Abstract
This report supplements the Revolution Wind Farm Construction and Operations Plan.
Revolution Wind, LLC (Revolution Wind), a 50/50 joint venture between Ørsted North America Inc. (Ørsted NA) and Eversource Investment LLC (Eversource), proposes to construct, own, and operate the Revolution Wind Farm (RWF) in the designated Bureau of Ocean Energy Management (BOEM) Renewable Energy Lease Area OCS-A 0486. RWF includes up to 100 foundations consisting of wind turbine generators (WTG) and two offshore substations (OSS), as well as inter-array cables (IAC) connecting the WTG and OSS. The WTG will each be supported by a tapered monopile foundation that is 7 m on top and 12 m diameter at the mudline, while the OSS will be supported by a tapered 7 m (top) to 15 m (mudline) monopile foundation.
Underwater noise associated with the construction of the RWF will predominantly result from the impact pile driving of the monopile foundations. A quantitative assessment of the sounds produced by the impact pile driving of the monopile foundations was undertaken in this study. Other sources of sound, such as dynamic positioning (DP) vessel thrusters used during cable installation and vessel propulsion during transit, were considered here as a qualitative assessment.
WTG monopile foundations consisting of a single pile, tapered from 7 to 12 m in diameter, were modeled at two representative locations in the lease area. Forcing functions for impact pile driving were computed for each pile type using GRLWEAP (GRLWEAP, Pile Dynamics 2010). The resulting forcing functions were used as inputs to JASCO’s impact pile driving source model to characterize the sounds generated by the piles. Acoustic sound fields were estimated using JASCO’s Marine Operations Noise model (MONM) and Full Wave Range Dependent Acoustic Model (FWRAM). To account for the likely minimum sound reduction resulting from noise abatement systems (NAS) such as bubble curtains, the modeling study included hypothetical broadband attenuation levels of 0, 6, 10, and 15 dB for all impact pile driving acoustic modeling results. Based on a recent analysis of NAS (Bellmann et al. 2020), the 10 dB level was conservatively chosen as an achievable sound reduction level when one NAS is in use during pile driving, and is highlighted in this analysis.
The goal of the study was to determine the number of individual animals that may be impacted and the associated monitoring distances (exposure and acoustic ranges) for mitigation purposes. JASCO’s animal movement modeling software, JASMINE, was used to integrate the computed sound fields with speciestypical movement (e.g., dive patterns) to estimate received sound levels for the modeled marine mammals and sea turtles that may occur near the construction area. Using the time history of the received levels, exposure estimates and exposure ranges accounting for 95% of exposures above regulatory-defined injury and behavioral disruption thresholds (NMFS 2018, McCauley et al. 2000a, Finneran et al. 2017) were calculated. Fish were considered static receivers, so the acoustic distance to their regulatory thresholds (FHWG Andersson et al. 2007, Wysocki et al. 2007, 2008, Stadler and Woodbury 2009, Mueller-Blenkle et al. 2010, Purser and Radford 2011) were calculated. Exposure ranges (marine mammals) and acoustic ranges (fish) are reported for various levels (0, 6, 10, and 15) of broadband attenuation that could be expected from the use of mitigation systems such as a bubble curtain.