Boskalis_Annual Report_2017

43

BUND

“After a long tender period, our design teams started drawing up the frst plans for the civil-engineering work in close consultation with our subcontractor end-2016. We knew we had to work fast. The frst part of the quay wall and the port area behind it will have to be completed by the end of Q1 2018 because that is when the construction work starts on the tank terminal located on the part of the port built by us,” explains Pröpper. Soil drilling and soil surveys began in the spring of 2017 as a basis for the defnitive designs. “We decided at an early stage to build a heavy ring dike – a bund – of sand that contains a large, eighteen-meter-deep construction pit where we are building the quay and the two jetties,” he explains. SAND SUPPLIES Work began on bringing in the sand for the bund in June 2017. The mega hopper Queen of the Netherlands was deployed frst, and the work was taken over in July by the Prins der Nederlanden. “We were taking the sand from a borrow area about twenty miles offshore,” says Pröpper. “The trailing suction hopper dredgers sailed three times a day from the borrow area to the connection point, where it pumped more than 30,000 cubic meters of sand through a floating pipe to the location. Obviously, we took the prevailing environmental requirements relating to turbidity into account during this operation. In addition, we put procedures in place to ensure that we didn’t disturb the colony of whales living in the area. The client was represented by mammal observers on the trailing suction hopper dredger.” COORDINATION “For the dry excavation of the pit we drew on the equipment and expertise of our colleagues from Boskalis Nederland,” continues Pröpper. “Some of the subsurface was rocky ground and you couldn’t just spoon that out. Some of the excavated material will be used for the construction of the terminal and the jetties.” The project includes a large number of activities requiring precise coordination. “Large concrete blocks are needed for the construction of the quay wall and they are being produced elsewhere in the port area,” is one example that Pröpper brings forward. “The land reclamation operations are progressing in line with the construction of the quay wall. To execute all the different tasks, perfect coordination between all disciplines is required. Keeping all the balls in the air is the main challenge on this project.” COMPACTION To comply with the stringent demands for the compaction of reclaimed land Boskalis subsidiary Cofra was called in. “Cofra set up a special testing area to study the best possible approach to compaction,” says Pröpper. “Boskalis Nederland is also involved in the construction of the rock slope next to the quay wall and the two large jetties, which we will be covering with geotextile and rock. Some of the rock will come from the current breakwater, which will form one edge of the port area. We will be removing rock from the inside of the breakwater before putting in the sand.” NEXT PHASE The next phase of the project involves the removal of the bund and deepening the port to -18 meters. “We started on that work in December,” says Pröpper. “That will involve dredging a total of 24 million cubic meters for which we are deploying our new mega cutter Helios amongst others.” Project completion is expected in the second half of 2019.