Dredging, mitigative measures?

Question

Are there ways to reduce the impacts of dredging?

Answer 1

This is a complex question, since dredging can cause a number of different environmental impacts.

When you dredge a harbor or channel, you physically disrupt and destroy the habitat of the benthic (bottom-dwelling) organisms found there.  This is unavoidable, so if you want to mitigate or prevent this particular impact, the only choice is to not dredge.  It should be mentioned, however, that since most dredging takes place in harbors and channels where there is a lot of shipping traffic, such disruption and damage has probably already taken place, since the ships themselves tend to disrupt and damage the benthis environment.

Once you dredge, you have to dispose of the material brought up from the bottom (known as dredge "spoils").  In some places, these spoils have been used to create small coastal islands that are designated as wildlife refuges; this has happened around the Great Lakes and in some coastal harbors like Charleston, SC.  In other places along the coast, the dredge spoils are simply taken out into the ocean and dumped.  If they are taken into water that is deep enough for the spoils to adequately disperse, this is usually an environmentally safe practice.

Finally, these dredge spoils are often contaminated with toxic substances.  If they are, they have to be safely contained in a disposal facility designed for that purpose and not just piled up on an island or dumped into the ocean.  Special disposal facilities similar to landfills are often constructed to keep the contaminated spoils from being released back into the environment.  In some cases of very high contamination (like the sediments in the harbor at Waukegan, Illinois) the spoils must be treated to destroy the toxic contaminants.

Answer 2

here, see this link

http://www.city.burnaby.bc.ca/cityhall/d...

it has some proposals on how to reduce the effects of dredging. i think not all the things proposed there is quite effective but it could be a mitigative measure as well