DRAFT SUPPLEMENTAL OVERSEAS ENVIRONMENTAL ASSESSMENT For Office of Naval Research Arctic Research Activities in the Beaufort Sea October 2021 – October 2022

The Office of Naval Research (ONR) prepared this Supplemental Overseas Environmental Assessment (SOEA) in compliance with the Executive Order (E.O.) 12114, Department of Defense regulations found at 32 Code of Federal Regulations Part 187and the Chief of Naval Operations Instruction 5090.1 and its accompanying manual (M-5090). This SOEA updates and revises the OEA ONR prepared in 2018 and the supplement to that document prepared in 2019, both of which this SOEA incorporates by reference. This SOEA evaluates the potential harm to the environment from ONR Arctic Research Activities that would occur because of changes in the 2018 and 2019 Proposed Actions resulting from revised 2021-2022 research activities. The Naval requirement for this continuing scientific research still relates to the need to understand environmental conditions to ensure combat capable forces ready to deploy worldwide in accordance with Title 10 United States Code (U.S.C.) § 8062, and to support the aims of the Arctic Research and Policy Act (15 U.S.C. §§ 4101 et seq.). For the Arctic this consists of potential submarine and surface ship operations with active sonar for anti-submarine warfare and submarine/surface ship force protection. The characterization of the potential Arctic battlespace, given the changes in water properties and ice cover, is critical to performance predictions for active and passive acoustic systems. The year-round characterization of the Arctic environment requires the development of a navigation system for vehicles operating under the ice through the use of intermittent acoustic source transmissions, and rapid characterization of the environment by leave-behind sources. The purpose of the Proposed Action is still to conduct scientific research in the Arctic and to gather data on environmental conditions and acoustics in an Arctic environment. This SOEA evaluates three alternatives: the No Action Alternative and two Action Alternatives. The No Action Alternative would be limited to a cruise for the retrieval of previously deployed acoustic sources. Alternative 1, the Preferred Alternative, starting with the next research cruise scheduled for October 2021, reflects proposed changes and additions to the location and use of active acoustic sources to improve ONR’s ability to meet scientific objectives including a very low frequency source. Alternative 2 includes everything within the Preferred Alternative except the use of the very low frequency source. In this SOEA, the Navy analyzes potential harm to the environment that could result from the updates to two Action Alternatives in comparison to the No Action Alternative. Only marine mammals were analyzed for potential for “significant harm” (as defined by E.O. 12114) by the Proposed Action updates. This is the fourth year of activities for a longer project. Previous Incidental Take Authorizations (ITAs) have been issued, including 2 standard Incidental Harassment Authorizations (IHAs) and one renewal IHA.