Date: Mon 09 Jan 2017

Light weighted putting greens – the solution to building on peaty soil

By Michiel van der Vaart, EIGCA Associate Member

Hole 4 at Zeegersloot GC Netherlands during construction

Hole 4 at Zeegersloot GC Netherlands during construction

The finished hole 4 at Zeegersloot GC Netherlands

The finished hole 4 at Zeegersloot GC Netherlands

Construction of a floating green

Construction of a floating green

Building a floating green at GC Zeegersloot using PE foam blocks

Building a floating green at GC Zeegersloot using PE foam blocks

The challenge when designing a golf course in The Netherlands is that almost half of the country is below sea level. Large parts of The Netherlands used to be lakes and marshlands and after a huge effort to create dry land by pumping out water (back in the 14th century), the lakes became polders (see below) surrounded by dykes.

Since 1980, many new golf courses have been built around the big cities of Amsterdam, Rotterdam and The Hague – and these are among the worst peaty soil areas in the country. So, how is this possible?

Zeegersloot Golf Course

The 18-hole Zeegersloot Golf Course is a good example of how to build on peaty soil - 9 of the holes are on a landfill and 9 holes are in a polder which is two metres below sea-level. The soil conditions in the polder are 15cm of cultivated farm land (clay), underneath that are at least 6 metres of peaty soil, and a water table approximately 60cm below the average level.

In theory, it is virtually impossible to create a golf course in these conditions … except when you create lightweight constructions and let it float.

Green construction

To create a green construction which conforms to the ‘Dutch-Green-method’, the construction height should be at least 45cm (without elevation changes!). The use of 25cm sand (D) plus 20cm topsoil (E) means quite a few tons of downwards pressure – far more than the original subsoil of peat (A). These green complexes are built on top of (PE) Polyethylene foam blocks (C) to create just enough floating capacity to compensate for the weight difference - without these foam blocks (C), the green complex will sink several metres underneath the water table.


How we did it

  1. Cleared an area somewhat bigger than the green complex itself, then created an area that falls slightly (2%) (layer B – at Zegersloot this was a clay layer – the old farm land).
  2. Strings of drainage were installed every 4-6 metres, before laying out the PE blocks.
  3. The first layer of polyethylene foam blocks – measuring 3 x 1 x 0.1 metres – were laid on top of a 5-10 cm coarse sand layer so the base of the PE blocks is soft enough to prevent them from breaking.
    (On top of the first layer the irrigation and extra drainage was installed. If there is a severe ‘step’ designed in the green, it is possible to add a third layer of PE-blocks)
  4. Finally, we used the ‘Dutch-Green-Method’ to finalise the two top layers of 25cm foundation sand and 20cm top layer of root zone.

The future

The PE foam blocks make it possible to design and build more varied green-complexes with more elevation changes ... without them sinking into the peaty subsoil. Up to now, we only know of one green that has been re-built with a floating construction. The aim for the future is to source a more environment-friendly product than polyethylene.

Polder

Polder

A low-lying tract of land enclosed by dikes that forms an artificial hydrological entity, meaning it has no connection with outside water other than through manually operated devices. Source: Wikipedia (https://en.wikipedia.org/wiki/Polder)

Click here for more information about Michiel.

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