Notice of Availability of a Draft Supplemental Site-Specific Environmental Assessment for the NSF OOI Pioneer Array Modifications and Relocation to the Mid-Atlantic Bight

The National Science Foundation (NSF) gives notice of the availability of the “Draft Supplemental Site-Specific Environmental Assessment for Pioneer Array Modifications and Relocation to the Mid-Atlantic Bight” (Draft SSSEA) for review and public comment on the NSF website (, closing on October 28, 2023. Comments may be submitted to:  Comments received will be addressed in the Final SSSEA.

NSF proposes to fund the relocation, operation, and maintenance of the NSF Ocean Observatory Initiative’s (OOI) Pioneer Array to the Mid-Atlantic Bight (MAB) off North Carolina in the Northwest Atlantic Ocean (Proposed Action). The OOI is a globally distributed, networked, ocean-focused research observatory with arrays of sophisticated instruments that utilize cutting-edge technologies to observe and study ocean processes.  The Pioneer MAB Array would represent a Coastal Scale Node component of the OOI.

The Proposed Action would (1) relocate the Pioneer New England Shelf (Pioneer NES) Array to the southern MAB (Pioneer MAB Array); 2) modify the mooring designs for the new site water depths; and 3) include additional scientific instrumentation on the moorings. The Proposed Action would occur within the Exclusive Economic Zone (EEZ) of the U.S. but outside of state waters.  The Pioneer MAB Array would be a T-shape array located off the coast of Nags Head, North Carolina, starting ~24 kilometers (km) (~13 nautical miles [nm]) offshore, extending ~59 km (~32 nm) east/west and ~49 km (~26 nm) north/south across the continental shelf, centered at the shelf-break front.  The Project Area, including the surrounding area of potential effect, would consist of 10 moorings and a 2 km by 2 km (1 nm by 1 nm) square around the center point of each of the mooring locations. In addition, there would be mobile assets, such as autonomous underwater vehicles (AUVs) and gliders that would operate around the moorings. Gliders and AUVs would run underwater missions along tracks in the vicinity of the moored array. Two (2) AUVs and four (4) gliders would be used to provide underwater monitoring abilities along and across the shelf and within the waters of the continental slope. Gliders would be deployed on a 60-90-day rotation schedule and would be operated continuously along pre-determined paths, while the AUVs would be deployed for limited periods of ~4 days every 2 months. 

Additional information about the proposed Pioneer MAB Array can be found in the Draft SSSEA and tiered OOI NEPA documentation, including details on relocation, operations, and maintenance; scientific instrumentation; potential effects, and diagrams of the array components. The Draft SSSEA evaluated the potential impacts of the Proposed Action on the human and natural environment, pursuant to the National Environmental Policy Act (NEPA) and tiers to existing OOI NEPA documentation1. The Draft SSSEA focused on activities and associated potential impacts on marine resources (e.g., geological, marine biological, socioeconomic, etc.) that were not previously assessed by existing OOI NEPA analyses. The conclusions from the Draft SSSEA were used to inform the NSF Division of Ocean Sciences (OCE) of potential environmental impacts of the Proposed Action. After reviewing and considering all public comments received during the public comment period and regulatory processes, NSF will issue a Final Supplemental Site-Specific Environmental Assessment (Final SSSEA), accompanied by a decision document.