up to several hours per day.

HRCP plans to conduct work during daylight hours although pile installation and removal may extend into evening or nighttime hours as needed to accommodate pile installation requirements (

e.g.,

once pile driving begins, a pile will be driven to design tip elevation). In order to maintain pile integrity and follow safety precautions, pile installation or removal will continue after dark only for piles already in the process of being installed or removed. Installation or removal will not commence on new piles after dark.

Specific Geographic Region

The proposed project area is located in the waterway of Hampton Roads adjacent to the existing bridge and island structures of the HRBT. Hampton Roads is located at the confluence of the James River, the Elizabeth River, the Nansemond River, Willoughby Bay, and the Chesapeake Bay. Navigational channels are maintained by the U.S. Army Corps of Engineers (USACE) within Hampton Roads to provide transit to the many ports in the region. Maintained navigation channels near the project area consist of:

• Norfolk Harbor Entrance Reach (1,000 to 1,400 feet wide and is maintained at a depth of 50 feet Mean Lower Low Water [MLLW]);

• Hampton Creek Entrance Channel (200 feet wide and is maintained at a depth of 12 feet MLLW);

• Phoebus Channel (150 feet wide and is maintained at a depth of 12 feet MLLW); and

• Willoughby Channel (200 feet wide and is maintained at a depth of 10 feet MLLW).

Sediments are mostly fine and medium sands with various amounts of coarse sand and gravel, and low organic carbon content. There is no naturally occurring rocky or cobble bottom present at or adjacent to the project area. The North Shore in Hampton contains estuarine intertidal sandy shore,

estuarine intertidal reef, as well as submerged aquatic vegetation (SAV) in shallow estuarine open water. The North Trestle is located in estuarine open water with depths less than 15 feet below MLLW. The North Island is surrounded by estuarine intertidal sandy shore and rocky shore. Estuarine open water depths are primarily less than 15 feet below MLLW, but drop to approximately 25 feet below MLLW near the southwest corner of the island expansion closer to the Hampton Creek Entrance Channel. The South Island is also surrounded by estuarine intertidal sandy shore and rocky shore, followed by estuarine open water. The proposed island expansion is mainly in deep water (15 to 30 feet below MLLW), with a pocket of deeper water approximately 35 feet below MLLW to the west. The South Trestle is primarily located in estuarine open water with depths less than 15 feet below MLLW, with the exception of deep water (15 to 30 feet below MLLW) near the South Island approach. The north shore of Willoughby Bay contains estuarine intertidal sandy shore with two small pockets of estuarine intertidal emergent wetlands to the east. The Willoughby Bay Trestles are located in estuarine open waters with depths of less than 15 feet below MLLW, with the entire west bound trestle in water less than 6.6 feet below MLLW. Willoughby Bay contains an estuarine intertidal sandy shore and consists of estuarine open water with depths to 15 feet below MLLW.

A map of the HRBT Project Area is provided in Figure 1 below and Figures 1-1 and 2-1 in HRCP's application.

BILLING CODE 3510-22-P

EP08JA21.002

BILLING CODE 3510-22-C

The proposed project will widen I-64 for approximately 9.9 miles along I-64 from Settlers Landing Road in Hampton, Virginia, to the I-64/I-564 interchange in Norfolk, Virginia. The project will create an eight-lane facility with six consistent use lanes and will include full replacement of the North and South Trestle-Bridges, two new parallel tunnels constructed using a tunnel boring machine (TBM), expansion of the existing portal islands, and widening of the Willoughby Bay Trestle-Bridges, Bay Avenue Bridges, and Oastes Creek Bridges. Also, upland portions of I-64 will be widened to accommodate the additional lanes, the Mallory Street Bridge will be replaced, and the I-64 overpass bridges will be improved.

Table 1—HRBT Expansion Project Design Segments

Project design segment number and name

Construction area

Segment 1a (Hampton)

Area 1.

Segment 1b (North Trestle-Bridges)

Area 2.

Segment 2a (Tunnel)

Area 3.

Segment 3a (South Trestle-Bridge)

Area 2.

Segment 3b (Willoughby Spit)

Area 4.

Segment 3c (Willoughby Bay Trestle-Bridges)

Area 2.

Segment 3d (4th View Street Interchange)

Area 4.

Segment 4a (Norfolk-Navy)

Area 4.

Segment 5a (I-564 Interchange)

Area 4.

Indicates segment includes in-water construction activities.

The proposed project design is divided into five segments as shown in Table 1. However, only the sub-segments identified in Table 1 and described below would include in-water marine construction activities that have the potential to affect marine mammals:

Segment 1b—North Trestle-Bridges

This segment includes new and replacement north tunnel approach trestles, This segment is located in Construction Area 2 as shown in Figure 1 above and Figure 1-1 in HRCP's application.

Temporary Work Trestles for Bridge Construction at the North Trestle—Several temporary work trestles will support construction of the permanent eastbound and westbound North Trestle-Bridges. The temporary North Shore Work Trestle will support construction of the permanent eastbound North Trestle-Bridge in the shallow water (<4 to 6 feet Mean Low Water (MLW)) closer to the North Shore, avoiding the need to dredge or deepen this area. The temporary North Shore Work Trestle (194 36-inch steel pipe piles) will be installed under the 2020 IHA (85 FR 48153; August 10, 2020) and will be removed using a vibratory hammer at the end of the project under this LOA (See Table 6). Unless stated otherwise, all of the work described below will be conducted as part of the proposed LOA.

Additional temporary work trestles will support construction of the permanent westbound North Trestle-Bridge in the shallow water near the North Island. These work trestles will be the same or similar to the North Shore Work Trestle, steel structures founded on 36-inch diameter steel pipe piles with 30 to 40 feet spans sized to accommodate a 300-ton crane. Approximately 182 36-inch steel piles will be installed to support these trestles using a combination of vibratory and impact hammers except along the shoreline where drilling with a DTH hammer may be needed to install piles through the armor stone.

Once that portion of the permanent eastbound and westbound North Trestle-Bridge is complete, the temporary pile foundations will be removed using a vibratory hammer and the work trestle reused for similar purposes at a different location on the project (

e.g.,

Willoughby Bay Work Trestles).

Jump Trestles for Bridge Construction at the North Trestle—Jump Trestles are temporary heavy duty platforms used to support cranes and other equipment, will be used the North Trestle for constructing trestle bridges. Jump trestles are built with a maximum of three spans which are progressively removed and reinstalled one span at a time, moving forward with the construction of the adjacent structure. Each span is supported by six (6) temporary 36-inch steel pipe piles. The steel pipe piles will be installed, removed, and reinstalled as the spans move forward using a combination of vibratory and impact hammers for installation except along the shoreline where drilling with a DTH hammer may be needed to install piles through the armor stone and vibratory hammers will be used for removal. Approximately 270 individual pile installations and 270 removals will be needed to support the Jump Trestle movement for construction of the permanent westbound North Trestle-Bridge.

Templates and Permanent Piles at the North Trestle—Temporary template piles will be used to guide installation of the permanent concrete piles used to support the new North Trestle-Bridge (Table 7). The templates will be supported by four temporary steel piles up to 36-inch in diameter, generally one at each corner of the template. A two-tier template will be used to account for the possible batter of the permanent piles. Each template will allow installation of multiple permanent concrete piles. A vibratory hammer will be used to install and remove the temporary 36-inch steel piles supporting the template.

Five hundred and sixty-two (562) permanent 54-inch concrete cylinder piles will be installed using an impact hammer and will remain in place at the end of construction. Pre-drilling will be done in the open without the use of a casing.

The drill, drill steel, and auger would be in leads and either attached to the pile leads or used independently and indexed to the template to resist rotation. The auger is anticipated to be 54-inch in diameter and 10 feet or less in height.

In areas containing rock obstructions, a casing will be advanced prior to installation of the permanent North Trestle piles. The DTH hammer will advance a 60-inch (outer diameter) steel pipe pile casing before installation of the 54-inch concrete cylinder pile. Approximately 15 60-inch steel pipe casings may be required. The 60-inch steel pipe casings will be left in place and cut to an appropriate length to accommodate final island construction.

Demolition Trestle at the North Trestle—The North Trestle Demolition Trestle will consist of a series of jump trestles, similar to or the same as that used to construct the permanent westbound North Trestle-Bridge. The jump trestles will be located in the shallow water near the North Shore and will be installed, removed, and reinstalled as demolition of the existing structures moves from the shoreline towards deeper water. Each jump trestle used for demolition will be 45 feet wide and approximately 1,200 feet long. Each jump trestle span will be supported by temporary 36-inch steel pipe piles. Approximately 344 individual pile installations and 344 removals will be needed to support the jump trestle movements using a combination of vibratory and impact hammers for installation except along the shoreline where a DTH hammer may be needed to install piles through the armor stone and vibratory hammers will be used for removal.

Moorings at the North Shore Work Trestle—Mooring dolphins that were installed under the existing IHA (85 FR 48153; August 10, 2020) at the southern end and along the outside edge of the North Shore Work Trestle will be removed as part of the LOA. Each dolphin consists of three 24-inch steel piles (Table 6). An additional thirteen

(13) 42-inch steel pipe piles were installed along the outer edge of the work trestle to provide additional single mooring points for barges and vessels delivering material and accessing the trestle. The 24-inch steel pipe piles and 42-inch steel pipe piles will be removed using a vibratory hammer.

Sheet Piles at the North Shore Abutment—Approximately 187 temporary panels of steel sheet piles (AZ-700-19) will be installed using a vibratory hammer at the North Shore shoreline to support excavation and construction of the North Shore Abutment. Most of this work is planned to be done at lower tides so that in-water work is minimized. However, some installation work below the tidal elevations (in-water) can be expected. Sheet piles will be removed using a vibratory hammer.

Segment 2a—Tunnel

This segment includes new bored tunnels, the tunnel approach structures, buildings, the North Island improvements for tunnel facilities, and South Island improvements. This segment is located in Construction Area 3 as shown in Figure 1.

Moorings at the North Island Expansion—Eighty (80) temporary moorings were installed along the perimeter of the North Island Expansion (North and South) under the existing IHA (HRCP 2020). All moorings will be removed using a vibratory hammer or cut to approximately 3 feet below the mudline.

Hampton Creek Approach Channel Marker at the North Island—An existing pile-mounted (Aid to Navigation) channel marker at the entrance to the Hampton Creek Approach Channel will be removed and relocated to allow expansion of the North Island. It will be removed using a vibratory hammer and a new permanent pile (36-inch steel pile) will be installed using a vibratory hammer.

Steel sheet piles will be installed as part of the North Island Expansion and at the shoreline of the North Island (Attachment 1, Figure 9) to support excavation and construction of the North Island Abutments and Expansion. Approximately 54 panels of sheet pile will be installed using a vibratory hammer around the perimeter of the North Island Expansion to support dredge and replacement of native soft soils. An additional 122 sheet pile panels will be installed around the perimeter of the North Island Expansion to support construction of the abutment and tunnel approach structure.

Approximately 128 panels of sheet pile will be installed at the North Island shoreline to support excavation and construction of the North Island Abutment. Most of this work is expected to be done at lower tides so that in-water work is minimized. However, some sheet pile installation work below the tidal elevations (in-water) can be expected. All sheet piles will be removed using a vibratory hammer.

TBM Platform at the South Island—HRCP is constructing the temporary TBM Platform or “quay” at the South Island to allow for the delivery, unloading, and assembly of the TBM components from barges to the Island. The installation of the TBM platform will occur under the existing IHA (HRCP 2020).

The TBM Platform is a steel structure erected on 216 36-inch diameter steel piles, with an overall area of approximately 0.70 acre (approximately 377 feet x 81 feet). The TBM Platform piles will be removed using a vibratory hammer or cut to approximately 3 feet below the mudline at the conclusion of the project.

Conveyor Trestle at the South Island—Tunnel boring spoils and other related materials will be moved between the South Island and barges via a conveyor belt and other equipment inside the tunnel boring. The Conveyor Trestle will also be used for maintenance and mooring of barges and vessels carrying TBM materials and other project-related materials. The Conveyor Trestle will be erected on 84 36-inch diameter steel piles. Installation of the Conveyor Trestle will occur under the existing IHA (85 FR 48153; August 10, 2020). At the conclusion of the project, the Conveyor Trestle piles will be removed using a vibratory hammer or cut to approximately 3 feet below the mudline.

Settlement Reduction Piles and Deep Foundation Piles at the South Island—Existing geotechnical conditions at the planned South Island Expansion will require additional considerations to reduce island settlement and support roadway construction. Therefore, approximately 394 24-inch steel pipe settlement reduction piles and 507 30-inch concrete-filled steel pipe deep foundation piles will be installed at the South Island Expansion to address these geotechnical conditions. The settlement reduction piles and the deep foundation piles will be installed using vibratory and impact hammers. Furthermore, the use of drilling with a DTH hammer may be needed to install the deep foundation piles through the armor stone. Temporary templates (Table 7) will be supported by four temporary steel pipe piles up to 36-inch in diameter that will be spudded in place and used to align the piles during installation. Steel sheet piles will be installed to partially enclose the deep foundation piles as installation progresses north to south along the island expansion area. For steel pipe piles in water depths greater than 20 feet, a bubble curtain will be used for pile installation to reduce hydroacoustic impacts caused by the impact hammer. A portion of the settlement reduction piles and deep foundation piles will be installed using a bubble curtain. See Mitigation for additional detail.

Moorings at the South Island—Temporary moorings will be installed along the perimeter of the South Island Expansion to support the construction of the island expansion. Twenty-five (25) 42-inch steel pipe piles will be installed to provide mooring points for barges and vessels. The mooring point piles will be installed using a vibratory hammer and eventually removed using a vibratory hammer.

Sheet Piles at the South Island Expansion and Abutment—Steel sheet piles will be installed as part of the South Island Expansion and at the shoreline of the South Island to support excavation and construction of the South Island Abutment. Approximately 152 panels of AZ-700-26 sheet pile will be installed around the perimeter of the South Island Expansion deep foundation piles using a vibratory hammer as pile installation progresses to support backfilling.

