DOP Submersible dredge pumps

DOP Dredge Pump 250 is lowered under contaminated layer

PROJECT SUMMARY

Location: Harderwijk, the Netherlands

Period : Q2,2015- Q2, 2016

Product type : DOP250 with special head

Contractor : Boskalis Nederland B.V.

The DOP200 has been skid-mounted to a CATERPILLAR385 excavator. The DOP250’s Boskalis’ design suction pipe is equipped with high pressure jets, loosening the soil. Thus, a hole is created in the top soil layer.

Along the waterfront in Harderwijk, an old town in the centre of The Netherlands, a new residential area is to be built. The site was formerly used as industrial area, which has resulted in a polluted top layer of the soil. To avoid handling this polluted material, Boskalis used an innovative and challenging method: a DOP250 was used to mine clean sand from deeper down, and cover the polluted layer - which remained in place.

DOP250 was used to mine clean sand from deeper down, and cover the polluted layer

The DOP200 has been skid-mounted to a CATERPILLAR385 excavator. The DOP250’s Boskalis’ design suction pipe is equipped with high pressure jets, loosening the soil. Thus, a hole is created in the top soil layer. The DOP is lowered in this hole using its own weight, to a max depth of ca -8.5m. Once at this depth plenty of jetnozzles spaying sideways create a pumpable mixture. The dredged mixture is pumped to a spoil field approx. 600 m away. The mined sand is entirely clean, good quality, coarse building sand – excellent for sealing of the polluted soil. When the projects is ready, the entire area will be covered with a 2m layer of clean top soil.

The DOP200 has been skid-mounted to a CATERPILLAR385 excavator

Great care is taken to control the complex dredging process. The jetwater used for losing the soil and transporting the sand, is recirculated. During the recirculating process the quality of the water is monitored. For the full duration of the process the water has been tested as clean and unpolluted. The 3m thick polluted layer of soil has proven to remain in situ. Moreover, the sand won is continually checked and found clean and unpolluted. Currently, the polluted soil is gradually covered with the clean sand. The project will be ready in time for the start of the home construction works.

For the full duration of the process the water has been tested as clean and unpolluted.