Cleaning up a contaminated marine site is not as easy as simply dredging the material from the bottom and placing elsewhere. Marine Tech has developed a unique process to transport materials that hold toxins in place with hydraulic capping. Using specialized software, layers of sand, along with activated charcoal, work to compress, seal and cap the hazardous sediment below.

These processes can help return aquatic sites to clean, safe and productive environments.

Such was the case in Stryker Bay in the St. Louis River. The underwater toxins posed environmental and health concerns that needed to be resolved. Marine Tech worked with the responsible parties remediation engineers to remove, transport and cap contaminated sediments. First item needed was to build a “Confined Aquatic Disposal Facility”. Marine Tech built and lined a containment area to house all of the contaminated sediment. After completion of the removal of sediments Marine Tech began the capping process.

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 charcoal fabric 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 over 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. This environmental media was harvested with our hydraulic dredge almost two miles away and delivered to its final location with the same accuracy as the sand cap.

When completed, we placed more than 150,000 cubic yards of a combination of sand cap and environmental media.


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