In addition, approximately 226 panels of AZ-700-26 temporary steel sheet pile will be installed around the perimeter of the South Island Expansion to support dredge and replacement of native soft soils. Temporary steel sheet piles will be installed using a vibratory hammer and will be removed using a vibratory hammer after completion of dredging/replacement works.

Approximately 70 panels of AZ-700-19 sheet pile will be installed at the South Island shoreline to support excavation and construction of the abutment and tunnel approach structure at the South Island. Similar to the North Shore Abutment work, most of this work is expected to be done at lower tides so that in-water work is minimized. However, some sheet pile installation work below the tidal elevations (in-water) can be expected. All sheet piles will be removed using a vibratory hammer.

Segment 3a—South Trestle-Bridge

This segment includes the new South Trestle-Bridge and any bridge elements that interface with the South Island to the south end of the south abutments at Willoughby Spit. This segment is

located in Construction Area 2 as shown in Figure 1.

Moorings at the South Trestle—Temporary moorings will be installed in the area of the South Trestle to support the construction of temporary work trestles and permanent trestle bridges. The installation of the moorings at the South Trestle will be performed under the existing IHA (HRCP 2020). The temporary moorings will be removed at the conclusion of the project using a vibratory hammer.

Temporary Work Trestles for Bridge Construction at the South Trestle—Several temporary work trestles will support construction of the temporary bridges used for maintaining traffic at the South Trestle during construction (

i.e.,

temporary MOT bridges) and will serve as temporary docks for delivery of deck elements and other materials. The South Trestle Work Trestles will consist of two separate structures at the South Island shoreline (South Island South 1 and 2) and a third structure at the South Shore or Norfolk shoreline.

The temporary South Trestle Work Trestle at South Island South 1 is a steel structure approximately 504 feet long and 44 feet wide, founded on 72 36-inch diameter steel piles with 30 to 40 feet spans sized to accommodate a 300-ton crane. Once the permanent roadway is complete, the temporary MOT Bridge will be removed as well as the South Island South 1 Work Trestle, including the temporary pile foundations and mooring piles. They will be removed via vibratory hammer and the work trestle will be reused for similar purposes at a different project location.

The temporary South Trestle Work Trestle at South Island South 2 is a steel structure approximately 634 feet long and 54 feet wide, founded on 90 36-inch diameter steel piles with 30 to 40 feet spans sized to accommodate a 300-ton crane. The pile foundations will be removed using a vibratory hammer once the permanent roadway is complete.

The temporary South Trestle Work Trestle at the South Shore or Norfolk shoreline will be similar to that used elsewhere on the project. The work trestle will be approximately 500 feet long and 66 feet wide with four 30 feet wide finger piers. The finger piers will consist of 94 36-inch diameter steel piles installed using a vibratory hammer.

Temporary steel pile foundations for each of the work trestles will be installed using vibratory and impact hammers. A bubble curtain will be used during installation of steel pipe piles in water depths greater than 20 feet. Some areas near the shores and islands will require the use of drilling with a DTH hammer to install the temporary piles. The South Trestle Work Trestle pile foundations will be removed using a vibratory hammer.

Templates and Permanent Piles at the South Trestle—Temporary template piles (Table 7) will be used to guide installation of the permanent concrete piles used to support the new South Trestle-Bridge. The templates will use four temporary steel piles up to 36-inch in diameter as supports, generally one at each corner of the template. A two-tier template will be used to account for the possible batter of the piles. Each template will allow installation of multiple permanent concrete piles. A vibratory hammer will be used to install and remove the temporary 36-inch steel piles supporting the template.

Eight hundred and ten (810) permanent 54-inch concrete cylinder piles will be installed using an impact hammer and will remain in place at the end of construction. Pre-drilling will be done in the open without the use of a casing. The drill, drill steel, and drill auger would be in leads and either attached to the pile leads or used independently and indexed to the template to resist rotation. The drill auger is anticipated to be 54-inch in diameter and 10-feet less in height. It is expected that the drill, drill steel, and drill auger would have almost no impact on noise levels.

In areas where there may be rock obstructions, such as at the toe of the existing South Island slope, a casing will be advanced prior to installation of the permanent South Trestle piles. The DTH hammer will advance a 60-inch (outer diameter) steel pipe pile casing before installation of the 54-inch concrete cylinder pile. Approximately 65 60-inch steel pipe casings may be required. The 60-inch steel pipe casings will be left in place and cut to an appropriate length to accommodate final island construction.

Jump Trestle for Bridge Construction at the South Trestle—Temporary jump trestles will be used for constructing trestle bridges (both new permanent and temporary MOT bridges) at the South Trestle. A combination of jump trestles and working from the existing trestles will be used to build the new trestle bridges.

The 36-inch steel pipe piles will be installed, removed, and reinstalled as the spans move forward using a combination of vibratory and impact hammers for installation except along the shoreline where drilling with a DTH hammer may be needed to install piles through the armor stone. Vibratory hammers will be used for removal. A bubble curtain will be used for installation of steel pipe piles in water depths greater than 20 feet. Approximately 420 individual pile installations and 420 removals will be needed to support the jump trestle movement for construction of the permanent westbound South Trestle-Bridge.

Temporary MOT Trestles at the South Trestle—Two temporary MOT Trestle bridges at the South Trestle will be used to phase construction and carry traffic prior to completion of the new structures. The eastbound traffic will be shifted on the new MOT Trestle to allow for a partial demolition of the existing eastbound bridge-trestle. Once the partial demolition is completed, the new eastbound connection to the eight-lane trestle will be built with the support of a jump trestle and eastbound traffic will be shifted on it. A temporary MOT Trestle will be built from South Island next to the existing westbound trestle. The westbound traffic will be shifted on the new MOT Trestle to allow for a partial demolition of the existing westbound bridge-trestle. A portion of the existing eastbound bridge-trestle will also be demolished to allow the new connection between the eight-lane structure and the new westbound bridge-trestle. The temporary MOT Trestle at the South Trestle will be a steel structure erected on 218 36-inch steel pipe piles that will be installed using a combination of vibratory and impact hammers except along the shoreline where drilling with a DTH hammer may be needed to install piles through the armor stone. A bubble curtain will be used for installation of steel pipe piles in water depths greater than 20 feet. Pile foundations will be removed using a vibratory hammer.

Thirty 42-inch steel pipe pile casings will be installed using a vibratory hammer in areas where the MOT trestle is in the footprint of the South Island Expansion. The 42-inch steel pipe pile casings will be left in place and cut to an appropriate length to accommodate final island construction.

Demolition Trestle at the South Trestle—The South Trestle Demolition Trestle will be similar to the work trestles previously described (

e.g.

Demolition Trestle at the North Trestle). Located at the South Shore, the South Trestle Demolition Trestle will be used to access the shallow water at the South Shore and support equipment used to remove the existing trestle structure. Approximately 72 36-inch steel pipe piles will be installed with a combination of vibratory and impact hammers. Some areas near the shores and islands will require the use of a DTH hammer to install the temporary

piles. At the conclusion of the project, the South Trestle Demolition Trestle will be removed using a vibratory hammer.

Segment 3C—Willoughby Bay Trestle-Bridges

This segment includes the new South Trestle-Bridge and any bridge elements that interface with the South Island to the south end of the south abutments at Willoughby Spit. This segment is located in Construction Area 2 as shown in Figure 1.

Moorings at Willoughby Bay—Temporary moorings will be installed in Willoughby Bay to support the construction of temporary work trestles and permanent trestle bridges, and to provide a safe haven (harbor of safe refuge) for vessels in the event of severe weather. Moorings will consist of six dolphins—each consisting of three 24-inch steel piles—and 50 42-inch steel pipe piles. The mooring dolphin piles and the single mooring point piles will be installed under the existing IHA (85 FR 48153; August 10, 2020).

An additional 40 42-inch steel pipe piles will be installed in Willoughby Bay to complete the safe haven (50 42-inch piles will be installed under the existing IHA; HRCP 2020). The moorings will be configured as two 2,000-feet long lines with a 42-inch mooring pile every 80-feet. The piles will be installed using a vibratory hammer and removed at the conclusion of the project using a vibratory hammer.

Temporary Work Trestles for Bridge Construction at Willoughby Bay—The existing Willoughby Bay Bridge structure will be modified by widening the two existing structures to the outside in both directions to accommodate new travel lanes, shoulders, and new sound walls. This will require installation of two to three additional piles at each pier location on the outside of both eastbound and westbound structures. Two temporary work trestles, each approximately 500 feet long and 45 feet wide, will be installed along the outside edge of the existing eastbound structure to provide access in the shallow water area near both shorelines. Approximately 212 36-inch steel pipe piles will be installed using a combination of vibratory and impact hammers to support the temporary work trestles. The temporary steel piles will be removed using a vibratory hammer.

Jump Trestle for Bridge Construction at Willoughby Bay—A combination of jump trestles and working from the existing trestles will be used to construct the widening of the existing Willoughby Bay westbound roadway. Similar to other locations (

e.g.,

Jump Trestle at the North Trestle see Section), the jump trestle will be supported by temporary 36-inch steel pipe pile foundations that will be installed, removed, and reinstalled as the spans move forward using a combination of vibratory and impact hammers for installation and vibratory hammers for removal. Approximately 544 individual pile installations and 544 removals will be needed to support the jump trestle movement across Willoughby Bay.

Templates and Permanent Piles at Willoughby Bay—Temporary template piles (Table 7) will be used to guide installation of the permanent concrete piles used to support widening of the eastbound and westbound Willoughby Bay roadway. The templates will be supported by four temporary steel piles up to 36-inch in diameter with one at each corner of the template.

A vibratory hammer will be used to install and remove the temporary 36-inch steel piles supporting the template. Some areas near the shorelines may require the use of a DTH hammer to install the templates (Table 7).

Five hundred and four (504) 24-inch concrete square permanent piles will be installed using an impact hammer and will remain in place at the end of construction. Where geotechnical conditions require, the permanent piles may also be installed via jetting. Where jetting is required, an outer steel pipe pile casing (up to 42-inch in diameter) may be installed using a vibratory hammer before installation of the concrete pile. Approximately 300 casings (60 percent of the 504 concrete piles) will be installed prior to installing the concrete piles. The casing will be driven and the sediment and sand removed from the casing prior to installing the permanent pile. The casing will be removed using a vibratory hammer.

Segment 3b—Willoughby Spit Laydown Area

This segment includes the Willoughby Spit Laydown Area which is a temporary construction staging and laydown area that will include the installation and removal of temporary piers. This segment is located in Construction Area 4 as shown in Figure 1.

Temporary Docks on Spuds and Piles at the Willoughby Spit Laydown Area—HRCP has been granted use of property on Willoughby Spit next to the South Trestle-Bridge to be used for laydown areas and as a base for marine operations. Two temporary piers will be constructed to allow barge access: One will be a fixed pier on 44 36-inch steel pipe piles, and the other will be a floating dock on 8 36-inch steel pipe (spuds) piles. Piles will be installed using vibratory and impact hammers, as well as a pile template. The pile template will be supported by four temporary steel piles up to 36-inch in diameter (Table 7). The temporary piers, including the steel pile foundations, will be removed upon completion of the Project via vibratory hammer.

Temporary Finger Piers on Timber Piles at the Willoughby Spit Laydown Area—The existing bulkheads and piers located on the inside of Willoughby Spit will be repaired to provide access for crew boats and similar-sized vessels. Three timber piers will replace the existing piers and will be constructed using 36 16-inch CCA timber piles, each pier consisting of 12 16-inch CCA timber piles. The piles will be installed using a vibratory hammer. Any existing timber piers will be pulled out of place.

HRCP plans to employ five methods of pile installation including vibratory hammer, impact hammer, pre-drilling, jetting, and use of DTH hammers. More than one installation method could be used within a day and at each location and multiple piles could be installed and/or removed concurrently. Steel pipe piles will most likely be installed using a combination of vibratory (ICE 416L or similar) and impact hammers (S35 or similar). Approximately 80 percent of the time steel pipe piles will be installed using a vibratory hammer while an impact hammer will be used approximately 20 percent of the time. Most piles will be advanced using vibratory methods and then impact driven to final tip elevation.

Temporary steel pile templates will be used to set permanent piles. Templates will be positioned and held in place using spuds or steel pipe piles, up to 36-inch diameter with one at each corner of the template. Template piles are temporary and generally do not bear significant vertical loads, therefore installation (

i.e.,

driving) and removal of template piles requires minimal driving time, estimated at approximately 5 minutes per spud (see Table 7). Permanent concrete piles will be installed using an impact hammer only, although permanent concrete piles may also be installed via jetting at Willoughby Bay. During jetting, high-pressure water is sprayed out of the bottom of the pile to help penetrate dense sand layers and allow pile driving with lower hammer impact energies. Jetting will only be conducted at depth once sufficient resistance to pile installation has been met. Where jetting is required, an outer steel pipe pile casing may be installed before

installation of the square concrete piles at Willoughby Bay. Casings will be driven using a vibratory hammer and the sediment and sand removed from the casing prior to driving the permanent concrete pile. HRCP assumed, and NMFS agrees, that jetting will be quieter than vibratory installation of the same pile size, but data for this activity are limited; therefore, sound source levels (SSLs) for vibratory installation were applied to jetting.

Pre-drilling will be performed on the 54-inch concrete cylinder permanent piles without the use of a casing in the open. The drill, drill steel, and auger will be in leads and either attached to the pile leads or used independently and indexed to the template to resist rotation. A 54-inch diameter auger 10-feet or less in height is expected to be employed. Pre-drilling will be conducted to loosen soils directly underneath the pile to maximize pile advancement before the drive and shorten the length of driving time. Pre-drilling may reduce driving times by as much as 50 percent and pre-drilling depth is expected to be less than half the pile length. HRCP may drill to within 3-4 diameters above the final tip elevation in cases of dense sand. HRCP assumed and NMFS agrees that use of the drill, drill turntable, drill steel, drill auger, and drill bit will not result in harassment. These devices have low source levels and, therefore, low signal-to-noise ratios. The signal characteristics (continuous noise) would be occurring in a relatively noisy coastal environment where low-level continuous noise is common. Therefore, they would be unlikely to provoke a reaction consistent with what we would consider to be harassment. Therefore, harassment zone sizes were not estimated for these activities. These devices simply rotate in the sediments and do not displace them without creating a hole. No pile is installed during pre-drilling, and much less energy is expended than during pile installation. The equipment and nature of the act of pre-drilling in soils produce minimal noise and the pre-drilling will significantly reduce the driving time which in turn reduces the total noise levels.

