Remediation of old industrial sites: Removal of contaminated sludge
From today’s perspective, it sometimes seems inconceivable how humans treated nature in the past. When it comes to environmental pollution, fingers are quickly pointed in the direction of Asia or developing countries with a lack of regulation and infrastructure for waste and pollutants.
But even in Europe, it was not too long ago that awareness of environmental pollution was very low. On the one hand, because of priorities, building the economy and fighting poverty was more important than protecting nature, and on the other hand, because scientific knowledge about pollutants and their effects on nature and humans was not yet sufficiently known.
Even today, there are still many polluted former factory sites or landfills.
One such example can be found in the idyllic Swedish town of Åsbro. In the midst of breathtaking and seemingly untouched nature, two impregnation plants were located there for many years.
In the past, railway sleepers, electricity and telephone poles were treated with chemicals to protect them from the weather. These chemicals entered the local rivers and spread into the nearby lake.
The challenge
Drinking water protection under difficult conditions
Despite its local pollution, the lake is used as a drinking water source for the region. As a result, special care had to be taken to ensure that the sediments from the contaminated areas were not allowed to be stirred up unhindered. This could have caused the sediment to spread throughout the entire lake.
In addition to these critical requirements, access to the work sites is very limited. The contaminated inflow of the lake is surrounded by trees and marshy areas. This makes access difficult for conventional machines.
The solution
Efficient sediment removal WITH our BERKY Poseidon 770
The ProGroupe company from Slovakia is an expert in difficult sediment removal projects. On behalf of the Swedish Geological Institute (SGI), the experienced team set to work.
Their concept was based on the use of a BERKY Poseidon 770 amphibious multi-purpose dredger, silt curtains, geotextile tubes and activated carbon filters.
Step 1
First, sheet pile walls were placed in the river using the BERKY Poseidon 770. This stopped the flow of water and created a demarcated area from which stirred-up sediments could not enter the lake.
The river’s inflow was diverted directly into the lake via piping.
After that, a sediment barrier was built in the lake, where the Poseidon 770 was also able to demonstrate its versatility. With the help of the boom arm, the machine was able to support the spreading and installation of the barrier.
Step 2
After the installation of these protective mechanisms, the sediment had to be removed. One of the special requirements of the project was the need for precise work. The task was to remove the specified areas at specified depths to ensure that all contaminated material was removed.
The stable working position of the Poseidon 770 with its four stabilizers and precisely operated boom were helpful. In addition, ProGroupe has equipped its machine with its special GPS-based SMART DREDGING system, so that the working position and depth can be determined and logged with centimeter accuracy.
Step 3
The sediments are pumped into geotextile tubes using a pipeline. These function like a coffee filter. The sediments remain in the textile, while the water runs out through the pores. This is how mud and water are separated.
In this particular case, the discharged water was then treated using an activated carbon-based water treatment system and discharged back into the lake.
The result
Safe drinking water thanks to successful remediation
The area was successfully cleaned of the contaminated sludge. A total of 16,000m³ of material was removed. This was excavated over an area of 20,000m².
The measurement results showed that the arsenic and polycyclic aromatic hydrocarbon (PAH) levels had been reduced to a level that posed no health risk.
The residents of Åsbro can now use and enjoy their drinking water for decades to come without concern.
the conclusion
Amphibious suction dredger as the key to successful remediation
Complex and unique projects such as cleaning this waterway require special solutions implemented by experts. In this case, the BERKY Poseidon 770 Dredger was the perfect tool for the ProGroupe team.
The machine was able to move around easily in this difficult-to-access area. With the boom, the machine was able to ram sheet pile walls, assist in the installation of the silt curtain and pump sediments. Coupled with the stable working position and precise operation, there is arguably no other type of machine than an amphibious multi-purpose suction dredger that could have completed this project.
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