OCS Study BOEM 2017-049 Geophysical and Geotechnical Investigation Methodology Assessment for Siting Renewable Energy Facilities on the Atlantic OCS US Department of the Interior Bureau of Ocean Energy Management Office of Renewable Energy Programs OCS Study BOEM 2017-049 Geophysical and Geotechnical Investigation Methodology Assessment for Siting Renewable Energy Facilities on the Atlantic OCS February 2017 Prepared under BOEM Contract M15PX00051 by Fugro Marine GeoServices, Inc. 101 West Main Street Suite 350 Norfolk, Virginia 23510 US Department of the Interior Bureau of Ocean Energy Management Office of Renewable Energy Programs OCS Study BOEM 2017-049 DISCLAIMER Study concept, oversight, and funding were provided by the US Department of the Interior, Bureau of Ocean Energy Management (BOEM), Environmental Studies Program, Washington, DC, under Contract Number M15PX00051. This report has been technically reviewed by BOEM, and it has been approved for publication. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the US Government, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. REPORT AVAILABILITY To download a PDF file of this report, go to the US Department of the Interior, Bureau of Ocean Energy Management Renewable Energy Environmental Studies webpage (http://www.boem.gov/Environmental- Studies-EnvData/). The report is also available at the National Technical Reports Library at https://ntrl.ntis.gov/NTRL/. CITATION Fugro Marine GeoServices Inc. 2017. Geophysical and Geotechnical Investigation Methodology Assessment for Siting Renewable Energy Facilities on the Atlantic OCS. US Dept. of the Interior, Bureau of Ocean Energy Management, Office of Renewable Energy Programs, Herndon. OCS Study BOEM 2017-049. FUGRO MARINE GEOSERVICES, INC. EXECUTIVE SUMMARY Study Title: Geophysical and Geotechnical Investigation Methodology Assessment for Siting Renewable Energy Facilities on the Atlantic OCS Bureau of Ocean Energy Management (BOEM) Executive Summary INTRODUCTION BOEM is responsible for managing energy and mineral resources on the Outer Continental Shelf (OCS). This includes ensuring that future renewable energy facilities located within the Atlantic Outer Continental Shelf (OCS) are properly studied using appropriate geophysical and geotechnical equipment and employing a series of standardized methodologies. Offshore renewable energy includes, but is not limited to, wind, wave, ocean current, solar, and hydrogen production energy. The Atlantic OCS is considered by BOEM to be a “Frontier Region” where little information exists about the geologic conditions and how those conditions may impact development of offshore wind farms. In contrast, regions such as the Gulf of Mexico, Baltic and North Seas have significantly more information and experience regarding geologic conditions and how those conditions may affect construction and performance of oil and gas structures and offshore wind structures. Although experience in planning, designing, constructing, and operating marine structures in those regions provide valuable knowledge that can be transferred to the Atlantic OCS wind industry, the combination of water depths, geologic conditions, and wind farm developments will present a unique combination of variables for the nascent US Atlantic wind industry. The purpose of this study is to investigate and assess the various methodologies and equipment choices for providing site investigations that identify shallow hazards, geologic hazards, biological conditions, geotechnical properties, and archaeological resources in accordance with 30 CFR 585.626 and 585.627. The information presented in this study is based on decades of experience accumulated by the oil and gas industry offshore, about a decade of experience accumulated by the offshore wind industry in Europe, and the understanding of the geology within the Atlantic OCS. Hence, the information developed during this study should prove to be a valuable resource for future US offshore wind development projects especially within the Atlantic OCS. We note that geophysical and geotechnical equipment and investigation techniques are continually evolving in response to industry needs. In the offshore wind industry evolution is driven in a large part based on a desire to reduce construction and operational costs, developing larger wind turbines, developing wind farms in frontier regions, and knowledge gained from construction and operation of existing wind farms. Site investigation methods for seismic reflection surveying, seismic data processing, and measuring dynamic soil properties are among the most rapidly evolving areas for the industry. Therefore, we believe that this study represents a snap