The pile installation methods used will depend on sediment depth and conditions at each pile location. Table 2 through Table 7 provides additional information on the pile driving operation including estimated pile driving times. Note that the sum of the days of pile installation and removal is greater than the anticipated number of days because more than one pile installation method will be used within a day and at each location. The overall number of anticipated days of pile installation and removal is 312 per year, based on a six-day work week for years 1-4. Year 5 will require an estimated 181 days of in-water work. It is possible that installation and removal numbers might shift from one month to another depending on schedule constraints.

HRCP will employ a bubble curtain when installing steel pipe piles in water depths greater than 20 feet to minimize hydroacoustic impacts caused by the impact hammer. Bubble curtains will be used at the South Island to install a portion of the permanent settlement reduction piles and deep foundation piles and at the South Trestle to install a portion of the Temporary MOT Trestle, Jump Trestle, and Work Trestle.

Before installing steel pipe piles near shorelines protected with rock armor and/or rip rap (

e.g.,

South Island shoreline; North Shore shoreline) the rock armoring that protects the shoreline will need to be temporarily shifted to an adjacent area to allow for the installation of the piles. The rock armor should only be encountered at the shoreline and at relatively shallow depths below the mudline. Any rock armor stone and/or rip rap that has been moved will be reinstalled near its original location following the completion of pile installation.

DTH pile installation uses both rotary and percussion-type drill devices and will be used frequently. The device consists of a drill bit that drills through stone using both rotary and pulse impact mechanisms. This breaks up the stone to allow removal of the fragments and insertion of the pile. The pile is usually advanced at the same time that drilling occurs. Drill cuttings are expelled from the top of the pile using compressed air and will be directed through a pipe to a designated location for waste.

Piles may be also be installed without moving the armor stone by first drilling through the stone with a DTH hammer. It is estimated that drilling with a DTH hammer will be used for approximately 1 to 2 hours per pile, when necessary. It is anticipated that approximately 7 percent of the North Shore Work Trestle piles, 4 percent of the North Trestle Jump Trestle piles, 7 percent of the North Trestle Demolition Trestle piles, 100 percent of the North Trestle Casings, 14 percent of the South Trestle Work Trestle piles, 6 percent of the South Trestle Jump Trestle piles, 10 percent of the South Trestle Temporary MOT Trestle piles, 17 percent of the South Trestle Demolition Trestle piles, 100 percent of the South Trestle Casings, and 10 percent of the South Island deep foundation piles may require installation with a DTH hammer (See Table 2 through Table 6).

Temporary steel sheet piles and steel pipe piles will be removed using a vibratory hammer or cut to approximately 3 feet below the mudline. Temporary concrete piles will only be removed by cutting to approximately 3 feet below the mudline.

Table 2 through 6 below show the number and types of piles planned for installation and removal each year by component and segment while Table 7 shows the total number of template piles over five years by location.

Table 2—Numbers and Types of Piles To Be Installed and Removed During LOA Year One for Each HRBT Project Component and Segment

Project

component

Pile size/

type and

material

Total

number of

piles

to be

installed

Total

number of

piles to be

removed

Embedment

length

(feet)

Number of

piles

down-the-

hole

Average

down-the-

hole

duration per pile

(minutes)

Number of

piles vibrated/

hammered

Average

vibratory

duration

per pile

(minutes)

Approximate

number of

impact strikes per pile

Number of

piles per

day per

hammer

Estimated

total number

of hours of

installation

and removal

Number of

days of

installation

and removal

North Trestle (Segment 1b)

Permanent Piles

54-inch Concrete Cylinder Pipe

188

140

188

2,100

376

188

Casing

60-inch Steel Pipe

120

North Shore Abutment

AZ 700-19 Steel Sheet

126

North Island (Segment 2a)

Hampton Creek Approach Channel Marker

Existing, 36-inch Steel Pipe

North Island Expansion

AZ 700-26 Steel Sheet

176

352

176

Willoughby Bay (Segment 3c)

Work Trestle

36-inch Steel Pipe

212

100

212

177

106

Moorings (Safe Haven)

42-inch Steel Pipe

Permanent Piles

24-inch Concrete Square Pipe

402

140

402

2,100

804

402

Casing

42-inch Steel Pipe

240

480

160

Willoughby Spit (Segment 3b)

Dock on Spuds, Floating Dock

36-inch Steel Pipe

100

Dock on Piles, Fixed Pier

36-inch Steel Pipe

100

Finger Piers on Timber Piles

16-inch CCA* Timber

South Trestle (Segment 3a)

Work Trestle

36-inch Steel Pipe

156

100

120

134

130

Temporary MOT * Trestle

36-inch Steel Pipe

113

100

120

102

Casing

42-inch Steel Pipe

Permanent Piles

54-inch Concrete Cylinder Pipe

252

140

252

2,100

504

252

Casing

60-inch Steel Pipe

120

130

South Island (Segment 2a)

Settlement Reduction Piles

24-inch Steel Pipe

Deep Foundation Piles

30-inch Steel Pipe, Concrete Filled

120

Moorings

42-inch Steel Pipe

South Island Abutment

AZ 700-19 Steel Sheet

Total

2,184

480

1,296

Table 3—Numbers and Types of Piles To Be Installed and Removed During LOA Year Two for Each HRBT Project Component and Segment

Project

component

Pile size/

type and

material

Total

number of

piles

to be

installed

Total

number of

piles to be

removed

Embedment

length

(feet)

Number of

piles

down-the-

hole

Average

down-the-

hole

duration

per pile

(minutes)

Number of

piles vibrated/

hammered

Average

vibratory

duration

per pile

(minutes)

Approximate

number of

impact strikes per pile

Number of

piles per

day per

hammer

Estimated

total number

of hours of

installation

and removal

Number of

days of

installation

and removal

North Trestle (Segment 1b)

North Shore Work Trestle

36-inch Steel Pipe

194

100

194

162

Work Trestle

36-inch Steel Pipe

182

100

120

170

152

Jump Trestle

36-inch Steel Pipe

100

120

Permanent Piles

54-inch, Concrete Cylinder Pipe

102

140

102

2,100

204

102

North Island (Segment 2a)

North Island Abutment

AZ 700-19 Steel Sheet

Willoughby Bay (Segment 3c)

Jump Trestle

36-inch Steel Pipe

100

160

134

Work Trestle

36-inch Steel Pipe

126

100

126

105

Permanent Piles

24-inch Concrete Square Pipe

102

140

102

2,100

204

102

Casing

42-inch Steel Pipe

120

South Trestle (Segment 3a)

Work Trestle

36-inch Steel Pipe

100

120

Jump Trestle

36-inch Steel Pipe

175

100

120

350

292

175

Temporary MOT * Trestle

36-inch Steel Pipe

105

100

120

Permanent Piles

54-inch Concrete Cylinder Pipe

168

140

168

2,100

336

168

South Island (Segment 2a)

Settlement Reduction Piles

24-inch Steel Pipe, Steel

370

Deep Foundation Piles

30-inch Steel Pipe, Concrete Filled

425

120

383

425

South Island Abutment

AZ 700-19 Steel Sheet

South Island Expansion

AZ 700-26 Steel Sheet

378

756

189

Total

2,401

1,071

1,226

Table 4—Numbers and Types of Piles To Be Installed and Removed During LOA Year Three for Each HRBT Project Component and Segment

Project

component

Pile size/type and material

Total

number of

piles to be

installed

Total number

of piles to be

removed

Embedment length

(feet)

Number of piles down-the-hole

Average down-

the-hole

duration

per pile

(minutes)

Number of piles

vibrated/

hammered

Average vibratory duration per pile

(minutes)

Approximate number of impact strikes per pile

Number of piles per day per hammer

Estimated

total number

of hours of

installation

and removal

Number of days of

installation and removal

North Trestle (Segment 1b)

Jump Trestle

36-inch Steel Pipe

228

232

100

120

451

376

226

Permanent Piles

54-inch, Concrete Cylinder Pipe

187

140

187

2,100

374

187

North Shore Abutment

AZ 700-19 Steel Sheet

124

North Island (Segment 2a)

North Island Abutment

AZ 700-19 Steel Sheet

128

160

Willoughby Bay (Segment 3c)

Jump Trestle

36-inch Steel Pipe

460

468

100

928

774

464

Work Trestle

36-inch Steel Pipe

100

South Trestle (Segment 3a)

Jump Trestle

36-inch Steel Pipe

245

100

120

476

397

238

Demolition Trestle

36-inch Steel Pipe

100

120

Work Trestle

36-inch Steel Pipe

182

100

182

152

Temporary MOT * Trestle

36-inch Steel Pipe

110

100

110

Permanent Piles

54-inch Concrete Cylinder Pipe

196

140

196

2,100

392

196

South Island (Segment 2a)

South Island Abutment

AZ 700-19 Steel Sheet

Total

1,471

1,559

1,569

Table 5—Numbers and Types of Piles To Be Installed and Removed During LOA Year Three for Each HRBT Project Component and Segment

Project

component

Pile size/type and material

Total

number of piles to be

installed

Total number of piles to be removed

Embedment length

(feet)

Number of piles down-the-hole

Average down-

the-hole

duration

per pile

(minutes)

Number of piles

vibrated/

hammered

Average vibratory duration per pile

(minutes)

Approximate number of impact strikes per pile

Number of piles per day per hammer

Estimated total number of hours of

installation and removal

Number of days of

installation and removal

North Trestle (Segment 1b)

Demolition Trestle

36-inch Steel Pipe

344

172

100

120

492

410

246

Permanent Piles

54-inch, Concrete Cylinder Pipe

140

2,100

170

North Shore Abutment

AZ 700-19 Steel Sheet

124

South Trestle (Segment 3a)

Demolition Trestle

36-inch Steel Pipe

100

120

119

Work Trestle

36-inch Steel Pipe

100

Temporary MOT * Trestle

36-inch Steel Pipe

108

100

108

Permanent Piles

54-inch Concrete Cylinder Pipe

194

140

194

2,100

388

194

South Island (Segment 2a)

TBM Platform

36-inch Steel Pipe

216

140

216

108

Conveyor Trestle

36-inch Steel Pipe

100

Total

742

788

839

Table 6—Numbers and Types of Piles to be Installed and Removed during LOA Year Five for Each HRBT Project Component and Segment

Project

component

Pile size/type and material

Total

number of piles to be

installed

Total number of piles to be removed

Embedment length

(feet)

Number of piles down-the-hole

Average down-

the-hole

duration per pile

(minutes)

Number of piles

vibrated/

hammered

Average

vibratory

duration per pile

(minutes)

Approximate number of impact strikes per pile

Number of piles per day per hammer

Estimated total number of hours of

installation and removal

Number of days of

installation and removal

North Trestle (Segment 1b)

Moorings

42-inch Steel Pipe

Moorings

24-inch Steel Pipe

Work Trestle

36-inch Steel Pipe

182

100

182

152

Demolition Trestle

36-inch Steel Pipe

172

100

172

144

North Island (Segment 2a)

Moorings

42-inch Steel Pipe

Willoughby Bay (Segment 3c)

Moorings

42-inch Steel Pipe

Moorings

24-inch Steel Pipe

Moorings

(Safe Haven)

42-inch Steel Pipe

Willoughby Spit (Segment 3b)

Dock on Spuds, Floating Dock

36-inch Steel Pipe

100

Dock on Piles, Fixed Pier

36-inch Steel Pipe

100

Finger Piers on Timber Piles

16-inch CCA *, Timber

South Trestle (Segment 3a)

Moorings

42-inch Steel Pipe

Moorings

24-inch Steel Pipe

South Island (Segment 2a)

Mooring

42-inch Steel Pipe

Total

830

271

Table 7—Numbers of Template Piles (Up to 36-Inch Steel Pipe Piles) To Be Installed and Removed Using a Vibratory Hammer for the HRBT Project

Project component/location

Pile size/type and material

Estimated

number of

template piles to be installed

Estimated

number of

template piles to be removed

Average down-the-hole

duration per pile

(minutes)

Average

vibratory

duration per

template pile

(minutes)

Number of piles per day per

component

(install and

removal)

North Trestle Permanent Piles

54-inch Concrete Cylinder Pipe

750

South Trestle Permanent Piles

54-inch Concrete Cylinder Pipe

1080

Willoughby Bay Permanent Piles

24-inch Concrete Square Pipe

672

Willoughby Spit Fixed Pier *

36-inch Steel Pipe

Willoughby Spit Floating Pier *

36-inch Steel Pipe

South Island Deep Foundation Piles

30-inch Steel Pipe, Concrete Filled

676

120

South Island Settlement Reduction Piles

24-inch Steel Pipe

526

Estimated Total Template Pile Driving Actions

3,774

Total number of Temporary Template Pile Driving action

7,584

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

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. Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SAR);

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

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 8 lists all species with expected potential for occurrence in the project area and summarizes information related to the population or stock, including regulatory status under the MMPA and ESA and potential biological removal (PBR), where known. For taxonomy, we follow Committee on Taxonomy (2020). 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 mortality is anticipated or authorized here, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species 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's 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 managed stocks in this region are assessed in NMFS's U.S. Atlantic and Gulf of Mexico SARs (

e.g.,

Hayes

et al.,

2020). All values presented in Table 8 are the most recent available at the time of publication and are available in the 2019 SARs (Hayes

et al.,

2020).

