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Federal Register / Vol. 86, No. 24 / Monday, February 8, 2021 / Notices
TABLE 5NMFS TECHNICAL GUIDANCE USER SPREADSHEET INPUT TO CALCULATE LEVEL A ISOPLETHS FOR A
COMBINATION OF PILE DRIVING
Method Vibratory Vibratory Vibratory Vibratory
Pile type
Driving
Driving
Removal
Removal

Sheet H pile Sheet H pile
Source level db RMS

165
150
165
150

Minutes per pile
Piles per day 30
30
15
15

8
8 16
16

Note: Transmission Loss for all methods is 15 LogR and the weighting factor adjustment is 2.5.

Marine Mammal Occurrence and Take Calculation and Estimation In this section we provide the information about the presence, density, or group dynamics of marine mammals that will inform the take calculations.
The main source of density information for the area is the U.S. Navys database used to establish baseline density estimates for their construction and testing and training activities in Puget Sound U.S. Navy, 2019. The Navy database includes seasonal estimates of abundance where available and appropriate. Where such estimates existed, we used the larger density estimate for the fall or summer seasons, when this project is scheduled to occur.
These density estimates are shown in Table 6. No density estimates exist for the rarer short-beaked common dolphin so we used more qualitative data on observations from The Whale Museums sightings database and project specific report to WADOT TWM, 2020.

TABLE 6DENSITY OF MARINE MAMMALS USED TO CALCULATE EXPECTED TAKE
Species
Density /km2

Harbor seal
California sea lion
Steller sea lion
Gray whale
Short-beaked common dolphin
Harbor porpoise

3.91
0.2211
0.0478
0.000086

0.86

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See text, no density estimate exists for short-beaked common dolphins.

Here we describe how the information provided above is brought together to produce a quantitative take estimate.
Given the geography of the project area, the area ensonified when driving or removing H piles is 1.36 square kilometers km2 0.53 square miles mi2, the area ensonified when driving or removing sheetpiles is 17.9 km2 6.9
mi2, and the area ensonified when using the needle gun is 0.06 km2 0.023
mi2 for phocids and 0.01 km2 0.004
mi2 for otariids. As noted above, there will be a total of 5 days driving or removing H piles, 9 days driving or
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removing sheetpiles, and 6 days of using the needle gun. For species with density estimates, the estimated take is calculated as the sum of the density times the area and days for each pile type/activity with the results for each activity added to give a total estimated take. Additional qualitative factors may be considered for species with small estimated take calculations see below.
Take by Level B harassment is authorized and summarized in Table 7.
Gray Whale The Navy Marine Species Density Database U.S. Navy 2019 estimates the density of gray whales in the Henderson Bay area as 0.000086/km2. Based on this density estimate, the following number of gray whales may be present in the Level B harassment zones:
H piles: 0.000086/km2 1.36 km2 5
days = 0.0005848
Sheetpiles: 0.000086/km2 17.9 km2
9 days = 0.0138546
Total Estimated Take = 0.014 animals The total represents less than one gray whale. In the event an individual enters the area and remains for some time and is harassed on multiple days, we are authorizing Level B harassment of 10
gray whales. Because the Level A
harassment zones are relatively small and we believe the PSO will be able to effectively monitor the Level A
harassment zones, we do not authorize take by Level A harassment of gray whales.
Short-Beaked Common Dolphin As mentioned above, the Navy Marine Species Density Database U.S. Navy 2019 does not provide an estimate of density of short-beaked common dolphins in the Henderson Bay area.
The Whale Museum data indicate that common dolphins have been documented in waters adjacent to the project TWM, 2020. Nearly all sightings were in 2016 and 2017
pointing out the variability and uncertainty of their presence. Shortbeaked common dolphins often occur in groups; for the Puget Sound data groups consisted of no more than five individuals Orca Network. 2020. Due
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to the low likelihood of occurrence an expectation of one group of five animals in the large level B harassment zone for sheetpiles per day is a reasonable representation of occurrence. With 9
days of sheetpiling maximum this equates to 45 level B takes. Because of the smaller size of the Level B
harassment zones for the H piles, we expect that one group of five animals over the course of the 5 work days with H piles is a reasonable representation of occurrence. We are thus authorizing Level B harassment of 50 short-beaked common dolphins. Because the Level A
harassment zones are relatively small and we believe the PSO will be able to effectively monitor the Level A
harassment zones, we do not authorize take by Level A harassment of shortbeaked common dolphins.
Harbor Porpoise The Navy Marine Species Density Database U.S. Navy 2019 estimates the density of harbor porpoise in the Henderson Bay area as 0.86/km2. Based on this density estimate, the following number of harbor porpoises may be present in the Level B harassment zones:
H piles: 0.86/km2 1.36 km2 5 days = 5.848
Sheetpiles: 0.86/km2 17.9 km2 9
days = 138.546
Total Estimated Take = 144.4 animals We are authorizing Level B
harassment of 145 harbor porpoises.
Because the Level A harassment zones are relatively small and we believe the PSO will be able to effectively monitor the Level A harassment zones, we do not authorize take by Level A
harassment of harbor porpoises.
California Sea Lion The Navy Marine Species Density Database U.S. Navy 2019 estimates the density of California sea lions in the Henderson Bay area as 0.2211/km2.
Based on this density estimate, the following number of California sea lions may be present in the Level B
harassment zones:
H piles: 0.2211/km2 1.36 km2 5 days = 1.503

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