New Focus on the soil remediation of a former gas plant site at Oude Tonge

Before 1969, the year that Goeree Overflakkee was connected to the natural gas network, most municipalities on the island used gas extracted from coal. In 1912 a gas plant was opened at Oude Tonge in order to produce this coal gas.

At that time, its main use was as a source for light and it was therefore called “light gas”. Today, the gas plant no longer exists, but the soil of the 1.2-hectares site still bears traces of the past. As a result of the production, the groundwater and the soil are contaminated with substances like thiocyanate, BTEX and PAHs.

In 2015 a partial remediation was carried out to reduce human and ecological risks. Unfortunately, the risk of slow dissemination of the contamination is not yet controlled sufficiently. Therefore, the Dienst Centraal Milieubeheer Rijnmond (DCMR) has commissioned Bioclear earth to study the possibilities of remediating the subsoil on this former industrial site.

The contamination situation is complex

The size and mix of contaminants, in addition to the fact that the soil consists of various types of soil (peat, clay and sand) make the remediation of the area a complex challenge. In addition, the site is located close to a flood defence. Taken together, these conditions require an approach that includes removal of the contaminant load and, possibly, multiple (in situ) remediation techniques.

In order to achieve this goal, we have considered the most optimal use of biological, chemical and civil technology. Because we are dealing with a complex situation, each of the techniques comes with important failure risks.