Table 8—Marine Mammal Species Likely To Occur Near the Project Area

Common name

Scientific name

Stock

ESA/MMPA status; strategic (Y/N)

Stock

abundance

(CV, N

min

most recent

abundance

survey)

PBR

Annual M/SI

Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)

Family Balaenopteridae (rorquals):

Humpback whale

Megaptera novaeangliae

Gulf of Maine

-,-; N

1,396 (0; 1,380; see SAR)

12.15

Superfamily Odontoceti (toothed whales, dolphins, and porpoises)

Family Delphinidae:

Bottlenose dolphin

Tursiops truncatus

Western North Atlantic (WNA) Coastal, Northern Migratory

-,-; Y

6,639 (0.41; 4,759; 2011)

6.1-13.2

WNA Coastal, Southern Migratory

-,-; Y

3,751 (0.06; 2,353; 2011)

0-14.3

Northern North Carolina Estuarine System (NNCES)

-,-; Y

823 (0.06; 782; 2013)

7.8

0.8-18.2

Family Phocoenidae (porpoises):

Harbor porpoise

Phocoena phocoena

Gulf of Maine/Bay of Fundy

-, -; N

95,543 (0.31; 74,034; see SAR)

851

217

Order Carnivora—Superfamily Pinnipedia

Family Phocidae (earless seals):

Harbor seal

Phoca vitulina

WNA

-; N

75,834 (0.15; 66,884, see SAR)

2,006

350

Gray seal

Halichoerus grypus

WNA

-; N

27,131 (0.19, 23,158, see SAR)

1,359

5,410

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.

NMFS marine mammal stock assessment reports online at:

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

CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.

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.

The NMFS stock abundance estimate applies to U.S. population only, however the actual stock abundance is approximately 451,431.

As indicated above, all five species (with seven managed stocks) in Table 8 temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur, and we have proposed authorizing take. While North Atlantic right whales (

Eubalaena glacialis

), minke whales (

Balaenoptera acutorostrata acutorostrata

), and fin whales (

Balaenoptera physalus

) have been documented in the area, the temporal and/or spatial occurrence of these whales is such that take is not expected to occur, and they are not discussed further beyond the explanation provided here.

Based on sighting data and passive acoustic studies, the North Atlantic right whale could occur off Virginia year-round (DoN 2009; Salisbury

et al.,

2016). They have also been reported seasonally off Virginia during migrations in the spring, fall, and winter (CeTAP 1981, 1982; Niemeyer

et al.,

2008; McLellan 2011b, 2013; Mallette

et al.,

2016a, 2016b, 2017, 2018a; Palka

et al.,

2017; Cotter 2019). Right whales are known to frequent the coastal waters of the mouth of the Chesapeake Bay (Knowlton

et al.,

2002) and the area is a seasonal management area (November 1-April 30) mandating reduced ship speeds out to approximately 20 nautical miles for the species; however, the project area is further inside the Bay.

North Atlantic right whales have stranded in Virginia, one each in 2001, 2002, 2004, 2005: Three during winter (February and March) and one in summer (September) (Costidis

et al.,

2017, 2019). In January 2018, a dead, entangled North Atlantic right whale

was observed floating over 60 miles offshore of Virginia Beach (Costidis

et al.,

2019). All North Atlantic right whale strandings in Virginia waters have occurred on ocean-facing beaches along Virginia Beach and the barrier islands seaward of the lower Delmarva Peninsula (Costidis

et al.,

2017). Due to the low occurrence of North Atlantic right whales near the project area, NMFS is not proposing to authorize take of this species.

Fin whales have been sighted off Virginia (Cetacean and Turtle Assessment Program (CeTAP) 1981, 1982; Swingle

et al.,

1993; DoN 2009; Hyrenbach

et al.,

2012; Barco 2013; Mallette

et al.,

2016a, b; Aschettino

et al.,

2018; Engelhaupt

et al.,

2017, 2018; Cotter 2019), and in the Chesapeake Bay (CeTAP 1981, 1982; Morgan

et al.,

2002; Barco 2013; Aschettino

et al.,

2018); however, they are not likely to occur in the project area. Sightings have been documented around the Chesapeake Bay Bridge Tunnel (CBBT), which is approximately 17 km from the project site, during the winter months (CeTAP 1981, 1982; Barco 2013; Aschettino

et al.,

2018).

Eleven fin whale strandings have occurred off Virginia from 1988 to 2016 mostly during the winter months of February and March, followed by a few in the spring and summer months (Costidis

et al.,

2017). Six of the strandings occurred in the Chesapeake Bay (three on eastern shore; three on western shore) with the remaining five occurring on the Atlantic coast (Costidis

et al.,

2017. Documented strandings near the project area have occurred: February 2012, a dead fin whale washed ashore on Oceanview Beach in Norfolk (Swingle

et al.,

2013); December 2017, a live fin whale stranded on a shoal in Newport News and died at the site (Swingle

et al.,

2018); February 2014, a dead fin whale stranded on a sand bar in Pocomoke Sound near Great Fox Island, Accomack (Swingle

et al.,

2015); and, March 2007, a dead fin whale near Craney Island, in the Elizabeth River, in Norfolk (Barco 2013). Only stranded fin whales have been documented in the project area; no free-swimming fin whales have been observed. Due to the low occurrence of fin whales in the project area, NMFS is not proposing to authorize take of this species.

Minke whales have been sighted off Virginia (CeTAP 1981, 1982; Hyrenbach

et al.

2012; Barco 2013; Mallette

et al.,

2016a, b; McLellan 2017; Engelhaupt

et al.,

2017, 2018; Cotter 2019), near the CBBT (Aschettino

et al.,

2018), but sightings in the project area are from strandings (Jensen and Silber 2004; Barco 2013; DoN 2009). In August 1994, a ship strike incident involved a minke whale in Hampton Roads (Jensen and Silber 2004; Barco 2013). It was reported that the animal was struck offshore and was carried inshore on the bow of a ship (DoN 2009). Twelve strandings of minke whales have occurred in Virginia waters from 1988 to 2016 (Costidis

et al.,

2017). There have been six minke whale stranding from 2017 through 2020 in Virginia waters. Because all known minke whale occurrences in the project area are due to strandings, NMFS is not proposing to authorize take of this species.

Humpback Whale

Humpback whales are distributed worldwide in all major oceans and most seas. Most humpback whale sightings are in nearshore and continental shelf waters; however, humpback whales frequently travel through deep oceanic waters during migration (Calambokidis

et al.,

2001; Clapham, P.J. and Mattila, D.K., 1990). Prior to 2016, humpback whales were listed under the ESA as an endangered species worldwide. Following a 2015 global status review (Bettridge

et al.,

2015), NMFS established 14 DPSs with different listing statuses (81 FR 62259; September 8, 2016) pursuant to the ESA. Humpback whales in the project area are expected to be from the West Indies DPS, which consists of the whales whose breeding range includes the Atlantic margin of the Antilles from Cuba to northern Venezuela, and whose feeding range primarily includes the Gulf of Maine, eastern Canada, and western Greenland. The West Indies DPS was delisted in 2016. Bettridge

et al.

(2003) estimated the size of the West Indies DPS at 12,312 (95 percent CI 8,688-15,954) whales in 2004-05, which is consistent with previous population estimates of approximately 10,000-11,000 whales (Stevick

et al.,

2003; Smith

et al.,

1999) and the increasing trend for the West Indies DPS (Bettridge

et al.,

2015).

Although humpback whales are migratory between feeding areas and calving areas, individual variability in the timing of migrations may result in the presence of individuals in high-latitude areas throughout the year (Straley, 1990). Records of humpback whales off the U.S. mid-Atlantic coast (New Jersey to North Carolina) from January through March suggest these waters may represent a supplemental winter feeding ground used by juvenile and mature humpback whales of U.S. and Canadian North Atlantic stocks (LaBrecque

et al.,

2015).

The immediate project area is not within normal humpback whale feeding or migration areas. They are most likely to occur near the mouth of the Chesapeake Bay and coastal waters of Virginia Beach between January and March; however, they could be found in the area year-round, based on shipboard sighting and stranding data (Barco and Swingle, 2014; Aschettino

et al.,

2015; 2016; 2017; 2018). Photo-identification data support the repeated use of the mid-Atlantic region by individual humpback whales. Results of the vessel surveys show site fidelity in the survey area for some individuals and a high level of occurrence within shipping channels (Aschettino

et al.,

2015; 2016; 2017; 2018). Nearshore surveys conducted in early 2015 reported 61 individual humpback whale sightings, and 135 individual humpback whale sightings in late 2015 through May 2016 (Aschettino

et al.,

2016). Subsequent surveys confirmed the occurrence of humpback whales in the nearshore survey area: 248 individuals were detected in 2016-2017 surveys (Aschettino

et al.,

2017), 32 individuals were detected in 2017-2018 surveys (Aschettino

et al.,

2018), and 80 individuals were detected in 2019 surveys (Aschettino

et al.,

2019). Sightings in the Hampton Roads area in the vicinity of Naval Station (NAVSTA) Norfolk were reported in nearshore surveys and through tracking of satellite-tagged whales in 2016, 2017 and 2019. The numbers of whales detected, most of which were juveniles, reflect the varying level of survey effort and changes in survey objectives from year to year, and do not indicate abundance trends over time. Therefore, humpback whales could occur near the Project area and incidental take could result from exposure to underwater sounds during pile driving and removal.

Bottlenose Dolphin

Along the U.S. East Coast and northern Gulf of Mexico, there are currently 53 management stocks identified by NMFS in the western North Atlantic and Gulf of Mexico, including oceanic, coastal, and estuarine stocks (Hayes

et al.,

2020; Waring

et al.,

2016).

The population structure of bottlenose dolphins off Virginia is complex. There are two morphologically and genetically distinct bottlenose dolphin morphotypes (distinguished by physical differences) described as coastal and offshore forms (Duffield

et al.,

1983; Duffield, 1986). The offshore form is larger in total length and skull length, and has wider nasal bones than the coastal form. Both inhabit waters in the western North Atlantic Ocean and Gulf of Mexico (Curry and Smith, 1997;

Mead and Potter, 1995) along the U.S. Atlantic coast. The coastal morphotype of bottlenose dolphin is continuously distributed along the Atlantic coast south of Long Island, New York, around the Florida peninsula, and along the Gulf of Mexico coast. This type typically occurs in waters less than 20 meters deep (Waring

et al.,

2015). The range of the offshore bottlenose dolphin includes waters beyond the continental slope (Kenney R. D., 1990), and offshore bottlenose dolphins may move between the Gulf of Mexico and the Atlantic (Wells

et al.,

1999). Bottlenose dolphins are the most abundant marine mammal along the Virginia coast and within the Chesapeake Bay, typically traveling in groups of 2 to 15 individuals, but occasionally in groups of over 100 individuals (Engelhaupt

et al.,

2014; 2015; 2016).

Two coastal stocks are likely to be present in the HRBT project area: Western North Atlantic Northern Migratory Coastal stock and Western North Atlantic Southern Migratory Coastal stock. Additionally, the Northern North Carolina Estuarine System stock may occur in the project area.

The northern migratory coastal stock is best defined by its distribution during warm water months when the stock occupies coastal waters from the shoreline to approximately the 20-m isobath between Assateague, Virginia, and Long Island, New York (Garrison

et al.

2017). The stock migrates in late summer and fall and, during cold water months (best described by January and February), occupies coastal waters from approximately Cape Lookout, North Carolina, to the North Carolina/Virginia border (Garrison

et al.

2017b). Historically, common bottlenose dolphins have been rarely observed during cold water months in coastal waters north of the North Carolina/Virginia border, and their northern distribution in winter appears to be limited by water temperatures. Overlap with the southern migratory coastal stock in coastal waters of northern North Carolina and Virginia is possible during spring and fall migratory periods, but the degree of overlap is unknown and it may vary depending on annual water temperature (Garrison

et al.

2016). When the stock has migrated in cold water months to coastal waters from just north of Cape Hatteras, North Carolina, to just south of Cape Lookout, North Carolina, it overlaps spatially with the Northern North Carolina Estuarine System (NNCES) Stock (Garrison

et al.

2017b).

The southern migratory coastal stock migrates seasonally along the coast between North Carolina and northern Florida (Garrison

et al.

2017b). During January-March, the southern migratory coastal stock appears to move as far south as northern Florida. During April-June, the stock moves back north past Cape Hatteras, North Carolina (Garrison

et al.

2017b), where it overlaps, in coastal waters, with the NNCES stock (in waters ≤1 km from shore). During the warm water months of July-August, the stock is presumed to occupy coastal waters north of Cape Lookout, North Carolina, to Assateague, Virginia, including the Chesapeake Bay.

The NNCES stock is best defined as animals that occupy primarily waters of the Pamlico Sound estuarine system (which also includes Core, Roanoke, and Albemarle sounds, and the Neuse River) during warm water months (July-August). Members of this stock also use coastal waters (≤1 km from shore) of North Carolina from Beaufort north to Virginia Beach, Virginia, including the lower Chesapeake Bay. A community of NNCES dolphins are likely year-round Bay residents (Patterson, Pers. Comm).

Vessel surveys conducted along coastal and offshore transects from NAVSTA Norfolk to Virginia Beach in most months from August 2012 to August 2015 reported bottlenose dolphins throughout the survey area, including the vicinity of NAVSTA Norfolk (Engelhaupt

et al.,

2014; 2015; 2016). The final results from this project confirmed earlier findings that bottlenose dolphins are common in the study area, with highest densities in the coastal waters in summer and fall months. However, bottlenose dolphins do not completely leave this area during colder months, with approximately 200-300 individuals still present in winter and spring months (Engelhaupt

et al.,

2016).

Harbor Porpoise

Harbor porpoises inhabit cool temperate-to-subpolar waters, often where prey aggregations are concentrated (Watts and Gaskin, 1985). Thus, they are frequently found in shallow waters, most often near shore, but they sometimes move into deeper offshore waters. Harbor porpoises are rarely found in waters warmer than 63 degrees Fahrenheit (17 degrees Celsius) (Read 1999) and closely follow the movements of their primary prey, Atlantic herring (Gaskin 1992).

