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TECHNICAL SUMMARY 

Study Title: Archaeological Damage from Offshore Dredging: Recommendations for PreOperational Surveys and Mitigation During Dredging to Avoid Adverse Impacts

Report Title: Archaeological Damage from Offshore Dredging: Recommendations for PreOperational Surveys and Mitigation During Dredging to Avoid Adverse Impacts 

Contract Number: 01-02-CT-85139 

Sponsoring OCS Region: Headquarters–Sand and Gravel Unit, Leasing Division

Applicable Planning Areas: East and Gulf of Mexico Coasts 

Completion Date of Report: February 2004

Costs: FY 2003: $123,326 

Project Manager: Jacqueline Michel, Ph.D.

Affiliation (Project Manager): Research Planning, Inc. 

Address: 1121 Park Street, Columbia, South Carolina 29201

Principal Investigators: Jacqueline Michel, Gordon P. Watts, Jr., Rob Nairn, Tim Kenny

Key Words: sand resources, OCS, dredging, archaeological resources, cultural resources

Background: The Minerals Management Service (MMS) is charged with environmentally 

responsible management of Federal Outer Continental Shelf (OCS) sand and gravel resources, 

that is, those resources lying seaward of the State/Federal boundary. The National Historic 

Preservation Act requires Federal agencies to protect historic and cultural resources which 

include shipwrecks, historic fortifications, and coastal settlements, as well as prehistoric human 

occupation sites that have become submerged due to the global and local rise in sea level. As a 

Federal agency, the MMS must protect the significant archaeological and historic sites that 

maybe impacted by its activities. In addition, regardless of the historical significance of a 

shipwreck or site, these structures provide fish habitat and are considered potential Essential Fish 

Habitat. These structures can, and in many cases do, support extensive sport fishing and diving 

industries. Therefore, MMS funded this current study to review its current practices and 

procedures related to identification and protection of archaeological resources. 

Objectives: The project objectives were to: 1) Review of the worldwide literature to determine 

current dredging practices in other countries; 2) review of the literature on the nature and type of 

submerged cultural resources likely to be encountered on the continental shelf; 3) review of the 

methods and technology for locating and identifying submerged cultural resources, as well as the 

current MMS criteria for remote-sensing surveys; 4) review of reports of cultural resources 

damaged by dredging operations and the reasons the damage occurred; 5) canvass the dredging 

industry to determine the current practices and procedures for mining sand, focusing on 

equipment and accuracy of the dredging process; 6) review of mitigation requirements of other 

jurisdictions to prevent adverse impacts on submerged resources. Particular emphasis was placed 

on buffer or exclusion zones; and 7) synthesis of the study results into a set of recommendations 

on dredging methods, protocols, policies, and monitoring requirements to minimize impacts on 

submerged cultural resources 
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Description: Based on the results of the study, recommendations to avoid adverse impacts to 

archaeological resources during dredging in the OCS were organized into the seven categories 

summarized below. 

1. Implement a GIS-based Data Management Strategy: Establish and maintain a GIS for 

management, research, and monitoring of submerged cultural resources in sand borrow areas 

under the jurisdiction of MMS. 

2. Refine and Test Existing Baseline Studies That Define Potential Archaeological Resources: 

MMS management of submerged cultural resources is essentially based on a series of baseline 

studies carried out over two decades ago. As the nature, scope and distribution of prehistoric and 

shipwreck resources are key elements in developing a responsible and effective management 

program, a comprehensive reexamination of those issues is highly recommended. Refined 

prehistoric and shipwreck models could be tested using data that will be generated by 

investigations designed to locate and identify submerged cultural resources in the OCS sand 

borrow areas. 

3. Revise the Requirements for Equipment and Methods for Locating and Identifying 

Submerged Cultural Resources: The existing requirements need to be updated to reflect the 

state-of-the-art means of locating and identifying cultural resources. Recommendations were 

made for a wide range of changes in MMS survey guidelines. Key recommendations include: 

positional accuracy (from 5 to 1 m), line spacing (from 50 to 30 m) and 10 m line spacing for 

anomaly definition, use of digital magnetometers and sonar systems that allow digital data 

recording integrated with differential GPS (DGPS) versus paper strip charts, use of multibeam 

echosounder systems (versus single beam), increase of range scale coverage (from 100% to 

150%), contouring magnetic data for target assessment and reporting, and use of heave, pitch, 

and roll compensation equipment to improve record quality. 

4. Develop Scientific Basis for Buffer Zones: Buffer zones to protect archaeological resources 

have no scientific basis, and the sizes and shapes used currently have not been tested. There are 

also concerns the buffer zones around a site could result in full pedestals that may eventually 

erode and damage the site. Two formulas were developed to calculate buffer zones and create a 

series of plots, based on simple assumptions. MMS should develop a program to test formulas 

for buffer zone definition and monitor field sites to determine effectiveness. 

5. Require Dredges to be Equipped with DGPS Positioning Equipment: DGPS will allow the 

position of the dredging equipment to be precisely tracked relative to buffer zones during the 

entire dredge cycle. MMS should require submittal of the track plot and buffer zones to show 

compliance. 

6. Require Monitoring During- and Post-Dredging: MMS should consider requiring an onboard archaeological monitor, particularly in high-potential areas. Alternatively, there could be a 

reward/penalty incentive program to encourage operators to report when there is evidence of an 

encounter with an archaeological site. Post-dredging monitoring data are critical to providing the 

documentation needed to validate the effectiveness of prescribed buffers, as well as monitor the 

stability of the borrow area over time particularly as it affects slope stability and edge effects. 
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Many of these stability concerns are applicable to infrastructure (e.g., pipelines, platforms, and 

wellheads). 

7. Revise Archaeological Report and Data Delivery Requirements: All data should be delivered 

in digital format, be georeferenced, and include magnetic contour maps of the survey area and all 

potentially significant anomalies, high-resolution sonar images of all anomalies, and multibeam 

mosaics of the survey area. 

 

Study Products: Research Planning, Inc., Tidewater Atlantic Research, Inc., and Baird & 

Associates Ltd., 2004. Archaeological Damage from Offshore Dredging: Recommendations for 

Pre-Operational Surveys and Mitigation During Dredging to Avoid Adverse Impacts. U.S. 

Department of the Interior, Minerals Management Service, Sand and Gravel Unit, Leasing 

Division, Herndon, VA. OCS Report MMS 2004-005, 75 pp. + appendices.