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Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations those listed in Table 7. The case studies used to inform the post-emergence period include one where an individual fell into a den and caused the female to abandon her cubs. Given that pipeline surveys would either occur with a plane or a vehicle driving along an established path adjacent to a pipeline, there would be no chance of falling into a den.
Therefore, we excluded this case study from the calculation of disturbance probabilities applied to our analysis, which led to a 0 percent probability of lethal take and a 100 percent probability of non-serious injury Level A
harassment.
For dens exposed to human activity, we used a multinomial distribution with the probabilities of different levels of take for that period Table 7. If a Level A harassment or lethal take was simulated to occur, a den was not allowed to be disturbed again during the subsequent denning periods because the outcome of that denning event was already determined. As noted above, Level A harassments and lethal takes only applied to cubs because proposed activities would not result in those levels of take for adult females. Adult females, however, could still receive Level B harassment during the den establishment period or any time cubs received Level B harassment, Level A
harassment i.e., serious injury and nonserious injury, or lethal take.

We developed the code to run this model in program R R Core Development Team 2021 and ran 10,000 iterations of the model i.e., Monte Carlo simulation to derive the estimated number of animals disturbed and associated levels of take. We ran the model for each of the five winters covered by the ITR i.e., 2021/2022, 2022/2023, 2023/2024, 2024/2025, 2025/2026. For each winters analysis, we analyzed the most impactful scenario that was possible. For example, seismic surveys may not occur every winter, but it is unclear which winters would have seismic surveys and which would not. Therefore, each of the scenarios were run with the inclusion of seismic surveys and their additional AIR surveys knowing that take rates will be less for a given winter if seismic surveys did not occur. Similarly, in some winters, winter travel between Deadhorse and Point Thomson will occur along an ice road running roughly parallel to the pipeline connecting the two locations. However, in other winters, the two locations will be connected via a tundra travel route farther south. Through preliminary analyses, we found that the tundra travel route led to higher annual take estimates. Therefore, for each of the scenarios, we only considered the tundra travel route knowing that take
rates will be less when the more northern ice road is used.
Model Results On average, we estimated 52 median = 51; 95% CI: 3080 land-based dens in the area of proposed activity in AOGAs Request within a 1.6-km 1-mi buffer.
Annual estimates for different levels of take are presented in Table 8. We also estimated that Level B harassment take from AIR surveys was never greater than a mean of 1.53 median = 1; 95% CI: 0
5 during any winter. The distributions of both non-serious Level A and serious Level A/Lethal possible takes were nonnormal and heavily skewed, as indicated by markedly different mean and median values. The heavily skewed nature of these distributions has led to a mean value that is not representative of the most common model result i.e., the median value, which for both nonserious Level A and serious Level A/
Lethal takes is 0.0 takes. Due to the low <0.29 for non-serious Level A and 0.462 for serious Level A/Lethal takes probability of greater than or equal to 1
non-serious or serious injury Level A
harassment/Lethal take each year of the proposed ITR period, combined with the median of 0.0 for each, we do not estimate the proposed activities will result in non-serious or serious injury Level A harassment or lethal take of polar bears.

TABLE 8RESULTS OF THE DEN DISTURBANCE MODEL FOR EACH WINTER OF PROPOSED ACTIVITY
Level B harassment
Non-serious Level A

Serious Level A/lethal
Winter 20XX
Prob 2122
2223
2324
2425
2526

Mean
0.89
0.90
0.90
0.90
0.90

Med
3.1
3.2
3.1
3.1
3.2

95% CI

3.0
3.0
3.0
3.0
3.0

09
09
09
09
09

Prob 0.28
0.29
0.28
0.28
0.28

Mean 0.7
0.7
0.6
0.6
0.7

Med
95% CI

0.0
0.0
0.0
0.0
0.0

04
04
04
04
04

Prob 0.45
0.46
0.46
0.46
0.46

Mean 1.2
1.2
1.2
1.2
1.2

Med 0.0
0.0
0.0
0.0
0.0

95% CI
05
06
05
06
05

Estimates are provided for the probability Prob, mean, median Med, and 95% Confidence Intervals CI for Level B, Non-Serious Level A, and Serious Level A/
Lethal take. The probabilities represent the probability of 1 take of a bear occurring during a given winter.

Maritime Activities
khammond on DSKJM1Z7X2PROD with RULES2

Vessel Traffic Maritime activities were divided into two categories of potential impact:
vessel traffic and in-water construction.
Vessel traffic was further divided into two categories: Repeated, frequent trips by small boats and hovercraft for crew movement and less frequent trips to move fuel and equipment by tugs and barges. We estimated the potential Level B harassment take from the repeated, frequent trips by crew boats and hovercraft in Polar Bear: Surface
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Interactions as marine roads using an occupancy rate of 0.2. This occupancy rate accounts for 20 percent of the impact area i.e., the length of the route buffered by 1.6 km 1 mi being impacted at any given point throughout the year, which is consistent with the daily trips described by AOGA.
For less frequent trips for fuel and equipment resupply by tugs and barges, AOGA has supplied the highest expected number of trips that may be taken each year. Because we have been supplied with a finite number of potential trips, we used the impact area
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of the barge/tug combination as it moves in its route from one location to the next. We estimated a 16.5-km2 6.37mi2 take area for the barge, tug, and associated tow line, which accounts for a barge, tow, and tug length of 200 m 656 ft, width of 100 m 328 ft, and a 1.6-km 1-mi buffer surrounding the vessels. We calculated the total hours of impact using an average vessel speed of two knots 3.7 km/hr, and then calculated the proportion of the openwater season that would be impacted Table 9.

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