In the western North Atlantic, harbor porpoise range from Cumberland Sound on the east coast of Baffin Island, southeast along the eastern coast of Labrador to Newfoundland and the Gulf of St. Lawrence, then southwest to about 34 degrees North on the coast of North Carolina (Waring

et al.,

2016). During winter (January to March), intermediate densities of harbor porpoises can be found in waters off New Jersey to North Carolina, and lower densities are found in waters off New York to New Brunswick, Canada (Waring

et al.,

2016). Harbor porpoises sighted off the mid-Atlantic during winter include porpoises from other western North Atlantic populations (Rosel

et al.,

1999). There does not appear to be a temporally coordinated migration or a specific migratory route to and from the Bay of Fundy region (Waring

et al.,

2016). During fall (October to December) and spring (April to June), harbor porpoises are widely dispersed from New Jersey to Maine, with lower densities farther north and south (LaBrecque

et al.,

2015).

Based on stranding reports, passive acoustic recorders, and shipboard surveys, harbor porpoise occur in coastal waters primarily in winter and spring months, but there is little information on their presence in the Chesapeake Bay. They do not appear to be abundant in the HRBT project area in most years, but this is confounded by wide variations in stranding occurrences over the past decade. Since 1999, stranding incidents have ranged widely from a high of 40 in 1999 to 2 in 2011, 2012, and 2016 (Barco

et al.

2017).

Harbor Seal

The Western North Atlantic stock of harbor seals occurs in the HRBT project area. Harbor seal distribution along the U.S. Atlantic coast has shifted in recent years, with an increased number of seals reported from southern New England to the mid-Atlantic region (DiGiovanni

et al.,

2011; Hayes

et al.,

2017; Kenney R. D. 2019; Waring

et al.,

2016). Harbor seals are the most common seal in Virginia (Barco and Swingle 2014) and regular sightings of seals in Virginia have become a common occurrence in winter and early spring (Costidis

et al.,

2019). Winter haulout sites for harbor seals have been documented in the Chesapeake Bay at the CBBT, on the Virginia Eastern Shore, and near Oregon Inlet, North Carolina (Waring

et al.,

2016; Rees

et al.,

2016; Jones

et al.,

2018).

Harbor seals regularly haul out on rocks around the portal islands of the CBBT and on mud flats on the nearby southern tip of the Eastern Shore from December through April (Rees

et al.,

2016; Jones

et al.,

2018). Seals captured in 2018 on the Eastern Shore and tagged with satellite-tracked tags that lasted from 2 to 5 months spent at least 60 days in Virginia waters before departing

the area. All tagged seals returned regularly to the capture site while in Virginia waters, but individuals utilized offshore and Chesapeake Bay waters to different extents (Ampela

et al.,

2019). The area that was utilized most heavily was near the Eastern Shore capture site, but some seals ranged into the Chesapeake Bay.

Gray Seal

The Western North Atlantic stock of gray seal occurs in the project area. The western North Atlantic stock is centered in Canadian waters, including the Gulf of St. Lawrence and the Atlantic coasts of Nova Scotia, Newfoundland, and Labrador, Canada, and the northeast U.S. continental shelf (Hayes

et al.,

2017). Gray seals range south into the northeastern United States, with strandings and sightings as far south as North Carolina (Hammill

et al.,

1998; Waring

et al.,

2004). Gray seal distribution along the U.S. Atlantic coast has shifted in recent years, with an increased number of seals reported in southern New England (DiGiovanni

et al.,

2011; Kenney R.D., 2019; Waring

et al.,

2016). Recent sightings included a gray seal in the lower Chesapeake Bay during the winter of 2014 to 2015 (Rees

et al.,

2016). Along the coast of the United States, gray seals are known to pup at three or more colonies in Massachusetts and Maine.

Gray seals are uncommon in Virginia and in the Chesapeake Bay. Only 15 gray seal strandings were documented in Virginia from 1988 through 2013 (Barco and Swingle, 2014). They are rarely found resting on the rocks around the portal islands of the CBBT from December through April alongside harbor seals. Seal observation surveys conducted at the CBBT recorded one gray seal in each of the 2014/2015 and 2015/2016 seasons while no gray seals were reported during the 2016/2017 and 2017/2018 seasons (Rees

et al.,

2016, Jones

et al.,

2018). Sightings have been reported off Virginia and near the project area during the winter and spring (Barco 2013; Rees

et al.,

2016; Jones

et al.,

2018; Ampela

et al.,

2019).

Unusual Mortality Events

An unusual mortality event (UME) is defined under Section 410(6) of the MMPA as a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response. Currently, ongoing UME investigations are underway for pinnipeds along the Northeast coast, and humpback whales along the Atlantic coast.

Northeast Pinniped UME

Since July 2018, elevated numbers of harbor seal and gray seal mortalities have occurred across Maine, New Hampshire and Massachusetts. This event has been declared an UME. Additionally, seals showing clinical signs have been stranding as far south as Virginia, although not in elevated numbers; therefore, the UME investigation now encompasses all seal strandings from Maine to Virginia. Lastly, while take is not proposed for these species in this proposed rule, ice seals (harp and hooded seals) have also started stranding with clinical signs, again not in elevated numbers, and those two seal species have also been added to the UME investigation. Additional information is available at

https://www.fisheries.noaa.gov/new-england-mid-atlantic/marine-life-distress/2018-2020-pinniped-unusual-mortality-event-along.

Atlantic Humpback Whale UME

Since January 2016, elevated humpback whale mortalities have occurred along the Atlantic coast from Maine through Florida. This event has been declared an UME. A portion of the whales have shown evidence of pre-mortem vessel strike; however, this finding is not consistent across all whales examined, and additional research is needed. Additional information is available at

https://www.fisheries.noaa.gov/national/marine-life-distress/2016-2020-humpback-whale-unusual-mortality-event-along-atlantic-coast

Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Current data indicate that not all marine mammal species have equal hearing capabilities (

e.g.,

Richardson

et al.,

1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall

et al.

(2007) recommended that marine mammals be divided into functional hearing groups based on directly measured or estimated hearing ranges on the basis of available behavioral response data, audiograms derived using auditory evoked potential techniques, anatomical modeling, and other data. Note that no direct measurements of hearing ability have been successfully completed for mysticetes (

i.e.,

low-frequency cetaceans). Subsequently, NMFS (2018) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65 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 9.

Table 9—Marine Mammal Hearing Groups

[NMFS, 2018]

Hearing group

Generalized

hearing range *

Low-frequency (LF) cetaceans (baleen whales)

7 Hz to 35 kHz.

Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales)

150 Hz to 160 kHz.

High-frequency (HF) cetaceans (true porpoises,

Kogia,

river dolphins, cephalorhynchid,

Lagenorhynchus cruciger

L. australis

)

275 Hz to 160 kHz.

Phocid pinnipeds (PW) (underwater) (true seals)

50 Hz to 86 kHz.

Otariid pinnipeds (OW) (underwater) (sea lions and fur seals)

60 Hz to 39 kHz.

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

i.e.,

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

et al.

2007) and PW pinniped (approximation).

The pinniped functional hearing group was modified from Southall

et al.

(2007) on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range (Hemilä

et al.,

2006; Kastelein

et al.,

2009; Reichmuth and Holt, 2013).

For more detail concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of available information. Five marine mammal species (three cetacean and two phocid pinniped species) have the reasonable potential to co-occur with the proposed construction activities. Please refer to Table 8. Of the cetacean species that may be present, one is classified as a low-frequency cetacean (

i.e.,

humpback whale) one is classified as a mid-frequency cetacean (

i.e.,

bottlenose dolphin), and one is classified as a high-frequency cetacean (

i.e.,

harbor porpoise).

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

This section includes a summary and discussion of the ways that components of the specified activity may impact marine mammals and their habitat. The Estimated Take section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The Negligible Impact Analysis and Determination section considers the content of this section, the Estimated Take section, and the Proposed Mitigation section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and how those impacts on individuals are likely to impact marine mammal species or stocks.

Description of Sound Sources

The marine soundscape is comprised of both ambient and anthropogenic sounds. Ambient sound is defined as the all-encompassing sound in a given place and is usually a composite of sound from many sources both near and far. The sound level of an area is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical (

e.g.,

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

e.g.,

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

e.g.,

vessels, dredging, aircraft, construction).

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

et al.

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

In-water construction activities associated with the project would include vibratory pile driving and pile removal, impact pile driving, jetting, and DTH pile installation. The sounds produced by these activities fall into one of two general sound types: Impulsive and non-impulsive. Impulsive sounds (

e.g.,

explosions, gunshots, sonic booms, impact pile driving) are typically transient, brief (less than one second), broadband, and consist of high peak sound pressure with rapid rise time and rapid decay (ANSI 1986; NIOSH 1998; ANSI 2005; NMFS, 2018). Non-impulsive sounds (

e.g.,

aircraft, machinery operations such as drilling or dredging, vibratory pile driving, and active sonar systems) can be broadband, narrowband or tonal, brief or prolonged (continuous or intermittent), and typically do not have the high peak sound pressure with raid rise/decay time that impulsive sounds do (ANSI 1995; NIOSH 1998; NMFS 2018). The distinction between these two sound types is important because they have differing potential to cause physical effects, particularly with regard to hearing (

e.g.,

Ward 1997 in Southall

et al.,

2007).

Impact hammers operate by repeatedly dropping a heavy piston onto a pile to drive the pile into the substrate. Sound generated by impact hammers is characterized by rapid rise times and high peak levels, a potentially injurious combination (Hastings and Popper, 2005). Vibratory hammers install piles by vibrating them and allowing the weight of the hammer to push them into the sediment. Vibratory hammers produce significantly less sound than impact hammers. Peak sound pressure levels (SPLs) may be 180 dB or greater, but are generally 10 to 20 dB lower than SPLs generated during impact pile driving of the same-sized pile (Oestman

et al.,

2009). Rise time is slower, reducing the probability and severity of injury, and sound energy is distributed over a greater amount of time (Nedwell and Edwards 2002; Carlson

et al.,

2005). A DTH hammer is used to place hollow steel piles or casings by drilling. A DTH hammer is a drill bit that drills through the bedrock using a pulse mechanism that functions at the bottom of the hole. This pulsing bit breaks up rock to allow removal of debris and insertion of the pile. The head extends so that the drilling takes place below the pile. The sounds produced by DTH hammers were previously thought to be continuous. However, recent sound source verification (SSV) monitoring has shown that DTH hammer can create sound that can be considered impulsive (Denes

et al.

2019). Since sound from DTH activities has both impulsive and continuous components, NMFS characterizes sound from DTH pile installation as being impulsive when evaluating potential Level A harassment (

i.e.,

injury) impacts and as being non-impulsive when assessing potential Level B harassment (

i.e.

behavior) effects.

The likely or possible impacts of HRCP's proposed activity on marine mammals could involve both non-acoustic and acoustic stressors. Potential non-acoustic stressors could result from the physical presence of the equipment and personnel; however, any impacts to marine mammals are expected to primarily be acoustic in nature. Acoustic stressors include effects of heavy equipment operation during pile driving and removal.

Acoustic Impacts

The introduction of anthropogenic noise into the aquatic environment from pile driving and removal is the primary means by which marine mammals may be harassed from HRCP's specified activity. In general, animals exposed to natural or anthropogenic sound may experience physical and psychological effects, ranging in magnitude from none to severe (Southall

et al.

2007). In general, exposure to pile driving noise has the potential to result in auditory threshold shifts and behavioral reactions (

e.g.,

avoidance, temporary cessation of foraging and vocalizing, changes in dive behavior). Exposure to anthropogenic noise can also lead to non-observable physiological responses such an increase in stress hormones. Additional noise in a marine mammal's habitat can mask acoustic cues used by

marine mammals to carry out daily functions such as communication and predator and prey detection. The effects of pile driving noise on marine mammals are dependent on several factors, including, but not limited to, sound type (

e.g.,

impulsive vs. non-impulsive), the species, age and sex class (

e.g.,

adult male vs. mom with calf), duration of exposure, the distance between the pile and the animal, received levels, behavior at time of exposure, and previous history with exposure (Wartzok

et al.

2004; Southall

et al.

2007). Here we discuss physical auditory effects (threshold shifts) followed by behavioral effects and potential impacts on habitat.

NMFS defines a noise-induced threshold shift (TS) as a change, usually an increase, in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS 2018). The amount of threshold shift is customarily expressed in dB. A TS can be permanent or temporary. As described in NMFS (2018), there are numerous factors to consider when examining the consequence of TS, including, but not limited to, the signal temporal pattern (

e.g.,

impulsive or non-impulsive), likelihood an individual would be exposed for a long enough duration or to a high enough level to induce a TS, the magnitude of the TS, time to recovery (seconds to minutes or hours to days), the frequency range of the exposure (

i.e.,

spectral content), the hearing and vocalization frequency range of the exposed species relative to the signal's frequency spectrum (

i.e.,

how an animal uses sound within the frequency band of the signal;

e.g.,

Kastelein

et al.

2014), and the overlap between the animal and the source (

e.g.,

spatial, temporal, and spectral).

Permanent Threshold Shift (PTS)

—NMFS defines PTS as a permanent, irreversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS 2018). Available data from humans and other terrestrial mammals indicate that a 40 dB threshold shift approximates PTS onset (see Ward

et al.

1958, 1959; Ward 1960; Miller 1974; Ahroon

et al.

1996; Henderson

et al.

2008). PTS levels for marine mammals are estimates, as with the exception of a single study unintentionally inducing PTS in a harbor seal (Kastak

et al.

2008), there are no empirical data measuring PTS in marine mammals largely due to the fact that, for various ethical reasons, experiments involving anthropogenic noise exposure at levels inducing PTS are not typically pursued or authorized (NMFS 2018).

Temporary Threshold Shift (TTS)

—TTS is a temporary, reversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS 2018). Based on data from cetacean TTS measurements (see Southall

et al.

2007), a TTS of 6 dB is considered the minimum threshold shift clearly larger than any day-to-day or session-to-session variation in a subject's normal hearing ability (Schlundt

et al.

