During March and April 2018, Apline Ocean Seismic Survey, Inc. (Alpine) was contracted by Statoil US Wind LLC (now known as Equinor US Wind LLC) to acquire high resolution geophysical (HRG), environmental and geotechnical survey data in sections of the Commercial Lease of Submerged Lands and Renewable Energy Development on the Outer Continental Shelf (OCS-A 0512). The survey data was required to inform the Site Assessment Plan (SAP) for the deployment of Floating Light Detection and Ranging Buoys and metocean moorings for site resource characterization. The SAP Survey Campaign area is located 22 to 39 kilometers south of Long Island, New York and covered an area of approximately 1380 km2.
The objective of the survey as defined by the scope of work was to obtain data for:
- Identification of historic properties on or within the seabed
- Identification of seafloor sediment and seafloor morphology
- Identification of seabed obstructions
- Identification of mobile sand deposits
- Quantify and describe the characteristics of seabed sediments
- Describe the biological nature of the seabed
- Mapping of sand thickness and identification of the unconformity related to the last sea level lowstand
- Identification of shallow paleolandforms that could represent high probability locations (e.g. former river bank areas) where humans would have inhabited when the continental shelf was emergent during the last sea level lowstand
- Identify geological or manmade hazards (e.g. buried objects, shallow gas, lithological heterogeneities, etc.) beneath the seafloor that could affect the mooring systems
- Image the shallow subsurface conditions to support the interpretation and mapping of stratigraphic layering and geologic structure
- Map shallow and deep channel infill
- Map presence of gravel lab
- Describe Unit formation and Stratigraphy
A full geophysical suite consisting of multi-beam bathymetry, side scan sonar, magnetometer, and shallow and medium penetration sub-bottom profiler (high-frequency CHIRP, and single channel sparker) was acquired. The original survey objective was to target up to three Flidar survey locations (Flidar 1 to Flidar 3), however a decision was made by the client to only survey two Flidar sites (Flidar 1 and Flidar 2). Subsequently the current report and the site assessment plan (SAP) will refer to and apply to the two discrete Flidar deployment areas. Four environmental sampling stations (ST18904-ENV1 to ST18904-ENV4) were pre-selected by the client to cover each Flidar location and metocean buoy location. Following review of the geophysical data, one additional station (ST18904-ENV6) was chosen to investigate an area of medium reflectivity to ensure good coverage of all seabed substrate types. The four environmental stations were investigated using a shallow water camera system to acquire seabed imagery and a modified 0.1m2 Day grab to acquire sediment samples. At each station, three modified 0.1m2 Day grab samples were collected and described. Two of the samples were acquired for macrofauna and sieved through a 1mm sized mesh, one of the samples (MFA) was later sent for analyses with the other (MFB) retained as a spare. The third sample (CHEM) was acquired for particle size and total organic matter analyses.