Soil remediation expert: Packaged PFOS soil takes nearly a century to …

The commission to investigate PFOS pollution in the Flemish parliament heard again from a number of experts on Friday who should provide more clarity about the contamination around the site of the 3M plant in Zwijndrecht. On this second day of the course, specialists in soil investigation and soil treatment attended.

Pollution at the site recently emerged as a result of Oosterweel’s work. The soil that had to be excavated was found to contain concentrations of PFOS well above the standards.

• Overview | PFOS contamination in Zwijndrecht

The most contaminated soil will be encased in a safety berm over 1 km long and 6.5 m high, which will be placed at the 3M site. This relates to 135,000 m3 of highly contaminated soil with a PFOS concentration of up to 1,000 mcg/kg.

Several MPs asked experts about the longevity of such encapsulation of contaminated soil. Soil remediation expert William Lees, of engineering firm AECOM, noted Friday the importance of good follow-up.

I would never myself say that such a film has a 100-year warranty. Follow-up is important at least, in groundwater and in the surrounding area. “Careful follow-up is always necessary,” he added.

“It is possible, for example, that something has been placed incorrectly, there are production errors or the tree roots are penetrating the chip. Semi-constant follow-up is needed in order to be able to intervene and recover if necessary.

Lis also indicated that there are different types of encapsulation. According to the expert, the best technique depends on the location and the risks.