shot in time of a changing industry. We thank the staff at the BOEM for their support in preparing this study. We also thank Dr. Melissa Landon and Dr. Mark Legg for their contributions to this study. ES.1 Bureau of Ocean Energy Management (BOEM) Executive Summary OVERVIEW OF THE STUDY This report is divided into six volumes that address various aspects of the scope of this study. Volume content is organized as follows: • Volume 1 – Wind Farm Facilities, Geologic and Bathymetric Conditions, and Site Investigation Approaches: Introduces the typical components of offshore wind farms, provides a concise introduction about geologic characteristics within the Atlantic OCS, introduces the various offshore foundation types and systems for offshore wind turbines, lists the main factors that control the selection of a specific foundation system, and provides examples of alternative plans that can be adopted to conduct geophysical and geotechnical site investigations. • Volume 2 – Geophysical Surveys Benefits and Risks: Analyzes the benefits and risks associated with the different techniques adopted during geophysical surveys and the viability of using the different techniques within the Atlantic OCS. • Volume 3 – Geotechnical Investigation Benefits and Risks: Analyzes the benefits and risks associated with the different in-situ tests adopted during geotechnical investigations and the viability of using the different techniques within the Atlantic OCS. It introduces the different laboratory tests and the design parameters that can be measured using each of them. It also presents additional details about choosing the number and type of in-situ and laboratory tests for each foundation type. • Volume 4 – Best Practice Recommendations for Geophysical Surveys: Presents best practice recommendations for survey techniques and equipment for geophysical surveys. • Volume 5 – Best Practice Recommendations for Geotechnical Investigations: Presents best practice recommendations for geotechnical site investigation techniques and equipment for these investigations. • Volume 6 – Geophysical and Geotechnical Guidebook: A guidebook for equipment selection and utilization dependent on the site conditions and structures anticipated for future offshore renewable projects within the Atlantic OCS. ES.2 FUGRO MARINE GEOSERVICES, INC. VOLUME 1 WIND FARM FACILITIES, GEOLOGIC AND BATHYMETRIC CONDITIONS, AND SITE INVESTIGATION APPROACHES Study Title: Geophysical and Geotechnical Investigation Methodology Assessment for Siting Renewable Energy Facilities on the Atlantic OCS Bureau of Ocean Energy Management (BOEM) Volume 1 - Wind Farm Facilities, Geologic and Bathymetric Conditions, and Site Investigation Approaches Table of Contents 1.1 Introduction ................................................................................................... 1.4 1.2 Overview of the Study .................................................................................. 1.8 1.3 Components of Offshore Wind Farms .......................................................... 1.9 1.3.1 Offshore Wind Turbine Structure ...................................................... 1.9 1.3.2 Electrical Service Platforms (ESPs) & Inter-Array Export Cables .... 1.9 1.4 Atlantic Outer Continental Shelf ................................................................. 1.11 1.4.1 Northern Atlantic OCS: Glacial and Proglacial Sites ...................... 1.12 1.4.2 Mid-Atlantic OCS: Non-Glacial in Origin ......................................... 1.13 1.4.3 Southern Atlantic OCS: Non-Glacial in Origin and Carbonates ...... 1.14 1.5 Foundation Systems ................................................................................... 1.19 1.5.1 Offshore Foundation Types ............................................................ 1.19 1.5.2 Foundation Systems (Support Structures or Sub-Structures) ........ 1.25 1.6 Selection of the Foundation System ........................................................... 1.29 1.6.1 Factor 1 – Geotechnical / Geological Site Conditions .................... 1.34 1.6.2 Factor 2 – Water Depth .................................................................. 1.38 1.6.3 Factor 3 – Environmental Loads .................................................... 1.38 1.6.4 Factor 4 – Size and Type of the Wind Turbines ............................. 1.40 1.6.5 Factor 5 – Manufacturing, Installation and Maintenance Costs ...... 1.40 1.6.6 Factor 6 – Environmental Regulations ........................................... 1.41 1.7 Planning for a Successful Site Investigation Campaign ............................. 1.42 1.7.1 Single Investigation / Survey .........................................................