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Beneficial use of sediments
in the Magdalen Islands
Dredged sediments operations

Dredged sediments operations

DFO  L. Bouffard

If you are familiar with the Magdalen Islands, you probably know that this beautiful region is facing a problem with shoreline erosion and its impact on coastal activities.

In fact, the archipelago, located in the middle of the Gulf of St. Lawrence, faces winds and tides of varying intensity every day. Combined with ocean currents, this results in the accumulation of sediments in ports, including those under the jurisdiction of Fisheries and Oceans Canada. To ensure the safe movement of fishing ships in these harbours, regular dredging must occur, specifically in spring from late March to early June.

Since last March, a very special operation has been carried out. Rather than discarding dredged sediments at sea as was done previously, sediments from dredging sites at Millerand and Pointe-Basse are used by Transporte Québec. They serve to reinforce Route 199, which is often subject to erosion, as well as to build the approaches of a new bridge near Havre-aux-Maisons.

How is this done? After being collected at sea and transported to shore by special barges, sediments settle over a 24-hour period in order to dry, which makes for easier handling. The sediment is then loaded onto trucks to be transported to various construction sites.

Because of the islands' fragile environment and geomorphology, sand for construction on the archipelago is becoming increasingly rare. "Sand from dredging activities, when not contaminated, is an excellent alternative supply source. With no scheduled opening of new sand pits in the near future, this approach has become crucial," says Louis Bouffard, associate project technician with the Islands' Regional Small Craft Harbours Branch (RSCHB). Sediments collected at sea could be stored for future use in old sand pits.

Is this type of operation possible in other areas? "Of course," replies Alex Harvey, project technician in charge of dredging for the RSCHB. "Last year we completed two relatively similar projects on the North Shore, at Baie-Trinité and Rivière-au-Tonnerre." But he added that a project on the scale of the Magdalen Islands is a first for the Department.

In fact, when possible, both environmentally and economically, the traditional practice of disposing of the dredged sand is being replaced by a beneficial use for the sediments, such as refilling beaches or reusing sediments for construction as in the Magdalen Islands. This beneficial use is also the preferred route for protecting fish habitat.

Video on operations describe in the article

Lyne Beaumont
Small Craft Harbours
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