OCS STUDY MMS 2004-005 ARCHAEOLOGICAL DAMAGE FROM OFFSHORE DREDGING: RECOMMENDATIONS FOR PRE-OPERATIONAL SURVEYS AND MITIGATION DURING DREDGING TO AVOID ADVERSE IMPACTS PREPARED FOR: U.S. DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT SERVICE Under Contract Number No. 01-02-CT-85139 February 2004 OCS Report MMS 2004-005 ARCHAEOLOGICAL DAMAGE FROM OFFSHORE DREDGING: RECOMMENDATIONS FOR PRE-OPERATIONAL SURVEYS AND MITIGATION DURING DREDGING TO AVOID ADVERSE IMPACTS Prepared for: Leasing Division, Sand and Gravel Unit Minerals Management Service U.S. Department of Interior Herndon, Virginia Prepared by: Research Planning, Inc. Columbia, South Carolina Tidewater Atlantic Research, Inc. Washington, North Carolina W.F. Baird & Associates Ltd. Madison, Wisconsin February 2004 DISCLAIMER This report has been reviewed by the Minerals Management Service and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Service, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Cover Art: Painting by Fitz Hugh Lane (M-19323). Published in Johnson, P. F., 1983. Steam and the Sea. Peabody Museum of Salem, Salem, Massachusetts, p.63. i TABLE OF CONTENTS 1.0 INTRODUCTION................................................................................................................1 2.0 METHODS OF STUDY......................................................................................................2 2.1 Worldwide Review of Current Dredging Practices .................................................2 2.2 Archaeological Review Methods ............................................................................3 3.0 THE NATURE OF SUBMERGED CULTURAL RESOURCES.......................................4 3.1 Inundated Prehistoric Sites.......................................................................................4 3.1.1 OCS Habitation Hypothesis and Lower Sea-level Stands ...........................4 3.1.2 Submerged Cultural Resource Baseline Studies..........................................5 3.1.3 Testing and Refining the OCS Baseline Models for Prehistoric Sites.........7 3.1.4 Dredging and Initial Evidence of Inundated Prehistoric Habitation ............8 3.1.5 Recent Evidence of Inundated Prehistoric Habitation in the OCS ..............9 3.1.6 Paleo-landforms with High Probability of Prehistoric Sites in the OCS ...10 3.1.7 Potential for Preservation of the Prehistoric Archaeological Record ........11 3.1.8 Technologies for the Search for Inundated Prehistoric Sites .....................11 3.2 Shipwreck Remains...............................................................................................12 3.2.1 Shipwreck Baseline Studies.......................................................................14 3.2.2 Vessel Types Potentially Present in OCS Borrow Areas...........................14 3.2.3 Classification of Shipwreck Remains ........................................................16 3.2.3.1 High Integrity Shipwrecks.............................................................16 3.2.3.2 Moderate Integrity Shipwrecks......................................................17 3.2.3.3 Low Integrity Shipwrecks..............................................................17 3.2.4 Remote Sensing in the Search for Historic Shipwreck Sites .....................17 4.0 STATE-OF-THE-ART REMOTE SENSING AND DATA ANALYTICAL TOOLS FOR SUBMERGED CULTURAL RESOURCE ASSESSMENT ...................................18 4.1 Recent Technological Advances in Magnetometers..............................................18 4.2 Recent Technological Advances in Acoustic Instruments ....................................19 4.3 Global Positioning Systems ..................................................................................22 4.4 Advanced Survey and Dredging Software and GIS Applications .........................23 5.0 DREDGING IMPACTS ON SUBMERGED CULTURAL RESOURCES .....................24 5.1 Direct Impacts of Dredging ...................................................................................24 6.0 DREDGING INDUSTRY SURVEY RESULTS ..............................................................31 6.1 Current Dredging Practices: Equipment ................................................................31 6.2 Current Dredging Practices: Location of the Dredge Position...............................31 6.3 Current Dredging Practices: Buffer Zones ............................................................32 7.0 ARCHAEOLOGICAL RESOURCE SURVEY REQUIREMENTS ................................33 ii 7.1 Current MMS Requirements for Gulf of Mexico Archaeological Resource Surveys..........................................................................33 7.2 Assessment of Current MMS Standards for Archaeological Resource Surveys ...35 7.2.1 Archaeological Resource Survey Navigation ............................................35 7.2.2 Survey Patterns: Impacts on Range and Resolution of Acoustic Imaging ......................................................................................................36 7.2.3 Survey Patterns: Impacts on Range and Resolution in Magnetic Imaging ......................................................................................39 7.3 Agency and Institution Survey Line Spacing Requirements .................................43 8.0 BUFFER ZONES...............................................................................................................44 8.1 Buffer Zone Criteria...............................................................................................44 8.2 Buffer Zone Design Considerations.......................................................................46 8.3 Proposed Formula for Establishing Buffer Zones..................................................47 8.4 Preventing Formation of Pedestals ........................................................................50 8.5 Buffer Zone Monitoring.........................................................................................51 9.0 RECOMMENDATIONS TO AVOID ADVERSE IMPACTS TO ARCHEOLOGICAL RESOURCES DURING DREDGING ...........................................52 9.1 Geographic Information System-Based Management ...........................................52 9.2 Refining, Refocusing, and Testing Baseline Studies .............................................52 9.3 Remote Sensing Equipment and Survey Methods for Location and Identification ..........................................................................................................54 9.3.1 Digital Data Display, Recording, and Storage ...........................................54 9.3.2 Digital Magnetometer Systems..................................................................54 9.3.3 Digital Sonar Systems................................................................................55 9.3.4 High Resolution Chirp Subbottom Profilers..............................................55 9.3.5 High Resolution Multibeam Echo Sounders..............................................55 9.3.6 Differential Global Positioning..................................................................56 9.3.7 Submerged Cultural Resource Survey Line Spacing and Anomaly Definition...................................................................................56 9.4 Buffer Zones ..........................................................................................................56 9.5 Dredging Operations..............................................................................................57 9.6 Monitoring Dredging Activity ...............................................................................59 9.7 Archaeological Resource Report Requirements ....................................................61 10.0 CITED REFERENCES......................................................................................................62 APPENDIX A: Letter and Questionaire Sent to Dredging Contractors APPENDIX B: Archaeological Questionnaire APPENDIX C: Assessment of the Risk of Sedimentation Over an Archaeological Site due to Dredging APPENDIX D: Table of Questionare Responses from Dredging Contractors iii LIST OF FIGURES FIGURE 1. Sea-level curve showing the rapid rise in sea level at the end of the Late Wisconsinian glaciation, starting about 10,000 years ago .......................................5 FIGURE 2. Map of the Holly Beach “fluvial system” at a 300 m spacing between tracklines for the geotechnical investigation and the higher density mapping (50 m) of the fluvial channels for cultural resources ...................................................................13 FIGURE 3. High-resolution Klein 500 kHz side scan sonar image of the Civil War blockade runners Georgiana and Mary Bowers sunk off Charleston, South Carolina .........20 FIGURE 4. Mosaic of dredging scars compiled from high-resolution 600 kHz sonar images ...................................................................................................................21 FIGURE 5. Reson Sea Bat 8125 image of a World War II LCT sunk off Omaha Beach, Normandy during the D-Day Landing ...................................................................22 FIGURE 6. Plan of the surviving remains of the mid-fifteenth century shipwreck discovered during dredging of the Ria de Averio, Portugal...................................27 FIGURE 7. Plan of the surviving remains of the steamship Mary sunk adjacent to the Aransas Pass,