The largest stones to become part of the future hard seawall will be 40-ton concrete blocks. The Blockbuster will soon be positioning the blocks in the sea at a distance of some 50 m off the shore. They will serve as a breakwater for the stony dune. This will ensure that the Maasvlakte 2 seawall can weather the heaviest storms – ones that occur once every 10,000 years.
The approximately 20,000 concrete blocks that are required for this operation will come from the existing block dam that protects Maasvlakte 1. A floating crane (backhoe) is currently picking up the blocks out of the sea with a ripper grab. They are temporarily stored. Once the quarrystone construction has been built in, the Blockbuster can set to work.
Precision Job Above and Below the Water Surface
The seawall cannot be constructed without the Blockbuster. No other crane in the world is up to this job: it can simultaneously lift over 40 tons and stretch to 50 m with this load, after which the crane carries out a precision job, for the most part below water. The margin for positioning the blocks is no more than 15 cm. Contractor PUMA came up with the concept for the Blockbuster. A counterweight of 9 concrete blocks (360 tons) makes sure that the crane maintains its equilibrium. Three double caterpillar treads in the track frame ensure stability. The position of the blocks below the water surface is precisely determined with the help of acoustic cameras. This allows the contractor to stack them in a special way, resulting in a super-strong block dam.
Source: Dredging Today