Our marine archaeologists lead and support cultural resource desktop studies, site evaluations, surveys, permitting, and reporting. Our staff plans and directs marine archaeological surveys using autonomous underwater vehicles (AUVs), remotely operated vehicles (ROVs), high-resolution conventional geophysical remote sensing, and diver-assisted surveys.

On behalf of clients, our staff endeavor to identify problems at the start of a project to help avoid project delays. We offer comprehensive support for marine archaeological requirements related to offshore energy projects; this work encompasses survey and project planning, permitting, Tribal engagements, Section 106 consultations, and necessary mitigation actions mandated by federal, state agencies, and global entities.

 Capabilities

  • Survey planning for high-resolution geophysical archaeological surveys (AUV and conventional surveys)
  • Shallow-water surveys and assessments including equipment selection, field survey oversight, and interpretation
  • Deep-water archaeological assessments for extensive project area studies, pipeline-route surveys, and site-specific surveys
  • ROV archaeological investigations
  • Diver evaluation operations

Shallow-Water Surveys

With over 40 years of experience in shallow-water surveying, our marine archaeologists offer expertise with planning, equipment recommendations, survey QA/QC, reporting, mitigation recommendations, and government correspondence. On behalf of clients, we conduct and interpret towed-equipment surveys globally for offshore renewables, fisheries, and oil and gas projects.

Generally the necessary equipment for these studies includes the following:

  • High-resolution side-scan sonar
  • Sub-bottom profilers and parametric sub-bottom profilers
  • Magnetometers and gradiometers
  • Single-beam and multibeam echosounders

In addition to shallow-water towed-equipment surveys, we provide planning and oversight for archaeological diver-assisted surveys. Our archaeologists have extensive experience using varied shallow-water data sets to create integrated reports for clients and regulatory agencies.

Side-Scan Sonar image of modern wreck
Side-Scan Sonar image of modern wreck

Challenges in Conducting Shallow-Water Surveys

Murphy’s Law applies when working with equipment on the water. Shallow-water surveys require towing multiple pieces of equipment simultaneously while considering factors like safety, vessel traffic, ocean currents, weather conditions, fishing activity, and seafloor depths.

When conducting shallow-water surveys the following equipment challenges often come into play:

Side-Scan Sonar: Many variables affect the quality of this data. In addition to altitude, speed, and frequency, environmental factors like wave chop, salinity, and currents must be accounted for before a survey can begin. We have experience processing and interpreting a wide range of data quality.

Magnetometers: Magnetometers are extremely sensitive instruments that measure the Earth’s magnetic field. To accurately detect magnetic anomalies, they must maintain a constant height from the seafloor. BOEM regulations stipulate that magnetometers must not exceed 7 meters above the seafloor.

Gradiometers: Gradiometers combine two or more magnetometers into a single flown array. Gradiometers can map tiny fluctuations in the survey area’s magnetic field and help determine the location and depth of burial on magnetic materials. Like magnetometers, gradiometers require an altitude of 7 meters or less above the seabed. Renewables projects, munitions-of-explosive-concern projects, and diver-assisted investigations rely on gradiometers to precisely map survey areas.

Geomagnetic Storms: These storms, caused by solar winds, impact Earth’s magnetic field and cause large fluctuations in the field during data collection. These fluctuations can mask anomalies and give false positives within data sets. Gradiometers can differentiate between a geomagnetic storm and an actual magnetic anomaly.

Sub-bottom Profilers: Sub-bottom profiler data can delineate buried relict landforms containing cultural material. During the last ice age, much of the continental shelf was exposed and populated by indigenous peoples. Many paleo landforms are buried or partially eroded by the natural movement of rivers across the landscape and can only be mapped using seismic data. Our archaeologists interpret data and work with our geoscience staff to identify ancient landscapes that could indicate areas of heightened cultural sensitivity for indigenous populations. We can then avoid these areas or collaborate with regulatory agencies to mitigate them.

Side-scan sonar image of Robert E. Lee collected by AUV.
Side-scan sonar image of Robert E. Lee collected by AUV.

AUV Deep-Water Surveys

AUVs are tools used to survey large areas at great depths. These vehicles can survey for 18 to 50 hours at a time while collecting multiple data sets. Additionally, they can carry many kinds of instruments and tools. While side-scan sonar, sub-bottom profilers, and multibeam echosounders are usually standard, AUVs can also be equipped with cameras, methane sensors, turbidity sensors, laser bathymetry systems, and, wellbore magnetometers.

Our archaeologists have extensive experience planning AUV surveys, making equipment recommendations, and conducting survey QA/QC. We also handle reporting, mitigation, and government correspondence for deep-water AUV surveys. Our staff has conducted AUV surveys since the first commercial deep-water AUVs entered the industry in 2000. We have interpreted AUV data from around the globe, including the US Gulf of Mexico, the Mediterranean Sea, offshore areas adjacent to East and West Africa, and the Atlantic Ocean adjacent to South America.

For these surveys, we often use the following:

  • Side-scan sonar
  • Sub-bottom profilers
  • Multibeam bathymetric echosounders for multibeam bathymetry and backscatter data
ROV on vessel ready for delployment
ROV on vessel ready for delployment

ROV Deep-Water Surveys

On behalf of clients, our archaeologists draft agency-compliant archaeological methods, plan and direct fieldwork, and complete archaeological assessment reports for ROV investigations required by federal agencies. To accomplish this, we draft BOEM-compliant archaeological methods and survey plans, work with the survey and ROV vendors to integrate the survey and meet archaeological needs, and help choose the correct equipment and personnel before the vessel leaves the dock. We also plan and manage personnel to minimize equipment downtime while surveying. We compile and incorporate data into comprehensive ROV reports for clients.

Typical GEMS recommendations for archaeological ROV surveys often include the following:

  • Ultra-short baseline (USBL) positioning systems
  • Sector-scanning sonar
  • Heave compensation
  • HD lights
  • Continuous recording
  • Live-streamed video and audio