Ex1: Dredge Landscape Park

Dredge Landscape Park

General Info:

Project by: Alexander Herrebout & Gerwin de Vries, Netherlands
Location: Haarlemmermeer polder, NL
Client: Wageningen University MSc thesis
Completed: 2007
Link: project site

Description:

Landscape infrastructure for cleaning polluted dredgeate

The inland water system of the urbanized Dutch delta is faced with an invisible problem; layers of polluted dredge deposited in the ’70 and ’80 cause both drainage and environmental problems. The need to remove this polluted dredge will increase due to climate change and growing urbanization.

The proposed solution is the Dredge Landscape Park; 12 million m3 dredge is shipped to a 300 ha. site in the Haarlemmermeer polder, decomposed, and cleaned with different cleaning techniques. Within 20 years of cleaning time this dredge cleaning machine will evolve into a dredge landscape park. Saline exfiltration water is used for the cleaning of certain dredge types and extracted sand—leftover after the cleaning process—can be used for the expanding building sites nearby. The variety of water-, soil- and pollution types in the dredge is used to grow a unique park. Different types of vegetation fixating heavy metals will form a heavy metal garden, an artificial dune strip of dredge sand runs straight through the park and different water and soil types are combined in a mosaic of cleaning environments with variable heights that change over time. Routes through the park connect bicyclists, car drivers and boat skippers to the dredge landscape park.

How it works

The design proposes a robust framework as the basis of the park, wherein natural and cultural forces and processes and time have a free hand to clean the soils and evolve into a park. The existing polder grid structure of fields surrounded by ditches is transformed into a new water system composed of ditches and separating dikes. The dikes separate the site into different contamination regimes, hereby creating a hierarchy in pollution with slightly polluted soils at the site’s borders and the most highly contaminated soils in the core of the site. Existing transport infrastructure is improved for importing dredge material by boat and truck.

Within the outer ‘voids’ of the framework, dredge polluted by organic material is injected by sand-spraying the dredge onto the site, hereby separating heavy soils (sand) from lighter (clay and finally peat), a cleaning method called sand separation. A new and varied morphology automatically arises by differences in material gravity, subsidence and soil types, resulting in height and soil differences. Contamination is cleaned by oxygenation and landfarming; the cleaning of dredge specimen by biological breakdown of organic pollution.

The core of the park is planned between the area where saline seepage exfiltrates and the supply channel. This second regime is separated from the outer are by a ring dike and ditch that hydrologically separate the two regimes. Here the more contaminated soils are cleaned;

A mosaic is created of fields of different soil types. Combined with a variety in contamination, a multitude of milieus will arise, expressing each dredge type. This variety is even more diversified by applying either fresh, brackish and saline water for different fields, resulting in a wide palette of vegetation types and appearances.

The sand street is strung between the N205 highway and the supply channel’s harbour. It consists of cleaned sand that has no economical value as construction sand due to its grain size and therefore will have to be stored on site. The sand will, due to excavation, wind and succession, form its own dune landscape.

The most contaminated soils containing high levels of heavy metals are brought to the most central part of the site, where the metals will be washed out with saline water. Over time, the left-over residue will be the basis of a metal garden where rare species such as the sink violin will fixate the pollution.

The park is designed by phasing in order to evolve over time and provides for the experience of each time period and dredge type:

  • starting phase: import of material, pioneer species, minimal access

  • machine phase: continuing import, first part is cleaned, more diversity, succession, experience

  • succession phase: major role for vegetation, climax species, majority of dredge is now within the site boundaries, transformation to a park

  • residue phase: dredge machine is finished, left-over residue is experienced in dredge landscape park

………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

Advertisements