Federal Register - February 22, 2021
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Source: Federal Register
10688
Federal Register / Vol. 86, No. 33 / Monday, February 22, 2021 / Notices
TABLE 15CALCULATED LEVEL A HARASSMENT TAKES BY SPECIES, PILE SIZE AND TYPE, AND INSTALLATION/REMOVAL
METHODContinued Activity
Estimated duration days
Anchor Pile 14-inch Hpile
Barge Bridge Mooring Dolphins 48inch Pipe Piles
Spud Piles 14-inch Hpiles
Total
Level A Harassment Take Authorized 75% of Total
Calculated level A harassment takes Bowhead whale
Gray whale
Beluga whale c d
Ringed seal c
Spotted seal c
Bearded seal c
1
a 0.05
0
0
0.2466
0.0495
0.0423
4
0.53
0
0
2.44
0.49
0.42
4
0
0
0
0
0
0
164
2.65
0
0
12.20
2.45
2.09
123
b0
0
0
9
2
2
a Note
that the notice of proposed IHA mistakenly stated 0.5, rather than 0.05. However, the Total cell was calculated correctly.
percent of the calculated total is 1.99 takes, however, we do not expect bowheads to occur within the Level A harassment zone, and we do not propose to authorize Level A harassment take of bowhead whale.
c In the proposed IHA, Level A harassment takes for beluga whale and phocids were erroneously calculated using the LF cetacean Level A
harassment zone sizes. The calculations in this table and in the final IHA reflect the corrected estimated Level A harassment take, calculated using the Level A harassment zone for belugas and phocids, respectively.
d Beluga whale take estimates were updated to reflect inclusion of the 2019 ASAMM data in the density calculation. However, the Level A
harassment Take Authorized did not change.
b 75
We do not expect bowhead whales to occur within the Level A harassment zones due to the shallow waters approximately 19 ft in depth at the isopleth, lack of historic sightings, and required mitigation. As previously noted, waters less than 15 ft 4.5 m deep are considered too shallow to support these whales, and in three decades of aerial surveys by BOEM
ASAMM, no bowhead whale has been recorded in waters less than 16.4 ft 5
m deep Clarke and Ferguson 2010.
Further, no bowhead whales have been observed during ASAMM surveys in Block 1a which encompasses the Level A harassment zone since Block 1a surveys in began in 2016. Additionally, shutdown requirements within designated shutdown zones for LF
cetaceans which include bowhead whales are expected to prevent take by Level A harassment given the large size and visibility of bowhead whales.
Additionally, Level A harassment zones are calculated with an associated duration component based on the amount of pile driving expected to
occur within one day. Therefore, a marine mammal is not taken by Level A
harassment instantaneously when it enters the Level A harassment zone, and given the shallow depths, even if a bowhead did enter the Level A
harassment zone, we would not expect it to remain within the zone for a long enough period to incur PTS. Therefore, we do not expect Level A harassment of bowhead whales to occur, and are not authorizing Level A harassment take of bowheads.
The likelihood of gray whales occurring in the Level A harassment zone is extremely low, as evidenced by the very low densities included in the Marine Mammal Occurrence section and the lack of modeled takes in Table 15. Further, shutdown requirements within designated shutdown zones for LF cetaceans which include gray whales are expected to prevent take by Level A harassment given the large size and visibility of gray whales, and the duration component associated with the Level A harassment zones. Even if a gray whale did enter the Level A
harassment zone, we would not expect
it to remain within the zone for a long enough period to incur PTS, given the mitigation and visibility. Therefore, we do not expect Level A harassment of gray whales to occur, and are not authorizing Level A harassment take of gray whale.
The largest Level A harassment zone for mid-frequency cetaceans including the beluga whale extends 56 m from the source during impact driving of the 48inch pipe piles Table 6. Considering the small size of the Level A harassment zones, and the low likelihood that a beluga will occur in this area, Level A
harassment take is unlikely to occur.
Further, no Level A harassment takes are modeled given the corrected zone size used in the calculation in this final IHA. Additionally, AGDC is planning to implement a 50 m shutdown zone during this activity, which includes the <1 m peak PTS isopleth. We expect shutdown zones will eliminate the potential for Level A harassment take of beluga whale. Therefore, we are not authorizing takes of beluga whale by Level A harassment.
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TABLE 16AUTHORIZED INCIDENTAL TAKE BY LEVEL A AND LEVEL B HARASSMENT, BY SPECIES AND STOCK
Common name
Stock
Level A
harassment take e
Level B
harassment take e
Total instances of take
Bowhead Whale
Gray Whale
Beluga Whale a
Western Arctic
Eastern North Pacific
Beaufort Sea
Chukchi Sea
Arctic d
Bering d
0
0
0
9b 2b
110
2
55
1,765
353
110
2
55
1,774
355
Ringed Seal
Spotted Seal
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Stock abundance 16,820
26,960
39,258
c 13,305
N/A
461,625
Percent of stock 0.65
0.007
0.14
0.4
N/A
0.08
