Dredging Contaminated Sediments

Should the Ashtabula River be dredged?

An Earth Systems Lesson Plan

Developed by Jeremy King

Background Information• When pollutants enter an aquatic ecosystem they can become

mixed into the sediments. These pollutants can be toxic to living organisms.

• Toxins can accumulate in the tissues of organisms. As the toxins move up the food chain, higher order predators become at risk for developing reproductive disorders and may experience other serious health effects.

• Some scientists believe that dredging is the solution to removing toxins from the aquatic environment.

• Others believe that dredging causes more problems as toxins are re-suspended in the water column.

• What is the best solution? Is it so cut and dried?

Learning Objectives• Describe methods for removing contaminated sediments

from the stream environment• Model the processes of dredging contaminated sediments• Evaluate data to determine the success of dredging• Make decisions based on scientific data• Develop a concept map

Earth Systems UnderstandingsESU #1 - Earth is a unique planet of rare beauty and great value

ESU #2 - Human activities affect Earth systems

ESU #3 - Development of scientific thinking and technology increases our ability to understand and utilize Earth

ESU #4 - The Earth system is composed of interacting subsystems

Activity IDredging Contaminated Sediments

•In groups, model three types of dredging

•Attempt to dredge without disturbing the water column

•Compare data to determine which method works the best

Hydraulic Dredge Clam-Shell Dredge Bucket Dredge

Activity IIShould the Ashtabula River be Dredged?

•Evaluate data from the Black River dredging project

•Determine whether dredging was successful

•Decide whether dredging should be attempted in a similar river - Ashtabula

•Develop a concept map for the process of dredging

References

• Report on Black River bullhead catfish tumors http://www.epa.gov/glnpo/sediment/Bullhead/report.html

• Ashtabula River report updating toxin information: http://www.fws.gov/midwest/AshtabulaNRDA/

• Baumann, P. and Harshbarger, J. (1996). Decline in liver neoplasms in wild brown bullhead catfish after coking plant closes and environmental PAH’s plummet. Environmental Health Perspectives. 103(2):168-170

• Ohio EPA: http://www.epa.state.oh.us/