North of the village Philippine in Zeeuws-Vlaanderen (the Netherlands) the former dumpsite Kanaalpolder is located. From 1967 to 1977 domestic waste, construction waste and chemical waste were dumped here in low-lying grassland, covering a 5-hectare area. Due to the absence of top and bottom sealing of the dump material, diffusion of particularly volatile aromatics and chlorinated hydrocarbons has taken place. The impact of the dumpsite can be measured up to some hundreds of meters downstream.
Commissioned by the province of Zeeland, ACV started with the preparation towards remediation in 2008. After a supplementary study, which included tests into degradation potential and diffusion behaviour, the province of Zeeland, as advised by ACV, opted for the ‘natural approach’. This is an approach where the former dumpsite is remediated in the most natural way possible.
In broad outline the ‘natural approach’ consists of two steps:
- covering the dump material with a water-resistant layer of soil, followed by natural rehabilitation
- constructing a barrier system in which contaminated percolate and phreatic groundwater are captured and purified
No intensive maintenance
The great advantage of this variant is that natural degradation processes can proceed and that there is no need for all kinds of facilities that require intensive maintenance. This means a considerable reduction in costs. In addition, the approach creates a splendid opportunity for natural restoration of the area. For, if required, this method can be combined with the growth of energy crops..
Testperiod
For the optimal dimensioning and design of the percolate barrier, lab-scale testing was conducted in the summer of 2009. Based on the laboratory results, a field pilot was subsequently constructed at the end of 2009.
In pilot trenches, the effect of compost and peat as percolate barrier is tested. Through lowering the surface water level in relation to the groundwater level, contaminated percolate and groundwater are drawn to the pilot trenches. Based on the results of the first half year it can be concluded that the pilot trenches capture a substantial part of the contamination, at the same time maintaining good surface water quality. Consequently, the percolate barrier has a purifying function. The next few months it will be further investigated to what extent we can speak of a natural degradation by the percolate barrier and/or natural fixation.
The pilot trenches in Zeeland confirm that the natural processes taking place in Volgermeer can also be translated to other locations.