DOP Submersible dredge pumps

The DOP200 is used to create a profiled building pit


Location: Royal Palace “Het Loo”, Apeldoorn, the Netherlands
Period : Q4, 2018 – Q1, 2019
Product type : DOP200 with sand mining head
Contractor : Ballast Nedam Specialistisch Grondverzet (for Volker Staal en Funderingen (VSF))

Various DOP pumps are used to excavate the new visitors centre for the Royal Palace Museum

The “Het Loo” Royal Palace is a well-known Dutch museum. To accommodate the increasing number of visitors, it had to be enlarged. In order not to spoil the fabulous view on the 17th century palace, the new visitor centre will be located fully underground in the central courtyard. This underground area is created by a number of DOP dredge pumps.

With a minute building pit in the Palace corner tower, a DOP200 is doing the dredge job

To pump away the bulk of the material – some 20.000 m3 of sand and gravel – a DOP250 is used. This DOP pump is fixed to the boom of a CAT345 by means of a quick coupling, and it runs on the excavators hydraulics. The DOP250 cleans the entire area of the inner court yard of the Palace, making use of 8 bar jet water on the suction head, to a dredging depth of -6.5 m. The dredged mixture is pumped through 220 m floating flexible pipe line and 310 m HDPE land line to a spoil field, located at a geodetic height of +14 m. A DOP250 is used as booster station midway in the piping to keep the velocity of the dredged mixture up.

The DOP is powered by the CAT345 hydraulics and is fed with 8 bar jet water to the suction head to break up the cohesive soil

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 same spoil field.

The DOP250 has a continuous feed of 8 bar jet water to the head to boost the mixture concentration by loosening the soil

Challenges did not stop here : also within the Palace, the basement had to be altered. As a result a number of small building pits are located in both the Palace’s wings and in the corner tower. As the space is very limited, no excavator or similar equipment can be used. The creative minds at Ballast Nedam created a small pontoon, which can be maneuvered around the small building pits. This pontoon also suspends and maneuvers the DOP200 using a winch.

After the job the DOP was returned to the DDE workshop for overhaul and check up