This proposal for a large landscape park in the Haarlemmermeer polder is to provide some good old fresh air and scenic splendour. At the same time it makes an effective contribution to one of the most important environmental issues faced by this country. The design addresses the demand for alternatives to today's facilities for storing contaminated dredge spoil. Not only that, it seeks to upgrade the position on dredged material, not least in its impact on the landscape and on society.

The western Netherlands is in big trouble because of the sheer quantity of contaminated sediment in the regional water system. Although a largely invisible issue, it obstructs the water discharge process, hinders shipping and causes environmental problems. The water management area chosen for this study is Rijnland, which roughly speaking extends from Alphen aan den Rijn down to Gouda. Climate change and urbanization are seriously increasing the need to remove the sediment from the water system of the Netherlands' economic heart. The main problem raised by dredge spoil lies in the great quantities of contaminated sludge, a legacy from the 1970s and '80s. According to us, there is to a profit to be made from cleaning and separating the dredge spoil. Our proposal is take 7 million cubic metres of contaminated sediment from Rijnland and almost as great a volume from a part of Noord Holland province and transport it to the Haarlemmermeer polder where it is to be cleaned using various methods of decontamination.

The design constructs an embankment in which the metal contaminated sediment can be cleaned. The heavy metal is flushed from the dredge spoil using the salty seepage water found in Haarlemmermeer. The salt water is kept in one place and away from the Rijnland water system and fragile ecosystems. Special plants species including the zinc violet, yellow star-of-bethlehem, corydalis and water lily then hold the metals in place. This 'garden of metals' will evolve into a disorienting place in the park whose brackish water and saline environments will provide a habitat for flamingos.

The sandy sediment can yield otherwise costly sand that can be conveyed along the N205 provincial road for use at building sites in the rapidly developing Haarlemmermeer. Any sand left over will be used to construct a large playground cutting through the park, an artificial dune landscape originating in dredge spoils. Organically polluted types of sediment are cleaned by land farming in which soil and water types are combined in a mosaic of environments at different heights. The contrasting man-made environments and volumes are crossed by routes through the park that lead visitors past a succession of spaces, vegetations, ambiences, colours and smells.

The park that gradually emerges is accessed from the docks, the ring canal and the road accompanying it (Ringvaartweg), the N205 and various cycle routes. It is visually anchored by sight lines to and from the sand street, the garden and surrounding points. The less contaminated dredge spoil is distributed beyond the embankment using spraying techniques to create gradients in soil types and heights that clearly show the different forms of spraying. Large willow groves provide additional cleaning as well as a varying picture of blocks of willow in the polder. Flushing water is fed through reed filter beds, a ring of filters and the neighbouring sewage treatment works and then discharged into the ring canal.

Twenty years on, all the dredge spoil will have been cleaned and this place will have grown into a public Landscape Park at a prominent location in the green structure. During that time, people will have been able to observe the park, become accustomed to it and evolve along with it, so to speak; a park consisting of unique habitats that can only exist by virtue of the products of dredging and post-dredging treatment. The Dredge Landscape Park is a relic of an effective means of dealing with a typical Dutch delta issue, and the history of this process is stamped all over it.

Place of education: Wageningen University
Specialization: landscape architecture
Tutors: Paul Roncken, Robbert de Koning