Voglio sapere a riguardo di…

43022

Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations
stretches between two air strips was considered the traveling area. We then applied the exposure area of 1,610
m 1 mi along the flight paths. The data used to estimate the probability of Level B harassments due to aircraft see section Estimating Harassment Rates of Aircraft Activities suggested 99% of groups of bears were observed within 1.6 km of the aircraft.
We then differentiated the coastal and inland zones. The coastal zone was the area offshore and within 2 km 1.2 mi of the coastline see section Spatially Partitioning the North Slope into coastal and inland zones, and the
inland zone was anything greater than 2
km 1.2 mi from the coastline. We calculated the areas in square kilometers for the exposure area within the coastal zone and the inland zone for all takeoffs, landings, and traveling areas. For flights that involve an inland and a coastal airstrip, we considered landings to occur at airstrips within the coastal zone. Seasonal encounter rates developed for both the coastal and inland zones see section Search Effort Buffer were applied to the appropriate segments of each flight path.
Surface encounter rates were calculated based on the number of bears
per season see section Search Effort Buffer. To apply these rates to aircraft activities, we needed to calculate a proportion of the season in which aircraft were flown. However, the assumption involved in using a seasonal proportion is that the area is impacted for an entire day i.e., for 24 hours.
Therefore, to prevent estimating impacts along the flight path over periods of time where aircraft are not present, we calculated a proportion of the day the area will be impacted by aircraft activities for each season Table 5.
BILLING CODE 433315P

Table 5-Variable definitions and constant values used in polar bear harassment estimates for winter and summer aircraft activities on the coast of the North Slope of Alaska.

Sp
f DpLT
tLT

DpTR
tTR
X

Bes B;
ac a;
eco
eci
khammond on DSKJM1Z7X2PROD with RULES2

eio
eii
fa
B1

VerDate Sep<11>2014

Definition days in each season proportion of the season an area of interest is impacted flight frequency proportion of the day landing/take-off areas are impacted by aircraft activities amount of time an aircraft is impacting landing/take-off areas within a day proportion of the day traveling areas are impacted by aircraft activities amount of time an aircraft is impacting traveling areas number of 3.22-km 2-mi segments within each traveling area bears encountered in an area of interest for the entire season bears impacted by aircraft activities coastal exposure area inland exposure area coastal open-water season bear-encounter rate in bears/season coastal ice season bear-encounter rate in bears/season inland open-water season bear-encounter rate in bears/season inland ice season bear-encounter rate in bears/season aircraft harassment rate number of estimated level B harassments
17:26 Aug 04, 2021

Jkt 253001

PO 00000

Frm 00042

Fmt 4701

Sfmt 4725

Value open-water season= 116, ice season = 249
varies by flight varies by flight varies by flight 10 minutes per flight varies by flight 1.5 minutes per 3.22 km f2 mil segment per flight varies by flight varies by flight varies by flight 1,610 m 1 mi 1,610 m 1 mi 3.45 bears/km2/season 0 .118 bears/km2I season 0.0116 bears/km2I season 0.0104 bears/km2I season 0.23
varies by flight
E:FRFM05AUR2.SGM

05AUR2

ER05AU21.009

Variable ds