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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices
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offshore WTGs and one OSS, an onshore substation, offshore and onshore cabling, and onshore operations and maintenance facilities. WTGs would be arranged in a grid-like pattern with spacing of 1.9 km 1.15 mi; 1 nautical miles nm between turbines. Each WTG would interconnect with the OSS
via an inter-array submarine cable system. The offshore export cable transmission system would connect the OSS to an existing mainland electric grid in East Hampton, New York. A
temporary cofferdam may be installed where the offshore export cable conduit exits from the seabed to contain drilling returns and prevent the excavated sediments from silting back into the Horizontal Directional Drill HDD exit pit. The final location of the cofferdam will be dependent upon the selected cable landing site. Construction of the WTGs and OSS, including pile driving, could occur on any day from May 1, 2022 through December 31, 2022.
Cofferdam installation and extraction requiring vibratory pile driving could occur for up to 3 days from October 2022 through May, 2023. HRG surveys would be conducted throughout the 12month project timeframe. Activities associated with the construction of the project are described in more detail below.
Cable Laying Cable burial operations will occur both in the SFWF for the inter-array cables connecting the WTGs to the OSS
and in the SFEC for the cables carrying power from the OSS to land. Inter-array cables will connect the 15 WTGs to the OSS. A single offshore export cable will connect the OSS to the shore. The offshore export and inter-array cables will be buried beneath the seafloor at a target depth of up to 1.22.8 m 46 ft.
Installation of the offshore export cable is anticipated to last approximately 2
months. The estimated installation time for the inter-array cables is approximately 4 months. All cable burial operations will follow installation of the monopile foundations, as the foundations must be in place to provide connection points for the export cable and inter-array cables. Installation days are not continuous and do not include equipment preparation or down time that may result from weather or maintenance. Equipment preparation is not considered a source of marine mammal disturbance or harassment.
Some dredging may be required prior to cable laying due to the presence of sand waves. The upper portions of sand waves may be removed via mechanical or hydraulic means in order to achieve the proper burial depth below the stable
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sea bottom. The majority of the export and inter-link cable is expected to be installed using simultaneous lay and bury via jet plowing. Jet plowing entails the use of an adjustable blade, or plow, which rests on the sea floor and is towed by a surface vessel. The plow creates a narrow trench at the desired depth, while water jets fluidize the sediment within the trench. The cable is then fed through the plow and is laid into the trench as it moves forward. The fluidized sediments then settle back down into the trench and bury the cable. The majority of the inter-array cable is also expected to be installed via jet plowing after the cable has been placed on the seafloor. Other methods, such as mechanical plowing or trenching, may be needed in areas of coarser or more consolidated sediment, rocky bottom, or other difficult conditions in order to ensure a proper burial depth. The jet plowing tool may be based from a seabed tractor or a sled deployed from a vessel. A mechanical plow is also deployed from a vessel.
More information on cable laying associated with the proposed project is provided in South Fork Winds Construction and Operations Plan SFWF COP; South Fork Wind, 2020.
As the only potential impacts from these activities is sediment suspension, the potential for take of marine mammals to result from these activities is so low as to be discountable and South Fork Wind did not request, and NMFS does not propose to authorize, any takes associated with cable laying. Therefore, cable laying activities are not analyzed further in this document.
Construction-Related Vessel Activity During construction of the project, South Fork Wind anticipates that an average of approximately 510 vessels will operate during a typical work day in the SFWF and along the SFEC. Many of these vessels will remain in the SFWF or SFEC for days or weeks at a time, potentially making only infrequent trips to port for bunkering and provisioning, as needed. The actual number of vessels involved in the project at one time is highly dependent on the projects final schedule, the final design of the projects components, and the logistics needed to ensure compliance with the Jones Act, a Federal law that regulates maritime commerce in the United States.
Existing vessel traffic in the vicinity of the project area southeast of Rhode Island is relatively high and marine mammals in the area are expected to be habituated to vessel noise. In addition, construction vessels would be stationary on site for significant periods of time
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and the large vessels would travel to and from the site at relatively low speeds. Project-related vessels would be required to adhere to several mitigation measures designed to reduce the potential for marine mammals to be struck by vessels associated with the project; these measures are described further below see Proposed Mitigation.
As part of various construction related activities, including cable laying and construction material delivery, dynamic positioning thrusters may be utilized to hold vessels in position or move slowly.
Sound produced through use of dynamic positioning thrusters is similar to that produced by transiting vessels, and dynamic positioning thrusters are typically operated either in a similarly predictable manner or used for short durations around stationary activities.
Sound produced by dynamic positioning thrusters would be preceded by, and associated with, sound from ongoing vessel noise and would be similar in nature; thus, any marine mammals in the vicinity of the activity would be aware of the vessels presence, further reducing the potential for startle or flight responses on the part of marine mammals. Construction-related vessel activity, including the use of dynamic positioning thrusters, is not expected to result in take of marine mammals and South Fork Wind did not request, and NMFS does not propose to authorize, any takes associated with construction related vessel activity. Accordingly, these activities are not analyzed further in this document.
Installation of WTGs and OSS
Monopiles are the only foundation type proposed for the project. A
monopile is a single, hollow cylinder fabricated from steel that is secured in the seabed. The 16 monopiles installed to support the 15 WTG and single OSS
would be 11.0 m 33.0 ft in diameter, up to 95 m 311.7 ft in length and driven to a maximum penetration depth of 50 m 164 ft. A schematic diagram showing potential heights and dimensions of the various components of a monopile foundation are shown in Figure 3.12 of the SFWF COP South Fork Wind, 2020, available online at:
https www.boem.gov/renewableenergy/state-activities/south-fork.
The monopile foundations would be installed by one or two heavy lift or jack-up vessels. The main installation vessels will likely remain at the SFWF
during the installation phase approximately 30 days and transport vessels, tugs, and/or feeder barges would provide a continuous supply of foundations to the SFWF. If appropriate vessels are available, the foundation
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