Dredging
Human Health Risk
Ecological Risk
Socioeconomic Risk
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Dredging is the removal of sediment from the bottom of a water body to deepen and/or
widen channels for navigation. In more recent years dredging has been used to remove
sediment that is known to be polluted. Dredging affects aquatic environments by killing
plants and animals, clouding the water with sediment, and destroying habitat. There
are also human health issues associated with dredging of contaminated sediments—
these risks are described for each specific contaminant (e.g., PCBs) in the appropriate sections.
STRESSOR SUMMARIES
What’s at risk?
Dredging activity affects aquatic plants, fish and
bottom-dwelling animals such as oysters, scallops, and juvenile lobsters. Dredging activities
and the creation of confined disposal facilities
can lead to habitat loss and habitat disturbance.
Dredging activities are concentrated in three
areas in New Jersey: New York Harbor, the
Atlantic Coastal Basin, and the Delaware Bay and
River.
What are the ecological impacts in New
Jersey?
Over 80 million cubic yards of material is
dredged annually in New Jersey. New York
Harbor accounts for more than 90% and nearly
all is disposed of in the ocean at the Historic
Area Remediation Site (HARS). New dredging
eliminates habitat, while maintenance dredging
keeps habitat in a continually disturbed state.
Where dredging has resulted in a decline in
aquatic species populations, they tend to recolonize in a few years, and dredging has never been
found to be the cause of a major population
decline. Disposal of dredged material can have
adverse effects due to high concentrations of
pollutants in the material. Bioaccumulation of
these contaminants often occurs in organisms
inhabiting the disposal areas.
What are the socioeconomic impacts in
New Jersey?
While there are costs associated with dredging,
they are small in comparison to the billions of
dollars in economic activity that dredging
supports.
What’s being done?
The amount of dredging per year has more than
quadrupled in New York Harbor since the
channel deepening project was initiated in 1999.
Dredging in the Atlantic Coastal Basin and
Delaware River and Bay regions is relatively
constant. Dredging is extensively regulated at the
state and federal levels of government to avoid
or minimize impacts. There are increasing
possibilities for beneficial disposal methods that
virtually eliminate contamination and
bioaccumulation problems associated with
disposal of polluted sediments.
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Final Report of the New Jersey State Comparative Risk Project