Dredge Planning Using Sub-Bottom SONAR

Brad Hubeny, Salem State University
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Initial Publication Date: June 9, 2014 | Reviewed: June 24, 2014


This project is designed to give students valuable geophysical experience in conducting an environmental assessment of a real-world problem. A scenario is developed in which students work for "Viking Consulting, LLC" as an environmental geologist. The company has been hired by the City of Salem to assess an appropriate confined aqueous disposal (CAD) cell location for contaminated dredge spoils from a proposed dredging project of the South River, Salem, MA. Students utilize sub-bottom SONAR technology to calculate volume of dredge spoils and potential CAD cell locations and analyze which location can accommodate the contaminated material.

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I use this project as the major environmental project in our department's required local 3-week field camp, which they typically take during the summer after their sophomore year. An advanced field camp occurs in Montana the following summer, and sedimentological and stratigraphic concepts are carried forward to that advance camp for sedimentary rock mapping projects.

Skills and concepts that students must have mastered

All students have had physical and historical geology, and I assume that they bring a basic understanding of sediments, facies, depositional environments, and stratigraphy.

How the activity is situated in the course

This is a culminating project that follows two smaller projects. The introductory projects are designed to introduce students to the background and software applications necessary for the geophysical component of this project.


Content/concepts goals for this activity

  1. Late Quaternary stratigraphy
  2. Produce lithologic logs of sediment cores
  3. Accurately measure, record, and summarize data in the field
  4. Take thorough and organized field and lab notes

Higher order thinking skills goals for this activity

  1. Plan and conduct coastal marine seismic surveys (bathymetry and sub-bottom sonar)
  2. Calculate the volume of sediment to be dredged to achieve the goals of the client.
  3. Process and interpret sub-bottom sonar data using state-of-the art processing software
  4. Interpret seismic reflectors and produce isopach maps of sediment unit thicknesses
  5. Address the theory of seismic reflection sub-bottom analyses, and the strengths and weaknesses of different seismic frequencies
  6. Identify and interpret the correlations between litho-stratigraphic units and seismic-stratigraphic units

Other skills goals for this activity

  1. Read a bathymetric chart
  2. Accurately locate yourself in a marine field environment (without GPS!)
  3. Synthesize and interpret data
  4. Work in a safe and productive manner on the water and on land
  5. Write a professional-quality environmental geologic report that synthesizes data collected and interpreted, and provides recommendations to the client regarding the original question of concern

Description and Teaching Materials

This assignment assumes that the instructor has access to geophysical equipment that can remotely sense underlying strata, in our case late Quaternary sediments preserved in a New England estuary. The assignment could be modified to utilize other technology, such as GPR, if the instructor has access to such a technology. Would it be useful to include SEGY files from Salem Sound for other instructors to be able to use?
Student Assignment (Microsoft Word 2007 (.docx) 144kB Jun9 14)

Teaching Notes and Tips


I correct the final report with a rubric, focusing on their geologic interpretations of the data, and on how well they answered the clients' questions.

References and Resources