DuPont™ Plantex® Platinium in Amsterdam-Zuidoost

Queeny de Haan

Between the A2 and A9 motorways near Amsterdam KING RootBarrier, commissioned by Rijkswaterstaat (the national Department of Waterways and Public Works) and in collaboration with IXAS (a joint venture of Ballast Nedam, Fluor, Heijmans and 3i) and Joosten Kunststoffen, has constructed a depot of ca 10,000 m2 for depositing soil contaminated by Japanese knotweed. This depot will be completed in two phases. Phase 1 involves the covering of the slopes on the edge of the depot, in phase 2 the depot will be completely covered.

In the area around the Zuidoost district of Amsterdam Japanese knotweed is rampant. This invasive exotic has introduced great risks and damage to newly installed infrastructure. The expansion of the A9 motorway produced large volumes of soil contaminated by residues of Japanese knotweed. Removing, transporting and incinerating this infested soil would have been extremely costly, so that an alternative solution had to be found.

A cheaper but effective alternative was to cover and wrap the depot. With IXAS’ expertise in the structuring of depots and KING RootBarrier’s experience covering contaminated soil, contact was soon established. DuPont™ Plantex® Platinium was selected, as this intrinsically strong weed fabric was especially designed to combat Japanese knotweed. The fabric is permeable to water and air, thus preventing erosion and allowing the whole area to be restructured as desired.

Phase 1 was delivered in September 2020. The depot’s slopes were covered with DuPont™ Plantex® Platinium and the seams were sewn together using a specially designed sewing method. In the next few months, the depot will be filled with knotweed-contaminated soil. As soon as the depot is full, phase 2 will begin: covering the depot with DuPont™ Plantex® Platinium, sewing the fabric and joining it to the fabric from phase 1. Next, the entire area will be covered with a minimum of 25 cm of clean soil. It can immediately be sown with grass or flower seed to activate biodiversity. Moreover, grass and flower roots will bond with the surface, which reduces soil erosion. This will allow the depot to assimilate into the public space and become part of the park that connects Amsterdam Zuidoost.

The residues of Japanese knotweed in the enclosed soil are expected to become dormant and to decompose in a few years time. It has not yet been decided for how long the soil may remain where it is. DuPont™ Plantex® Platinium carries a 35 year product warranty, so that it may be left for a long time to come.