21 May 2019

Dredging job at an iconic location

The Dutch Palace “Het Loo” is the former Royal residence of King William and Queen Mary Stuart. Built in the 17th century, it served as their residence and hunting lodge. For the past 3 decades, the Royal Palace has been a museum showcasing Dutch Royal collections and the fabulous formal gardens. Due to the ever increasing flow of visitors, the Palace badly needed a refurbishment. It was decided to close the Palace for visitors, and create a new space to welcome the visitors in style.

This new welcome includes a large underground area, located between the 2 wings of the Palace. For this, the central courtyard, or “Bassecour” as it is known, is transformed into a building pit. And that is where our interest lies : the central area is excavated by means of Damen DOP pumps.

cat345 and damen dop250 building pit

The building pit is located in the Palaces central courtyard

The job started with archaeological excavations in the top soil, followed by removing the top soil dry, that is using excavators with buckets. To minimise truck movements in the relatively densely populated area, it was decided to pump the sand to the spoil field, requiring a pipe line only – and no continuous truck movements. Ballast Nedam Specialistisch Grondverzet does this job as subcontractor for Volker Staal en Funderingen (VSF).

The job in the Bassecour is done in two stages. A DOP250 fixed to a CAT345 started off dredging the building pit to a depth of -6.5 m. The compacted sand and gravel was loosened by 8 bar jet water on the suction head. The material – some 20.000 m3 – was pumped through partly floating pipe line over some 530 m length including a geodetic height of 14m. As a result a DOP300 was located in the discharge line to keep the mixture velocity up.

Cleaning the last 50 cm of the building pit was done by a DOP200, also attached to a CAT345 and driven directly by its hydraulics. This DOP was connected by a chain spread though. The reason for this is that the DOP was to make profiles on the side of the building pit. Another DOP200 acted as booster to pump the mixture to the spoil field.

damen dop powered by the cat345 hydraulics

The DOP is powered by the CAT345 hydraulics

The Bassecour building pit is not the only dredging job at “Het Loo”. Astonishingly, also within the palace the DOP is at work : in the basement of both wings as well as the corner tower. Due to the restricted areas the DOP cannot be handled by an excavator. As a result, a small pontoon is used to suspend the DOP200 from. The winches on the pontoon control the DOP200 as well as the movement of the pontoon itself – another example of creative minds making maximum use of the versatility of the DOP pump.

cat345 and damen dop250 located on a pontoon

The CAT345 is located on a pontoon as a result the DOP250 can be moved


Damen DOP pumps
Volker Staal en Funderingen (VSF)


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