Abstract
This report supplements the Kitty Hawk North Wind Construction and Operations Plan.
Tetra Tech, Inc. (Tetra Tech) was contracted by Kitty Hawk Wind, LLC (the Company), a wholly owned subsidiary of Avangrid Renewables, LLC, to evaluate the potential suspended sediment transport and deposition associated with the Kitty Hawk North Wind Project (Project) construction activities, including installation of submarine export and inter-array cables. Disturbance of sediments during Project construction has the potential to affect water quality through increases to total suspended solids in the water column and deposition of sediments away from the location of sediment disturbance through resuspension, dispersal, and subsequent sedimentation.
In order to provide a conservative estimate of potential maximum suspended sediment transport and deposition impacts in the Construction and Operations Plan, site-specific sediment data and publicly available water circulation data covering the northwest portion of the designated Renewable Lease Area OCS-A 508 (Lease Area), closest to land (Wind Development Area) and along the offshore export cable corridor (altogether, offshore Project Area) were used to develop the sediment transport model. The modeling was undertaken to quantify potential maximum plume dispersion; suspended sediment concentrations; and potential maximum sediment deposition thicknesses that may occur due to Project construction.
Modeling performed for the previous COP submittal was limited to analysis of sediment disturbance due to jet-plow cable installation and HDD at landfall and used site-specific sediment characteristics described in the Kitty Hawk Project Benthic Assessment Report – Phase 2 Reconnaissance dated June 16, 2020. To address BOEM comments provided in March 2022 based on the previous COP submittal, Tetra Tech analyzed the sediment disturbance due to pre-cable installation dredging and used site-specific sediment characteristics described in the Kitty Hawk Project Benthic Assessment Report – Phase 2 Reconnaissance and the newer Kitty Hawk Wind Project Benthic Assessment Report – Phase 3 dated June 24, 2021.