2000; Finneran

et al.

2000, 2002). As described in Finneran (2015), marine mammal studies have shown the amount of TTS increases with cumulative sound exposure level (SELcum) in an accelerating fashion: At low exposures with lower SELcum, the amount of TTS is typically small and the growth curves have shallow slopes. At exposures with higher SELcum, the growth curves become steeper and approach linear relationships with the noise sound exposure level (SEL).

Depending on the degree (elevation of threshold in dB), duration (

i.e.,

recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious (similar to those discussed in auditory masking, below). For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that takes place during a time when the animal is traveling through the open ocean, where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical for successful mother/calf interactions could have more serious impacts. We note that reduced hearing sensitivity as a simple function of aging has been observed in marine mammals, as well as humans and other taxa (Southall

et al.

2007), so we can infer that strategies exist for coping with this condition to some degree, though likely not without cost.

Currently, TTS data only exist for four species of cetaceans (bottlenose dolphin, beluga whale (

Delphinapterus leucas

), harbor porpoise, and Yangtze finless porpoise (

Neophocoena asiaeorientalis

)) and five species of pinnipeds exposed to a limited number of sound sources (

i.e.,

mostly tones and octave-band noise) in laboratory settings (Finneran 2015). TTS was not observed in trained spotted (

Phoca largha

) and ringed (

Pusa hispida

) seals exposed to impulsive noise at levels matching previous predictions of TTS onset (Reichmuth

et al.

2016). In general, harbor seals and harbor porpoises have a lower TTS onset than other measured pinniped or cetacean species (Finneran 2015). Additionally, the existing marine mammal TTS data come from a limited number of individuals within these species. No data are available on noise-induced hearing loss for mysticetes. For summaries of data on TTS in marine mammals or for further discussion of TTS onset thresholds, please see Southall

et al.

(2007), Finneran and Jenkins (2012), Finneran (2015), and Table 5 in NMFS (2018). Installing piles requires a combination of impact pile driving and vibratory pile driving. For this project, these activities would not occur at the same time and there would be pauses in activities producing the sound during each day. Given these pauses and that many marine mammals are likely moving through the ensonified area and not remaining for extended periods of time, the potential for TS declines.

Behavioral Harassment

—Exposure to noise from pile driving and removal also has the potential to behaviorally disturb marine mammals. Available studies show wide variation in response to underwater sound; therefore, it is difficult to predict specifically how any given sound in a particular instance might affect marine mammals perceiving the signal. If a marine mammal does react briefly to an underwater sound by changing its behavior or moving a small distance, the impacts of the change are unlikely to be significant to the individual, let alone the stock or population. However, if a sound source displaces marine mammals from an important feeding or breeding area for a prolonged period, impacts on individuals and populations could be significant (

e.g.,

Lusseau and Bejder 2007; Weilgart 2007; NRC 2005).

Disturbance may result in changing durations of surfacing and dives, number of blows per surfacing, or moving direction and/or speed; reduced/increased vocal activities; changing/cessation of certain behavioral activities (such as socializing or feeding); visible startle response or aggressive behavior (such as tail/fluke slapping or jaw clapping); avoidance of areas where sound sources are located. Pinnipeds may increase their haul out time, possibly to avoid in-water disturbance (Thorson and Reyff 2006). Behavioral responses to sound are highly variable and context-specific and any reactions depend on numerous intrinsic and extrinsic factors (

e.g.,

species, state of maturity, experience,

current activity, reproductive state, auditory sensitivity, time of day), as well as the interplay between factors (

e.g.,

Richardson

et al.

1995; Wartzok

et al.

2003; Southall

et al.,

2007; Weilgart 2007; Archer

et al,.

2010). Behavioral reactions can vary not only among individuals but also within an individual, depending on previous experience with a sound source, context, and numerous other factors (Ellison

et al.

2012), and can vary depending on characteristics associated with the sound source (

e.g.,

whether it is moving or stationary, number of sources, distance from the source). In general, pinnipeds seem more tolerant of, or at least habituate more quickly to, potentially disturbing underwater sound than do cetaceans, and generally seem to be less responsive to exposure to industrial sound than most cetaceans. Please see Appendices B-C of Southall

et al.

(2007) for a review of studies involving marine mammal behavioral responses to sound.

Disruption of feeding behavior can be difficult to correlate with anthropogenic sound exposure, so it is usually inferred by observed displacement from known foraging areas, the appearance of secondary indicators (

e.g.,

bubble curtains or sediment plumes), or changes in dive behavior. As for other types of behavioral response, the frequency, duration, and temporal pattern of signal presentation, as well as differences in species sensitivity, are likely contributing factors to differences in response in any given circumstance (

e.g.,

Croll

et al.

2001; Nowacek

et al.

2004; Madsen

et al.

2006; Yazvenko

et al.

2007). A determination of whether foraging disruptions incur fitness consequences would require information on or estimates of the energetic requirements of the affected individuals and the relationship between prey availability, foraging effort and success, and the life history stage of the animal.

Stress responses

—An animal's perception of a threat may be sufficient to trigger stress responses consisting of some combination of behavioral responses, autonomic nervous system responses, neuroendocrine responses, or immune responses (

e.g.,

Seyle 1950; Moberg 2000). In many cases, an animal's first and sometimes most economical (in terms of energetic costs) response is behavioral avoidance of the potential stressor. Autonomic nervous system responses to stress typically involve changes in heart rate, blood pressure, and gastrointestinal activity. These responses have a relatively short duration and may or may not have a significant long-term effect on an animal's fitness.

Neuroendocrine stress responses often involve the hypothalamus-pituitary-adrenal system. Virtually all neuroendocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction, altered metabolism, reduced immune competence, and behavioral disturbance (

e.g.,

Moberg 1987; Blecha 2000). Increases in the circulation of glucocorticoids are also equated with stress (Romano

et al.,

2004).

The primary distinction between stress (which is adaptive and does not normally place an animal at risk) and “distress” is the cost of the response. During a stress response, an animal uses glycogen stores that can be quickly replenished once the stress is alleviated. In such circumstances, the cost of the stress response would not pose serious fitness consequences. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other functions. This state of distress will last until the animal replenishes its energetic reserves sufficient to restore normal function.

Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses are well studied through controlled experiments and for both laboratory and free-ranging animals (

e.g.,

Hood

et al.,

1998; Jessop

et al.,

2003; Krausman

et al.,

2004; Lankford

et al.,

2005). Stress responses due to exposure to anthropogenic sounds or other stressors and their effects on marine mammals have also been reviewed (Fair and Becker 2000; Romano

et al.,

2002b) and, more rarely, studied in wild populations (

e.g.,

Romano

et al.,

2002a). For example, Rolland

et al.

(2012) found that noise reduction from reduced ship traffic in the Bay of Fundy was associated with decreased stress in North Atlantic right whales. These and other studies lead to a reasonable expectation that some marine mammals will experience physiological stress responses upon exposure to acoustic stressors and that it is possible that some of these would be classified as “distress.” In addition, any animal experiencing TTS would likely also experience stress responses (NRC, 2003), however distress is an unlikely result of this project based on observations of marine mammals during previous, similar projects in the area.

Masking

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

e.g.,

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

et al.,

1995). Masking occurs when the receipt of a sound is interfered with by another coincident sound at similar frequencies and at similar or higher intensity, and may occur whether the sound is natural (

e.g.,

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

e.g.,

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

e.g.,

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

e.g.,

sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age or TTS hearing loss), and existing ambient noise and propagation conditions. Masking of natural sounds can result when human activities produce high levels of background sound at frequencies important to marine mammals. Conversely, if the background level of underwater sound is high (

e.g.,

on a day with strong wind and high waves), an anthropogenic sound source would not be detectable as far away as would be possible under quieter conditions and would itself be masked. The project area contains numerous, naval, commercial, and recreational vessels; therefore, it is possible that background underwater sound levels in the area are elevated, meaning that continuous noise from sources such as vibratory pile driving would be less likely to cause disruption of behavioral patterns when detected.

Airborne Acoustic Effects

— Pinnipeds that occur near the project site could be exposed to airborne sounds associated with pile driving, pile removal and DTH pile installation that have the potential to cause behavioral harassment, depending on their distance from pile driving activities. Cetaceans are not expected to be exposed to airborne sounds that would result in harassment as defined under the MMPA.

Airborne noise would primarily be an issue for pinnipeds that are swimming or hauled out near the project site within the range of noise levels exceeding the acoustic thresholds. We recognize that pinnipeds in the water could be exposed to airborne sound that may result in behavioral harassment when looking with their heads above

water. Most likely, airborne sound would cause behavioral responses similar to those discussed above in relation to underwater sound. For instance, anthropogenic sound could cause hauled-out pinnipeds to exhibit changes in their normal behavior, such as reduction in vocalizations, or cause them to temporarily abandon the area and move further from the source. However, these animals would previously have been taken by Level B harassment because of exposure to underwater sound above the behavioral harassment thresholds, which are, in all cases, larger than those associated with airborne sound. Therefore, we do not believe that authorization of incidental take resulting from airborne sound for pinnipeds is warranted, and airborne sound is not discussed further here.

Marine Mammal Habitat Effects

HRCP's construction activities could have localized, temporary impacts on marine mammal habitat by increasing in-water sound pressure levels and slightly decreasing water quality. Construction activities are of short duration and would likely have temporary impacts on marine mammal habitat through increases in underwater sound. Increased noise levels may affect acoustic habitat (see masking discussion above) and adversely affect marine mammal prey in the vicinity of the project area (see discussion below). During impact and vibratory pile driving, elevated levels of underwater noise would ensonify the project area where both fish and mammals may occur and could affect foraging success. Additionally, marine mammals may avoid the area during construction, however, displacement due to noise is expected to be temporary and is not expected to result in long-term effects to the individuals or populations.

A localized increase in turbidity near the seafloor during construction would occur in the immediate area surrounding the area where piles are installed (and removed in the case of the temporary piles). The sediments on the sea floor will be disturbed during pile driving; however, suspension will be brief and localized and is unlikely to measurably affect marine mammals or their prey in the area. In general, turbidity associated with pile installation is localized to about a 25-ft (7.6-meter) radius around the pile (Everitt

et al.

1980). Cetaceans are not expected to be close enough to the pile driving areas to experience effects of turbidity, and any pinnipeds could avoid localized areas of turbidity. Therefore, we expect the impact from increased turbidity levels to be discountable to marine mammals and do not discuss it further.

In-Water Construction Effects on Potential Foraging Habitat

The proposed activities would not result in permanent impacts to habitats used directly by marine mammals except for the actual footprint of the project. The total seafloor area affected by pile installation and removal is small compared to the vast foraging area available to marine mammals in the project area and lower Chesapeake Bay.

Avoidance by potential prey (

i.e.,

fish) of the immediate area due to the temporary loss of this foraging habitat is also possible. The duration of fish avoidance of this area after pile driving stops is unknown, but we anticipate a rapid return to normal recruitment, distribution and behavior. Any behavioral avoidance by fish of the disturbed area would still leave large areas of fish and marine mammal foraging habitat in the nearby vicinity in the project area and lower Chesapeake Bay.

In-Water Construction Effects on Potential Prey (Fish)

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

e.g.,

fish). Marine mammal prey varies by species, season, and location. Here, we describe studies regarding the effects of noise on known marine mammal prey.

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

e.g.,

Zelick

et al.,

1999; Fay, 2009). Depending on their hearing anatomy and peripheral sensory structures, which vary among species, fishes hear sounds using pressure and particle motion sensitivity capabilities and detect the motion of surrounding water (Fay

et al.,

2008). The potential effects of noise on fishes depends on the overlapping frequency range, distance from the sound source, water depth of exposure, and species-specific hearing sensitivity, anatomy, and physiology. Key impacts to fishes may include behavioral responses, hearing damage, barotrauma (pressure-related injuries), and mortality.

Fish react to sounds which are especially strong and/or intermittent low-frequency sounds, and behavioral responses such as flight or avoidance are the most likely effects. Short duration, sharp sounds can cause overt or subtle changes in fish behavior and local distribution. The reaction of fish to noise depends on the physiological state of the fish, past exposures, motivation (

e.g.,

feeding, spawning, migration), and other environmental factors. Hastings and Popper (2005) identified several studies that suggest fish may relocate to avoid certain areas of sound energy. Additional studies have documented effects of pile driving on fish (

e.g.,

Scholik and Yan, 2001, 2002; Popper and Hastings, 2009). Several studies have demonstrated that impulse sounds might affect the distribution and behavior of some fishes, potentially impacting foraging opportunities or increasing energetic costs (

e.g.,

Fewtrell and McCauley, 2012; Pearson

et al.,

1992; Skalski

et al.,

1992; Santulli

et al.,

1999; Paxton

et al.,

2017). However, some studies have shown no or slight reaction to impulse sounds (

e.g.,

Wardle

et al.,

2001; Jorgenson and Gyselman, 2009; Cott

et al.,

2012).

SPLs of sufficient strength have been known to cause injury to fish and fish mortality. However, in most fish species, hair cells in the ear continuously regenerate and loss of auditory function likely is restored when damaged cells are replaced with new cells. Halvorsen

et al.

(2012a) showed that a TTS of 4-6 dB was recoverable within 24 hours for one species. Impacts would be most severe when the individual fish is close to the source and when the duration of exposure is long. Injury caused by barotrauma can range from slight to severe and can cause death, and is most likely for fish with swim bladders. Barotrauma injuries have been documented during controlled exposure to impact pile driving (Halvorsen

et al.,

2012b; Casper

et al.,

2013).

The most likely impact to fish from pile driving activities at the project areas would be temporary behavioral avoidance of the area. The duration of fish avoidance of an area after pile driving stops is unknown, but a rapid return to normal recruitment, distribution and behavior is anticipated.

In summary, given the relatively small areas being affected, and the fact that these areas do not include habitat of particularly high quality or importance, pile driving and removal activities associated with the proposed action are not likely to have a permanent, adverse effect on any fish habitat, or populations of fish species. Thus, we conclude that impacts of the specified activity are not likely to have more than short-term adverse effects on any prey habitat or populations of prey species. Further, any impacts to marine mammal habitat are not expected to result in significant or long-term consequences for individual marine mammals, or to

contribute to adverse impacts on their populations.

