Dredging for Environmental Remediation - Ancil Taylor, Bean Environmental.

objective of environmental dredging. The important "risk-based" factors that determine the

effectiveness of environmental dredging differ substantially from many of the important effective-

ness factors associated with navigational dredging. As such, environmental and navigation dredging

risks were contrasted, while "Dredging Effectiveness" and how to interpret it in the context of

several key issues and important measurements were defined. Actual data from completed projects

were used to help illustrate the central themes of the presentation. Some of the key observations

include the following:

Most experience to date is limited to relatively small sites with small databases.

Dredging has limitations in reducing surface layer contaminant concentrations.

Resuspended solids can be controlled; however, elevated concentrations are seen in the water

column during the time of dredging.

Effects of dredging on fish tissue concentrations are not quantifiable.

Environmental dredging is distinctively different from navigation dredging.

Dredging for Environmental Remediation - Ancil Taylor, Bean Environmental. A new

environmental dredge was deployed at New Bedford Harbor, Massachusetts, as part of the

Superfund Remediation project. The dredging technology selected for field study was the Horizon-

tal Profiling Grab (HPG) dredge designed and operated by Bean Environmental. The HPG was

selected from more than sixty dredge technologies surveyed around the world for application at

New Bedford Harbor. The key performance measures evaluated in the test were sediment removal

accuracy (within 4 in. [102 mm]), transportation and disposal efficiency (70 percent solids by

volume), polychlorinated biphenyl (PCB) removal effectiveness (97 percent removal), air and water

quality impacts by the dredging operation (limited impacts), and dredged material production

(95 to120 cu yd [73 to 92 cu m] per hour).