Envisan helps tackle historic pollution in De Lieve

Envisan, the environmental subsidiary of dredging and construction company Jan De Nul Group, will be supporting the Public Waste Agency of Flanders (OVAM) for the next six weeks with the installation of innovative reactive mats in De Lieve watercourse to address historical soil and groundwater pollution caused by 19th century industrial activities. The works are part of the European RESANAT project ('REstverontreiniging SAneren met NATure-based technieken'), a Flemish-Dutch partnership.

High-tech mats for water treatment

In the next few weeks, OVAM and the project team will install specially designed mats on the Lieve riverbed and embankment. These innovative mats replace the old, contaminated silt layer and protect the surface water from contamination pending the complete remediation of the surrounding land. The mats will filter the pollutants out of the groundwater and break it down naturally.

The mats have a permeable geotextile structure, comparable to the structure of a duvet. A filler material is applied within the cells that retain pollutants to help break them down. The filler consists of natural materials such as peat and biochar (a type of charcoal). The project will run for another 2 years although the mats themselves will remain in place even longer, until further remediation works eliminate the impact of historic pollutants on De Lieve.

A Flemish-Dutch partnership 

The project team that tackles De Lieve consists of Envisan-Jan De Nul Group, Tauw, TTE Consultants, Witteveen+Bos and iFLUX, who are all active in the soil remediation industry and with a shared focus on innovative, sustainable environmental techniques.

An Smet, Director of Envisan: “Our participation in this European RESANAT project is driven by our hunger for innovation. Innovation is part of our strategic pillars to achieve sustainable solutions for a better planet. At Envisan, we distinguish ourselves through research & development for unique and innovative solutions. This project fits perfectly with our vision. We are proud and happy that we can enter into this partnership with OVAM and our Flemish and Dutch colleagues".

Within the European RESANAT project, seven small and large Dutch and Flemish companies cooperate with knowledge centre Deltares and the Openbare Vlaamse Afvalstoffenmaatschappij (OVAM) to stimulate the redevelopment of contaminated land in the Netherlands and Flanders. Conventional remediation and management techniques are expensive, energy-intensive, take a long time and sometimes consume a lot of groundwater.

RESANAT stimulates innovation of remediation techniques whereby plants, micro-organisms, natural materials and wind and solar power are used to control residual contamination. Thousands of locations in Flanders and Holland that are still tackling (residual) pollution will be able to use these new techniques for residential and business estates. RESANAT is implemented with funding from Interreg Vlaanderen-Nederland.

Historic pollution in De Lieve

Between the Durmeschipstraat and the Watlingtonstraat in Wondelgem, De Lieve drains off excess rainwater. This is important to protect the area against floods and the canal was also dredged late 2019, eliminating the risk of any possible issues in the event of heavy rainfall.

At this project location, heavy pollution was found in De Lieve riverbed, with mineral oils and PAH components. This contamination of tarry substances originated from a factory at the Watlingtonstraat, producing tar, asphalt and roofing products from the 19th until the late 20th century.

Over the years, a fine silt layer deposited on top of the tar. Therefore, the tar and soil contaminants did not have any impact on the surface water quality. However, due to the dredging of the canal over the past year, more contaminated groundwater ended up in De Lieve and the water quality degraded again.

De Lieve, a medieval watercourse

De Lieve is a canal of medieval origin that ran from Ghent to the Zwin. For a few centuries, it was crucial to the Ghent economy. Because wider and deeper canals were dug later on, De Lieve fell into disuse. The City of Ghent now wants to upgrade the watercourse and have it play a role in the green-blue network.