Federal Register - August 5, 2021
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Source: Federal Register
Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations The number of times each flight path was flown i.e., flight frequency was determined from the Request. We used the description combined with the
approximate number of weeks and months within the open-water season and the ice season to determine the total number of flights per season for each
43023
year f. We then used flight frequency and number of days per season ds to calculate the seasonal proportion of flights Sp; Equation 6.
f sp -- ds Equation 6
After we determined the seasonal proportion of flights, we estimated the amount of time an aircraft would be impacting the landing/take-off areas within a day tLT. Assuming an aircraft is not landing at the same time another is taking off from the same airstrip, we
estimated the amount of time an aircraft would be present within the landing or take-off zone would be tLT = 10 minutes.
We then calculated how many minutes within a day an aircraft would be impacting an area and divided by the number of minutes within a 24-hour
period 1,440 minutes. This determined the proportion of the day in which a landing/take-off area is impacted by an aircraft for each season DpLT;
Equation 7.
1440
Equation 7
To estimate the amount of time an aircraft would be impacting the travel areas tTR, we calculated the minimum amount of time it would take for an aircraft to travel the maximum exposure area at any given time, 3.22 km 2.00
mi. We made this estimate using average aircraft speeds at altitudes less than 305 m 1,000 ft to account for
DpTR
=
slower flights at lower altitudes, such as summer cleanup activities and determined it would take approximately 1.5 minutes. We then determined how many 3.22-km 2-mi segments are present along each traveling path x.
We determined the total number of minutes an aircraft would be impacting any 3.22-km 2-mi segment along the
Sp tTR
travel area in a day and divided by the number of minutes in a 24-hour period.
This calculation determined the proportion of the day in which an aircraft would impact an area while traveling during each season DpTR;
Equation 8.
x
1440
Equation 9
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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.
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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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khammond on DSKJM1Z7X2PROD with RULES2
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
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Equation 8
