CONTAMINATED SEDIMENT REMEDIATION

Sometimes, cleaning up a contaminated marine site isn’t as easy as simply dredging the material from the bottom surface.

Such was the case in Stryker Bay in the St. Louis River. The underwater toxins posed environmental and health concerns and any attempt at removal would lead to the spread of the toxins down the river and into Lake Superior.

For environmental and time reasons, hydraulic capping was the solution. The first challenge was to engineer a way to deliver capping material while holding the contaminants in place.

Marine Tech set up a feed conveyor system on shore to hydraulically pump capping material to a placement barge. Using specialized software, we put down a 6” layer of sand to give structure to the contaminated sediments.

Then we put down a layer of activated carbon to filter any sediment that works through the cover cap.

Then, slowly and methodically, more layers of sand were applied, six inches at a time, until it totaled four and a half feet. The weight of the sand compressed the substrate, sealing and capping the hazardous sediments below.

Topping it all, Marine Tech added a six-inch layer of environmental media to bring the underwater eco-system back to its natural state.

When completed, we placed more than 150,000 cubic yards of a combination of sand cap and environmental media – the majority in one summer season.