Estimated Take

This section provides an estimate of the number of incidental takes proposed for authorization through this LOA, which will inform both NMFS' consideration of small numbers and the negligible impact determination.

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 would primarily be by Level B harassment, as noise generated from in-water pile driving (vibratory and impact) 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 low- and high-frequency species and phocids because predicted auditory injury zones are larger than for mid-frequency species. Auditory injury is unlikely to occur for mid-frequency species. The proposed mitigation and monitoring measures are expected to minimize the severity of such taking to the extent practicable.

As described previously, no serious injury or mortality is anticipated or proposed to be authorized for this activity. Below we describe how the take is estimated.

Generally speaking, we estimate take by considering: (1) Acoustic thresholds above which marine mammals will be behaviorally disturbed 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) and the number of days of activities. We note that while these basic factors can contribute to a basic calculation to provide an initial prediction of 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 proposed take estimate.

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 experience behavioral disturbance (equated to Level B harassment) or to incur PTS of some degree (equated to Level A harassment).

Level B Harassment for non-explosive sources

—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 (

e.g.,

frequency, predictability, duty cycle), the environment (

e.g.,

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

et al.,

2007, Ellison

et al.,

2012). Based on what the available science indicates and the practical need to use a threshold based on a factor that is both predictable and measurable for most activities, NMFS uses a generalized acoustic threshold based on received level to estimate the onset of Level B harassment. NMFS predicts that marine mammals are likely to experience behavioral disturbance in a manner we consider Level B harassment when exposed to underwater anthropogenic noise above received levels of 120 dB re 1 μPa (rms) for continuous (

e.g.,

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

e.g.,

seismic airguns) or intermittent (

e.g.,

scientific sonar) sources.

HRCP's proposed activity includes the use of continuous (vibratory pile driving, DTH pile installation) and impulsive (impact pile driving, DTH pile installation), sources, and therefore the 120 and 160 dB re 1 μPa (rms) criteria are applicable. Note that the 120 dB criterion is used for DTH pile installation, as the continuous noise produced through the activity will produce the largest harassment isopleths.

Level A harassment for non-explosive sources

—NMFS'

Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing

(Version 2.0) (Technical Guidance, 2018) identifies dual criteria to assess auditory injury (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). As noted previously, HRCP's proposed activity includes the use of impulsive (impact pile driving, DTH pile installation) and non-impulsive (vibratory pile driving/removal, DTH pile installation) sources.

These thresholds are provided in the Table 10 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:

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

Table 10—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:

pk,flat

219 dB;

E,LF,24h

183 dB

Cell 2:

E,LF,24h

199 dB.

Mid-Frequency (MF) Cetaceans

Cell 3:

pk,flat

230 dB;

MF,24h

185 dB

Cell 4:

E,MF,24h

198 dB.

High-Frequency (HF) Cetaceans

Cell 5:

pk,flat

202 dB;

E,HF,24h

155 dB

Cell 6:

E,HF,24h

173 dB.

Phocid Pinnipeds (PW) (Underwater)

Cell 7:

pk,flat

218 dB;

E,PW,24h

185 dB

Cell 8:

E,PW,24h

201 dB.

Otariid Pinnipeds (OW) (Underwater)

Cell 9:

pk,flat

232 dB;

E,OW,24h

203 dB

Cell 10:

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 (

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

) has a reference value of 1μPa

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 will feed into identifying the area ensonified above the acoustic thresholds, which include 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.,

vibratory pile driving, vibratory pile removal, impact pile driving, jetting, and DTH pile installation).

Sound source levels (SSLs) for each method of installation and removal were estimated using empirical measurements from similar projects in Norfolk and Little Creek (Craney Island), elsewhere in Virginia, or outside of Virginia (California, Florida, Washington, Alaska) (Table 11). It is assumed that jetting will be quieter than vibratory installation of the same pile size, but data for this activity are limited; therefore, SSLs for vibratory installation have been applied to jetting.

DTH pile installation includes drilling (non-impulsive sound) and hammering (impulsive sound) to penetrate rocky substrates (Denes

et al.

2016; Denes

et al.

2019; Reyff and Heyvaert 2019). DTH pile installation was initially thought be a primarily non-impulsive noise source. However, Denes

et al.

(2019) concluded from a study conducted in Virginia, nearby the location for this project, that DTH should be characterized as impulsive based on Southall

et al.

(2007), who stated that signals with a >3 dB difference in sound pressure level in a 0.035-second window compared to a 1-second window can be considered impulsive. Therefore, DTH pile installation is treated as both an impulsive and non-impulsive noise source. In order to evaluate Level A harassment, DTH pile installation activities are evaluated according to the impulsive criteria. Level B harassment isopleths are determined by applying non-impulsive criteria and using the 120 dB threshold which is also used for vibratory driving. This approach ensures that the largest ranges to effect for both Level A and Level B harassment are accounted for in the take estimation process.

The source level employed to derive Level B harassment isopleths for DTH pile installation of all pile sizes was derived from the Denes

et al.

(2016) study at Kodiak, Alaska. The median source value for drilling was reported to be 166 dB RMS.

The source level employed to derive Level A harassment isopleths for DTH pile installation of piles/holes above 24-inch up to 42-inch in diameter came from a combination of (whichever higher for given metric) Reyff and Heyvaert (2019), Denes

et al.

(2019), and Reyff (2020). For pile/holes 60-inch in diameter, values were provided by Reyff (Reyff personal communication) and are shown in Table 11. Note that during some driving scenarios bubble curtains will be used to reduce sound source levels by 7 dB from the values recorded by Denes

et al.

(2019) at the nearby Chesapeake Bay Bridge Tunnel. These are also noted in Table 11.

Table 11—Summary of Project Sound Source Levels

[a 10 m]

Method and pile type

Sound source level at 10 meters

Literature source

Vibratory Hammer

dB rms

42-inch steel pile

168

Austin

et al.

2016.

36-inch steel pile

167

DoN 2015.

30-inch steel pile, concrete filled

167

DoN 2015.

24-inch steel pile

161

DoN 2015.

16-inch CCA timber pile *

162

Caltrans 2015.

AZ 700-19 steel sheet pile

160

Caltrans 2015.

AZ 700-26 steel sheet pile

160

Caltrans 2015.

Jetting

dB rms

42-inch steel pile

161

Austin

et al.

2016.

DTH Pile Installation

dB rms

dB SEL

dB peak

30-inch and 36-inch steel pipe piles

166

164

196

Denes

et al.

2016, 2019; Reyff and Heyvaert 2019; Reyff 2020.

60-inch steel pipe pile

166

175

196

Denes

et al.

2016; Reyff pers. comm.

Impact Hammer

dB rms

dB SEL

dB peak

36-inch steel pile

193

183

210

Caltrans 2015; Chesapeake Tunnel Joint Venture 2018.

36-inch steel pile, attenuated **

186

176

203

Caltrans 2015; Chesapeake Tunnel Joint Venture 2018

30-inch steel pile, concrete filled

195

186

216

DoN 2015.

30-inch steel pile, concrete filled, attenuated **

188

179

209

DoN 2015.

24-inch steel pile

190

177

203

Caltrans 2015.

24-inch steel pile, attenuated **

183

170

196

Caltrans 2015.

54-inch concrete cylinder pile ***

187

177

193

MacGillivray

et al.

2007.

24-inch concrete square pile

176

166

188

Caltrans 2015.

Note:

It is assumed that noise levels during pile installation and removal are similar. dB = decibel: SEL = sound exposure level; dB peak = peak sound level; rms = root mean square; DoN = Department of the Navy; CCA = Chromated Copper Arsenate, Caltrans = California Department of Transportation.

SSL taken from 12-inch timber piles in Norfolk, Virginia.

SSLs are a 7 dB reduction from Chesapeake Tunnel Joint Venture 2018 values due to usage of a bubble curtain.

***

SSLs taken from 36-inch concrete square piles, no project specific information provided.

The primary literature source for 36-inch steel pipe attenuated piles is Caltrans 2015; however, the Chesapeake Tunnel Joint Venture 2018 is also cited due to the proximity of the project to the HRBT Project

Simultaneous use of hammers could result in increased SPLs and harassment zone sizes given the proximity of the component driving sites and the rules of decibel addition. Impact pile installation is projected to take place concurrently at 3 to 4 locations and there is the potential for as many as 7 pile installation locations operating concurrently. NMFS (2018b) handles overlapping sound fields created by the use of more than one hammer differently for impulsive (impact hammer and Level A harassment zones for drilling with a DTH hammer) and continuous sound sources (vibratory hammer and Level B harassment zones for drilling with a DTH hammer) (See Table 12). It is unlikely that the two impact hammers would strike at the same instant, and therefore, the SPLs will not be adjusted regardless of the distance between impact hammers. In this case, each impact hammer will be considered to have its own independent Level A and Level B harassment zones and drilling with a DTH hammer will be considered to have its own independent Level A harassment zones. It will be unlikely that more than one DTH hammer will be used within a day at more than one location; therefore, only one DTH hammer was included in the multiple hammer calculations for Level B harassment zones.

When two continuous noise sources, such as vibratory hammers, have overlapping sound fields, there is potential for higher sound levels than for non-overlapping sources. The method described below was used by Washington State Department of Transportation (WSDOT) and has been used by NMFS (WSDOT 2020).

When two or more vibratory hammers are used simultaneously, and the isopleth of one sound source encompasses the sound source of another isopleth, the sources are considered additive and combined using the following rules (Table 12) for addition of two simultaneous vibratory hammers, the difference between the two SSLs is calculated, and if that difference is between 0 and 1 dB, 3 dB are added to the higher SSL; if difference is between 2 or 3 dB, 2 dB are added to the highest SSL; if the difference is between 4 to 9 dB, 1 dB is added to the highest SSL; and with differences of 10 or more decibels, there is no addition.

Table 12—Rules for Combining Sound Levels Generated During Pile Installation

Hammer types

Difference in SSL

Level A harassment zones

Level B harassment zones

Vibratory, Impact

Any

Use impact zones

Use vibratory zone.

Impact, Impact

Any

Use zones for each pile size and number of strikes

Use zone for each pile size.

Vibratory, Vibratory

0 or 1 dB

Add 3 dB to the higher source level

Add 3 dB to the higher source level.

2 or 3 dB

Add 2 dB to the higher source level

Add 2 dB to the higher source level.

4 to 9 dB

Add 1 dB to the higher source level

Add 1 dB to the higher source level.

10 dB or more

Add 0 dB to the higher source level

Add 0 dB to the higher source level.

When three or more continuous sound sources are used concurrently, such as vibratory hammers, the three overlapping sources with the highest SSLs are identified. Of the three highest SSLs, the lower two are combined using

the above rules, then the combination of the lower two is combined with the highest of the three.

It is common for pile installation to start and stop multiple times as each pile is adjusted and its progress is measured and documented. For short durations, it is anticipated that multiple hammers could be in use simultaneously. Following an approach modified from WSDOT in their Biological Assessment manual and described in Table 13, decibel addition calculations were carried out for possible combinations of vibratory installations of 24-, 30-, 36-, and 42-inch steel pipe piles throughout the Project area.

EP08JA21.003

These source levels are used to compute the Level A harassment zones and to estimate the Level B harassment zones.

Level A Harassment Zones

When the NMFS' Technical Guidance (2016) was published, in recognition of the fact that ensonified area/volume could be more technically challenging to predict because of the duration component in the new thresholds, we developed a User Spreadsheet that includes tools to help predict a simple isopleth that can be used in conjunction with marine mammal density or occurrence to help predict takes. We note that because of some of the assumptions included in the methods used for these tools, we anticipate that isopleths produced are typically going to be overestimates of some degree, which may result in some degree of overestimate of Level A harassment take. However, these tools offer the best way to predict appropriate isopleths when more sophisticated 3D modeling methods are not available, and NMFS continues to develop ways to quantitatively refine these tools, and will qualitatively address the output where appropriate. For stationary sources such as in-water pile driving activities during the HRBT project, NMFS User Spreadsheet predicts the closest distance at which, if a marine mammal remained at that distance the whole duration of the activity, it would incur PTS.

Inputs used in the User Spreadsheet (Table 14 and Table 15) and the resulting isopleths are reported below (Table 14). Level A harassment thresholds for impulsive sound sources (impact pile driving, DTH pile installation) are defined for both SELcum and Peak SPL, with the threshold that results in the largest modeled isopleth for each marine mammal hearing group used to establish the effective Level A harassment isopleth.

For purposes of estimated take by Level A harassment, NMFS assumed that the strike rate for impact pile installation was 50 percent of the estimated number of strikes displayed in Table 14 and 15. Similarly, for vibratory driving NMFS assumed that the driving time for each pile was 50 percent of the estimated total. For the DTH hammer calculations, Reyff and Heyvaert 2019 identified a strike rate of 10 Hz. This was also reduced by 50 percent to 5 Hz which to achieve the same 50 percent Level A harassment reduction as was done for impact and vibratory driving. Strikes per Pile values were not altered when calculating Level A harassment zones for DTH pile installation.

Since the marine mammals proposed for authorization are highly mobile, it is unlikely that an animal would remain within an established Level A harassment zone for the entire duration or number of strikes associated with installation or removal of a specified number of piles throughout a given day. This was done to provide more realistic take estimates by Level A harassment. NMFS applied this reduction across all pile sizes, types, and installation/removal methods as shown in Tables 14 and 15. Additionally, note that under some driving scenarios a 7 dB attenuation was applied to impact installation of 24-inch steel, 30-inch Steel, and 36-inch steel due to use of bubble curtains as shown in Table 14.

The calculated Level A isopleths for different size pile and driving types are shown in Tables 16-18.

