June 9, 2021

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Geosyntec Assisted with Investigation and Evaluation of Offshore Soils

Geosyntec assisted with investigation and evaluation of offshore soils at selected locations for an inter-array cable and potential export cable routes for an offshore wind farm location off the coast of New Jersey.  The investigation included vibrocore sampling, borehole sampling, ball and piezocone Cone Penetration Testing (CPT), and Thermal Resistivity Testing.

Geosyntec's scope of work included:

  • provide offshore support for CPT and sampling activities with personnel certified in Basic Offshore Safety Induction and Emergency Training (BOSIET);
  • perform offshore CPT quality assurance and test tolerance checks in real time (i.e., on the vessel);
  • perform preliminary offshore processing of the CPT data;
    • derived CPT parameters such as corrected tip resistance, friction ratio, normalized pore pressure ratio;
    • CPT undrained shear strength and relative density/ friction angle;
    • stratigraphic unit identification;
    • preliminary graphs for measured and calculated test data;
  • perform offshore soil classification and laboratory testing on the vibrocore and borehole samples (moisture content, density, pH, thermal conductivity, torvane, and pocket penetrometer);
  • coordinate onshore laboratory testing (photographs, moisture content, density, particle size, Atterberg limits, particle density, maximum/minimum dry density, organic content, sulfate, chloride, calcium carbonate, pH, unconsolidated undrained (UU) compression, thermal conductivity, electrical resistivity, torvane, and pocket penetrometer);
  • process final CPT results onshore;
  • compile onshore and offshore geotechnical laboratory data into files consistent with the Association of Geotechnical and Geoenvironmental Specialists format (i.e., AGS4 format), and
  • prepare the measured and derived geotechincal parameters reports for each cable installation, including measured and derived data, geotechnical profiles, and a summary of CPT processing and results.

The CPTs were performed for the inter-array cable and the three possible export cable routes over multiple months by two different contractors.  Geosyntec processed the data, clarified data gaps, resolved inconsistencies between test methods by the two contractors, and presented the results in a uniform format.  The vibrocore and borehole samples were collected over multiple deployments.  Geosyntec processed over 250 CPTs, organized and tracked nearly 1,300 samples and over 4,000 onshore and offshore test results, coordinated data management and evaluation by cable route, and prepared three separate reports simultaneously.  Geosyntec also provided guidance in resolving differences between estimated properties from the CPT investigation and laboratory test results.

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May 18, 2021 - Offshore and Nearshore Site Investigations

More Information

Learn more about Ternan: https://www.ternan-energy.com/about-us/

For consultation regarding marine geosciences and geotechnical engineering contact Rodolfo Sancio at RSancio@Geosyntec.com and/or Mark Finch mark.finch@ternan-energy.com.