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In the United States, the ocean serves as a receiving area for a variety of particulate wastes including dredged materials, sewage sludge, construction debris, and selected industrial residue. By mass, dredged materials dominate this waste stream. These sediments are removed using mechanical or hydraulic techniques and deposited at near-shore sites in water depths ranging from 20 to 100 m. Methods developed over the past ten years permit accurate placement of the dredged sediments at the disposal areas and the formation of coherent mounds of material. The degree of heterogeneity characterizing these mounds complicates sampling intended to detail short- and long-term environmental effects associated with material placement. This variability requires care in survey design and execution beyond that routinely used. In particular, surveys intended to complement quantitative evaluation of mass and material transport from the disposal mounds require an increased understanding of the geotechnical properties of the deposit over spatial scales ranging from millimetres to hundreds of metres and temporal scales from minutes to months. Measurements would place primary emphasis on the characteristics governing mound consolidation, the migration of interstitial waters and associated contaminants, and the factors affecting the physical stability of the deposit.
Acquisition of data adequate to detail these characteristics requires the development of a new generation of geotechnical sensors able to provide high resolution in situ measurements over extended periods of time and modification of survey procedures to encourage use of the sensors and incorporation of the resulting data within interdisciplinary studies. Such modification appears essential within efforts to develop the quantitative predictive methods required for the future management of oceanic waste disposal areas.
ocean dumping, dredging, dredged material, disposal, marine sediments, geotechnical properties, environmental monitoring, in situ systems
Associate professor, University of Connecticut, Groton, CT