BILLING CODE 3510-22-P

EP08JA21.004

EP08JA21.005

BILLING CODE 3510-22-C

Table 15—User Spreadsheet Input Parameters Used for Calculating Level A Harassment Isopleths for Drilling With a DTH Hammer *

Model parameter

30-inch steel,

concrete filled

DTH

36-inch steel

DTH

60-inch steel

DTH

Spreadsheet Tab

E.2

Weighting Factor Adjustment (kilohertz)

SEL

E, p, single strike

) at 10 meters

164

175

p, 0-pk

at 10 meters

196

Number of piles per day

Duration to drive a pile (minutes)

120

Transmission loss coefficient

Distance from source (meters)

Estimated Number of Strikes per 24-hour period

432,000

144,000

216,000

50% of Strikes per 24-hour period

216,000

72,000

108,000

Strike rate (Hz) average strikes per second

50% of Strike rate (Hz) average strikes per second

To provide a more realistic estimate of take by Level A harassment, NMFS assumes that an animal would occur within the vicinity of the construction activity for 50 percent of the pile installation and removal time, which equates to 50 percent of the piles planned for installation and removal. HRCP has implemented this reduction across all pile sizes, types, and installation and removal methods. For drilling with a DTH hammer installation, the strike rate (Hz) was reduced by half to accomplish the reduction. A 10 Hz strike rate was identified from Reyff and Heyvaert 2019 which was then reduced by 50% to 5 Hz to accomplish the 50% Level A reduction.

Table 16—Calculated Distances to Level A Harassment Isopleths During Vibratory Installation, and Vibratory Removal and Jetting Installation With No Attenuation

Project component

Pile size/type

Minutes per pile (reduced by half)

Number of piles per day

Level A harassment isopleth distance

(meters)

Cetaceans

Pinnipeds

Level A Harassment isopleth areas

(km

)

Cetaceans

Pinnipeds

Vibratory Hammer

North Trestle

Moorings

42-inch Pipe, Steel

<0.01

Template Piles

36-inch Pipe, Steel

2.5

<0.01

North Shore Work Trestle, Jump Trestle, Work Trestle, Demolition Trestle

36-inch Pipe, Steel

<0.01

Moorings

24-inch Pipe, Steel

<0.01

North Shore Abutment

AZ 700-19 Sheet, Steel

<0.01

North Island

Moorings

42-inch Pipe, Steel

<0.01

Hampton Creek Approach Channel Marker

Existing, 36-inch Pipe, Steel

<0.01

North Island Expansion

AZ 700-26 Sheet, Steel

<0.01

North Island Abutment

AZ 700-19 Sheet, Steel

South Island Abutment

AZ 700-19 Sheet, Steel

<0.01

South Island Expansion

AZ 700-26 Sheet, Steel

Settlement Reduction Piles

24-inch Pipe, Steel

Deep Foundation Piles

30-inch Pipe, Steel, Concrete Filled

TBM Platform

36-inch Pipe, Steel

Conveyor Trestle

36-inch Pipe, Steel

Moorings

42-inch Pipe, Steel

<0.01

Template Piles

36-inch Pipe, Steel

2.5

<0.01

South Trestle

Template Piles

36-inch Pipe, Steel

2.5

<0.01

Moorings, Casings

42-inch Pipe, Steel

<0.01

Work Trestle, Jump Trestle, Demolition Trestle, Temporary MOT Trestle

36-inch Pipe, Steel

Moorings

24-inch Pipe, Steel

Willoughby Bay

Moorings

24-inch Pipe, Steel

<0.01

Work Trestle, Jump Trestle

36-inch Pipe, Steel

Moorings (Safe Haven)

42-inch Pipe, Steel

<0.01

Casing

42-inch Pipe, Steel

<0.01

Template Piles

36-inch Pipe, Steel

2.5

<0.01

Willoughby Spit Laydown Area

Finger Piers on Timber Piles

16-inch CCA, Timber

<0.01

Dock on Spuds, Dock on Piles

36-inch Pipe, Steel

<0.01

Template Piles

36-inch Pipe, Steel

2.5

<0.01

Jetting

Willoughby Bay

Casing

42-inch Pipe, Steel

<0.01

Table 17—Calculated Distances to Level A Harassment Isopleths During Impact Installation and DTH Pile Installation With No Attenuation

Project component

Pile size/type

Number of

strikes per

pile or

strike rate*

(reduced

by half)

Number

of piles

per day

Level A harassment isopleth distance

(meters)

Cetaceans

Pinnipeds

Level A harassment isopleth areas

(km

)

Cetaceans

Pinnipeds

North Trestle

Permanent Piles

54-inch Pipe, Concrete Cylinder

1,050

411

490

220

0.53

<0.001

0.75

0.15

Work Trestle, Jump Trestle, Demolition Trestle

36-inch Pipe, Steel

117

140

0.04

<0.001

0.06

0.01

South Island

Settlement Reduction Piles

24-inch Pipe, Steel

116

0.02

<0.001

0.03

0.01

Deep Foundation Piles

30-inch Pipe, Steel, Concrete Filled

386

459

207

0.35

<0.001

0.49

0.10

South Trestle

Work Trestle, Jump Trestle, Demolition Trestle, Temporary MOT Trestle

36-inch Pipe, Steel

117

140

0.04

<0.001

0.06

0.01

Permanent Piles

54-inch Pipe, Concrete Cylinder

1,050

411

490

220

0.53

<0.001

0.75

0.15

Willoughby Bay

Work Trestle, Jump Trestle

36-inch Pipe, Steel

117

140

0.04

<0.001

0.06

0.01

Permanent Piles

24-inch Pipe, Concrete Square

1,050

0.02

<0.001

0.03

<0.01

Willoughby Spit Laydown Area

Dock on Spuds, Dock on Piles

36-inch Pipe, Steel

154

183

0.12

0.09

<0.001

0.03

DTH Pile Installation *

North Trestle

Work Trestle, Jump Trestle, Demolition Trestle

36-inch Pipe, Steel

36,000

936

1,115

501

1.81

<0.01

2.27

0.78

Casing

60-inch Pipe, Steel

36,000

6,633

236

7,901

3,550

34.04

0.18

43.75

13.03

South Island

Deep Foundation Piles

30-inch Pipe, Steel, Concrete Filled

36,000

1,946

2,318

1,042

8.28

<0.01

11.30

2.49

South Trestle

Work Trestle, Jump Trestle, Temporary MOT Trestle, Demolition Trestle

36-inch Pipe, Steel

36,000

936

1,115

501

2.67

<0.01

3.67

0.79

Casing

60-inch Pipe, Steel

36,000

6,633

236

7,901

3,550

77.50

0.18

102.16

27.12

For DTH Hammer calculations, a 10 Hz strike rate was identified from Reyff and Heyvaert 2019 which was then reduced by 50% to 5 Hz to accomplish the 50% Level A harassment reduction. Strikes per Pile values were not reduced for DTH methods.

Table 18—Calculated Distances to Level A Harassment Isopleths During Impact Installation With Attenuation

Project component

Pile size/type

Number of

strikes per pile

(reduced by half)

Number of piles per day

Level A harassment isopleth distance

(meters)

Cetaceans

Pinnipeds

Level A harassment isopleth areas

(km

)

Cetaceans

Pinnipeds

Impact Hammer

South Island

Settlement Reduction Piles

24-inch Pipe, Steel

<0.01

Deep Foundation Piles

30-inch Pipe, Steel, Concrete Filled

132

157

0.04

<0.001

0.06

0.01

South Trestle

Temporary MOT Trestle

Jump Trestle.

Work Trestle.

36-inch Pipe, Steel

<0.001

0.007

0.002

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

TL = transmission loss in dB

B = transmission loss coefficient; for practical spreading equals 15

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

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

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 HRCP's proposed activity.

Using the practical spreading model, HRCP determined underwater noise would fall below the behavioral effects threshold of 120 dB rms for marine mammals at a maximum radial distance of 15,849 m for vibratory pile driving of 42- and 36-inch diameter piles. Other activities including impact driving and vibratory installation sheet piles have smaller Level B harassment zones. All Level B harassment isopleths are reported in Table 19 below. It should be noted that based on the geography of the project area, and pile driving locations, in many cases sound will not reach the full distance of the Level B harassment isopleth. The radial distances provided in Table 19 and Table 20 are shown as calculated. However, the land areas presented in these tables take into account truncation by various land masses in the project area and only shows the in-water ensonified area.

Table 19—Distances to Level B Harassment Isopleths for Different Pile Sizes and Types and Methods of Installation and Removal With No Attenuation

Location and component

Method and pile type

Level B

isopleth (m),

unattenuated

Level B area

unattenuated

(km

)

Vibratory Hammer (Level B Isopleth = 120 dB)

North Trestle

Moorings

42-inch steel piles

15,849

96.78

Template Piles

36-inch steel piles

13,594

85.53

Demolition Trestle

36-inch steel piles

13,594

85.53

North Shore Work Trestle

36-inch steel piles

13,594

85.53

Jump Trestle

36-inch steel piles

13,594

85.53

Work Trestle

36-inch steel piles

13,594

85.53

Moorings

24-inch steel piles

5,412

25.34

North Shore Abutment

AZ 700-19 steel sheet piles

4,642

19.81

North Island

Moorings North

42-inch steel piles

15,849

103.86

Moorings South

42-inch steel piles

15,849

201.04

Hampton Creek Approach Channel Marker

36-inch steel pile

13,594

93.99

North Island Expansion North

AZ 700-26 steel sheet piles

4,642

26.06

North Island Expansion South

AZ 700-26 steel sheet piles

4,642

36.73

North Island Abutment North

AZ 700-19 steel sheet piles

4,642

26.06

North Island Abutment South

AZ 700-19 steel sheet piles

4,642

36.73

South Island

Moorings

42-inch steel piles

15,849

246.86

Template Piles

36-inch steel piles

13,594

81.75

TBM Platform

36-inch steel piles

13,594

81.75

Conveyor Trestle

36-inch steel piles

13,594

81.75

Deep Foundation Piles

30-inch steel piles, concrete filled

13,594

194.04

Settlement Reduction Piles

24-inch steel piles

5,412

45.10

South Island Expansion

AZ 700-26 steel sheet piles

4,642

34.69

South Island Abutment

AZ 700-19 steel sheet piles

4,642

34.69

South Trestle

Moorings, Casings

42-inch steel piles

15,849

305.30

Template Piles

36-inch steel piles

13,594

235.60

Temporary MOT Trestle

36-inch steel piles

13,594

235.60

Jump Trestle

36-inch steel piles

13,594

235.60

Work Trestle

36-inch steel piles

13,594

235.60

Demolition Trestle

36-inch steel piles

13,594

235.60

Moorings

24-inch steel piles

5,412

55.87

Willoughby Bay

Moorings (Safe Haven)

42-inch steel piles

15,849

5.52

Moorings

42-inch steel piles

15,849

5.52

Casing

42-inch steel piles

15,849

5.52

Template Piles

36-inch steel piles

13,594

5.52

Work Trestle

36-inch steel piles

13,594

5.52

Jump Trestle

36-inch steel piles

13,594

5.52

Moorings

24-inch steel piles

5,412

5.52

Willoughby Spit Laydown Area

Template Piles

36-inch steel piles

13,594

74.45

Dock on Spuds

36-inch steel piles

13,594

74.45

Dock on Piles

36-inch steel piles

13,594

74.45

Finger Piers

16-inch CCA timber piles

6,310

40.62

DTH Pile Installation (Level B Isopleth = 120 dB)

North Trestle Casings

60-inch steel piles

11,659

72.28

North Trestle Work Trestle, Jump Trestle, Demolition Piles, Templates

36-inch steel piles

11,659

72.28

South Island Deep Foundation Piles

30-inch steel piles, concrete filled

11,659

152.79

South Trestle Casings

60-inch steel piles

11,659

184.12

South Trestle Work Trestle, Jump Trestle, Demolition Trestle, Temporary MOT Trestle, Templates

36-inch steel piles

11,659

14.12

Willoughby Bay Templates

36-inch steel piles

11,659

5.52

Jetting (Level B Isopleth = 120 dB)

Willoughby Bay

Casing

42-inch steel piles

5,412

5.52

Impact Hammer (Level B Isopleth = 160 dB)

North Trestle

Permanent Piles

54-inch concrete cylinder piles

631

1.14

Work Trestle

36-inch steel piles

1,585

3.81

Jump Trestle

36-inch steel piles

1,585

3.81

Demolition Trestle

36-inch steel piles

1,585

3.81

South Island

Deep Foundation Piles

30-inch steel piles, concrete filled

2,154

9.91

Settlement Reduction Piles

24-inch steel piles

1,000

2.29

South Trestle

Permanent Piles

54-inch concrete cylinder piles

631

1.25

Work Trestle

36-inch steel piles

1,585

6.84

Jump Trestle

36-inch steel piles

1,585

6.84

Temporary MOT Trestle

36-inch steel piles

1,585

6.84

Demolition Trestle

36-inch steel piles

1,585

6.84

Willoughby Bay

Permanent Piles

24-inch concrete cylinder piles

117

0.04

Work Trestle

36-inch steel piles

1,585

3.15

Jump Trestle

36-inch steel piles

1,585

3.15

Willoughby Spit Laydown Area

Dock on Spuds

36-inch steel piles

1,585

6.03

Dock on Piles

36-inch steel piles

1,585

6.03

Table 20—Distances to Level B Harassment Isopleths for Installation and Removal of Steel Pipe Piles With Attenuation Bubble Curtain

Location and component

Method and pile type

Level B

isopleth (m),

attenuated

Level B area

attenuated

(km

)

Impact Hammer (Level B Isopleth = 160 dB)

South Island

Deep Foundation Piles

30-inch steel piles, concrete filled

736

1.25

Settlement Reduction Piles

24-inch steel piles

341

0.27

South Trestle

Temporary MOT Trestle, Work Trestle, Jump Trestle

36-inch steel piles

541

0.68

The daily duration in which more than one vibratory hammer or DTH pile installation could occur is difficult to predict and quantify. As noted previously, DTH pile installation is considered by NMFS to be both impulsive and continuous. Therefore, decibel addition will not be used to calculate Level A harassment zones

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