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Federal Register / Vol. 86, No. 33 / Monday, February 22, 2021 / Notices
impact on our critical fall bowhead whale subsistence harvest at Utqiagvik.
In its initial letter, the commenter stated that suspension of pile driving activities until Utqiagvik completes its fall harvest would help to ensure adequate mitigation of impacts from that sound source, and the commenter initially recommended such a shutdown. However, in a second letter, the commenter stated that it recognizes that because the timing of the migration and completion of the harvest are difficult to predict, a shutdown throughout this period could be prohibitive from the perspective of the operator. Therefore, because the risk of interference will be borne by the Utqiagvik Whaling Captains should the project go forward, the AEWC requests that NMFS direct AGDC to meet directly with the Whaling Captains Associations and to continue meeting with the AEWC. The AEWC also requests that NMFS reiterate the requirement for signing the Conflict Avoidance Agreement CAA as the Federal Energy Regulatory Commission FERC has done in its Order Granting Authorization of the Project.
Response: Utqiagvik is approximately 320 km 200 mi from West Dock, and farther north and disruption of bowhead whale behavioral patterns as a result of AGDCs pile driving is not expected to impact individuals in the vicinity of Utqiagvik. As described in the Estimated Take section, only a small number of bowhead whales a maximum of 110, less than 0.65% of the stock are expected to be disturbed by the construction activities, and even if some subset of these individuals deflected farther offshore near the project site, it is reasonable to predict that most individuals would likely resume a more typical migration path by the time they reach the Utqiagvik hunting area and, therefore, significant impacts to the Utqiagvik hunt would not be expected. Further, as noted by the commenter, it is impracticable for AGDC to cease pile driving during the Utqiagvik whaling season, given the relatively short open water work window, the potential long duration of the whaling season, and the requirement to cease pile driving during the Nuiqsut whaling season, which occurs closer to the project site. As such, NMFS is not requiring AGDC to cease pile driving during the Utqiagvik whaling season.
However, AGDC is required to continue coordinating with subsistence groups, including the Whaling Captains Associations Utqiagvik, Nuiqsut, and Kaktovik, as described in the Plan of Cooperation POC. This additional coordination may result in additional
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mitigation measures, if agreed upon by the communities and AGDC. AGDC will also conduct an SSV to determine sound source levels and propagation for the construction noise, which will further inform and refine our understanding of the distance to which the construction noise is expected to propagate and the likely impact on marine mammals including bowhead whales.
Regarding the CAA, AGDC is required by FERC to enter the CAA for the construction season. NMFS supports and encourages participation of applicants in the CAA process. Where measures likely to be identified through the CAA process are necessary to ensure an unmitigable adverse impact on subsistence uses or that the activities have the least practicable adverse impact on the affected species or stocks and their habitat paying particular attention to the availability of the species or stock for taking for certain subsistence uses, similar or identical measures would be appropriately included in the IHA; however, NMFS
does not require applicants to sign the CAA.
Comment 5: Commenters suggested that NMFS require AGDC to use sound attenuation such as a bubble curtain. In a related comment, a commenter stated that NMFS thoughtlessly adopted the applicants justification that bubble curtains would be very difficult to deploy, and may not result in significant sound reduction. The commenter stated that while NMFS could and should require bubble curtains to reduce pile driving noise, there are also other technologies available to reduce the noise from pile driving. For example, the commenter stated that NMFS should consider the effectiveness of pile caps, dewatered cofferdams, and other physical barrier mitigation. The PRP
recommended consideration of bubble curtains, noise mitigation screens, and hydro sound dampers nets with airfilled or foam-filled elastic balloons Bellmann 2014; Elmer and Savery 2014 to decrease the size of the Level A and Level B harassment zones. In a related comment, the Commission suggested consideration of other noise attenuation devices, but did not suggest specific devices. Rather, it recommended that NMFS determine whether any type of sound attenuation device could be effective in the shallowwater conditions of the proposed project site.
In another related comment, a commenter stated that the benefit of sound attenuation is reducing risk of injury to seals and whales, diminishing the amount of sound that would propagate to the area of the main
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bowhead migration, and decreasing the size of Level A and Level B harassment zones. Reduction in the size of these zones would achieve more realistically observable zones see PRP comments.
Therefore, observers can do a better job of implementing mitigation measures to avoid Level A harassment takes more efficiently and realistically observe the entire Level B harassment zone to estimate actual takes. The commenter stated that if NMFS does not require sound attenuation devices, it should require AGDC to strengthen their proposed monitoring plan by requiring that observers be able to see most of the Level A and B monitoring zones during the open water period.
Response: NMFS fully considered whether requiring the use of bubble curtains or other sound attenuation methods was appropriate for this IHA, and included additional explanation of these considerations below. Where conditions are appropriate, bubble curtains, cofferdams, and pile caps are generally the most common noise attenuation methods used in construction projects. The West Dock area is an industrial location with existing piles and dock structures.
Conditions in the project area mean that the common practice of using bubble curtains for attenuation is not appropriate, as the water is shallow and therefore sound source level reductions are likely to be minimal Caltrans, 2020, effective deployment of a bubble curtain system is logistically challenging in shallow water, and there is potential for sea ice. Sound attenuation devices have not been used for pile driving in this area during past projects.
NMFS notes that in some instances during the project, such as during the gravel pouring at the barge bridge abutments, sheet piles will act as a cofferdam. NMFS considered this noise isolation in its effects analysis, but did not refer to the sheet piles as a cofferdam or mitigation measure, as they are a planned construction component, rather than an additional mitigation measure.
Regarding the noise mitigation screens and hydro sound dampeners suggested by the PRP, as stated previously, the window for working in this area is extremely short, and construction will occur on a tight schedule in an effort to complete construction during one season. Given the short construction schedule, experimentation with less-common sound attenuation methods, such as mitigation screens and hydro sound dampeners, is not practicable.

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