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Federal Register / Vol. 86, No. 103 / Tuesday, June 1, 2021 / Proposed Rules We then used observations of behavioral reactions from aerial surveys see section Estimating Harassment Rates of Aircraft Activities to determine the appropriate harassment rate in the exposure area 1,610 m 1 mi from the center of the flight line; see above in this
section. The harassment rate areas were then calculated separately for the landing and take-off areas along each flight path as well as the traveling area for all flights with altitudes at or below 457.2 m 1,500 ft.
To estimate number of polar bears harassed due to aircraft activities, we
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first calculated the number of bears encountered Bes for the landing/takeoff and traveling sections using both coastal eci or co and inland eii or io encounter rates within the coastal ac and inland ai exposure areas Equation 9.

Equation 9
Using the calculated number of coastal and inland bears encountered for each season, we applied the daily seasonal proportion for both landings/
take-offs and traveling areas to
determine the daily number of bears impacted due to aircraft activities Bi.
We then applied the aircraft harassment rate ta associated with the exposure area see section Estimating Harassment
Rates of Aircraft Activities, resulting in a number of bears harassed during each season Bt; Equation 10. Harassment associated with AIR surveys was analyzed separately.

Equation 10
Analysis Approach for Estimating Harassment During Aerial Infrared Surveys Typically, during every ice season Industry conducts polar bear den surveys using AIR. Although the target for these surveys is polar bear dens, bears on the surface can be impacted by the overflights. These surveys are not conducted along specific flight paths and generally overlap previously flown areas within the same trip. Therefore, the harassment estimates for surface bears during AIR surveys were estimated using a different methodology.
Rather than estimate potential flight paths, we used the maximum amount of flight time that is likely to occur for AIR
surveys during each year. The period of AIR surveys lasts November 25th to January 15th 52 days, and we
estimated a maximum of 6 hours of flight time per day, resulting in a total of 312 flight hours per year. To determine the amount of time AIR
flights are likely to survey coastal and inland zones, we found the area where industry activities and denning habitat overlap and buffered by 1.6 km 1 mi.
We then split the buffered denning habitat by zone and determined the proportion of coastal and inland denning habitat. Using this proportion, we estimated the number of flight hours spent within each zone and determined the proportion of the ice season in which AIR surveys were impacting the survey areas see General Approach to Estimating Harassment for Aircraft Activities. We then estimated the aircraft footprint to determine the area that would be impacted at any given time as well as the area accounting for two take-offs and two landings. Using
the seasonal bear encounter rates for the appropriate zones multiplied by the area impacted and the proportion of the season AIR flights were flown, we determined the number of bears encountered. We then applied the aircraft harassment rate to the number of bears encountered per zone to determine number of bears harassed.
Estimated Harassment From Aircraft Activities Using the approach described in General Approach to Estimating Harassment for Aircraft Activities and Analysis Approach for Estimating Harassment during Aerial Infrared Surveys, we estimated the total number of bears expected to be harassed by the aircraft activities included in the analyses during the proposed Beaufort Sea ITR period of 20212026 Table 6.

TABLE 6ESTIMATED LEVEL B HARASSMENT OF POLAR BEARS ON THE NORTH SLOPE OF ALASKA BY YEAR AS A RESULT
OF AIRCRAFT OPERATIONS DURING THE 20212026 PROPOSED ITR PERIOD
2122

2223

2324

2425

2526

26

Total
0.89

0.95

0.95

1.09

1.09

0.15

5.45

Est. Harassment

Case Studies Analysis To assess the likelihood and degree of exposure and predict probable responses of denning polar bears to
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activities proposed in the AOGA
application, we characterized, evaluated, and prioritized a series of rules and definitions towards a predictive model based on knowledge of published and unpublished information on denning ecology, behavior, and cub
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survival. Contributing information came from literature searches in several major research databases and data compiled from polar bear observations submitted by the oil and gas Industry. We considered all available scientific and observational data we could find on
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Methods for Modeling the Effects of Den Disturbance
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Average estimated polar bear harassments per year = 1.09 bears.