Sediment

Sediment Collection & Characterization

Boxcore DeploymentCSA has over 45 years of experience collecting, characterizing, and assessing sediment in marine and coastal environments. CSA has conducted hundreds of surveys in numerous countries that have included sediment collection and analysis components. We have the capability and equipment necessary to collect sediment samples in water depths ranging from shallow coastal waters to full ocean depth. Our environmental services include the design and implementation of sediment sampling programs identifying spatial and temporal changes in chemical and biological processes. Our staff has extensive experience designing comprehensive survey plans with industry-standard methodologies with the goal of expediting regulatory approval for our clients. We offer our customers comprehensive survey planning and management, survey implementation, GIS, and scientific reporting.

Projects and Activities Supported by Sediment Collection and Characterization

  • Offshore oil and gas Environmental Baseline Surveys (EBSs) and monitoring
  • Compliance monitoring
  • Benthic habitat monitoring
  • Environmental Impact Studies (EISs)
  • Beach renourishment
  • Ocean disposal of dredged material
  • Habitat evaluations
  • Toxicity testing and bioaccumulation studies
  • Macroinvertebrate analyses of marine invertebrates
  • Ground-truthing seabed mapping investigations

Sediment Grab RecoveryCSA employs two basic types of sediment collection sampling devices: grab samplers (used to collect surface and near-surface sediments) and sediment coring devices (used to collect a vertical column of the subsurface sediment and can be used to determine a temporal pattern of contamination). CSA owns and utilizes a wide range of sediment grabs (e.g., Smith McIntyre, Van Veen, and Ponar grabs) and cores (e.g., box, push, multi- and mega). Our sediment grabs and ancillary support equipment, such as winches and A-frames, are strategically located at our facilities worldwide. This extensive array of in-house sampling equipment allows us to cost effectively respond to a wide range of multidisciplinary environmental monitoring programs.

ROV Sediment Collection

CSA is one of a few firms that have extensive experience utilizing remotely operated vehicles (ROVs) to collect sediment samples. Using an ROV as a sampling platform offers distinct advantages, including the ability to visually target where the sample is collected, extremely accurate sample positioning, and the collection of “undisturbed” samples in deep water.

CSA has developed and utilized ROV-deployed sediment sampling systems on numerous projects. Two ROV sediment collection methods that CSA has frequently utilized are push cores and grab samplers. ROV push cores are specially designed plastic tubes that are pushed into the surface sediment by the ROV’s hydraulic manipulator. The push cores are fabricated with a “T” handle specifically designed to be manipulated with the ROV hydraulic arm. The recovered core sample is placed in a sample basket on the front of the ROV and is transported back to the ship.

The ROV-deployed grab sampler designed and fabricated by CSA is based on the Ekman grab sampler, which is used to collect infaunal samples where larger sediment volumes are required. In this application, the ROV is typically equipped with three grab samplers, each with a sediment surface area of 0.0625 m2. The ROV manipulator arm is used to deploy the grabs and collect the infaunal samples. Similar to the core samplers, once the sediment grabs are collected, the grabs are stowed in a specially designed rack on the front of the ROV and transported back to the ship.

It is critically important to have accurate positioning for any sampling activity. CSA uses a computerized navigation and positioning system (Hypack®) to accurately record the position of the collected sediment samples. Determining the position of the grab or core in deep water is problematic due to current and wind impacts. To deal with this issue, CSA utilizes an Ultra Short Baseline (USBL) positioning system that provides accurate horizontal positioning of the sediment sampler in deep water.

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