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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices
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animat starting out in or transitioning into a given behavioral state can be defined in terms of the animats current behavioral state, depth, and the time of day. In addition, each travel parameter and behavioral state has a termination function that governs how long the parameter value or overall behavioral state persists in the simulation.
The output of the simulation is the exposure history for each animat within the simulation, and the combined history of all animats gives a probability density function of exposure during the project. Scaling the probability density function by the real-world density of animals Table 13 results in the mean number of animats expected to be exposed over the duration of the project.
Due to the probabilistic nature of the process, fractions of animats may be predicted to exceed threshold. If, for example, 0.1 animats are predicted to exceed threshold in the model, that is interpreted as a 10% chance that one animat will exceed a relevant threshold during the project, or equivalently, if the simulation were re-run ten times, one of the ten simulations would result in an animat exceeding the threshold.
Similarly, a mean number prediction of 33.11 animats can be interpreted as rerunning the simulation where the number of animats exceeding the threshold may differ in each simulation but the mean number of animats over all of the simulations is 33.11. A portion of an individual marine mammal cannot be taken during a project, so it is common practice to round mean number animat exposure values to integers using standard rounding methods. However, for low-probability events it is more precise to provide the actual values.
Sound fields were input into the JASMINE model and animats were programmed based on the best available information to behave in ways that reflect the behaviors of the 16 marine mammal species expected to occur in the project area during the proposed activity. The various parameters for forecasting realistic marine mammal behaviors e.g., diving, foraging, surface times, etc. are determined based on the available literature e.g., tagging studies; when literature on these behaviors was not available for a
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particular species, it was extrapolated from a similar species for which behaviors would be expected to be similar to the species of interest. Please refer to the footnotes on Tables 16 and 17, and Appendix P2 of SFWF COP for a more detailed description of the species that were used as proxies when data on a particular species was not available. The parameters used in JASMINE describe animat movement in both the vertical and horizontal planes e.g., direction, travel rate, ascent and descent rates, depth, bottom following, reversals, inter-dive surface interval.
More information regarding modeling parameters can be found in Denes et al.
2020c.
The mean number of animats that may be exposed to noise exceeding acoustic thresholds were calculated for two construction schedules; one representing the most likely schedule, and one representing a more aggressive, or maximum schedule Denes et al., 2019. The most likely schedule assumes that three foundations are installed per week with an average of one pile installed every other day. The maximum schedule assumes six monopile foundations are installed per week with one pile installation per day.
Within each of the construction schedules, a single difficult-to-drive pile was included in the model assumptions to account for the potential for additional strikes Denes et al., 2019.
Animats were modeled to move throughout the three-dimensional sound fields produced by each construction schedule for the entire construction period. For PTS exposures, both SPLpk and SELcum were calculated for each species based on the corresponding acoustic criteria. Once an animat is taken within a 24-hrs period, the model does not allow it to be taken a second time in that same period but rather resets the 24-hrs period on a sliding scale across 7 days of exposure. An individual animats exposure levels are summed over that 24-hrs period to determine its total received energy, and then compared to the threshold criteria.
Potential behavioral exposures are estimated when an animat is within the area ensonified by sound levels exceeding the corresponding thresholds.

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It should be noted that the estimated numbers of individuals exceeding any of the thresholds is conservative because the 24-hrs evaluation window allows individuals to be counted on multiple days or can be interpreted as different individuals each 24-hrs period when in the real world it may in fact be the same individual experiencing repeated exposures Denes et al., 2019.
Also note that animal aversion was not incorporated into the JASMINE model runs that were the basis for the take estimate for any species. See Appendix P2 of the SFWF COP for more details on the JASMINE modeling methodology, including the literature sources used for the parameters that were input in JASMINE to describe animal movement for each species that is expected to occur in the project area.
In summary, exposures were estimated in the following way:
1 The characteristics of the sound output from the proposed pile-driving activities were modeled using the GRLWEAP wave equation analysis of pile driving model and JASCOs PDSM;
2 Acoustic propagation modeling was performed within the exposure model framework using JASCOs MONM and FWRAM that combined the outputs of the source model with the spatial and temporal environmental context e.g., location, oceanographic conditions, seabed type to estimate sound fields;
3 Animal movement modeling integrated the estimated sound fields with species-typical behavioral parameters in the JASMINE model to estimate received sound levels for the animals that may occur in the operational area; and 4 The number of potential exposures above Level A and Level B harassment thresholds was calculated for each potential piling scenario standard, maximum.
All scenarios were modeled with no sound attenuation and 6, 10, 12, and 15
dB sound attenuation. The results of marine mammal exposure modeling for the potentially more impactful maximum piling scenarios are shown in Tables 16 and 17, as these form the basis for the take authorization proposed in this document.

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