Depollution of the former Awirs power plant near Liege: in 3 months time a total of 220,000 tonnes of soils were transported by waterway

Over the 3-month period of this construction site, 220,000 tonnes of soil – 120,000 tonnes extracted from the former coal yard of the Awirs power plant and 100,000 brought back to the site – were mobilised. This environmental and logistic performance was made possible by the use of waterways and the deployment of the Envisan physicochemical washing installation. A nice example of circularity too: a large part of the 120,000 tonnes of soil received by Envisan was transformed into washed sand and aggregate, to be reintegrated into the local construction market. This is excellent news for mobility and the environment in Liège.

M. Dimitri Descamps, Commercial Manager Envisan: « The project on the Awirs site represented a true logistic and environmental challenge for us. Thanks to our methodology based on waterway logistics and on the use of our processing centre located in the Port of Monsin in Liège, we did take on this challenge successfully. The Envisan physicochemical washing process, the first unit of this type in Wallonia, offers a decontamination solution for polluted soil and the transformation of these into secondary construction materials on the Walloon, Luxembourg and French markets. As a result, Envisan are a major link in the circular economy of the Autonomous Port of Liège. »

Raf Anné, ENGIE Project Director for the Flémalle site: « This project illustrates ENGIE’s capacity to tackle its industrial liabilities responsibly, while limiting to a minimum the impacts for local residents and the environment. That is the reason why the soil from the former coal yard of the Awirs power plant were transported by waterway. This made it possible to take 120 lorries off the road for each waterway transport and to reduce CO2 emissions by using an eco-friendly means of transport. This responsible management approach has been implemented by ENGIE since 2016 for the removal of ash from the Hénâ slag heap at the Awirs, from where they are transported via a covered conveyor belt to the Meuse River. From there, it is transported by barge to the cement plants. Just like ash, soil has a second lease of life. »

M. Emile-Louis Bertrand, Director-General of the Autonomous Port of Liège: « The Autonomous Port of Liège, first Belgian inland port and third European inland port, does indeed intend to play a key role in the circular economy. Because of its logistic facilities, its central role in the local economy and its interaction with industry, a port such as Liège has so many assets that turn it into a major player in the circular economy. As crossroads for the flow of raw materials, products and waste that circulate in our economy, our concession-holders possess a huge expertise in the logistics, storage, management and processing of waste. Therefore, we support Envisan who chose the circular economy path and who, with this project and its activities, aims at reducing its carbon footprint and its environmental impact, noise and the number of lorries on the road. Finally, it is important to think of using waterways and prioritise this mode of transport for soil and rubble from similar construction sites … »

The decontamination of the Awirs power plant

ENGIE entrusted Envisan with the implementation of the depollution works of the coal yard of this former power plant « Les Awirs ». The pollution was caused by the historical industrial activities on the site: for example, glass works until 1949 and then the storage of coal for the former power plant. The purpose of this project is to prepare the site for the construction of the new combined gas and steam turbine power plant (GST power plant) of ENGIE. This is a unique project, that has the following main constraints:

• The soil volume to be mobilised is large and represents a total of 220,000 tonnes, of which 120,000 tonnes are contaminated with heavy metals, oils, etc... to be processed. This soil mobilisation must be achieved minimising the impact on local residents and on road traffic near the project site.
• The deadline is very short: there is only a 3-month window between validation by the Walloon authorities of the site rehabilitation plan and the start of construction operations of the new ENGIE plant. This means the mean daily yield to achieve is about 3,500 tonnes.

Waterway Transport

As a major player in the maintenance of waterways, Envisan assesses the fluvial mobility solutions for the transport of contaminated soils for each project. In the case of the depollution project of the Awirs site in Flémalle, the fluvial mobility made it possible to reach daily yields of up to 7,000 tonnes and therefore avoid increasing the current mobility issues on the streets of Liège.

The fluvial logistics represented a saving of almost 8,500 lorries on our roads and a C02 saving of 750 tonnes, which corresponds to a reduction of CO2 emissions by a factor 3.5.

First in Wallonia: a physicochemical washing installation

In 2021, Envisan installed the first Walloon physicochemical washing unit in Liège. This processing technique is well-suited to the spoils originating from the large steel working areas characterised by complex pollutions, and obviously high heavy metal concentrations.

This depollution unit has a processing capacity of 70 tonnes per hour and operates on the wet soil treatment principle. It makes it possible to reduce the pollutant contents significantly, such as heavy metals, hydrocarbons, PAH, BTEX, etc.

The treatment process also generates washed aggregates that have a high added value: sand and a rougher fraction, both washed. 1,000 tonnes of contaminated soil generate 700 tonnes of washed aggregates, destined for the local construction materials sector. A textbook example of a circular process.

Circular solution at the heart of Liège

The Envisan processing centre has been operational since 2014 on a 3.5 ha port concession in the fluvial port of the Ile Monsin, one of the 33 port areas managed by the Autonomous Port of Liège.

The centre is aimed at Jan De Nul Group civil engineering and environmental projects, contractors in the construction industry in the Liège area and industry beyond provincial and national borders. Thanks to the trimodal accessibility of Liège, neighbouring countries, such as Luxembourg and France, can also benefit from Envisan solutions for the processing of all categories of polluted, hazardous and non-hazardous soil and slurry.